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Sample records for rapid concrete deterioration

  1. Concrete pavement joint deterioration.

    Science.gov (United States)

    2015-12-01

    Concrete pavements are an important part of our national infrastructure. In recent years the relatively small number of reported joints deteriorating prematurely in concrete pavements around Indiana has increased. Changes over the past 45 years in IN...

  2. Deterioration of Concrete Structures

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Chloride ingress is a common cause of deterioration of reinforced concrete bridges. Concrete may be exposed to chloride by seawater or de-icing salts. The chloride initiates corrosion of the reinforcement, which through expansion disrupts the concrete. In addition, the corrosion reduces the cross...

  3. Microscopic examination of deteriorated concrete

    NARCIS (Netherlands)

    Nijland, T.G.; Larbi, J.A.

    2010-01-01

    Concrete petrography is the integrated microscopic and mesoscale (hand specimen size) investigation of hardened concrete, that can provide information on the composition of concrete, the original relationships between the concrete's various constituents, and any changes therein, whether as a result

  4. Prediction of Deterioration of Concrete Bridges

    NARCIS (Netherlands)

    Gaal, G.C.M.

    2004-01-01

    In the early 20th century, the general idea was that concrete structures would never show deterioration. However, in the 1990s concrete structures showed an increase in number of cracks and area of spalling. Especially spalling of the concrete cover could create a harmful situation to the users.

  5. On some microstructural aspects of concrete deterioration

    Directory of Open Access Journals (Sweden)

    Draper, E. A.

    1993-12-01

    Full Text Available There are numerous mechanisms that can lead to deterioration of portland-cement concrete in service. The best known are corrosion of reinforcement, freezing-thawing expansion, alkali-silica reaction, acid attack, and sulfate-related problems, including delayed ettringite formation. Additionally, concrete can deteriorate as a consequence of improper processing, including curing. Often, several of the above mechanisms of deterioration are jointly responsible for the observed damage. This paper briefly reviews the light-optical and electronoptical microscopic methods available to study some of the causes of concrete deterioration, and briefly describes selected case studies. Specifically, microstructural features resulting from physical (e.g., freezing-thawing and chemical (e.g., alkali-silica reaction, delayed ettringite formation deterioration of concrete are highlighted. Corrosion of reinforcement is not discussed.

    Hay numerosos procesos que pueden afectar al hormigón de cemento portland. Los más conocidos son: la corrosión de las armaduras, el efecto expansivo del hielo-deshielo, la reacción álcali-árido, el ataque ácido y los problemas que atañen a los sulfates, incluyendo la formación de ettringita expansiva. Además, el hormigón puede deteriorarse como consecuencia de determinados procesos, entre los que se cuenta el curado. A menudo, más de uno de los mecanismos citados influyen conjuntamente en el daño observado en el hormigón. El presente artículo revisa brevemente métodos de microscopía óptica y electrónica utilizados para estudiar las causas que motivaron deterioro en el hormigón, y resume algún caso seleccionado; concretamente, se destacan los efectos microestructurales que resultan de mecanismos físicos (por ejemplo, de hielo-deshielo y químicos (p.ej., reacción álcali-sílice; formación de ettringita expansiva. No se hace mención de aspectos relativos a corrosión de armaduras.

  6. Investigation of deterioration of joints in concrete pavements.

    Science.gov (United States)

    2016-01-01

    Premature deterioration of concrete at the joints in concrete pavements and parking lots has been reported across the northern states. The distress may first appear as shadowing when microcracking near the joints traps water, or as cracks parallel to...

  7. Modelling of the Deterioration of Reinforced Concrete Structures

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Stochastic modelling of the deterioration of reinforced concrete structures is addressed in this paper on basis of a detailed modelling of corrosion initiation and corrosion cracking. It is proposed that modelling of the deterioration of concrete should be based on a sound understanding...

  8. Ultrasonic measurements of undamaged concrete layer thickness in a deteriorated concrete structure

    NARCIS (Netherlands)

    Demcenko, A.; Visser, Roy; Akkerman, Remko

    2016-01-01

    Ultrasonic wave propagation in deteriorated concrete structures was studied numerically and experimentally. Ultrasonic single-side access immersion pulse-echo and diffuse field measurements were performed in deteriorated concrete structures at 0.5 MHz center frequency. Numerically and experimentally

  9. Polarization Induced Deterioration of Reinforced Concrete with CFRP Anode.

    Science.gov (United States)

    Zhu, Ji-Hua; Wei, Liangliang; Zhu, Miaochang; Sun, Hongfang; Tang, Luping; Xing, Feng

    2015-07-15

    This paper investigates the deterioration of reinforced concrete with carbon fiber reinforced polymer (CFRP) anode after polarization. The steel in the concrete was first subjected to accelerated corrosion to various extents. Then, a polarization test was performed with the external attached CFRP as the anode and the steel reinforcement as the cathode. Carbon fiber reinforced mortar and conductive carbon paste as contact materials were used to adhere the CFRP anode to the concrete. Two current densities of 1244 and 2488 mA/m², corresponding to the steel reinforcements were applied for 25 days. Electrochemical parameters were monitored during the test period. The deterioration mechanism that occurred at the CFRP/contact material interface was investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques. The increase of feeding voltage and the failure of bonding was observed during polarization process, which might have resulted from the deterioration of the interface between the contact material and CFRP. The formation and accumulation of NaCl crystals at the contact material/CFRP interface were inferred to be the main causes of the failure at the interface.

  10. An attempt to describe a relationship between concrete deterioration quantities and bridge deck condition assessment techniques

    Science.gov (United States)

    Varnavina, Aleksandra V.; Sneed, Lesley H.; Khamzin, Aleksey K.; Torgashov, Evgeniy V.; Anderson, Neil L.

    2017-07-01

    This paper presents a study of the performance of four techniques - visual inspection, Ground Penetrating Radar (GPR), Ultrasonic Surface Wave (USW), and core control - that were used to assess condition of a concrete bridge deck. The bridge deck was then rehabilitated using hydrodemolition, and the concrete removed during hydrodemolition was assumed to be deteriorated. LiDAR measurements of concrete depth removal collected after hydrodemolition were used as ground truth. Comparisons of bridge deck condition assessment data and LiDAR concrete removal measurements were performed in this study. The comparisons attempt to find and describe a possible relationship between bridge deck assessment techniques and quantities of concrete deterioration.

  11. Deterioration of concrete structures in coastal environment due to carbonation.

    Science.gov (United States)

    Balaji, K V G D; Gopalaraju, S S S V; Trilochan, Jena

    2010-07-01

    Failure of existing concrete structures takes place due to lack of durability, and not due to less structural strength. One of the important aspects of durability is carbonation depth. The rate of carbonation in concrete is influenced by both its physical properties and exposure conditions. Rebar corrodes when carbonation reaches to a depth of concrete cover provided. In the present work, various concrete structures with different life periods and exposed to different weather conditions have been considered to study the carbonation effect. It is observed that the effect of carbonation is more in the structures located near to the sea coast and on windward face of the structure.

  12. Evaluation of Seismic Behaviors of Partially Deteriorated Reinforced Concrete Circular Columns Retrofitted with CFRP

    Directory of Open Access Journals (Sweden)

    Dongxu Hou

    2014-01-01

    Full Text Available Deficiency of the concrete strength in some regions of reinforced concrete (RC columns in practice may weaken the seismic behaviors of columns. Its effects on RC columns should be well understood. This paper aims to investigate the influences of deteriorated segment on the seismic behaviors of partially deteriorated RC columns and attempts to recover the seismic behaviors of partially deteriorated columns with Carbon Fiber Reinforced Polymer (CFRP composites. A finite element analysis was carried out to simulate the seismic behaviors of CFRP-confined partially deteriorated RC columns. The numerical results were verified by the laboratory tests of six specimens. Based on the finite element results, the failure location of partially deteriorated columns in an earthquake was predicted, and the effectiveness of CFRP retrofitted on partially deteriorated columns was evaluated.

  13. Rapid clinical deterioration in an individual with Down syndrome.

    Science.gov (United States)

    Jacobs, Julia; Schwartz, Alison; McDougle, Christopher J; Skotko, Brian G

    2016-07-01

    A small percentage of adolescents and young adults with Down syndrome experience a rapid and unexplained deterioration in cognitive, adaptive, and behavioral functioning. Currently, there is no standardized work-up available to evaluate these patients or treat them. Their decline typically involves intellectual deterioration, a loss of skills of daily living, and prominent behavioral changes. Certain cases follow significant life events such as completion of secondary school with friends who proceed on to college or employment beyond the individual with DS. Others develop this condition seemingly unprovoked. Increased attention in the medical community to clinical deterioration in adolescents and young adults with Down syndrome could provide a framework for improved diagnosis, evaluation, and treatment. This report presents a young adult male with Down syndrome who experienced severe and unexplained clinical deterioration, highlighting specific challenges in the systematic evaluation and treatment of these patients. © 2016 Wiley Periodicals, Inc. © 2016 Wiley Periodicals, Inc.

  14. Deterioration Mechanisms and Durability of Sprayed Concrete for Rock Support in Tunnels

    NARCIS (Netherlands)

    Hagelia, P.

    2011-01-01

    Steel fibre reinforced sprayed concretes used for rock support in tunnels are subjected to variable and complex exposure conditions. Structurally weakened concretes (5 to 35 years old) were investigated with respect to deterioration mechanisms, sources of aggressive agents and related engineering

  15. Multi-Physics and Multi-Scale Deterioration Modelling of Reinforced Concrete

    DEFF Research Database (Denmark)

    Michel, Alexander; Stang, Henrik; Lepech, M.

    2016-01-01

    , methods and tools for modelling decades-long deterioration and maintenance are much less developed. In this paper, a multi-physics and multi-scale modelling approach for structural deterioration of reinforced concrete components due to reinforcement corrosion is presented. The multi-disciplinary modelling...... approach includes physical, chemical, electrochemical, and fracture mechanical processes at the material and meso-scale, which are further coupled with mechanical deterioration processes at the structural scale....

  16. Research on Deterioration Mechanism of Concrete Materials in an Actual Structure

    Directory of Open Access Journals (Sweden)

    Shiping Zhang

    2014-01-01

    Full Text Available The cause for deterioration of the concrete structure located in severe environment has been explored both in field and in laboratory. Serious cracking and spalling appeared upon surface of the concrete structure soon after the structure was put into service. Both alkali-aggregate reaction and freeze-thaw cycles may result in similar macro visible cracking and spalling. The possibility of alkali-aggregate reaction was excluded by both field survey and lab examination such as chemical analysis, petrographic analysis, and determination of alkali reactivity of aggregates. According to results of freeze-thaw cycles, impermeability testing, and microstructure analysis, it is deduced that the severe environmental conditions plus the relatively inferior frost resistance cause the deterioration of concrete. Usage of air entraining admixture can improve frost resistance and impermeability. Furthermore, new approaches to mitigate the deterioration of concrete used in severe environmental condition are discussed.

  17. Deteriorated Concrete from Liner of WIPP Waste Shaft

    Science.gov (United States)

    1992-06-01

    for US Department of Energy. Bensted, J. 1989. "Novel Cements - Sorel and Related Chemical Cements," il Cemento , Vol 86, No. 4, pp 217-228. Ben-Yair, M...Waste Isolation Pilot Plant. Massazza, F. 1985. "Concrete Resistance to Sea Water and Marine Environment," il Cemento , Vol 82, No. 1, pp 3-26. Mather

  18. Estimation of Concrete Carbonation Depth Considering Multiple Influencing Factors on the Deterioration of Durability for Reinforced Concrete Structures

    Directory of Open Access Journals (Sweden)

    Hae-Chang Cho

    2016-01-01

    Full Text Available While the durability of concrete structures is greatly influenced by many factors, previous studies typically considered only a single durability deterioration factor. In addition, these studies mostly conducted their experiments inside the laboratory, and it is extremely hard to find any case in which data were obtained from field inspection. Accordingly, this study proposed an Adaptive Neurofuzzy Inference System (ANFIS algorithm that can estimate the carbonation depth of a reinforced concrete member, in which combined deterioration has been reflected based on the data obtained from field inspections of 9 buildings. The proposed ANFIS algorithm closely estimated the carbonation depths, and it is considered that, with further inspection data, a higher accuracy would be achieved. Thus, it is expected to be used very effectively for durability estimation of a building of which the inspection is performed periodically.

  19. Monitoring of Reinforced Concrete Corrosion and Deterioration by Periodic Multi-Sensor Non-Destructive Evaluation

    Science.gov (United States)

    Arndt, R. W.; Cui, J.; Huston, D. R.

    2011-06-01

    The paper showcases a collaborative benchmark project evaluating NDE methods for deterioration monitoring of laboratory bridge decks. The focus of this effort is to design and build concrete test specimens, artificially induce and monitor corrosion, periodically perform multi-sensor NDE inspections, followed by 3D imaging and destructive validations. NDE methods used include ultrasonic echo array, ground penetrating radar (GPR), active infrared thermography with induction heating, and time-resolved thermography with induction heating.

  20. Experimental Study on Detection of Deterioration in Concrete Using Infrared Thermography Technique

    Directory of Open Access Journals (Sweden)

    Jungwon Huh

    2016-01-01

    Full Text Available Concrete is certainly prone to internal deteriorations or defects during the construction and operating periods. Compared with other nondestructive techniques, infrared thermography can easily detect the subsurface delamination in a very short period of time, but accurately identifying its size and depth in concrete is a very challenging task. In this study, experimental testing was carried out on a concrete specimen having internal delaminations of various sizes and at varying depths. Delaminations at 1 and 2 cm deep showed a good temperature contrast after only 5-minute heating, but delaminations at 3 cm practically identified the value of the temperature contrast from heating of 15 minutes. In addition, the size of the delamination at 3 cm deep could be estimated with a difference of 10% to 28% for 20 minutes of heating. The depth of the delamination was linearly correlated with the increase in its size.

  1. Assessing and updating the reliability of concrete bridges subjected to spatial deterioration - principles and software implementation

    DEFF Research Database (Denmark)

    Schneider, Ronald; Fischer, Johannes; Bügler, Maximilian

    2015-01-01

    presents an approach for assessing and updating the reliability of prestressed concrete bridges subjected to chloride-induced reinforcement corrosion. The system deterioration state is determined based on a Dynamic Bayesian Network (DBN) model that considers the spatial variability of the corrosion process......Inspection and maintenance of concrete bridges is a major cost factor in transportation infrastructure, and there is significant potential for using information gained during inspection to update predictive models of the performance and reliability of such structures. In this context, this paper...... is a step towards developing a software tool that can be used by engineering practitioners to perform reliability assessments of ageing concrete bridges and update their reliability with inspection and monitoring data....

  2. Minimum expected cost-oriented optimal maintenance planning for deteriorating structures: application to concrete bridge decks

    Energy Technology Data Exchange (ETDEWEB)

    Estes, Allen C.; Frangopol, Dan M

    2001-09-01

    Civil engineering structures are designed to serve the public and often must perform safely for decades. No matter how well they are designed, all civil engineering structures will deteriorate over time and lifetime maintenance expenses represent a substantial portion of the total lifetime cost of most structures. It is difficult to make a reliable prediction of this cost when the future is unknown and structural deterioration and behavior are assumed from a mathematical model or previous experience. An optimal maintenance program is the key to making appropriate decisions at the right time to minimize cost and maintain an appropriate level of safety. This study proposes a probabilistic framework for optimizing the timing and the type of maintenance over the expected useful life of a deteriorating structure. A decision tree analysis is used to develop an optimum lifetime maintenance plan which is updated as inspections occur and more data is available. An estimate which predicts cost and behavior over many years must be refined and reoptimized as new information becomes available. This methodology is illustrated using a half-cell potential test to evaluate a deteriorating concrete bridge deck. The study includes the expected life of the structure, the expected damage level of the structure, costs of inspection and specific repairs, interest rates, the capability of the test equipment to detect a flaw, and the management approach of the owner towards making repairs.

  3. Monitoring Concrete Deterioration Due to Reinforcement Corrosion by Integrating Acoustic Emission and FBG Strain Measurements.

    Science.gov (United States)

    Li, Weijie; Xu, Changhang; Ho, Siu Chun Michael; Wang, Bo; Song, Gangbing

    2017-03-22

    Corrosion of concrete reinforcement members has been recognized as a predominant structural deterioration mechanism for steel reinforced concrete structures. Many corrosion detection techniques have been developed for reinforced concrete structures, but a dependable one is more than desired. Acoustic emission technique and fiber optic sensing have emerged as new tools in the field of structural health monitoring. In this paper, we present the results of an experimental investigation on corrosion monitoring of a steel reinforced mortar block through combined acoustic emission and fiber Bragg grating strain measurement. Constant current was applied to the mortar block in order to induce accelerated corrosion. The monitoring process has two aspects: corrosion initiation and crack propagation. Propagation of cracks can be captured through corresponding acoustic emission whereas the mortar expansion due to the generation of corrosion products will be monitored by fiber Bragg grating strain sensors. The results demonstrate that the acoustic emission sources comes from three different types, namely, evolution of hydrogen bubbles, generation of corrosion products and crack propagation. Their corresponding properties are also discussed. The results also show a good correlation between acoustic emission activity and expansive strain measured on the specimen surface.

  4. a rare but treatable cause of rapid neurological deterioration in ...

    African Journals Online (AJOL)

    Pneumocephalus is a frequent complication following head injury and craniotomies. It can become an acute neurosurgical emergency when associated with raised intracranial pressure and neurological deterioration. Early diagnosis and timely appropriate intervention will reduce morbidity and unnecessary mortality from a ...

  5. A real case of steam-cured concrete track slab premature deterioration due to ASR and DEF

    Directory of Open Access Journals (Sweden)

    Kunlin Ma

    2017-06-01

    Full Text Available Deterioration mechanisms of some premature damaged steam-cured concrete track slabs (CTS in Chinese railway less than 4 years were investigated. Field investigation, raw materials test and suspicious products analysis were carried out. Results show that steam-cured heat damage (SCHD of concrete takes place in steam-cured process. Expansion products are ettringite in hydrated products and alkali-silica gels between the interface of hydrated products and coarse aggregate. SCHD makes CTS surface layer loose, porous and more micro-cracks. Long-term fatigue load from high-speed train acting on CTS enlarges concrete microcracks, leading to water penetrating into concrete easily in moist and rainy environment. In the process of water ingression, alkali-silica reaction (ASR and delayed ettringite formation (DEF take place, hence resulting in CTS cracking and premature deterioration.

  6. A real case of steam-cured concrete track slab premature deterioration due to ASR and DEF

    OpenAIRE

    Kunlin Ma; Guangcheng Long; Youjun Xie

    2017-01-01

    Deterioration mechanisms of some premature damaged steam-cured concrete track slabs (CTS) in Chinese railway less than 4 years were investigated. Field investigation, raw materials test and suspicious products analysis were carried out. Results show that steam-cured heat damage (SCHD) of concrete takes place in steam-cured process. Expansion products are ettringite in hydrated products and alkali-silica gels between the interface of hydrated products and coarse aggregate. SCHD makes CTS surfa...

  7. Are early warning scores the only way to rapidly detect and manage deterioration?

    Science.gov (United States)

    Odell, Mandy

    A systematic literature review recently highlighted the complexity of nursing practice in terms of detecting and managing deteriorating ward patients (Odell et al, 2009). The findings suggest that rapid response systems, including early warning scores, may not be the only solution to the problems of detecting and managing signs of deterioration. This article summarises the findings of this review.

  8. Deterioration and Microstructural Evolution of the Fly Ash Geopolymer Concrete against MgSO4 Solution

    Directory of Open Access Journals (Sweden)

    Tao Long

    2017-01-01

    Full Text Available Fly ash geopolymer concrete (FAGC and ordinary Portland cement concrete (OPCC specimens were immersed in 5% MgSO4 solution undergoing 32 wetting-drying and heating-cooling cycles. Their compressive behavior was investigated after every 8 cycles. Several microstructure analysis techniques were applied on the samples to identify the materials formed due to magnesium sulfate attack, including XRD, FTIR, SEM, and EDS. Experimental results elucidated that the compressive strength loss ratio in the heating group of FAGC was 12.7%, while that of OPCC was 17.8%, which means that FAGC had better magnesium sulfate resistance than OPCC. The compressive strength loss of OPCC was due to the formation of gypsum under the magnesium sulfate attack exposed to wetting-drying and heating-cooling cycles. The deterioration mechanisms of FAGC against MgSO4 solution were discovered to be that sodium aluminum silicate hydrate (N-A-S-H gels reacted with MgSO4, leading to the creation of low strength magnesium aluminum silicate hydrate (M-A-S-H gels.

  9. Multi-physical and multi-scale deterioration modelling of reinforced concrete part II: Coupling corrosion and damage at the structural scale

    DEFF Research Database (Denmark)

    Lepech, Michael; Rao, Anirudh; Kiremidjian, Anne

    2015-01-01

    Deterioration of reinforced concrete infrastructure such as bridges, tunnels, and buildings represents one of the major challenges currently facing developed countries. This deterioration leads to economic costs for maintenance and replacement, environmental impacts such increased global warming...... in this paper, when the time-dependent assessment of structures is integrated with life cycle assessment models that quantify the economic, environmental, and social impacts of infrastructure, the result is a comprehensive assessment methodology for the sustainability of deteriorating reinforced concrete...

  10. Assessing the service life of corrosion-deteriorated reinforced concrete member highway bridges in West Virginia.

    Science.gov (United States)

    2014-09-01

    Corrosion of steel-reinforced concrete bridges is a serious problem facing the WVDOT. This : paper provides an overview of techniques for evaluating the condition of reinforced concrete : bridge elements; methods for modeling the remaining service li...

  11. Coatings, sealants and filters to address bridge concrete deterioration and aesthetics : Phase I.

    Science.gov (United States)

    2006-06-01

    The study addresses experimental evaluation and testing of concrete coatings for maintenance purposes on structural (steel reinforced) concrete. The test methods employed are intended to identify coatings and sealers for eventual incorporation into a...

  12. An overview of joint deterioration in concrete pavement : mechanisms, solution properties, and sealers.

    Science.gov (United States)

    2013-01-01

    Concrete pavements represent a large portion of the transportation : infrastructure. While the vast majority of concrete pavements : provide excellent long-term performance, a portion of these : pavements have recently shown premature joint deteriora...

  13. Use of Just in Time Maintenance of Reinforced Concrete Bridge Structures based on Real Historical Data Deterioration Models

    Directory of Open Access Journals (Sweden)

    Abu-Tair A.

    2016-01-01

    Full Text Available Concrete is the backbone of any developed economy. Concrete can suffer from a large number of deleterious effects including physical, chemical and biological causes. Large owning bridge structures organizations are facing very serious questions when asking for maintenance budgets. The questions range from needing to justify the need for the work, its urgency, to also have to predict or show the consequences of delayed rehabilitation of a particular structure. There is therefore a need for a probabilistic model that can estimate the range of service lives of bridge populations and also the likelihood of level of deteriorations it can reached for every incremental time interval. A model was developed for such estimation based on statistical data from actual inspection records of a large reinforced concrete bridge portfolio. The method used both deterministic and stochastic methods to predict the service life of a bridge, using these service lives in combination with the just in time (JIT principle of management would enable maintenance managers to justify the need for action and the budgets needed, to intervene at the optimum time in the life of the structure and that of the deterioration. The paper will report on the model which is based on a large database of deterioration records of concrete bridges covering a period of over 60 years and include data from over 400 bridge structures. The paper will also illustrate how the service life model was developed and how these service lives combined with the JIT can be used to effectively allocate resources and use them to keep a major infrastructure asset moving with little disruption to the transport system and its users.

  14. Integrated modelling of corrosion-induced deterioration in rein-forced concrete structures

    DEFF Research Database (Denmark)

    Michel, Alexander; Geiker, M.R.; Stang, Henrik

    2013-01-01

    An integrated finite element based modelling approach is presented, which allows for fully coupled simulation of reinforcement corrosion and corrosion-induced concrete damage. While a finite element method (FEM) based corrosion model was used to describe electrochemical processes...... at the reinforcement surface, a FEM based me-chanical model was used to simulate corrosion-induced concrete damage. Both FEM models were fully coupled, i.e. information, such as corrosion current density, dam-age state of concrete cover, etc., were constantly exchanged between the models. To demonstrate the potential...

  15. Assessment Of The Deterioration Degree Of Airfield Pavement Functional Constituents Made Of Cement Concrete

    Directory of Open Access Journals (Sweden)

    Barszcz Piotr

    2014-12-01

    Full Text Available The characteristic feature of the approach to the analysis of the airfield pavement deterioration degree as outlined in this paper is the fact that not only existing deteriorations are taken into account of but also already completed historical repairs. This approach enables determination of resources needed to conduct repairs and setting up reasonable schedules of future overhauls. The proposed index of the pavement deterioration degree, calculated on the basis of measured deficiencies and past repairs, makes it possible to assess the technical condition of the airfield pavement in a comprehensive manner. The key information indispensable to evaluate the degree of deterioration of the airfield pavement surface includes data which can be acquired from already completed stocktaking inventories. The stocktaking process is based on the catalogue of deficiencies typical for airfield pavements and the rules for stocktaking measurements.

  16. An Investigation of Concrete Deterioration at South Florida Water Management District Structure S65E

    Science.gov (United States)

    2014-02-01

    19 Figure 14. Photomicrograph of exposed surface of concrete showing biofilm growth and lack of damage to siliceous fine aggregates that...occur by inorganic dissolution reactions, will proceed in the absence of biofilms , and occur at neutral pH. Inorganic dissolution from contact with...reached depths approaching 25 mm, which was approximately half of the cover depth observed over embedded reinforcing steel . Concrete from the lock

  17. Cool barnacles: Do common biogenic structures enhance or retard rates of deterioration of intertidal rocks and concrete?

    Science.gov (United States)

    Coombes, Martin A; Viles, Heather A; Naylor, Larissa A; La Marca, Emanuela Claudia

    2017-02-15

    Sedentary and mobile organisms grow profusely on hard substrates within the coastal zone and contribute to the deterioration of coastal engineering structures and the geomorphic evolution of rocky shores by both enhancing and retarding weathering and erosion. There is a lack of quantitative evidence for the direction and magnitude of these effects. This study assesses the influence of globally-abundant intertidal organisms, barnacles, by measuring the response of limestone, granite and marine-grade concrete colonised with varying percentage covers of Chthamalus spp. under simulated, temperate intertidal conditions. Temperature regimes at 5 and 10mm below the surface of each material demonstrated a consistent and statistically significant negative relationship between barnacle abundance and indicators of thermal breakdown. With a 95% cover of barnacles, subsurface peak temperatures were reduced by 1.59°C for limestone, 5.54°C for concrete and 5.97°C for granite in comparison to no barnacle cover. The amplitudes of short-term (15-30min) thermal fluctuations conducive to breakdown via 'fatigue' effects were also buffered by 0.70°C in limestone, 1.50°C in concrete and 1.63°C in granite. Furthermore, concentrations of potentially damaging salt ions were consistently lower under barnacles in limestone and concrete. These results indicate that barnacles do not enhance, but likely reduce rates of mechanical breakdown on rock and concrete by buffering near-surface thermal cycling and reducing salt ion ingress. In these ways, we highlight the potential role of barnacles as agents of bioprotection. These findings support growing international efforts to enhance the ecological value of hard coastal structures by facilitating their colonisation (where appropriate) through design interventions. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Evaluation of E. coli biofilm as a protective barrier against microbiologically influenced deterioration of concrete (MICD) under mesophilic temperatures.

    Science.gov (United States)

    Soleimani, S; Ormeci, B; Isgor, O B

    2013-01-01

    In this study, Escherichia coli DH5α biofilm was evaluated for its potential to control and minimize microbiologically influenced concrete deterioration (MICD) under mesophilic temperatures (37 °C). Escherichia coli DH5α biofilm was first grown on Portland cement mortar disks for 8 days. Mortar disks were then exposed to two different types of sulfur oxidizing bacteria (SOB) (Thiobacillus neapolitanus and Thiobacillus thiooxidans), which use sulfur compounds as substrate and oxidize them to sulfate and sulfuric acid. The effectiveness of the biofilm against MICD was evaluated by measuring pH, sulfate, calcium concentrations in the reactors and surface analysis of the mortar samples using X-ray diffraction and visual inspection. Overall, the results indicate that the E. coli DH5α biofilm showed good protection against MICD induced by SOB at 37 °C.

  19. Rapid Deterioration of Basic Life Support Skills in Dentists With Basic Life Support Healthcare Provider.

    Science.gov (United States)

    Nogami, Kentaro; Taniguchi, Shogo; Ichiyama, Tomoko

    2016-01-01

    The aim of this study was to investigate the correlation between basic life support skills in dentists who had completed the American Heart Association's Basic Life Support (BLS) Healthcare Provider qualification and time since course completion. Thirty-six dentists who had completed the 2005 BLS Healthcare Provider course participated in the study. We asked participants to perform 2 cycles of cardiopulmonary resuscitation on a mannequin and evaluated basic life support skills. Dentists who had previously completed the BLS Healthcare Provider course displayed both prolonged reaction times, and the quality of their basic life support skills deteriorated rapidly. There were no correlations between basic life support skills and time since course completion. Our results suggest that basic life support skills deteriorate rapidly for dentists who have completed the BLS Healthcare Provider. Newer guidelines stressing chest compressions over ventilation may help improve performance over time, allowing better cardiopulmonary resuscitation in dental office emergencies. Moreover, it may be effective to provide a more specialized version of the life support course to train the dentists, stressing issues that may be more likely to occur in the dental office.

  20. Early warning systems and rapid response to the deteriorating patient in hospital: A realist evaluation.

    Science.gov (United States)

    McGaughey, Jennifer; O'Halloran, Peter; Porter, Sam; Trinder, John; Blackwood, Bronagh

    2017-12-01

    To test the Rapid Response Systems programme theory against actual practice components of the Rapid Response Systems implemented to identify those contexts and mechanisms which have an impact on the successful achievement of desired outcomes in practice. Rapid Response Systems allow deteriorating patients to be recognized using Early Warning Systems, referred early via escalation protocols and managed at the bedside by competent staff. Realist evaluation. The research design was an embedded multiple case study approach of four wards in two hospitals in Northern Ireland which followed the principles of Realist Evaluation. We used various mixed methods including individual and focus group interviews, observation of nursing practice between June-November 2010 and document analysis of Early Warning Systems audit data between May-October 2010 and hospital acute care training records over 4.5 years from 2003-2008. Data were analysed using NiVivo8 and SPPS. A cross-case analysis highlighted similar patterns of factors which enabled or constrained successful recognition, referral and response to deteriorating patients in practice. Key enabling factors were the use of clinical judgement by experienced nurses and the empowerment of nurses as a result of organizational change associated with implementation of Early Warning System protocols. Key constraining factors were low staffing and inappropriate skill mix levels, rigid implementation of protocols and culturally embedded suboptimal communication processes. Successful implementation of Rapid Response Systems was dependent on adopting organizational and cultural changes that facilitated staff empowerment, flexible implementation of protocols and ongoing experiential learning. © 2017 John Wiley & Sons Ltd.

  1. Cost-effective and rapid concrete repair techniques.

    Science.gov (United States)

    2016-02-08

    Concrete is a principal component of many transportation structures. While highly durable, a : variety of processes degrade and damage concrete. Replacement is expensive. Many cases : warrant repair instead of replacement. Since many damage processes...

  2. Performance of Engineered Cementitious Composites for Concrete Repairs

    NARCIS (Netherlands)

    Zhou, J.

    2011-01-01

    Background and goals of this thesis The concrete repair, rehabilitation and retrofitting industry grows rapidly, driven by deterioration of, damage to and defects in concrete structures. However, it is well known that to achieve durable concrete repairs is very difficult. The failure of concrete

  3. Grout Impregnation of Pre-Placed Recycled Concrete Pavement (RCP) for Rapid Repair of Deteriorated Portland Cement Concrete Airfield Pavement

    Science.gov (United States)

    2007-04-01

    and water, with or without filler (UFGS, 2004). UFC 3-270-07 (Unified Facilitates Criteria, 2002) describes a stone and grout method as a current...Pavemend™ Repair 2 Type III Grout Not to Scale 12.2 m (40 ft) -63- 510-mm- (20-in.-) thick crushed limestone base course and the 90-day...crushed limestone ). 240 mm (9.5 in.) PCC Repair 5 Type III Grout Not to Scale Repair 6 Type III Grout Repair 8 Pavemend™ Repair 7 Pavemend

  4. Development and validation of deterioration models for concrete bridge decks - phase 1 : artificial intelligence models and bridge management system.

    Science.gov (United States)

    2013-06-01

    This research documents the development and evaluation of artificial neural network (ANN) models to predict the condition ratings of concrete highway bridge decks in Michigan. Historical condition assessments chronicled in the national bridge invento...

  5. Field Testing of Rapid Electrokinetic Nanoparticle Treatment for Corrosion Control of Steel in Concrete

    Science.gov (United States)

    Cardenas, Henry E.; Alexander, Joshua B.; Kupwade-Patil,Kunal; Calle, Luz Marina

    2009-01-01

    This work field tested the use of electrokinetics for delivery of concrete sealing nanoparticles concurrent with the extraction of chlorides. Several cylinders of concrete were batched and placed in immersion at the Kennedy Space Center Beach Corrosion Test Site. The specimens were batched with steel reinforcement and a 4.5 wt.% (weight percent) content of sodium chloride. Upon arrival at Kennedy Space Center, the specimens were placed in the saltwater immersion pool at the Beach Corrosion Test Site. Following 30 days of saltwater exposure, the specimens were subjected to rapid chloride extraction concurrent with electrokinetic nanoparticle treatment. The treatments were operated at up to eight times the typical current density in order to complete the treatment in 7 days. The findings indicated that the short-term corrosion resistance of the concrete specimens was significantly enhanced as was the strength of the concrete.

  6. Rapid deterioration of preexisting renal insufficiency after autologous mesenchymal stem cell therapy

    Directory of Open Access Journals (Sweden)

    Jun-Seop Kim

    2017-06-01

    Full Text Available Administration of autologous mesenchymal stem cells (MSCs has been shown to improve renal function and histological findings in acute kidney injury (AKI models. However, its effects in chronic kidney disease (CKD are unclear, particularly in the clinical setting. Here, we report our experience with a CKD patient who was treated by intravenous infusion of autologous MSCs derived from adipose tissue in an unknown clinic outside of Korea. The renal function of the patient had been stable for several years before MSC administration. One week after the autologous MSC infusion, the preexisting renal insufficiency was rapidly aggravated without any other evidence of AKI. Hemodialysis was started 3 months after MSC administration. Renal biopsy findings at dialysis showed severe interstitial fibrosis and inflammatory cell infiltration, with a few cells expressing CD34 and CD117, 2 surface markers of stem cells. This case highlights the potential nephrotoxicity of autologous MSC therapy in CKD patients.

  7. ATP bioluminescence method: tool for rapid screening of organic and microbial contaminants on deteriorated mural paintings.

    Science.gov (United States)

    Unković, Nikola; Ljaljević Grbić, Milica; Stupar, Miloš; Vukojević, Jelena; Subakov-Simić, Gordana; Jelikić, Aleksa; Stanojević, Dragan

    2015-11-24

    The extent of the microbial contamination of the seventeenth-century wall paintings in the nave of the old Church of the Holy Ascension (Veliki Krčimir, Serbia) was evaluated via newly implemented ATP bioluminescence method, and traditional cultivation-based method, utilising commercially available dip slides. To assess the validity of ATP, as a biomarker for rapid detection of mural surface contamination, obtained zones of cleanliness values, in range from 1.0 to 5.3, were compared to documented total microbial counts, ranging between seven and 247 CFU/cm 2 . Small coefficients of determination, 0.0106-0.0385, suggest poor correlation between microbial counts and surface ATP levels; however, zones of cleanliness values are of great help in determining the high points of contamination, aka 'hotspots', which should be given special attention during sampling and investigation using other methods. In addition, various aspects of the possible implementation of the ATP bioluminescence method in an integrated system of wall painting conservation are discussed.

  8. Engineering aspects and time effects of rapid deterioration of sandstone in the tropical environment of Sabah, Malaysia

    NARCIS (Netherlands)

    Tating, F.F.; Hack, H.R.G.K.; Jetten, V.G.

    2013-01-01

    Cut slopes in rock masses start to deteriorate directly after excavation due to stress relief and weathering. The deterioration is a time dependent process that depends on the local climate and the rock mass including its history, and the environment. The amount of deterioration per time unit (‘the

  9. FINITE ELEMENT ANALYSIS OF THE BEHAVIOUR OF REINFORCED CONCRETE COLUMNS CONFINED BY OVERLAPPING HOOPS SUBJECTED TO RAPID CONCENTRIC LOADING

    Directory of Open Access Journals (Sweden)

    Xiang Zeng

    2017-12-01

    Full Text Available The strain rate sensitivity of concrete material was discovered approximately one hundred years ago, and it has a marked effect on the behaviour of concrete members subjected to dynamic loadings such as strong earthquake and impact loading. Because of the great importance of the confined reinforced concrete (RC columns in RC structures, the dynamic behaviour of the columns induced by the strain rate effect has been studied, but only few experiments and analyses have been conducted. To investigate the behaviour of overlapping hoop-confined square reinforced normal-strength concrete columns, considering the strain rate effect at a strain rate of 10-5/sec to 10-1/sec induced by earthquake excitation, an explicit dynamic finite element analysis (FEA model was developed in ABAQUS to predict the behaviour of confined RC columns subjected to the rapid concentric loading. A locally modified stress-strain relation of confined concrete with the strain rate sensitivity of the concrete material and the confining effect of overlapping hoops were proposed to complete the simulation of the dynamic behaviour of concrete with the concrete plastic-constitutive model in ABAQUS. The finite element predictions are consistent with the existing test results. Based on the FEA model, a parametric investigation was conducted to capture more information about the behaviour of confined RC columns under varying loading rates.

  10. Perceptions of interactions between staff members calling, and those responding to, rapid response team activations for patient deterioration.

    Science.gov (United States)

    Chalwin, Richard; Flabouris, Arthas; Kapitola, Karoline; Dewick, Leonie

    2016-09-01

    Objectives The aim of the present study was to investigate experiences of staff interactions and non-technical skills (NTS) at rapid response team (RRT) calls, and their association with repeat RRT calls. Methods Mixed-methods surveys were conducted of RRT members and staff who activate the RRT (RRT users) for their perceptions and attitudes regarding the use of NTS during RRT calls. Responses within the survey were recorded as Likert items, ranked data and free comments. The latter were coded into nodes relating to one of four NTS domains: leadership, communication, cooperation and planning. Results Two hundred and ninety-seven (32%) RRT users and 79 (73.8%) RRT members provided responses. Of the RRT user respondents, 76.5% had activated the RRT at some point. Deficits in NTS at RRT calls were revealed, with 36.9% of users not feeling involved during RRT calls and 24.7% of members perceiving that users were disinterested. Unresolved user clinical concerns, or persistence of RRT calling criteria, were reasons cited by 37.6% and 23%, respectively, of RRT users for reactivating an RRT to the same patient. Despite recollections of conflict at previous RRT calls, 92% of users would still reactivate the RRT. The most common theme in the free comments related to deficiencies in cooperation (52.9%), communication (28.6%) and leadership (14.3%). Conclusions This survey of RRT users and members revealed problems with RRT users' and members' interactions at the time of an RRT call. Both users and members considered NTS to be important, but lacking. These findings support NTS training for RRT members and users. What is known about the topic? Previous surveying has related experiences of criticism and conflict between clinical staff at RRT activations. This leads to reluctance to call the RRT when indicated, with risks to patient safety, especially if subsequent RRT activation is necessary. Training in NTS has improved clinician interactions in simulated emergencies, but the

  11. Mechanical and Failure Criteria of Air-Entrained Concrete under Triaxial Compression Load after Rapid Freeze-Thaw Cycles

    Directory of Open Access Journals (Sweden)

    Feng-kun Cui

    2017-01-01

    Full Text Available The experiment study on the air-entrained concrete of 100 mm cubes under triaxial compression with different intermediate stress ratio α2=σ2D : σ3D was carried out using a hydraulic-servo testing system. The influence of rapid freeze-thaw cycles and intermediate stress ratio on the triaxial compressive strength σ3D was analyzed according to the experimental results, respectively. The experimental results of air-entrained concrete obtained from the study in this paper and the triaxial compression experimental results of plain concrete got through the same triaxial-testing-system were compared and analyzed. The conclusion was that the triaxial compressive strength is greater than the biaxial and uniaxial compressive strength after the same rapid freeze-thaw cycles, and the increased percentage of triaxial compressive strength over biaxial compressive strength or uniaxial compressive strength is dependent on the middle stress. The experimental data is useful for precise analysis of concrete member or concrete structure under the action complex stress state.

  12. Rapid analysis of 14C and 3H in graphite and concrete for decommissioning of nuclear reactor

    DEFF Research Database (Denmark)

    Hou, Xiaolin

    2005-01-01

    A rapid oxidizing combustion method using a commercial Sample Oxidizer has been investigated to determine separately the C-14 and H-3 activities in graphite and concrete. By this method the sample preparation time can be reduced to 2-3min. The detection limits for H-3 and C-14 are 0.96 and 0.58Bq...... the Danish Reactors DR-2 and DR-3, in addition to two concrete cores drilled in the Danish reactor DR-2; these were analysed for H-3 and C-14 using the method that has been developed. (c) 2005 Elsevier Ltd. All rights reserved....

  13. High-early-strength high-performance concrete for rapid pavement repair.

    Science.gov (United States)

    2016-01-01

    In the construction industry, High Early-Age Strength (HES) concrete was : traditionally regarded as a concrete that achieves a loading strength in matter of days : rather than weeks. However, in the last 10-15 years, this time has been reduced down ...

  14. Performance Analysis of a Recycled Concrete Interfacial Transition Zone in a Rapid Carbonization Environment

    Directory of Open Access Journals (Sweden)

    Gongbing Yue

    2018-01-01

    Full Text Available Based on the characteristics of recycled concrete interface structures, a multi-interface reconstruction model was established. To study the microstructure evolution of the interfacial transition zone (ITZ during the carbonization process of recycled concrete, the microstructure characteristics of the ITZ of C30, C40, and C50 grade recycled concrete and the mortar matrix before and after carbonization were studied through the microhardness tester and SEM. The results show that the microhardness values of the ITZ and the mortar matrix are obviously increased and that the width of the ITZ decreases, while the ITZ performance of the C50 grade recycled concrete is not significantly changed. The ITZ exhibits a large amount of granular CaCO3 after carbonization, the pores are refined, and microcracks are generated. Overall, there are significant differences in the microstructures between the ITZ and the mortar matrix before and after carbonization.

  15. Individualized dosimetry-based activity reduction of {sup 90}Y-DOTATOC prevents severe and rapid kidney function deterioration from peptide receptor radionuclide therapy

    Energy Technology Data Exchange (ETDEWEB)

    Binnebeek, Sofie van; Baete, Kristof; Vanbilloen, Bert; Terwinghe, Christelle; Mortelmans, Luc [University Hospitals Leuven, Nuclear Medicine, Leuven (Belgium); KU Leuven, Department of Imaging and Pathology, Leuven (Belgium); Koole, Michel [University Medical Centre Groningen, Department of Nuclear Medicine, Groningen (Netherlands); Mottaghy, Felix M. [University Hospital Aachen, Department of Nuclear Medicine, Aachen (Germany); Maastricht University Medical Center, Department of Nuclear Medicine, Maastricht (Netherlands); Clement, Paul M. [University Hospitals Leuven, Medical Oncology, Leuven (Belgium); KU Leuven, Laboratory of Experimental Oncology, Leuven (Belgium); Haustermans, Karin [University Hospitals Leuven, Radiation Oncology, Leuven (Belgium); KU Leuven, Department of Oncology, Leuven (Belgium); Cutsem, Eric van; Verslype, Chris [KU Leuven, Department of Oncology, Leuven (Belgium); University Hospitals Leuven, Division of Digestive Oncology, Leuven (Belgium); Verbruggen, Alfons [KU Leuven, Laboratory for Radiopharmacy, Leuven (Belgium); Bogaerts, Kris [KU Leuven, Division of Public Health and Primary Care (I-Biostat), Leuven (Belgium); Deroose, Christophe M. [University Hospitals Leuven, Nuclear Medicine, Leuven (Belgium); KU Leuven, Department of Imaging and Pathology, Leuven (Belgium); UZ Leuven, Nuclear Medicine, Leuven (Belgium)

    2014-06-15

    Assessment of kidney function evolution after {sup 90}Y-DOTATOC peptide receptor radionuclide therapy (PRRT) with capped activity administration based on a 37-Gy threshold of biological effective dose (BED) to the kidney. In a prospective phase II study, patients with metastasized neuroendocrine tumours were evaluated for therapy using 185 MBq {sup 111}In-pentetreotide with amino acid coinfusion. Planar whole-body images were acquired at four time-points after injection and kidney volumes were measured using CT/MRI. BED to the kidneys was estimated using an extended BED formula and biexponential renal clearance. Based on published BED dose-toxicity relationships, we allowed a maximal kidney BED of 37 Gy; if the calculated BED exceeded 37 Gy, treatment activity was reduced accordingly. Kidney function was assessed at baseline and at 18 months, predominantly using {sup 51}Cr-EDTA. The rate of renal function decline was expressed as annual glomerular filtration rate loss (aGFRL). Only 22 of 50 patients reached the 18-months time-point, with most missing patients having died due to disease progression. In the 22 patients who reached 18 months, no rapid kidney function deterioration was observed over the 18 months, aGFRL >33 % was not seen, and only three patients showed an increase of one toxicity grade and one patient an increase of two grades. No significant correlations between kidney volume (p = 0.35), baseline GFR (p = 0.18), risk factors for renal function loss (p = 0.74) and aGFRL were observed. Among the 28 patients who did not reach 18 months, one developed grade 4 kidney toxicity at 15 months after PRRT. Prospective dosimetry using a 37 Gy BED as the threshold for kidney toxicity is a good guide for {sup 90}Y-DOTATOC PRRT and is associated with a low risk of rapid renal function deterioration and evolution to severe nephrotoxicity. (orig.)

  16. Multi-physics and multi-scale deterioration modelling of reinforced concrete part I: Coupling transport and corrosion at the material scale

    DEFF Research Database (Denmark)

    Michel, Alexander; Geiker, Mette Rica; Stang, Henrik

    2015-01-01

    models are sketched to describe (i) transport of heat and matter in porous media as well as phase assemblage in hardened Portland cement, (ii) corrosion of reinforcement, and (iii) material performance including corrosion-induced damages on the meso and macro scale. The presented modelling framework...... is fully coupled, i.e. information, such as temperature and moisture distribution, phase assemblage, corrosion current density, damage state of concrete cover, etc., are continuously exchanged between the models. Although not explicitly outlined in this paper, such an analysis may be further integrated...

  17. Evaluation of the Structural Performance of CTS Rapid Set Concrete Mix

    Science.gov (United States)

    2016-08-01

    from a local source. The material was placed in 6- to 8-in.-thick lifts and compacted with a jumping jack compactor (Figure 13) to a target subgrade...2012. Standard test method for slump of hydraulic -cement concrete. Designation: C143/C143M-12. West Conshohocken, PA: American Society for Testing

  18. Modelling the Loss of Steel-Concrete Bonds in Corroded Reinforced Concrete Beams

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    2007-01-01

    The existing stochastic models for deterioration of reinforced concrete structures is extended by adding modelling of "loss of bond" due to corrosion between the reinforcement bars and the surrounding concrete.......The existing stochastic models for deterioration of reinforced concrete structures is extended by adding modelling of "loss of bond" due to corrosion between the reinforcement bars and the surrounding concrete....

  19. Capturing early signs of deterioration: the dutch-early-nurse-worry-indicator-score and its value in the Rapid Response System.

    Science.gov (United States)

    Douw, Gooske; Huisman-de Waal, Getty; van Zanten, Arthur R H; van der Hoeven, Johannes G; Schoonhoven, Lisette

    2017-09-01

    of dutch-early-nurse-worry-indicator-score indicators showed higher positive predictive values. Dutch-early-nurse-worry-indicator-score indicators alert in an early stage of deterioration, before reaching the trigger threshold to call a rapid response team and can improve interdisciplinary communication on surgical wards during regular rounds, and when calling for assistance. Dutch-early-nurse-worry-indicator-score structures communication and recording of signs known to be associated with a decline in a patient's condition and can empower nurses to call assistance on the 'worry' criterion in an early stage of deterioration. © 2016 John Wiley & Sons Ltd.

  20. Rapid chloride permeability test as durability index of the concrete structure

    Directory of Open Access Journals (Sweden)

    Martínez-Sánchez, B.

    2003-12-01

    Full Text Available From the RCPT publication, this test has been frequently used in the concrete structures durability assessment. This test it could be determined in a relatively short time the material permeability, within a rank or quality level that allows comparing concretes as far as their characteristics. In this document, is present an intense investigation to evaluate mix designs with the principal objective to measure the participation and contribution of the components that take part in the concrete manufacture. A detailed review of the components contribution is applied to know specifically the properties in the product during any state: fresh or hard path. In this paper, are identified and included the most influence variables in the concrete properties modification.

    Desde su lanzamiento, la prueba de permeabilidad rápida a la penetración de cloruros ha sido usada frecuentemente en la evaluación de la durabilidad en las estructuras de hormigón, ya que se puede establecer, en un tiempo relativamente corto, la determinación de la permeabilidad del material, dentro de un nivel de calidad que permite comparar hormigones en cuanto a esta característica. En este articulo se presenta una investigación en donde se evalúan diseños de mezcla con la finalidad de medir la participación y contribución de cada uno de los componentes que intervienen en la fabricación del hormigón, revisando con detalle su contribución en las propiedades finales del producto, sin olvidar sus efectos en su comportamiento en estado fresco o cuando se encuentra en fase de endurecimiento. En el trabajo se incluyen e identifican las variables de mayor influencia y su relación con la propiedad que modificaron en el hormigón.

  1. Development and Evaluation of a Procedure for the Rapid Analysis of Fresh Concrete.

    Science.gov (United States)

    1984-12-01

    additives like flyash to be corrected for. For this study, a sample of tap water was tested instead of a 2-kg blank sample to establish the zero cement...Concrete Batches (Series 208C)," paper presented at ASTM Committee S C9-9.03 Meeting, Philadelphia, PA (JOunt 19, 1979). 21 biasing the sample’s mortar ...of 2 kg + 200 gram. The samples were tested nonethe- less under the premise that altering the sample mass might bias the aggre- gate/ mortar ratio. One

  2. Separation and collection of coarse aggregate from waste concrete by electric pulsed power

    Science.gov (United States)

    Shigeishi, Mitsuhiro

    2017-09-01

    Waste concrete accounts for a substantial fraction of construction waste, and the recycling of waste concrete as concrete aggregate for construction is an important challenge associated with the rapid increase in the amount of waste concrete and the tight supply of natural aggregate. In this study, we propose a technique based on the use of high-voltage pulsed electric discharge into concrete underwater for separating and collecting aggregate from waste concrete with minimal deterioration of quality. By using this technique, the quality of the coarse aggregate separated and collected from concrete test specimens is comparable to that of coarse aggregate recycled by heating and grinding methods, thus satisfying the criteria in Japan Industrial Standard (JIS) A 5021 for the oven-dry density and the water absorption of coarse aggregate by advanced recycling.

  3. Sustainable Concrete Technology

    Directory of Open Access Journals (Sweden)

    Sim J.

    2015-12-01

    Full Text Available The growing concern over global warming and significant ecological changes requires sustainable development in all fields of science and technology. Concrete not only consumes huge amount of energy and natural sources, but also emits large amount of CO2, mainly due to the production of cement. It is evident that such large amount of concrete production has put significant impact on the energy, resource, environment, and ecology of the society. Hence, how to develop the concrete technology in a sustainable way has become a significant issue. In this paper, some of Korean researches for sustainable development of concrete are presented. These are sustainable strengthening for deteriorated concrete structure, sustainable reinforcement of new concrete structure, sustainable concrete using recycled aggregate and supplementary cementing materials and finally application of each technique to precast concrete.

  4. Mechanical and Permeability Characteristics of Latex-Modified Pre-Packed Pavement Repair Concrete as a Function of the Rapid-Set Binder Content

    OpenAIRE

    Jae-Woong Han; Ji-Hong Jeon; Chan-Gi Park

    2015-01-01

    We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC) with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited a compressive strength of ¥21 MPa and a flexural strength of ¥3.5 MPa after 4 h of curing (i.e., the traffic opening term for emergency repairs of pavement). The ratio of latex polymer t...

  5. Performance assessment of deteriorated and retrofitted steel HP piles.

    Science.gov (United States)

    2016-06-01

    Steel piles are known to deteriorate at high rates in Nebraska, partially as a result of exposure to weathering, and partially due to corrosive soils. The Nebraska Department of Roads (NDOR) employs a reinforced concrete jacket to slow the progressio...

  6. A rapid, non-destructive methodology to monitor activity of sulfide-induced corrosion of concrete based on H2S uptake rate.

    Science.gov (United States)

    Sun, Xiaoyan; Jiang, Guangming; Bond, Philip L; Wells, Tony; Keller, Jurg

    2014-08-01

    Many existing methods to monitor the corrosion of concrete in sewers are either very slow or destructive measurements. To overcome these limitations, a rapid, non-invasive methodology was developed to monitor the sulfide-induced corrosion process on concrete through the measurement of the H2S uptake rates of concrete at various corrosion stages. The H2S uptake rate for a concrete coupon was determined by measuring the gaseous H2S concentrations over time in a temperature- and humidity-controlled gas-tight reactor. The reliability of this method was evaluated by carrying out repeated tests on different concrete coupons previously exposed to 50 ppm of H2S, at 30 °C and 100% relative humidity for over 32 months. The H2S uptake measurements showed good reproducibility. It was also shown that a severely corroded coupon exhibited higher sulfide uptake rates than a less corroded coupon. This could be explained by the corrosion layer in the more corroded coupon having a higher biological sulfide oxidation activity than the less corroded coupon. Additionally, temperature changes had a stronger effect on the uptake rate of the heavily corroded coupon compared to the less corroded coupon. A corrosion rate of 8.9 ± 0.5 mm/year, estimated from the H2S uptake results, agreed well with the corrosion rate observed in real sewers under similar conditions. The method could be applied to investigate important factors affecting sulfide-induced concrete corrosion, particularly temperature, fluctuating gaseous H2S concentrations, oxygen concentrations, surface pH and relative humidity. Copyright © 2014 Elsevier Ltd. All rights reserved.

  7. Fiber reinforcement of concrete structures

    Science.gov (United States)

    2002-09-01

    Deterioration of concrete structures due to steel corrosion is a matter of considerable concern since the repairing of these structures proved to be a costly process. Repair and rehabilitation of the civil structures needs an enduring repair material...

  8. Co-precipitation of ettringite of rapid and slow formation. Consequence: Expansive Synergic Effect. Its demonstration by mortars and concretes

    Directory of Open Access Journals (Sweden)

    Talero, R.

    2011-09-01

    Full Text Available Several prior papers have shown that enough pozzolans can bring about rapid formation ettringite (from its Al2O3r-. It has likewise been found that the formation rate of this ettringite is higher than the of slower forming ettringite originating from OPC (from its C3A. In this context: What type of effect will they ultimately produce? Addition? Synergism? Antagonism? or perhaps Inversion of final expansive action?. To reply to these questions, 4 PC and 12 blended cements containing 20%, 30% or 40% metakaolin, were tested using the ASTM C 452-68, EN 196-1 and RT-86:ΔL tests and also concrete specimens. The experimental results have shows that the joint precipitation in a common sulfate medium, of ettringite from pozzolan and from OPC, was always more synergic than additive, and the technical consequences of the Expansive Synergic Effect may be classified as beneficial, adverse or indifferent according to its sulfates content in excess is more or less adequate.En investigaciones anteriores se ha demostrado que bastantes puzolanas pueden originar ettringita de rápida formación (de su Al2O3r- cuya velocidad es mayor que la de la ettringita de lenta formación, o de origen CPO (de su C3A. En este contexto: ¿qué tipo de efecto será el que produzcan finalmente ambas ettringitas?, ¿adición?, ¿sinergismo?, ¿antagonismo? o ¿inversión de la acción expansiva?. Para responder a estas cuestiones, 4 CPO y 12 cementos con 20%, 30% y 40% de metakaolín fueron ensayados mediante los métodos ASTM C 452-68, EN 196-1 y RT-86:ΔL, y también mediante hormigones. Los resultados obtenidos han demostrado que la precipitación conjunta en un medio selenitoso común, de ettringita de origen puzolana y de origen CPO, es siempre cuantitativamente hablando, más que aditiva, sinérgica, pudiendo ser por ello las consecuencias técnicas del Efecto Sinérgico Expansivo, beneficiosas, adversas o indiferentes, según que el exceso de sulfatos presentes sea más o

  9. Mechanical and Permeability Characteristics of Latex-Modified Pre-Packed Pavement Repair Concrete as a Function of the Rapid-Set Binder Content

    Directory of Open Access Journals (Sweden)

    Jae-Woong Han

    2015-10-01

    Full Text Available We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited a compressive strength of ¥21 MPa and a flexural strength of ¥3.5 MPa after 4 h of curing (i.e., the traffic opening term for emergency repairs of pavement. The ratio of latex polymer to rapid-set binder material was varied through 0.40, 0.33, 0.29, and 0.25. Mechanical characterization revealed that the mechanical performance, permeability, and impact resistance increased as the ratio of latex polymer to rapid-set binder decreased. The mixture exhibited a compressive strength of ¥21 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.29. The mixture exhibited a flexural strength of ¥3.5 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.33. The permeability resistance to chloride ions satisfied 2000 C after 7 days of curing for all ratios. The ratio of latex polymer to rapid-set binder material that satisfied all conditions for emergency pavement repair was ¤0.29.

  10. Mechanical and Permeability Characteristics of Latex-Modified Pre-Packed Pavement Repair Concrete as a Function of the Rapid-Set Binder Content.

    Science.gov (United States)

    Han, Jae-Woong; Jeon, Ji-Hong; Park, Chan-Gi

    2015-10-01

    We evaluated the strength and durability characteristics of latex-polymer-modified, pre-packed pavement repair concrete (LMPPRC) with a rapid-set binder. The rapid-set binder was a mixture of rapid-set cement and silica sand, where the fluidity was controlled using a latex polymer. The resulting mix exhibited a compressive strength of ¥21 MPa and a flexural strength of ¥3.5 MPa after 4 h of curing (i.e., the traffic opening term for emergency repairs of pavement). The ratio of latex polymer to rapid-set binder material was varied through 0.40, 0.33, 0.29, and 0.25. Mechanical characterization revealed that the mechanical performance, permeability, and impact resistance increased as the ratio of latex polymer to rapid-set binder decreased. The mixture exhibited a compressive strength of ¥21 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.29. The mixture exhibited a flexural strength of ¥3.5 MPa after 4 h when the ratio of latex polymer to rapid-set binder material was ¤0.33. The permeability resistance to chloride ions satisfied 2000 C after 7 days of curing for all ratios. The ratio of latex polymer to rapid-set binder material that satisfied all conditions for emergency pavement repair was ¤0.29.

  11. Capturing early signs of deterioration: the dutch-early-nurse-worry-indicator-score and its value in the Rapid Response System

    NARCIS (Netherlands)

    Douw, G.; Huisman-de Waal, G.J.; Zanten, A.R. van; Hoeven, J.G. van der; Schoonhoven, L.

    2017-01-01

    AIMS AND OBJECTIVES: To determine the predictive value of individual and combined dutch-early-nurse-worry-indicator-score indicators at various Early Warning Score levels, differentiating between Early Warning Scores reaching the trigger threshold to call a rapid response team and Early Warning

  12. How Concrete Is Concrete?

    Science.gov (United States)

    Gravemeijer, Koeno

    2011-01-01

    If we want to make something concrete in mathematics education, we are inclined introduce, what we call, "manipulatives", in the form of tactile objects or visual representations. If we want to make something concrete in a everyday-life conversation, we look for an example. In the former, we try to make a concrete model of our own,…

  13. The economy of preventive maintenance of concrete bridges : final report.

    Science.gov (United States)

    2016-03-01

    The most economical approach to maintain existing concrete bridges is by adopting an active preventive maintenance : approach. An in-depth investigation of the combined deterioration effects of various deterioration mechanisms is needed : to establis...

  14. The Impact of Traffic-Induced Bridge Vibration on Rapid Repairing High-Performance Concrete for Bridge Deck Pavement Repairs

    Directory of Open Access Journals (Sweden)

    Wei Wang

    2014-01-01

    Full Text Available Based on forced vibration tests for high-performance concrete (HPC, the influence of bridge vibration induced by traveling vehicle on compressive strength and durability of HPC has been studied. It is concluded that 1 d and 2 d compressive strength of HPC decreased significantly, and the maximum reduction rate is 9.1%, while 28 d compressive strength of HPC had a slight lower with a 3% maximal drop under the action of two simple harmonic vibrations with 2 Hz, 3 mm amplitude, and 4 Hz, 3 mm amplitude. Moreover, the vibration had a slight effect on the compressive strength of HPC when the simple harmonic vibration had 4 Hz and 1 mm amplitude; it is indicated that the amplitude exerts a more prominent influence on the earlier compressive strength with the comparison of the frequency. In addition, the impact of simple harmonic vibration on durability of HPC can be ignored; this shows the self-healing function of concrete resulting from later hydration reaction. Thus, the research achievements mentioned above can contribute to learning the laws by which bridge vibration affects the properties of concrete and provide technical support for the design and construction of the bridge deck pavement maintenance.

  15. TRANSPARENT CONCRETE

    OpenAIRE

    Sandeep Sharma*, Dr. O.P. Reddy

    2017-01-01

    Transparent concrete is the new type of concrete introduced in todays world which carries special property of light transmitting due to presence of light Optical fibres. Which is also known as translucent concrete or light transmitting concrete, it is achieved by replacing coarse aggregates with transparent alternate materials (Optical fibres). The binding material in transparent concrete may be able to transmit light by using clear resins the concrete mix. The concrete used in industry in pr...

  16. How Concrete is Concrete

    OpenAIRE

    Koeno Gravemeijer

    2010-01-01

    If we want to make something concrete in mathematics education, we are inclined introduce, what we call, ‘manipulatives’, in the form of tactile objects or visual representations. If we want to make something concrete in a everyday-life conversation, we look for an example. In the former, we try to make a concrete model of our own, abstract, knowledge; in the latter, we try to find an example that the others will be familiar with. This article first looks at the tension between these two diff...

  17. A novel abutment construction technique for rapid bridge construction : controlled low strength Materials (CLSM) with full-height concrete panels.

    Science.gov (United States)

    2012-01-01

    One of the major obstacles facing rapid bridge construction for typical span type bridges is the time required to construct bridge abutments and foundations. This can be remedied by using the controlled low strength materials (CLSM) bridge abutment. ...

  18. Corrosion resistant alloys for reinforced concrete [2009

    Science.gov (United States)

    2009-04-01

    Deterioration of concrete bridges because of reinforcing steel corrosion has been recognized for four-plus decades as a major technical and economic challenge for the United States. As an option for addressing this problem, renewed interest has focus...

  19. Advances in Modeling Concrete Service Life : Proceedings of 4th International RILEM PhD Workshop

    CERN Document Server

    Gulikers, Joost

    2012-01-01

    In this book, a critical analysis is made on service life models related to reinforcement corrosion. The contributors are on the frontier of knowledge in the field of durability of reinforced concrete. Topics covered in the book include: causes and mechanisms of deterioration, transport mechanisms in concrete, numerical modeling of concrete behavior, durability modeling and prediction, reliability approach to structural design for durability, structural behavior following degradation of concrete structures, deterioration and repair of concrete structures, and corrosion measurement techniques.

  20. How Concrete is Concrete

    Directory of Open Access Journals (Sweden)

    Koeno Gravemeijer

    2010-07-01

    Full Text Available If we want to make something concrete in mathematics education, we are inclined introduce, what we call, ‘manipulatives’, in the form of tactile objects or visual representations. If we want to make something concrete in a everyday-life conversation, we look for an example. In the former, we try to make a concrete model of our own, abstract, knowledge; in the latter, we try to find an example that the others will be familiar with. This article first looks at the tension between these two different ways of making things concrete. Next another role of manipulatives, will be discussed, namely that of means for scaffolding and communication. In this role, manipulatives may function as means of support in a process that aims at helping students to build on their own thinking while constructing more sophisticated mathematics

  1. Visualising Deteriorating Conditions

    Directory of Open Access Journals (Sweden)

    Tom Andrews, RN, B.Sc. (Hons, M.Sc., Ph.D.

    2005-03-01

    Full Text Available The research aims were to investigate the difficulties ward staff experienced in detecting deterioration and how these were resolved. The emphasis within the literature tends to be on identifying premonitory signs that may be useful in predicting deterioration. Changes in respiratory rate is the most consistent of these (Fieselmann et al. 1993; Sax and Charlson 1987; Schein et al. 1990; Smith and Wood 1998 but in common with other signs, it lacks sensitivity and specificity. The sample consisted of 44 nurses, doctors (Interns and health care support workers from a general medical and surgical ward. Data were collected by means of nonparticipant observations and interviews, using grounded theory as originated by (Glaser and Strauss 1967 and (Glaser 1978. As data were collected, the constant comparative method and theoretical sensitivity were used as outlined in grounded theory. A core category of “visualising deteriorating conditions” emerged, together with its sub-core categories of “intuitive knowing”, “baselining” and “grabbing attention”.The main concern in visualising deteriorating conditions is to ensure that patients suspected of deterioration are successfully referred to medical staff. The aim is to convince those who can treat or prevent further deterioration to intervene. Through intuitive knowing they pick up that patients have changed in a way that requires a medical assessment. To make the referral more credible, nurses attempt to contextualise any changes in patients by baselining (establishing baselines. Finally with the backup of colleagues, nurses refer patients by providing as much persuasive information as possible in a way that grabs attention. The whole process is facilitated by knowledge and experience, together with mutual trust and respect.

  2. Re-Assessment of Concrete Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    In this paper two aspects of re-assessment of the reliability of concrete bridges are discussed namely modelling of the corrosion of reinforcement and updating of uncertain variables. The main reason for deterioration of concrete bridges is corrosion of the reinforcement. Therefore, modelling...

  3. Evaluation of concrete inlay for continuously reinforced concrete pavement rehabilitation.

    Science.gov (United States)

    2010-06-01

    In 1996, WisDOT constructed a concrete inlay test section on I43 in Manitowoc County. The existing pavement was CRCP constructed in 1978 and was badly deteriorated with punchouts. In the area of the 2777foot test section, the existing paveme...

  4. Evaluation of Durability Parameters of Concrete with Manufacture Sand and River Sand

    Science.gov (United States)

    Sangoju, Bhaskar; Ramesh, G.; Bharatkumar, B. H.; Ramanjaneyulu, K.

    2017-09-01

    Most of the states in our country have banned sand quarrying from the river beds, causing a scarcity of natural river sand for the construction sector. Manufacture sand (M-sand) is one of the alternate solutions to replace the river sand (R-sand) in concrete. The main aim of the present study is to evaluate the durability parameters of concrete with M-sand when compared to that of concrete with R-sand. Corrosion of reinforcement is one of the main deteriorating mechanisms of reinforced concrete due to the ingress of chloride ions or carbon-di-oxide. For comparative evaluation of durability parameters, accelerated tests such as Rapid Chloride Permeability Test, Rapid Chloride Migration Test and accelerated carbonation test were carried out on specimens of R-sand and M-sand. All tests were carried out after 90 days of casting. Test results reveal that the durability parameters of the concrete with M-sand in chloride induced environment is relatively better than that of concrete with R-sand and hence is recommended to use M-sand as a replacement to R-sand.

  5. Ageing of portland cement concrete cured under moist conditions

    NARCIS (Netherlands)

    Yu, Z.; Ye, G.; Van Breugel, K.; Chen, W.

    2014-01-01

    Deterioration of microstructure in cement concrete will cause changes in the transport properties of the concrete. Transport properties at different ages of the concrete provide information about the microstructural changes of the material. A way to measure the transport properties, i.e. the

  6. How Concrete is Concrete?

    Directory of Open Access Journals (Sweden)

    Koeno Gravemeijer

    2011-01-01

    Full Text Available If we want to make something concrete in mathematics education, we are inclined introduce, what we call, ‘manipulatives’, in the form of tactile objects or visual representations. If we want to make something concrete in a everyday-life conversation, we look for an example. In the former, we try to make a concrete model of our own, abstract, knowledge; in the latter, we try to find an example that the others will be familiar with. This article first looks at the tension between these two different ways of making things concrete. Next another role of manipulatives, will be discussed, namely that of means for scaffolding and communication. In this role, manipulatives may function as means of support in a process that aims at helping students to build on their own thinking while constructing more sophisticated mathematics.Key words:  Conceret Learning Materials, School Math, Common Sense, Scaffolding, Communication DOI: http://dx.doi.org/10.22342/jme.2.1.780.1-14

  7. Performance of concrete incorporating colloidal nano-silica

    Science.gov (United States)

    Zeidan, Mohamed Sabry

    Nanotechnology, as one of the most modern fields of science, has great market potential and economic impact. The need for research in the field of nanotechnology is continuously on the rise. During the last few decades, nanotechnology was developing rapidly into many fields of applied sciences, engineering and industrial applications, especially through studies of physics, chemistry, medicine and fundamental material science. These new developments may be attributed to the fact that material properties and performance can be significantly improved and controlled through nano-scale processes and nano-structures. This research program aims at 1) further understanding the behavior of cementitious materials when amended on the nano-scale level and 2) exploring the effect of this enhancement on the microstructure of cement matrix. This study may be considered as an important step towards better understanding the use of nano-silica in concrete. The main goal of the study is to investigate the effect of using colloidal nano-silica on properties of concrete, including mechanical properties, durability, transport properties, and microstructure. The experimental program that was conducted included a laboratory investigation of concrete mixtures in which nano-silica was added to cement or to a combination of cement and Class F fly ash. Various ratios of nano-silica were used in concrete mixtures to examine the extent and types of improvements that could be imparted to concrete. The conducted experimental program assessed these improvements in terms of reactivity, mechanical properties, and durability of the mixtures under investigation. Advanced testing techniques---including mercury intrusion porosimetry (MIP) and scanning electron microscopy (SEM)---were used to investigate the effect of nano-silica on the microstructure of the tested mixtures. In addition, the effect of nano-silica on the alkali-silica reaction (ASR) was examined using various techniques, including testing

  8. Experimental investigation of the relation between damage at the concrete-steel interface and initiation of reinforcement corrosion in plain and fibre reinforced concrete

    DEFF Research Database (Denmark)

    Michel, Alexander; Solgaard, Anders Ole Stubbe; Pease, Bradley Justin

    2013-01-01

    Cracks in covering concrete are known to hasten initiation of steel corrosion in reinforced concrete structures. To minimise the impact of cracks on the deterioration of reinforced concrete structures, current approaches in (inter)national design codes often limit the concrete surface crack width...... embedded in plain and fibre reinforced concrete. Comparisons of experimental and numerical results indicate a strong correlation between corrosion initiation and interfacial condition.......Cracks in covering concrete are known to hasten initiation of steel corrosion in reinforced concrete structures. To minimise the impact of cracks on the deterioration of reinforced concrete structures, current approaches in (inter)national design codes often limit the concrete surface crack width....... Recent investigations however, indicate that the concrete-reinforcement interfacial condition is a more fundamental criterion related to reinforcement corrosion. This work investigates the relation between macroscopic damage at the concrete-steel interface and corrosion initiation of reinforcement...

  9. Durability of precast prestressed concrete piles in marine environment : reinforcement corrosion and mitigation - Part 1.

    Science.gov (United States)

    2011-06-01

    Research conducted in Part 1 has verified that precast prestressed concrete piles in : Georgias marine environment are deteriorating. The concrete is subjected to sulfate and : biological attack and the prestressed and nonprestressed reinforcement...

  10. A review on the suitability of rubberized concrete for concrete bridge decks

    Science.gov (United States)

    Syamir Senin, Mohamad; Shahidan, Shahiron; Radziah Abdullah, Siti; Anting Guntor, Nickholas; Syazani Leman, Alif

    2017-11-01

    Road authorities manage a large population of ageing bridges, a substantial number of which fail to meet the current requirements either due to deterioration and other structural deficiencies or as a result of the escalating demands imposed by increased traffic. This problem is related to the dynamic load from vehicles. This problem can be solved by producing a type of concrete that can reduce the amplitude of oscillation or vibration such as rubberized concrete. Green construction has been a very important aspect in concrete production field in the last decade. One of the most problematic waste materials is scrap tires. The use of scrap tires in civil engineering is increasing by producing rubberized concrete. Rubberized concrete is a type of concrete that is mixed with rubber. The purpose of this review is to justify the suitability of rubberized concrete for concrete bridge decks. Several parameters named physical, chemical and mechanical properties were measured to ensure the suitability of rubberized concrete for concrete bridge decks. Rubberized concrete has similar workability to normal concrete. The rubber reduced the density and compressive strength of the concrete while increased the flexural strength, water absorption and damping ratio. The used of rubber in concrete beyond 20% is not recommended due to decreasing in compressive strength. Rubberized concrete recommended to be used in circumstances where vibration damping was required such as in bridge construction as shock-wave absorber.

  11. The Use of Coral as an Aggregate for Portland Cement Concrete Structures

    Science.gov (United States)

    preparation sites, evaluate existing coral concrete structures , and analyze coral aggregate and coral concrete samples in the laboratory. The results of...deterioration observed in coral concrete structures was the cracking and spalling of concrete associated with corroding reinforcing steel. The severity

  12. Structural Precast Concrete Handbook

    DEFF Research Database (Denmark)

    Kjærbye, Per Oluf H

    Structural concept for precast concrete systems. Design og precast reinforced concrete components. Design of precast concrete connections. Illustrations on design of precast concrete buildings. Precast concrete assembly.......Structural concept for precast concrete systems. Design og precast reinforced concrete components. Design of precast concrete connections. Illustrations on design of precast concrete buildings. Precast concrete assembly....

  13. Glazed Concrete

    DEFF Research Database (Denmark)

    Bache, Anja Margrethe

    2010-01-01

    Why glazed concrete? Concrete hardens and finds its strength at room temperature whereas clay products must first be fired before they achieve this strength. They are stronger and three times as durable as clay products, which is a weighty reason for choosing concrete.5 Another reason, which....... If this succeeds, it will be possible to manufacture thin, large-scale glazed concrete panels comparable in size to concrete sandwich construction and larger which, with or without back-casting, can work as load-bearing construction elements....

  14. Review on Potential of Geopolymer for Concrete Repair and Rehabilitation

    Directory of Open Access Journals (Sweden)

    Warid Wazien A.Z.

    2016-01-01

    Full Text Available Cracking, spalling, surface deterioration, seepage and other concrete damage of the existing infrastructure have raised concern among residents, local authorities and developers. Dealing with concrete infrastructure rehabilitation is an important issue due to most of infrastructures today are concrete based. To simply patch up the spalling concrete as temporary solution and sooner or later, the cracks will return to haunt. This paper reviewed the current research and studies on concrete repair materials, highlighting the properties of geopolymer. It covers geopolymer repair materials which addressed in the field of concrete infrastructure rehabilitation. Geopolymer had good repair characteristics and displays the potential as an excellent repair material.

  15. Concrete Hinges

    DEFF Research Database (Denmark)

    Halding, Philip Skov; Hertz, Kristian Dahl; Schmidt, Jacob Wittrup

    2014-01-01

    . The present paper uses the prior research results to optimize a test-setup for concrete hinge testing by means of a universal method taking into account the application of the hinge in an arch structure. 3D CAD is utilized in all steps of the planning to reduce errors during assembly of the parts in the test......In the first part of the 20th century concrete hinges developed by Freyssinet and Mesnager were widely tested and implemented in concrete structures. The concrete hinges were used a great deal in closed-spandrel arch bridges. Since such a bridge type has not been competitive for the past 40 years......, the research in concrete hinges has not evolved significantly in that period. But introducing a new state-of-the-art concrete arch bridge solution (Pearl-Chain arches invented at the Technical University of Denmark) creates a necessity of a concrete hinge research based on modern standards. Back when research...

  16. Concrete structures

    CERN Document Server

    Setareh, Mehdi

    2017-01-01

    This revised, fully updated second edition covers the analysis, design, and construction of reinforced concrete structures from a real-world perspective. It examines different reinforced concrete elements such as slabs, beams, columns, foundations, basement and retaining walls and pre-stressed concrete incorporating the most up-to-date edition of the American Concrete Institute Code (ACI 318-14) requirements for the design of concrete structures. It includes a chapter on metric system in reinforced concrete design and construction. A new chapter on the design of formworks has been added which is of great value to students in the construction engineering programs along with practicing engineers and architects. This second edition also includes a new appendix with color images illustrating various concrete construction practices, and well-designed buildings. The ACI 318-14 constitutes the most extensive reorganization of the code in the past 40 years. References to the various sections of the ACI 318-14 are pro...

  17. Rapid Testing of Fresh Concrete

    Science.gov (United States)

    1975-05-01

    The system is shielded in a 32-1n. diameter steel cylinder filled with a borated-water extended polyester resin (WEP). Source-detector shielding...drainage sump were provided. Bottle gas was used tc operate the flame photometer. Six mixes ranging from 1:4-1/2 to 1:16 nominal proportions, which...mixer. Fitted with widemouthed polyethylene bottle of approximately 1/2 gal capacity. 2. Constant volume dispensers. One 10-ml, one 5-ml, one

  18. Corrosion of Steel in Concrete, Part I – Mechanisms

    DEFF Research Database (Denmark)

    Küter, André; Møller, Per; Geiker, Mette Rica

    2006-01-01

    prematurely. Reinforcement corrosion is identified to be the foremost cause of deterioration. Steel in concrete is normally protected by a passive layer due the high alkalinity of the concrete pore solution; corrosion is initiated by neutralization through atmospheric carbon dioxide and by ingress...... of depassivation ions, especially chloride ions. The background and consequences of deterioration of reinforced concrete structures caused by steel corrosion are summarized. Selected corrosion mechanisms postulated in the literature are briefly discussed and related to observations. The key factors controlling...... initiation and propagation of corrosion of steel in concrete are outlined....

  19. Evaluation of three state-of-the-art water-jet systems for cutting/removing concrete

    Science.gov (United States)

    Pace, C. E.

    1982-09-01

    This report documents a demonstration project to evaluate the capability of three waterjet systems for cutting or removing concrete or both. The Corps of Engineers is interested in the potential of this technology for such applications as rapid cutting of bomb-damaged selection of airfield pavement and removing of deteriorated sections of concrete structures at Civil Works projects. Because water-jet systems are capable of transmitting, without mechanical constraint, all of the available horsepower of their power sources into the concrete cutting/removing operation, they may prove to be an extremely efficient means of conducting such operations. The low-pressure water jets were able to cut a 6-in. slot in the concrete for a distance of 1-1/2 ft. in a period of 24 minutes (a rate of 6.4 ft. per hour). The relatively high-pressure water jet cut at rates of 9.6 ft. per hour for shallow cuts (less than 5 in.) and 3 ft. per hour for deeper cuts (greater than 5 in.). In addition, one of the low-pressure systems was used to remove some surface concrete. The results of this evaluation indicate that, although these water-jet systems did not demonstrate a capability for efficiently cutting concrete airfield pavements, the technology has potential. The low-pressure system demonstrated a capability for removing surface concrete efficiently.

  20. Mental deterioration in childhood epilepsy

    OpenAIRE

    Oka, Eiji; Sanada, Satoshi; Asano, Takashi; Ishida, Takashi

    1997-01-01

    Mental retardation is detected in 20-30% of children with epilepsy at hospitals specializing in treatment of childhood epilepsy. However, the incidence of mental deterioration in childhood epilepsy is not high. In this study, mental deterioration was found in 52 (1.8%) of the 2,880 children with epilepsy at Okayama University Hospital. The patients showing mental deterioration mostly suffered from specific epileptic syndromes, such as West syndrome, Lennox-Gastaut syndrome, severe myoclonic e...

  1. Reviewing the Carbonation Resistance of Concrete

    Directory of Open Access Journals (Sweden)

    S P Singh

    2016-07-01

    Full Text Available The paper reviews the studies on one of the important durability properties of concrete i.e. Carbonation. One of the main causes of deterioration of concrete is carbonation, which occurs when carbon dioxide (CO2 penetrates the concrete’s porous system to create an environment with lower pH around the reinforcement in which corrosion can proceed. Carbonation is a major cause of degradation of concrete structures leading to expensive maintenance and conservation operations. Herein, the importance, process and effect of various parameters such as water/cement ratio, water/binder ratio, curing conditions, concrete cover, super plasticizers, type of aggregates, grade of concrete, porosity, contaminants, compaction, gas permeability, supplementary cementitious materials (SCMs/ admixtures on the carbonation of concrete has been reviewed. Various methods for estimating the carbonation depth are also reported briefly

  2. NANOMODIFIED CONCRETE

    Directory of Open Access Journals (Sweden)

    B. M. Khroustalev

    2015-01-01

    Full Text Available One of the main directions in construction material science is the development of  next generation concrete that is ultra-dense, high-strength, ultra-porous, high heat efficient, extra corrosion-resistant. Selection of such direction is caused by extreme operational impacts on the concrete, namely: continuously increasing load on the concrete and various dynamics of such loads; the necessity in operation of concrete products in a wide temperature range and their exposure to various chemical and physical effects.The next generation concrete represents high-tech concrete mixtures with additives that takes on and retain the required properties when hardening and being used under any operational conditions. A differential characteristic of the next generation concrete is its complexity that presumes usage of various mineral dispersed components, two- and three fractional fine and coarse aggregates, complex chemical additives, combinations of polymer and iron reinforcement.Design strength and performance properties level of the next generation concrete is achieved by high-quality selection of the composition, proper selection of manufacturing techniques, concrete curing, bringing the quality of concrete items to the required level of technical condition during the operational phase. However, directed formation of its structure is necessary in order to obtain high-tech concrete.Along with the traditional methods for regulation of the next generation concrete structure, modification of concrete while using silica nanoparticles is also considered as a perspective one because the concrete patterning occurs due to introduction of a binder in a mineral matrix. Due to this it is possible to obtain nano-modified materials with completely new properties.The main problem with the creation of nano-modified concrete is a uniform distribution of nano-materials in the volume of the cement matrix which is particularly important in the cases of adding a modifier in

  3. Finite Element Investigation of the Deterioration of Doweled Rigid Pavements

    CERN Document Server

    Ghauch, Ziad G

    2011-01-01

    The purpose of this study is to describe the failure of concrete around dowel bars in jointed rigid pavements, and the resulting effect on the pavement performance. In fact, under repetitive vehicle loading, concrete in contact with the dowel bar deteriorates, particularly at the joint face. The degradation of concrete around the dowel negatively affects the latter's performance in terms of transferring wheel loads through vertical shear action. In this context, a nonlinear 3D Finite Element analysis was performed using the commercial FE code Abaqus (v-6.11). The FE model was validated with classical analytical solutions of shear and moment along the dowel. A concrete damaged plasticity model was used for the PCC slab to model the degradation of concrete matrix around the dowels under incremental loading. Results obtained show, among other things, that the degradation of concrete matrix around the dowel was found to initiate at the face of the joint and propagate towards the interior of the dowel. Also, resul...

  4. Severe ASR damaged concrete bridges

    DEFF Research Database (Denmark)

    Antonio Barbosa, Ricardo; Gustenhoff Hansen, Søren

    2015-01-01

    Technical University of Denmark (DTU) and University of Southern Denmark (SDU) have conducted several full-scale experiments with severe ASR deteriorated bridges. This paper presents few and preliminary results from both the shear tests and the measuring of the material properties. The shear test...... show that the shear capacity is almost unaffected of ASR despite significant reduction in compressive concrete strength. Furthermore, measurements show a significant tensile reinforcement strain developed due to ASR expansion....

  5. Effects of Reinforcing Fiber and Microsilica on the Mechanical and Chloride Ion Penetration Properties of Latex-Modified Fiber-Reinforced Rapid-Set Cement Concrete for Pavement Repair

    Directory of Open Access Journals (Sweden)

    Woong Kim

    2018-01-01

    Full Text Available This study evaluated the influence of reinforcement fiber type and microsilica content on the performance of latex-modified fiber-reinforced roller-compacted rapid-hardening cement concrete (LMFRCRSC for a concrete pavement emergency repair. Experimental variables were the microsilica substitution ratio (1, 2, 3, and 4%, and the reinforcement fiber (jute versus macrosynthetic fiber. In the tests, compressive, flexural, and splitting tensile strength; chloride ion penetration resistance; and abrasion resistance were assessed. From the compressive and flexural strength tests with microsilica substitution, the 4-hour curing strength decreased as the microsilica substitution ratio increased. From the chloride ion penetration test, as the microsilica substitution ratio increased, chloride ion penetration decreased. The abrasion resistances increased with the substitution ratio of microsilica increase. Based on these test results, microsilica at a substitution ratio of 3% or less and macrosynthetic fiber as the reinforcement improved the performance of LMFRCRSC for a concrete pavement emergency repair and satisfied all of the target strength requirements.

  6. Clinical deterioration: a concept analysis.

    Science.gov (United States)

    Padilla, Ricardo M; Mayo, Ann M

    2017-12-21

    To present a concept analysis of clinical deterioration and introduce an operational definition. Hospitalized patients who endure cardiopulmonary arrest and unplanned intensive care unit admissions often exhibit physiological signs preceding these events. Clinical deterioration not promptly recognized can result in increased patient morbidity and mortality. A barrier to recognizing and responding to clinical deterioration stems from practice variations among health care clinicians. Concept analysis. Eight step method of concept analysis proposed by Walker and Avant. Defining attributes include dynamic state, decompensation, and objective and subjective determination. Antecedents identified include clinical state, susceptibility, pathogenesis, and adverse event. Increased mortality, resuscitation, implementation of higher level of care, and prolonged hospital admission were the consequences identified. Defining attributes, antecedents, and consequences identified led to an operational definition of clinical deterioration as a dynamic state experienced by a patient compromising hemodynamic stability, marked by physiological decompensation accompanied by subjective or objective findings. Clinical deterioration is a key contributor to inpatient mortality and its recognition is often underpinned by contextual factors and practice variances. Variation in the uniformity of the concept of clinical deterioration causes a gap in knowledge and necessitated clarification of this phenomenon for nursing research and practice. Identifying and intervening on clinical deterioration plays a vital role in the inpatient setting demonstrated by the dynamic nature of a patients' condition during hospitalization. It is anticipated that this concept analysis on clinical deterioration will contribute to further identification of clinically modifiable risk factors and accompanying interventions to prevent clinical deterioration in the inpatient setting. This article is protected by

  7. Inspection of the Engineering Condition of Underwater Concrete Structures

    Science.gov (United States)

    1989-04-01

    civil works structures. Specific objectives are: (a) to summarize the typical types of deterioration that occur in underwater concrete structures ; (b...Standardized and other methods that have proven satisfactory for inspection are emphasized. Methods that have potential for detection of the extent and cause of inadequacies in underwater concrete structures are also included.

  8. Bacteria-based self-healing concrete : An introduction

    NARCIS (Netherlands)

    Mors, R.M.; Jonkers, H.M.

    2012-01-01

    Crack formation in concrete is common, but a typical phenomenon related to durability. Percolation of cracks may lead to leakage problems or ingress of deleterious materials, causing deterioration of the concrete matrix or corrosion of embedded steel reinforcement. Durability can be enhanced by

  9. effect of uncertainty on the fatigue reliability of reinforced concrete ...

    African Journals Online (AJOL)

    user

    2016-07-03

    Jul 3, 2016 ... The deterioration of reinforced concrete bridge deck that has been damaged as a result of load action can affect the durability, safety and function of the structure. In this paper, a reliability time-variant fatigue analysis and uncertainty effect on the serviceability of reinforced concrete bridge deck was carried ...

  10. Failure Modes in Concrete Repair Systems due to Ongoing Corrosion

    NARCIS (Netherlands)

    Lukovic, M.; Savija, B.; Ye, G.; Schlangen, H.E.J.G.; van Breugel, K.

    2017-01-01

    Corrosion of steel reinforcement is the main cause of deterioration in reinforced concrete structures. It can result in cracking and spalling of the concrete cover. After the damaged cover is repaired, reinforcement corrosion might continue and even accelerate. While the development of the corrosion

  11. Thermal buffering of concrete by seaweeds during a prolonged summer heatwave

    Science.gov (United States)

    Naylor, Larissa; Coombes, Martin

    2014-05-01

    Hard coastal infrastructure is subject to aggressive environmental conditions, including a suite of weathering processes in the intertidal zone. These processes, along with waves, lead to costly deterioration of coastal structures. Existing methods (e.g. coatings, less porous concrete) to reduce the risk of concrete deterioration rapidly lose their effectiveness in the intertidal zone. Additionally, a changing climate will lead to increased frequency of storms, higher sea level and higher extreme temperatures - and therefore, pose an increased risk of deterioration. Might there be a biogenic solution? New research (Coombes et al. 2013) has shown that fucoid seaweeds reduce microclimatic extremes and variability under normal summer conditions. The results presented here supplement these findings in two ways. First, they demonstrate that fucoid seaweeds act as a thermal buffer during a prolonged summer heatwave in Britain (July 2013). Over 36 days of continuous monitoring at two sites in Cornwall, UK, 19 of which were during the official heatwave, there were statistically significant differences (p = 0.000) in the maximum temperatures between thick seaweed (7.5 - 9.5 cm thickness) and thin seaweed (2 - 2.5 cm thickness) plots. Maximum temperatures reached 22°C and 33°C, for thick seaweed and thin seaweed plots, respectively. Variations in maximum temperatures between the two sites appear to be related to aspect. Second, the significantly different maximum temperature results between plots also demonstrate that seaweed thickness is an important factor influencing thermal buffering capacity. These data clearly demonstrate that fucoid seaweeds buffer concrete seawalls against extreme temperature fluxes during a heatwave, probably limiting the efficiency of deteriorative processes such as thermal expansion and contraction and salt crystallisation.

  12. A Load-Deflection Study of Fiber-Reinforced Plastics as Reinforcement in Concrete Bridge Decks

    OpenAIRE

    Boyd, Curtis Barton

    1997-01-01

    Approximately fifty percent of the bridges in the United States are considered deficient. The deterioration of the concrete components is a leading cause of the problem. The deterioration of concrete bridge decks is due primarily to corrosion of the reinforcing steel in the concrete. A promising solution to the problem is the use of fiber reinforced plastics (FRP) as a replacement for reinforcing steel. The use of FRP as reinforcement has the following advantages of lightweight, high tensile ...

  13. Evaluating the Durability Properties of Self Compacting Concrete made with Recycled Concrete Aggregates

    Directory of Open Access Journals (Sweden)

    K Kapoor

    2016-08-01

    Full Text Available This paper reports the durability properties of Self Compacting Concrete (SCC made with Recycled Concrete Aggregates (RCA as partial/full replacement of Natural Coarse Aggregates (NCA. The effect of RCA on fresh properties of SCCs was measured using slump flow test, V-funnel test, L-box test and J-ring test. Whereas the durability properties like such as initial surface absorption, water permeability, capillary suction and rapid chloride penetrability were investigated to study the effect of varying content of RCA on SCC. The compressive strength of different SCC mixes was also determined for reference. The results indicate that increasing the content of RCA in SCC leads to deterioration in durability related properties of SCC. The compressive strength has also been found to decrease with increasing RCA content.  It has been seen that the reduction in the performance has been marginal up to 50% replacement level of RCA, but 100% replacement of RCA has been found to significantly affect the durability related properties and compressive strength.

  14. Internal curing of high performance concrete using lightweight aggregates and other techniques.

    Science.gov (United States)

    2014-02-01

    Internally cured concrete has been rapidly emerging over the last decade as an effective way to improve the : performance of concrete. Internal curing (IC) holds promise for producing concrete with an increased : resistance to early-age cracking and ...

  15. Bacteria-based self-healing concrete for application in the marine environment

    NARCIS (Netherlands)

    Palin, D.; Wiktor, V.; Jonkers, H.M.

    2013-01-01

    Marine concrete structures are exposed to one of the most hostile of natural environments. Many physical and chemical phenomena are usually interdependent and mutually reinforcing in the deterioration of marine exposed concrete: expansion and microcracking due to physical effects increases concrete

  16. Probabilistic design and management of environmentally sustainable repair and rehabilitation of reinforced concrete structures

    DEFF Research Database (Denmark)

    Lepech, Michael D.; Geiker, Mette Rica; Stang, Henrik

    2014-01-01

    This paper presents a probabilistic sustainability design framework for the design of concrete repairs and rehabilitations intended to achieve targeted improvements in quantitative sustainability indicators. The framework consists of service life prediction models combining deterioration mechanisms...... the probability that reinforced concrete repair strategies using thicker concrete cover will meet future greenhouse gas emission reduction targets proposed by the UN Intergovernmental Panel on Climate Change....

  17. Concrete spirituality

    National Research Council Canada - National Science Library

    Kritzinger, Johannes N J

    2014-01-01

    .... The basic contention of the article is that well designed liturgies that facilitate experiences of beauty can nurture a concrete spirituality to mobilise urban church members for a justice-seeking lifestyle...

  18. Photocatalyticpaving concrete

    Directory of Open Access Journals (Sweden)

    Lyapidevskaya Ol'ga Borisovna

    2014-02-01

    Full Text Available Today bituminous concrete is a conventional paving material. Among its advantages one can name dustlessness and noiselessness, fine wear (up to 1 mm a year and fine maintainability. As the main disadvantages of this material one can name high slipperiness under humidification, low durability and weather resistance. Besides that, during placement of the bituminous concrete a lot of different air pollutants are emitted, which are harmful for environment and human’s health (they are listed in the paper according to the US Environmental Protection Agency materials. As an alternative, one can use cement-concrete pavement, which is in many ways more efficient than the bituminous concrete. It is proposed to enhance environmental performance of the cement-concrete pavement via usage of photocatalysis. The mechanism of different photocatalytic reactions is described in the paper, namely heterogeneous and homogeneous photocatalysis, photo-induces, photoactivated catalysis and catalytical photoreactions. It is pro-posed to use heterogeneous photocatalysis with titanium dioxide as a photocatalyst. The mechanism of photo oxidation of air contaminants, with the usage of titanium dioxide is2described. The paper sets problems, connected with the sensibilization of TiOto thevisible light (it is proposed to use titanium dioxide, doped with the atoms of certain elements to increase its sensibility to the visible light and with the development of a new photocatalytic paving concrete, which will meet the requirements, specified for paving in the climatic and traffic conditions of the Russian Federation.

  19. Self-Placing Concrete

    OpenAIRE

    ECT Team, Purdue

    2007-01-01

    Certain concrete pours have areas where the congestion of reinforcing bars make placement of concrete almost impossible. Using conventional placing and vibration techniques, the resulting concrete can have considerable honeycombing due to the development of voids. Self-placing concrete is a possible solution to the problem. Also known as self-compactable concrete, self-consolidating concrete, flowable concrete, and non-vibration concrete. These concretes eliminate the need for vibration in a ...

  20. Corrosion and Cracking of Reinforced Concrete

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    Modelling of the deterioration of reinforced concrete has in recent years changed from being a deterministic modelling based on experience to be stochastic modelling based on sound and consistent physical, chemical and mechanical principles. In this paper is presented a brief review of modern mod...... for time to initial corrosion, time to initial cracking, and time to a given crack width may be obtained....

  1. Lifetime Reliability Assessment of Concrete Slab Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    A procedure for lifetime assesment of the reliability of short concrete slab bridges is presented in the paper. Corrosion of the reinforcement is the deterioration mechanism used for estimating the reliability profiles for such bridges. The importance of using sensitivity measures is stressed...

  2. Degradation of Waterfront Reinforced Concrete Structures

    African Journals Online (AJOL)

    especially those at Malindi dhow quay, which are found to need a major rehabilitation. However, carbonation test reVealed that all concrete structures have not been affected by carbonation. The observed deterioration of the structures at the port is due to other environmental factors, especially corrosion of the reinforcement.

  3. Cellular Concrete Bricks with Recycled Expanded Polystyrene Aggregate

    Directory of Open Access Journals (Sweden)

    Juan Bosco Hernández-Zaragoza

    2013-01-01

    Full Text Available Cellular concrete bricks were obtained by using a lightweight mortar with recycled expanded polystyrene aggregate instead of sandy materials. After determining the block properties (absorption, compressive strength, and tensile stresses, it was found that this brick meets the requirements of the masonry standards used in Mexico. The obtained material is lighter than the commercial ones, which facilitates their rapid elaboration, quality control, and transportation. It is less permeable, which helps prevent moisture formation retaining its strength due to the greater adherence shown with dry polystyrene. It was more flexible, which makes it less vulnerable to cracking walls due to soil displacements. Furthermore, it is economical, because it uses recyclable material and has properties that prevent deterioration increasing its useful life. We recommend the use of the fully dry EP under a dry environment to obtain the best properties of brick.

  4. Nanogranular origin of concrete creep

    Science.gov (United States)

    Vandamme, Matthieu; Ulm, Franz-Josef

    2009-01-01

    Concrete, the solid that forms at room temperature from mixing Portland cement with water, sand, and aggregates, suffers from time-dependent deformation under load. This creep occurs at a rate that deteriorates the durability and truncates the lifespan of concrete structures. However, despite decades of research, the origin of concrete creep remains unknown. Here, we measure the in situ creep behavior of calcium–silicate–hydrates (C–S–H), the nano-meter sized particles that form the fundamental building block of Portland cement concrete. We show that C–S–H exhibits a logarithmic creep that depends only on the packing of 3 structurally distinct but compositionally similar C–S–H forms: low density, high density, ultra-high density. We demonstrate that the creep rate (≈1/t) is likely due to the rearrangement of nanoscale particles around limit packing densities following the free-volume dynamics theory of granular physics. These findings could lead to a new basis for nanoengineering concrete materials and structures with minimal creep rates monitored by packing density distributions of nanoscale particles, and predicted by nanoscale creep measurements in some minute time, which are as exact as macroscopic creep tests carried out over years. PMID:19541652

  5. Historic Concrete : From Concrete Repair to Concrete Conservation

    NARCIS (Netherlands)

    Heinemann, H.A.

    2013-01-01

    Concrete like materials were already applied during the Roman Empire. After the decline of the Roman Empire, a wide scale application of concrete only reappeared in the 19th century. Here lies also the origin of modern (reinforced) concrete. Since then, both concrete application and composition have

  6. Concrete Memories

    DEFF Research Database (Denmark)

    Wiegand, Frauke Katharina

    2015-01-01

    and poetic appropriations and inscriptions of the bunker site are depicted. Ranging between overlooked side presences and an overwhelming visibility, the concrete remains of fascist war architecture are involved in and motivate different sensuous experiences and mnemonic appropriations. The article meets...

  7. Void structure of concrete with superabsorbent polymers and its relation to frost resistance of concrete

    DEFF Research Database (Denmark)

    Hasholt, Marianne Tange; Jensen, Ole Mejlhede; Laustsen, Sara

    2013-01-01

    surfactant prior to concrete mixing. The method comprises rinsing of the SAP with ethanol. This effectively removes the surfactant. Freeze-thaw testing of concrete with rinsed and non-rinsed SAP shows that for equal dosages of SAP, the extra air entrained due to surfactant is considerable and can make......Superabsorbent polymers (SAP) can be used to control air void formation in concrete. However, due to surfactant left on suspension polymerized SAP particles during production, they may not only create SAP voids but also entrain extra air. In the present investigation, a method is tested to remove...... the difference between poor and satisfactory frost-resistance. Furthermore, the results indicate that voids created directly by SAP protect concrete against frost deterioration just like other air voids; if the concrete contains enough SAP voids, these alone can provide sufficient frost resistance. © 2013 RILEM....

  8. Strategies to overcome post-harvest physiological deterioration in ...

    African Journals Online (AJOL)

    Cassava roots are notorious for their short shelf life due to Post-harvest physiological deterioration (PPD) leading to significant economic losses. PPD - a rapid oxidative reaction that initiates in cassava roots within 24 to 48 hours after harvest, discolouring them, thereby renders them unmarketable and unpalatable.

  9. Experiment Analysis of Concrete’s Mechanical Property Deterioration Suffered Sulfate Attack and Drying-Wetting Cycles

    Directory of Open Access Journals (Sweden)

    Wei Tian

    2017-01-01

    Full Text Available The mechanism of concrete deterioration in sodium sulfate solution is investigated. The macroperformance was characterized via its apparent properties, mass loss, and compressive strength. Changes in ions in the solution at different sulfate attack periods were tested by inductively coupled plasma (ICP. The damage evolution law, as well as analysis of the concrete’s meso- and microstructure, was revealed by scanning electron microscope (SEM and computed tomography (CT scanning equipment. The results show that the characteristics of concrete differed at each sulfate attack period; the drying-wetting cycles generally accelerated the deterioration process of concrete. In the early sulfate attack period, the pore structure of the concrete was filled with sulfate attack products (e.g., ettringite and gypsum, and its mass and strength increased. The pore size and porosity decreased while the CT number increased. As deterioration progressed, the swelling/expansion force of products and the salt crystallization pressure of sulfate crystals acted on the inner wall of the concrete to accumulate damage and accelerate deterioration. The mass and strength of concrete sharply decreased. The number and volume of pores increased, and the pore grew more quickly resulting in initiation and expansion of microcracks while the CT number decreased.

  10. Impact Capacity Reduction in Railway Prestressed Concrete Sleepers with Surface Abrasions

    Science.gov (United States)

    Ngamkhanong, Chayut; Li, Dan; Kaewunruen, Sakdirat

    2017-10-01

    Railway sleepers (also called ‘railroad tie’ in North America) embedded in ballasted railway tracks are a main part of railway track structures. Its important role is to transfer the loads evenly from the rails to a wider area of ballast bed and to secure rail gauge and enable safe passages of rolling stocks. By nature, railway infrastructure is nonlinear, evidenced by its behaviours, geometry and alignment, wheel-rail contact and operational parameters such as tractive efforts. Based on our critical review, the dynamic behaviour of railway sleepers has not been fully investigated, especially when the sleepers are deteriorated by excessive wears. In fact, the ballast angularity causes differential abrasions on the soffit or bottom surface of sleepers (especially at railseat zone). Furthermore, in sharp curves and rapid gradient change, longitudinal and lateral dynamics of rails increase the likelihood of railseat abrasions in concrete sleepers due to the unbalanced loading conditions. This paper presents a structural capacity of concrete sleepers under dynamic transient loading. The modified compression field theory for ultimate strength design of concrete sleepers under impact loading will be highlighted in this study. The influences of surface abrasions, including surface abrasion and soffit abrasion, on the dynamic behaviour of prestressed concrete sleepers, are firstly highlighted. The outcome of this study will improve the rail maintenance and inspection criteria in order to establish appropriate and sensible remote track condition monitoring network in practice. Moreover, this study will also improve the understanding of the fundamental dynamic behaviour of prestressed concrete sleepers with surface abrasions. The insight into these behaviours will not only improve safety and reliability of railway infrastructure but will enhance the structural safety of other concrete structures.

  11. High Performance Concrete

    Directory of Open Access Journals (Sweden)

    Traian Oneţ

    2009-01-01

    Full Text Available The paper presents the last studies and researches accomplished in Cluj-Napoca related to high performance concrete, high strength concrete and self compacting concrete. The purpose of this paper is to raid upon the advantages and inconveniences when a particular concrete type is used. Two concrete recipes are presented, namely for the concrete used in rigid pavement for roads and another one for self-compacting concrete.

  12. Dynamic Response of Concrete and Concrete Structures

    Science.gov (United States)

    1984-01-26

    low - . AFOSR-T... 84-0.165 DYNAMIC RESPONSE OF CONCRETE AND CONCRETE STRUCTURES FIRST ANNUAL TECHNICAL REPORT LAWRENCE E. 14ALVERN C. ALLEN ROSS...and Subtitle) S. TYPE OF REPORT I PERIOD COVERED DYNAMIC RESPONSE OF CONCRETE 1 DEC 1982 - 30 NOV 1983 AND CONCRETE STRUCTURES I_____198__-__0_NOV_198...Bar Dynamic Loads Fracture Materials Testing Dynamic Properties Impact Rate Effects Dynamic Testing Hopkinson Bar Reinforced Concrete Structures 20

  13. Hemp concretes

    OpenAIRE

    de Bruijn, Paulien

    2008-01-01

    Hemp (Cannabis sativa) is an agricultural crop that can be used as a building material in combination with lime and cement. A composite building material that combines a cementitious binder (building limes and cement) with hemp shives, the woody core of the hemp stalk is generally referred to as hemp concrete (HC). However, industrial facilities to separate hemp shives and fibres are currently not available in Sweden. HC has many advantages as a building material but it is not load-bearing an...

  14. THE STUDY ON THE DURABILITY OF SUBMERGED STRUCTURE DISPLACEMENT DUE TO CONCRETE FAILURE

    Directory of Open Access Journals (Sweden)

    M. Mohd

    2016-09-01

    Full Text Available Concrete structures that exposed to marine environments are subjected to multiple deterioration mechanisms. An overview of the existing technology for submerged concrete, pressure resistant, concrete structures which related such as cracks, debonds, and delamination are discussed. Basic knowledge related to drowning durability such as submerged concrete structures in the maritime environment are the durability of a concrete and the ability to resist to weathering, chemical attack, abrasion or other deterioration processes. The measuring techniques and instrumentation for geometrical monitoring of submerged structural displacements have traditionally been categorized into two groups according to the two main groups, namely as geodetic surveying and geotechnical structural measurements of local displacements. This paper aims to study the durability of submerged concrete displacement and harmful effects of submerged concrete structures.

  15. Gates Precast Concrete User Project Phase 1

    Energy Technology Data Exchange (ETDEWEB)

    Love, Lonnie J. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Post, Brian K. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Roschli, Alex C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Chesser, Phillip C. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

    2017-09-01

    The primary objective of the project was to demonstrate the viability of using carbon fiber reinforced ABS plastic and the Big Area Additive Manufacturing (BAAM) technology to rapidly manufacture molds for the precast concrete industry.

  16. Properties of Concrete Mixes with Carwash Wastewater

    Directory of Open Access Journals (Sweden)

    Shahidan Shahiron

    2017-01-01

    Full Text Available The rapid growth of the car wash industry today results in the need for wastewater reclamation. Thus, this paper aims to investigate the effect of using car wash wastewater on concrete properties in terms of mechanical properties. The basic characteristics of wastewater were investigated according to USEPA (Method 150.1 & 3 00.0 while the mechanical properties of concrete with car wash wastewater were compared according to ASTM C1602 and BS EN 1008 standards. In this research, the compressive strength, modulus of elasticity and tensile strength were studied. The percentages of wastewater replaced in the concrete mix ranged from 0% up to 40%. In addition, the results also suggest that the concrete with 20% car wash wastewater achieved the highest compressive strength and modulus of elasticity compared to other compositions of wastewater. Moreover, the results also recommended that concrete mixed with car wash wastewater has better compressive strength compared to conventional concrete.

  17. Evaluation of concrete pavements with materials-related distress : appendix D.

    Science.gov (United States)

    2010-03-02

    An evaluation of cores sampled from six concrete pavements was performed. Factors contributing to pavement distress observed in the field were determined, including expansive alkali-silica reactivity and freeze-thaw deterioration related to poor entr...

  18. Methods for Detecting Defects in Composite Rehabilitated Concrete Structures : Final Report

    Science.gov (United States)

    2005-04-01

    Fiber reinforced polymer (FRP) composites are increasingly being used to rehabilitate under-strength or deteriorating concrete structural elements and to prolong useful service-life of bridge structures. The rehabilitation is conducted through the ex...

  19. Evaluation of concrete pavements with materials-related distress : appendix E.

    Science.gov (United States)

    2010-03-02

    An evaluation of cores sampled from six concrete pavements was performed. Factors contributing to pavement distress observed in the field were determined, including expansive alkali-silica reactivity and freeze-thaw deterioration related to poor entr...

  20. Evaluation of concrete pavements with materials-related distress : appendix C.

    Science.gov (United States)

    2010-03-02

    An evaluation of cores sampled from six concrete pavements was performed. Factors contributing to pavement distress observed in the field were determined, including expansive alkali-silica reactivity and freeze-thaw deterioration related to poor entr...

  1. Evaluation of treatment options for ASR-affected concrete : final report, December 11, 2009.

    Science.gov (United States)

    2009-12-11

    This research project was undertaken to evaluate the potential of using surface treatments including lithium nitrate, : sodium tartarate, siloxanes, silane, and boiled linseed oil to mitigate or slow the rate of concrete deterioration : associated wi...

  2. Molecular analysis of differentially expressed genes during postharvest deterioration in cassava (Manihot esculenta Crantz) tuberous roots

    NARCIS (Netherlands)

    Huang, J.; Bachem, C.W.B.; Jacobsen, E.; Visser, R.

    2001-01-01

    One of the major problems for cassava is the rapid deterioration after harvesting cassava tuberous roots, which limits the possibilities for production and distribution of cassava in the world. Postharvest deterioration is an inherent problem for cassava since wounding and mechanical damage of the

  3. Concrete evidence

    Energy Technology Data Exchange (ETDEWEB)

    Provis, J.; Duxson, P.; van Deventer, J. [University of Melbourne, Vic. (Australia)

    2008-11-15

    The time is right for a revolution in the cement industry which is responsible for 5-8% of all human-derived carbon dioxide emissions. Zeobond, an Australian company, has developed E-Crete which is a geopolymer concrete using fly ash and blast furnace slags which reduces CO{sub 2} emissions by 80% from the 0.67t of CO{sub 2} per ton of cement emitted by the Australian triple blend of cement, fly ash and slag. The article discusses the products development, standards for cements and challenges to the commercialization of E-Crete. 5 refs., 3 figs.

  4. Concrete construction engineering handbook

    CERN Document Server

    Nawy, Edward G

    2008-01-01

    Provides coverage of concrete construction engineering and technology. This work features discussions focusing on: the advances in engineered concrete materials; reinforced concrete construction; specialized construction techniques; and, design recommendations for high performance.

  5. Evaluation offreeze-thaw damage in concrete by ultrasonic imaging

    OpenAIRE

    Molero, Miguel; Aparicio, S.; Al‐Assadi, Ghaida; Casati Calzada, María Jesús; Hernández, M. G.; Anaya, J. J.

    2012-01-01

    This work studies the use of ultrasonic imaging as an evaluation tool in concrete subjected to freeze–thaw (F–T) cycles. To evaluate the damage in this deterioration process, ultrasonic velocity and attenuation images have been generated from concrete specimens with and without air-entraining agents. Two parameters have been proposed from these ultrasonic images according to our experimental setup: the non-assessable area proportion (NAAP) and a weighted average velocity in terms of the NAAP....

  6. [Cognitive deterioration in Parkinson's disease].

    Science.gov (United States)

    Perea-Bartolomé, M V

    Whether there are mental changes in Parkinson s disease (EP) or not, has been a confused and contradictory subject since the earliest studies and semiological definition of the disorder. James Parkinson himself, in his study An essay on the shaking palsy (1817), stated that in the condition he described, the sense and intellect were not damaged. Thanks to the development of cognitive neuropsychology, at the present time there are rather more precise concepts regarding this fascinating area of neurology. We give a summary, as schematic as possible, of theory relating to the known data. 1. The presence or absence of cognitive deterioration in EP 2. The neuropsychological characteristics of cognitive involvement in EP, cognitive defects in incipient EP and in established EP. 3. The risk factor involved in the occurrence of cognitive deterioration. This knowledge should be used for better understanding of the patient s mental state at every stage of the disease, during follow up studies and for the neuro conductual therapeutic and socio familial approach in each case.

  7. Recycled concrete aggregate in portland cement concrete.

    Science.gov (United States)

    2013-01-01

    Aggregates can be produced by crushing hydraulic cement concrete and are known as recycled concrete : aggregates (RCA). This report provides results from a New Jersey Department of Transportation study to identify : barriers to the use of RCA in new ...

  8. The Future Concrete: Self-Compacting Concrete

    OpenAIRE

    Liana Iureş; Corneliu Bob

    2010-01-01

    The paper presents the characteristics of the self-compacting concretes, their advantages and disadvantages when they are used in buildings. Due to its properties and composition, the self-compacting concrete is described here as being one of the future friendly enviromental material for buildings. Tests concerning to obtaining a self-compacting concrete, together with the specific fresh concrete properties tests, are described.

  9. The Future Concrete: Self-Compacting Concrete

    Directory of Open Access Journals (Sweden)

    Liana Iureş

    2010-01-01

    Full Text Available The paper presents the characteristics of the self-compacting concretes, their advantages and disadvantages when they are used in buildings. Due to its properties and composition, the self-compacting concrete is described here as being one of the future friendly enviromental material for buildings. Tests concerning to obtaining a self-compacting concrete, together with the specific fresh concrete properties tests, are described.

  10. Concrete durability

    Directory of Open Access Journals (Sweden)

    Gaspar Tébar, Demetrio

    1991-03-01

    Full Text Available The evidence that the concrete is not a material for ever was noticed from the beginning of its industrial use. In the present work, the author describes the studies carried out during the last century and the early ages of the present one, mainly devoted to the study of the durability in sea water. At the present days, and in spite of the numerous papers published from then, the study of the concrete durability continues focusing the research priorities and economical resources of researchers and industries related with this material. Moreover, the new laboratory techniques are allowing to understand old problems and even to open again the discussion on reaction mechanisms which were believed to be completely understood. The article finalizes with a brief description of the numerous studies carried out at the Institute Eduardo Torroja on concrete durability, mainly those related with the resistance against gypsum attack (so abundant in our country land and against sea water attack.

    La realidad de que el hormigón no es un material eterno y es susceptible de sufrir ataques por agentes químicos, fue constatada desde el comienzo mismo de su uso industrial. En el presente trabajo el autor enumera los estudios realizados el siglo pasado y a comienzos del presente sobre la durabilidad del hormigón en agua de mar. En la actualidad y a pesar de los numerosos trabajos desarrollados desde entonces, el estudio de la durabilidad del hormigón sigue centrando la atención prioritaria y los recursos económicos de los investigadores e industrias relacionadas con este material. Además las nuevas técnicas de estudio están permitiendo comprender antiguos problemas e incluso reabrir la discusión sobre mecanismos de reacción que se creían completamente explicados. Finaliza el artículo con una descripción somera de los múltiples trabajos realizados en el Instituto Eduardo Torreja sobre la materia, en especial los estudios realizados sobre

  11. A Realistic Digital Deteriorating Patient to Foster Emergency Decision-Making Skills in Medical Students

    DEFF Research Database (Denmark)

    Blanchard, Emmanuel G.; Wiseman, Jeffrey; Naismith, Laura

    2012-01-01

    The Deteriorating Patient Activity (DPA) is a real-life educational simulation that prepares medical students to effectively approach emergency situations through a role play where their instructor plays the role of a patient whose state is rapidly deteriorating. Although proven engaging and effe......The Deteriorating Patient Activity (DPA) is a real-life educational simulation that prepares medical students to effectively approach emergency situations through a role play where their instructor plays the role of a patient whose state is rapidly deteriorating. Although proven engaging...... and effective in improving student decision making, DPA is difficult to carry out since it requires students and medical instructors, all busy people, to be available at the same time and location. The present paper describes the “Digital” Deteriorating Patient Activity (DDPA), an agent-based tutoring system...

  12. Performance of Microbial Concrete Developed Using Bacillus Subtilus JC3

    Science.gov (United States)

    Rao, M. V. Seshagiri; Reddy, V. Srinivasa; Sasikala, Ch.

    2017-12-01

    Concrete is vulnerable to deterioration, corrosion, and cracks, and the consequent damage and loss of strength requires immensely expensive remediation and repair. So need for special concrete that they would respond to crack formation with an autonomous self-healing action lead to research and development of microbial concrete. The microbial concrete works on the principle of calcite mineral precipitation by a specific group of alkali-resistant spore-forming bacteria related to the genus Bacillus called Bacillus subtilis JC3, this phenomenon is called biomineralization or Microbiologically Induced Calcite Crystal Precipitation. Bacillus subtilis JC3, a common soil bacterium, has inherent ability to precipitate calcite crystals continuously which enhances the strength and durability performance of concrete enormously. This microbial concrete can be called as a "Self healing Bacterial Concrete" because it can remediate its cracks by itself without any human intervention and would make the concrete more durable and sustainable. This paper discuss the incorporation of microorganism Bacillus subtilis JC3 (developed at JNTU, India) into concrete and presents the results of experimental investigations carried out to study the improved durability and sustainability characteristics of microbial concrete.

  13. Review of concrete biodeterioration in relation to nuclear waste.

    Science.gov (United States)

    Turick, Charles E; Berry, Christopher J

    2016-01-01

    Storage of radioactive waste in concrete structures is a means of containing wastes and related radionuclides generated from nuclear operations in many countries. Previous efforts related to microbial impacts on concrete structures that are used to contain radioactive waste showed that microbial activity can play a significant role in the process of concrete degradation and ultimately structural deterioration. This literature review examines the research in this field and is focused on specific parameters that are applicable to modeling and prediction of the fate of concrete structures used to store or dispose of radioactive waste. Rates of concrete biodegradation vary with the environmental conditions, illustrating a need to understand the bioavailability of key compounds involved in microbial activity. Specific parameters require pH and osmotic pressure to be within a certain range to allow for microbial growth as well as the availability and abundance of energy sources such as components involved in sulfur, iron and nitrogen oxidation. Carbon flow and availability are also factors to consider in predicting concrete biodegradation. The microbial contribution to degradation of the concrete structures containing radioactive waste is a constant possibility. The rate and degree of concrete biodegradation is dependent on numerous physical, chemical and biological parameters. Parameters to focus on for modeling activities and possible options for mitigation that would minimize concrete biodegradation are discussed and include key conditions that drive microbial activity on concrete surfaces. Copyright © 2015. Published by Elsevier Ltd.

  14. Electrical Resistivity of Concrete for Durability Evaluation: A Review

    Directory of Open Access Journals (Sweden)

    Pejman Azarsa

    2017-01-01

    Full Text Available Degradation processes in reinforced concrete structures that affect durability are partially controlled by transport of aggressive ions through the concrete microstructure. Ions are charged and the ability of concrete to hold out against transfer of ions greatly relies on its electrical resistivity. Hence, a connection could be expected between electrical resistivity of concrete and the deterioration processes such as increase in permeability and corrosion of embedded steel. Through this paper, an extensive literature review has been done to address relationship between concrete electrical resistivity and its certain durability characteristics. These durability characteristics include chloride diffusivity and corrosion of reinforcement as these have major influence on concrete degradation process. Overall, there exists an inverse or direct proportional correlation between these parameters. Evaluated results, from measuring the concrete electrical resistivity, can also be used as a great indicator to identify early age characteristics of fresh concrete and for evaluation of its properties, determination of moisture content, connectivity of the micropores, and even condition assessment of in-service structures. This paper also reviews and assesses research concerning the influential parameters such as environmental conditions and presence of steel rebar and cracks on measuring electrical resistivity of concrete. Moreover, concrete resistivity concept, application, and its various measurement techniques are introduced.

  15. Refractory concretes

    Science.gov (United States)

    Holcombe, Jr., Cressie E.

    1979-01-01

    Novel concrete compositions comprise particles of aggregate material embedded in a cement matrix, said cement matrix produced by contacting an oxide selected from the group of Y.sub.2 O.sub.3, La.sub.2 O.sub.3, Nd.sub.2 O.sub.3, Sm.sub.2 O.sub.3, Eu.sub.2 O.sub.3 and Gd.sub.2 O.sub.3 with an aqueous solution of a salt selected from the group of NH.sub.4 NO.sub.3, NH.sub.4 Cl, YCl.sub.3 and Mg(NO.sub.3).sub.2 to form a fluid mixture; and allowing the fluid mixture to harden.

  16. Concrete spirituality

    Directory of Open Access Journals (Sweden)

    Johannes N.J. Kritzinger

    2014-02-01

    Full Text Available This article reflects on a number of liturgical innovations in the worship of Melodi ya Tshwane, an inner-city congregation of the Uniting Reformed Church in Southern Africa (URCSA. The focus of the innovations was to implement the understanding of justice in Article 4 of the Confession of Belhar, a confessional standard of the URCSA. The basic contention of the article is that well designed liturgies that facilitate experiences of beauty can nurture a concrete spirituality to mobilise urban church members for a justice-seeking lifestyle. After exploring the message of Article 4 of Belhar, the article analyses eight liturgical features of Melodi ya Tshwane, showing how beauty and justice interact in those acts of worship.

  17. Investigation of the internal stresses caused by delayed ettringite formation in concrete.

    Science.gov (United States)

    2008-11-01

    Delayed ettringite formation (DEF) in concrete has been identified in recent as a significant cause of deterioration in : some of the reinforced concrete infrastructure in Texas. This report is part of a research project, TxDOT project : 5218, to inv...

  18. Tension Pneumocephalus with Diplegia and Deterioration of Consciousness

    Directory of Open Access Journals (Sweden)

    Harald Prüss

    2011-02-01

    Full Text Available Tension pneumocephalus results from intracranial air under pressure as a rare complication after head injury or craniofacial surgery. A 58-year-old man underwent ethmoid sinus surgery and subsequently developed rapidly progressive global headache, restlessness, diplegia with sensory loss, and deterioration of the conscious level. A head CT demonstrated extensive pneumocephalus with gross compression of the brain. The frontal retention of air caused widening of the interhemispheric fissure leading to a peaked appearance of the frontal poles, referred to as the ‘Mount Fuji sign’. Surgical revision of a dural air leak resulted in rapid improvement and full clinical resolution. Early diagnosis of tension pneumocephalus and emergent surgical treatment are crucial to prevent life-threatening deterioration.

  19. Tension pneumocephalus with diplegia and deterioration of consciousness.

    Science.gov (United States)

    Prüss, Harald; Klingebiel, Randolf; Endres, Matthias

    2011-02-14

    Tension pneumocephalus results from intracranial air under pressure as a rare complication after head injury or craniofacial surgery. A 58-year-old man underwent ethmoid sinus surgery and subsequently developed rapidly progressive global headache, restlessness, diplegia with sensory loss, and deterioration of the conscious level. A head CT demonstrated extensive pneumocephalus with gross compression of the brain. The frontal retention of air caused widening of the interhemispheric fissure leading to a peaked appearance of the frontal poles, referred to as the 'Mount Fuji sign'. Surgical revision of a dural air leak resulted in rapid improvement and full clinical resolution. Early diagnosis of tension pneumocephalus and emergent surgical treatment are crucial to prevent life-threatening deterioration.

  20. Acoustic Emission Analysis of Prestressed Concrete Structures

    Science.gov (United States)

    Elfergani, H. A.; Pullin, R.; Holford, K. M.

    2011-07-01

    Corrosion is a substantial problem in numerous structures and in particular corrosion is very serious in reinforced and prestressed concrete and must, in certain applications, be given special consideration because failure may result in loss of life and high financial cost. Furthermore corrosion cannot only be considered a long term problem with many studies reporting failure of bridges and concrete pipes due to corrosion within a short period after they were constructed. The concrete pipes which transport water are examples of structures that have suffered from corrosion; for example, the pipes of The Great Man-Made River Project of Libya. Five pipe failures due to corrosion have occurred since their installation. The main reason for the damage is corrosion of prestressed wires in the pipes due to the attack of chloride ions from the surrounding soil. Detection of the corrosion in initial stages has been very important to avoid other failures and the interruption of water flow. Even though most non-destructive methods which are used in the project are able to detect wire breaks, they cannot detect the presence of corrosion. Hence in areas where no excavation has been completed, areas of serious damage can go undetected. Therefore, the major problem which faces engineers is to find the best way to detect the corrosion and prevent the pipes from deteriorating. This paper reports on the use of the Acoustic Emission (AE) technique to detect the early stages of corrosion prior to deterioration of concrete structures.

  1. Reinforced concrete bridges: effects due to corrosion and concrete young modulus variation

    Directory of Open Access Journals (Sweden)

    P. T. C. Mendes

    Full Text Available Most of the Brazilian bridges of federal road network are made of reinforced concrete and are more than 30 years old, with little information about the mechanical properties of their constitutive materials. Along the service life of these bridges much modification occurred on vehicles load and geometry and in design standard. Many of them show signs of concrete and steel deterioration and their stability conditions are unknown. With the aim of contributing to the structural evaluation of reinforced concrete bridges it was decided to analyze the stresses in reinforced concrete bridge sections to verify the effects due to reinforcement corrosion and variation of the concrete Young modulus on the stress distribution regarding several load patterns and cracking effects in a representative bridge of the Brazilian road network with different longitudinal reinforcement taxes and two concrete Young modulus, Ec and 0.5Ec, and with different percentage of reinforcement corrosion. The analysis considered two finite element models: frame and shell elements as well as solid elements. The results indicate that these variation effects are more significant in reinforcement bars than in concrete.

  2. Repair, Evaluation, Maintenance, and Rehabilitation Research Program. Inspection of the Engineering Condition of Underwater Concrete Structures.

    Science.gov (United States)

    1989-04-01

    UNDERWATER CONCRETE STRUCTURES by Sandor Popovics Drexel University .!, Philadelphia, Pennsylvania 19104 and Willie E. McDonald Structures Laboratory...Tit TC)F> Ur1~:,JN: tr Q,;)r- i frer riSpe CtiOn of structulres in tiir- BOTTr;M Effoit, f 4 1kali -slca rpa(.to)r in concrete structures Unclassified...works structures. Specific objectives are: (a) to summarize the typical types of deterioration that occur in underwater concrete structures ; (b) to

  3. Flexible concrete link slabs used as expansion joints in bridge decks

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi; Fischer, Gregor

    2011-01-01

    of water through the expansion joint and subsequent corrosion of girders and girder bearings. Investigations on joint-less superstructures using conventional steel reinforcement in so-called concrete link slabs indicate improved performance and economic feasibility. However, this concept requires...... reinforcement serves as a flexible concrete element between the adjacent deck segments. The use of an Engineered Cementitious Composite (ECC) material instead of conventional concrete significantly reduces crack widths under service conditions and prevents deterioration of the link slab in the tension...

  4. Application of Idealized Materials Data for Calculation of Fire Exposed Concrete Constructions

    DEFF Research Database (Denmark)

    Hertz, Kristian Dahl

    2003-01-01

    and walls have recently been made extending the field of application to light aggregate concrete constructions as well. The Eurocode ENV1992-1-2 and the Danish code for concrete constructions DS411 have adopted the basics of the methods; but these codes are mainly focused on standard fire performance and do......The author has developed a system of methods for calculation of the load bearing capacity of concrete constructions at any time of any fully developed fire including the time of maximum temperature of a standard fire as a special case. The methods have been derived based on materials data from 180...... of the basic processes deteriorating concrete at elevated temperatures, and examples of idealized mechanical properties are given for a variety of concretes spanning from fire resistant concrete over heavy concretes with different aggregates to light aggregate concrete. It is explained how these data can...

  5. Self-Compacting Concrete

    OpenAIRE

    Okamura, Hajime; Ouchi, Masahiro

    2003-01-01

    Self-compacting concrete was first developed in 1988 to achieve durable concrete structures. Since then, various investigations have been carried out and this type of concrete has been used in practical structures in Japan, mainly by large construction companies. Investigations for establishing a rational mix-design method and self-compactability testing methods have been carried out from the viewpoint of making self-compacting concrete a standard concrete.

  6. FEM-models of cathodic protection systems for concrete structures

    NARCIS (Netherlands)

    Bertolini, L.; Lollini, F.; Redaelli, E.; Polder, R.B.; Peelen, W.H.A.

    2008-01-01

    A significant number of reinforced concrete structures shows deterioration due to the reinforcement corrosion and requires interventions to guarantee their residual service life. A wide range of maintenance options is available, among which cathodic protection (CP) has been found to be a successful

  7. Assessment of the Reliability Profiles for Concrete Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    In this paper calculation of reliability profiles is discussed. ULS as well as SLS limit states are formulated. Corrosion due to chloride penetration is the considered deterioration mechanism. Three models for corrosion are formulated. A definition of service lifetime for concrete bridges...

  8. On Reliability Based Optimal Design of Concrete Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle

    In recent years important progress has been made in assessment of the lifetime behaviour of concrete bridges. Due to the large uncertainties related to the loading and the deterioration of such bridges, an assessment based on stochastic modelling of the significant parameters seems to be only rel...

  9. Bacteria-based self-healing concrete : Introduction

    NARCIS (Netherlands)

    Mors, R.M.; Jonkers, H.M.

    2012-01-01

    Concrete in most structures is designed to crack in order to let embedded steel reinforcement take over tensile stresses. Crack formation is also a typical phenomenon related to durability. Percolation of cracks may lead to leakage problems or ingress of deleterious materials, causing deterioration

  10. Experimental and numerical investigation of chloride ingress in cracked concrete

    NARCIS (Netherlands)

    Šavija, B.

    2014-01-01

    Chloride induced corrosion of reinforcing steel is recognized as the most common deterioration mechanism affecting reinforced concrete structures. As such, it has been in focus of research for more than thirty years. Numerous studies of chloride ingress, corrosion initiation, and corrosion

  11. Unbonded portland cement concrete overlay/pavement monitoring with integrated grating and scattering optical fiber sensors.

    Science.gov (United States)

    2014-06-01

    This report summarizes the findings and results from a laboratory and field study on the strain distribution : and crack development in 3 thick concrete panels cast on top of existing concrete pavements as a rapid : rehabilitation strategy for roa...

  12. Waste steel wires modified structural lightweight concrete

    OpenAIRE

    Aghaee, Kamran; Yazdi,Mohammad Ali

    2014-01-01

    Nowadays, the use of different waste fibers in concrete has started to increase rapidly due to some reasons such as economic savings and positive effects on the environment. In this study, waste steel wires taken from reinforcement and formwork which were previously utilized in construction projects, were employed in structural lightweight concrete (SLWC). The objective was to investigate the possibility of using this type of fiber as reinforcement in the SLWC. Compressive, tensile, flexural ...

  13. Properties of Concrete Mixes with Carwash Wastewater

    OpenAIRE

    Shahidan Shahiron; Senin Mohamad Syamir; Abdul Kadir Aeslina Binti; Yee Lau Hai; Ali Noorwirdawati

    2017-01-01

    The rapid growth of the car wash industry today results in the need for wastewater reclamation. Thus, this paper aims to investigate the effect of using car wash wastewater on concrete properties in terms of mechanical properties. The basic characteristics of wastewater were investigated according to USEPA (Method 150.1 & 3 00.0) while the mechanical properties of concrete with car wash wastewater were compared according to ASTM C1602 and BS EN 1008 standards. In this research, the compressiv...

  14. Thaumasite formation in concrete and mortars containing fly ash

    Energy Technology Data Exchange (ETDEWEB)

    D.M. Mulenga; J. Stark; P. Nobst [Bauhaus-University, Weimar (Germany). F.A. Finger-Institute of Material Sciences

    2003-12-01

    Due to recent reports on deterioration of concrete structures, the thaumasite form of sulfate attack has become a subject of study and close investigation. This paper investigates the formation of thaumasite in concrete and mortars containing fly ash. The results show that thaumasite formation can occur within 84 days of exposure to sulfate solutions. High volumes of fly ash can limit or promote thaumasite formation depending on the type of cement used. Thaumasite and ettringite were found among the deterioration products. However, the thaumasite formation in the specimen prepared from sulfate resisting Portland cement was not accompanied by deterioration, except by 50% fly ash addition. The mixtures of Portland limestone cement with 40% fly ash exhibited a very limited thaumasite formation while the mixtures with 50% had no thaumasite at all. It is concluded that thaumasite can also be formed in mixtures incorporating fly ash.

  15. 40 CFR 1033.245 - Deterioration factors.

    Science.gov (United States)

    2010-07-01

    ...-hour test point. For example, if you use aftertreatment technology that controls emissions of a... CONTROLS CONTROL OF EMISSIONS FROM LOCOMOTIVES Certifying Engine Families § 1033.245 Deterioration factors... testing of similar locomotives. (b) Deterioration factors may be additive or multiplicative. (1) Additive...

  16. Ultrasound Transmission Times in Biologically Deteriorated Wood

    Science.gov (United States)

    Christopher Adam Senalik; Robert J. Ross; Rodney DeGroot

    2015-01-01

    The use of a variety of stress wave transmission techniques for the in-service condition assessment of deteriorated wood is well documented. This paper summarizes results from an extensive study designed to examine the relationship between ultrasound transmission times and the deterioration of exposed wood. Two hundred seventy (270) southern pine lumber specimens were...

  17. Geoenvironmental weathering/deterioration of landfilled MSWI-BA glass.

    Science.gov (United States)

    Wei, Yunmei; Saffarzadeh, Amirhomayoun; Shimaoka, Takayuki; Zhao, Chun; Peng, Xuya; Gao, Junmin

    2014-08-15

    Municipal solid waste incineration bottom ash (MSWI-BA) glass serves as a matrix of assorted bottom ash (BA) compounds. Deterioration of the BA glass phases is quite important as they regulate the distribution of a series of toxic elements. This paper studied landfilled MSWI-BA samples from the mineralogical and geochemical viewpoint to understand the deterioration behavior of the BA glass phases as well as mechanisms involved. Bulk analysis by PXRD as well as micro-scale analysis by optical microscopy and SEM/EDX was conducted for such purposes. The results revealed that dissolution of the BA glass phases has resulted in a deterioration layer of 10(0)-10(2)μm thickness after years of disposal. This rapid weathering process is highly relevant to the specific glass characteristics and solution pH. The BA glass phases with more embedded compounds and cracks/fissures tend to be more vulnerable. Moreover, the generally alkaline pH in ash deposit favors a rapid disruption of the glass phase. The weathering products are mainly gel phases (including Al-Si gel, Ca-Al-Si gel, Fe-Al-Si gel etc.) with iron oxide/hydroxide as accessory products. Breakdown of the BA glass phases triggers chemical evolution of the embedded compounds. Based on all the findings above, a model is proposed to illustrate a general evolution trend for the landfilled MSWI-BA glass phases. Copyright © 2014 Elsevier B.V. All rights reserved.

  18. Deterioration of Pracana Dam due to ASR. Main features and repair works

    Energy Technology Data Exchange (ETDEWEB)

    Matos, D.S.; Camelo, S. [HIDRORUMO, EDP, Porto (Portugal); Silva, H.S.; Pinho, J.S. [LNEC, Lisboa (Portugal)

    1995-12-31

    Some of the Portuguese concrete dams show evidences of ASR. In majority the phenomena is still benign. However, in a few cases some significant deterioration of ASR type have malfunctions arose. In such cases deteriorations of ASR type have been detected while in the others the ASSR type prevail, depending on the type of aggregate. The paper reports the most important case of ASR in Portuguese concrete dams. Pracana dam is a buttress structures built in 1948-51, being the aggregates predominantly of quartzitic and metapellitic nature. Subsequently to the intense fracturing due to a quick concrete cooling during the first filling of the reservoir, high levels of expansion rates had been detected by means of monitoring system. After 8 years emptied reservoir, rehabilitation works took place in 1991-92 aiming at the concrete mass regeneration and the installation of an upstream face membrane, the improvement of spillway capacity and of the foundation performances. The behaviour of the dam as well as the performed tests (petrographic, mechanic, ultrasonic and expansibility ones) and repair works are described in the paper.

  19. Fibre Concrete 2017

    Science.gov (United States)

    2017-09-01

    9th international conference on fibre reinforced concretes (FRC), textile reinforced concretes (TRC) and ultra-high performance concretes (UHPC) Preface The Fibre Concrete Conference series is held biennially to provide a platform to share knowledge on fibre reinforced concretes, textile concretes and ultra-high performance concretes regarding material properties and behaviour, technology procedures, topics of long-term behaviour, creep, durability; sustainable aspects of concrete including utilisation of waste materials in concrete production and recycling of concrete. The tradition of Fibre Concrete Conferences started in eighties of the last century. Nowadays the conference is organized by the Department of Concrete and Masonry Structures of the Czech Technical University in Prague, Faculty of Civil Engineering. The 9th International Conference Fibre Concrete 2017 had 109 participants from 27 countries all over the world. 55 papers were presented including keynote lectures of Professor Bažant, Professor Bartoš and Dr. Broukalová. The conference program covered wide range of topics from scientific research to practical applications. The presented contributions related to performance and behaviour of cement based composites, their long-term behaviour and durability, sustainable aspects, advanced analyses of structures from these composites and successful applications. This conference was organized also to honour Professor Zděnek P. Bažant on the occasion of his jubilee and to appreciate his merits and discoveries in the field of fibre reinforced composites, structural mechanics and engineering.

  20. Experimental and theoretical study of delayed ettringite damage in concrete

    Science.gov (United States)

    Ramadan, Elsaid Osman

    2000-12-01

    An experimental study is conducted to investigate the effect of a range of parameters on concrete expansion and premature deterioration associated with delayed ettringite formation (DEF). These parameters were identified from a comprehensive literature review; they include concrete curing conditions and cement chemistry. Specifically, the study investigated the effect of potassium and magnesium contents as well as the effect of water and steam curing conditions on concrete damage associated with DEF. An accelerated test method for DEF was evaluated and modifications are suggested. Concrete specimens were prepared with varying amounts of potassium and magnesium and subjected to different curing conditions. To accelerate any potential expansion, a beat cycle was employed. The change in length of the specimens was monitored for the duration of the study. Specimens were analyzed using the scanning electron microscope, x-ray dispersive analysis, and x-ray diffraction to determine the mechanism responsible for deterioration. Computed tomography x-ray was also employed as a non-destructive method for examining the internal crack patterns associated with expansion. The expansion data is fitted using the Kohnogorov-Avrami-Johenson-Mehl (KAJM) equation. This theory makes it possible to identify individual expansion processes and to identify the contribution of different expansion mechanisms. All concretes showed expansion following the beat cycle. Subjecting concrete to the heat cycle has a primary role in accelerating expansion. The age at which concrete is subjected to the beat cycle as well as the sample dimensions have a profound effect on the resulting expansion. The use of the concrete prisms as suggested in the modified test method offers a better alternative to cores suggested by Duggan. Increasing the potassium content has a deleterious effect on concrete expansion and premature deterioration and is also associated with dramatic reduction in compressive strength

  1. Properties of Sulfur Concrete.

    Science.gov (United States)

    1979-07-06

    sulfur 19 11 Effect of H2 S on compressive strength of sulfur concretes 21 12 Modulus of rupture vs. temperature for raw sulfur and a sulfur mortar 22 13...sulfur, Jordaan investigated the effects of hydrogen sulfide on sulfur concrete. Concretes were made with different mixtures of pyrrhotite and flyash ...temperature for raw sulfur and a sulfur mortar (Ref. 19). eabove results were obtained with a sulfur mortar and raw sulfur; however, sulfur concrete could be

  2. concrete5 for developers

    CERN Document Server

    Uzayr, Sufyan bin

    2014-01-01

    Whether you have had some previous experience with concrete5 or are entirely new to it, this book will help you understand all that you need to know in order to get started with concrete5 development. A background in PHP is required; some knowledge of HTML/CSS is needed in order to fully grasp the concepts underlying concrete5 theme development.

  3. Self-assembling particle-siloxane coatings for superhydrophobic concrete.

    Science.gov (United States)

    Flores-Vivian, Ismael; Hejazi, Vahid; Kozhukhova, Marina I; Nosonovsky, Michael; Sobolev, Konstantin

    2013-12-26

    We report here, for the first time in the literature, a method to synthesize hydrophobic and superhydrophobic concrete. Concrete is normally a hydrophilic material, which significantly reduces the durability of concrete structures and pavements. To synthesize water-repellent concrete, hydrophobic emulsions were fabricated and applied on portland cement mortar tiles. The emulsion was enriched with the polymethyl-hydrogen siloxane oil hydrophobic agent as well as metakaolin (MK) or silica fume (SF) to induce the microroughness and polyvinyl alcohol (PVA) fibers to create hierarchical surfaces. Various emulsion types were investigated by using different mixing procedures, and single- and double-layer hydrophobic coatings were applied. The emulsions and coatings were characterized with optical microscope and scanning electron microscope (SEM), and their wetting properties, including the water contact angle (CA) and roll-off angle, were measured. A theoretical model for coated and non-coated concrete, which can be generalized for other types of materials, was developed to predict the effect of surface roughness and composition on the CA. An optimized distance between the aggregates was found where the CA has the highest value. The maximal CA measured was 156° for the specimen with PVA fibers treated with MK based emulsion. Since water penetration is the main factor leading to concrete deterioration, hydrophobic water-repellent concretes have much longer durability then regular concretes and can have a broad range of applications in civil and materials engineering.

  4. Durability Study on High Calcium Fly Ash Based Geopolymer Concrete

    Directory of Open Access Journals (Sweden)

    Ganesan Lavanya

    2015-01-01

    Full Text Available This study presents an investigation into the durability of geopolymer concrete prepared using high calcium fly ash along with alkaline activators when exposed to 2% solution of sulfuric acid and 5% magnesium sulphate for up to 45 days. The durability was also assessed by measuring water absorption and sorptivity. Ordinary Portland cement concrete was also prepared as control concrete. The grades chosen for the investigation were M20, M40, and M60. The alkaline solution used for present study is the combination of sodium silicate and sodium hydroxide solution with the ratio of 2.50. The molarity of sodium hydroxide was fixed as 12. The test specimens were 150×150×150 mm cubes, 100×200 mm cylinders, and 100×50 mm discs cured at ambient temperature. Surface deterioration, density, and strength over a period of 14, 28, and 45 days were observed. The results of geopolymer and ordinary Portland cement concrete were compared and discussed. After 45 days of exposure to the magnesium sulfate solution, the reduction in strength was up to 12% for geopolymer concrete and up to 25% for ordinary Portland cement concrete. After the same period of exposure to the sulphuric acid solution, the compressive strength decrease was up to 20% for geopolymer concrete and up to 28% for ordinary Portland cement concrete.

  5. Durability Evaluation in Concrete Using Cracked Permeability and Chloride Permeability Tests

    Directory of Open Access Journals (Sweden)

    V. M. Sounthararajan

    2013-01-01

    Full Text Available The objective of this study is to identify the possibilities of utilizing the quarry dust in concrete to obtain an improved strength and durability properties of concrete. In the present study, the addition of quarry dust as alternative for natural sand has been investigated, and the durability properties of concrete were evaluated systematically by means of cracked water permeability and rapid chloride permeability tests. The permeability of concrete was assessed with initial stress applied to the concrete specimen and later checked for water permeability. Concrete mixes were casted using ordinary river sand and compared with 100% quarry dust substituted concrete. The addition of quarry dust significantly improved the concrete matrix properties in terms of strength and permeability resistance. The addition of fine quarry dust in concrete resulted in improved matrix densification compared to conventional concrete. Matrix densification has been studied qualitatively through petrographical examination using digital optical microscopy.

  6. D-cracking field performance of Portland cement concrete pavements containing limestone in Kansas : phase 1 report.

    Science.gov (United States)

    2012-05-01

    Premature deterioration of concrete pavement due to D-Cracking has been a problem in Kansas since the 1930s. : Limestone is the major source of coarse aggregate in eastern Kansas where the majority of the concrete pavements are : constructed. D-Crack...

  7. D-cracking field performance of portland cement concrete pavements containing limestone in Kansas : phase 1 report : technical summary.

    Science.gov (United States)

    2012-05-01

    Introduction: Premature deterioration of concrete pavement due to D-cracking has been a problem in Kansas since the 1930s. Limestone is the major source of coarse aggregate in eastern Kansas where the majority of the concrete pavements are constructe...

  8. Developing deterioration models for Nebraska bridges.

    Science.gov (United States)

    2011-07-01

    Nebraska Bridge Management System (NBMS) was developed in 1999 to assist in optimizing budget allocation for : the maintenance, rehabilitation and replacement needs of highway bridges. This requires the prediction of bridge : deterioration to calcula...

  9. Deterioration and cost information for bridge management.

    Science.gov (United States)

    2012-05-01

    This study applies contract bid tabulations and elementlevel condition records to develop elementlevel actions, : costs for actions, transition probabilities for models of deterioration of bridge elements, and transition probabilities : for imp...

  10. Recycled Concrete as Aggregate for Structural Concrete Production

    OpenAIRE

    Mirjana Malešev; Vlastimir Radonjanin; Snežana Marinković

    2010-01-01

    A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC) as a control concrete and two types of concrete made with natural fine and recycle...

  11. sugar cane juice as a retarding admixture in concrete production

    African Journals Online (AJOL)

    PROF. BARTH EKWEME

    lightweight aggregate exhibit a higher moisture movement than is the case with normal weight concrete (Neville et al, 2004). In many parts of the world, a combination of high temperatures, low relative humidity and hot wind that blows across the environment result in rapid evaporation of water from fresh concrete surface.

  12. Autogenous Deformation of Concrete

    DEFF Research Database (Denmark)

    Autogenous deformation of concrete can be defined as the free deformation of sealed concrete at a constant temperature. A number of observed problems with early age cracking of high-performance concretes can be attributed to this phenomenon. During the last 10 years , this has led to an increased...... focus on autogenous deformation both within concrete practice and concrete research. Since 1996 the interest has been significant enough to hold international, yearly conferences entirely devoted to this subject. The papers in this publication were presented at two consecutive half-day sessions...... at the American Concrete Institute’s Fall Convention in Phoenix, Arizona, October 29, 2002. All papers have been reviewed according to ACI rules. This publication, as well as the sessions, was sponsored by ACI committee 236, Material Science of Concrete. The 12 presentations from 8 different countries indicate...

  13. Evaluation of a Tramway’s Track Slab in Conventionally Reinforced Concrete or Steel Fibre Concrete

    OpenAIRE

    Zioris, Stavros; Vranjkovina, Alija

    2015-01-01

    The dominant reinforcement used widely for concrete structures is conventional steel bars (rebars). Nevertheless, the perpetual effort toward evolution and development could not exclude the engineering field, thus new innovative and sophisticated methods are introduced. It is true that, due to lack of extended regulations and standards, the fibre reinforced concrete (FRC) was limited to non-structural applications. However, the last years the situation is changing rapidly and already the appl...

  14. Semiempirical Methodology for Estimating the Service Life of Concrete Deck Panels Strengthened with Fiber-Reinforced Polymer

    OpenAIRE

    Eon-Kyoung Kim; Hongseob Oh; Jongsung Sim

    2014-01-01

    Deterioration of concrete bridge decks affects their durability, safety, and function. It is therefore necessary to conduct structural rehabilitation of damaged concrete decks by strengthening them with fiber-reinforced polymer. Of the recent studies on the strengthened structures, most have focused on static behavior; only a few studies have investigated fatigue behavior. Accurate analysis of fatigue in concrete deck performance requires a more realistic simulated moving load. This study dev...

  15. Chloride transport and chloride thresholdvalues-Studies on concretes and mortars with Portland cement and limestone blended cement

    OpenAIRE

    Boubitsas, Dimitrios

    2015-01-01

    Reinforced concrete is one of the most widely used building materials and if it is properly designed and produced, it is an extremely durable material with a service life up to 100 years. However, under certain environmental conditions the service life of reinforced concrete structures is more limited. Deterioration of concrete structure is in most cases caused by the penetration of aggressive media from the surrounding environment. Chloride initiated reinforcement corrosion is one of t...

  16. CONCRETE BASED ON MODIFIED DISPERSE CEMENT SYSTEM

    Directory of Open Access Journals (Sweden)

    D. V. Rudenko

    2016-08-01

    Full Text Available Purpose. The article considers definition of the bond types occurring in a modified cement concrete matrix, and the evaluation of the quality of these links in a non-uniform material to determine the geometrical and physical relationships between the structure and the cement matrix modifiers. Methodology. To achieve this purpose the studies covered the microstructure of dispersed modified concrete cement matrix, the structure formation mechanism of the modified cement concrete system of natural hardening; as well as identification of the methods of sound concrete strength assessment. Findings. The author proposed a model of the spatial structure of the concrete cement matrix, modified by particulate reinforcement crystal hydrates. The initial object of study is a set of volume elements (cells of the cement matrix and the system of the spatial distribution of reinforcing crystallohydrates in these volume elements. It is found that the most dangerous defects such as cracks in the concrete volume during hardening are formed as a result of internal stresses, mainly in the zone of cement matrix-filler contact or in the area bordering with the largest pores of the concrete. Originality. The result of the study is the defined mechanism of the process of formation of the initial strength and stiffness of the modified cement matrix due to the rapid growth of crystallohydrates in the space among the dispersed reinforcing modifier particles. Since the lack of space prevents from the free growth of crystals, the latter cross-penetrate, forming a dense structure, which contributes to the growth of strength. Practical value. Dispersed modifying cement matrix provides a durable concrete for special purposes with the design performance characteristics. The developed technology of dispersed cement system modification, the defined features of its structure formation mechanism and the use of congruence principle for the complex of technological impacts of physical

  17. 40 CFR 52.1929 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1929 Section 52.1929 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) Regulation for preventing significant deterioration of air... preventing significant deterioration of air quality. ...

  18. Proposal for the Evaluation of Eco-Efficient Concrete

    Directory of Open Access Journals (Sweden)

    Taehyoung Kim

    2016-07-01

    Full Text Available The importance of environmental consequences due to diverse substances that are emitted during the production of concrete is recognized, but environmental performance tends to be evaluated separately from the economic performance and durability performance of concrete. In order to evaluate concrete from the perspective of sustainable development, evaluation technologies are required for comprehensive assessment of environmental performance, economic performance, and durability performance based on a concept of sustainable development called the triple bottom line (TBL. Herein, an assessment method for concrete eco-efficiency is developed as a technique to ensure the manufacture of highly durable and eco-friendly concrete, while minimizing both the load on the ecological environment and manufacturing costs. The assessment method is based on environmental impact, manufacturing costs, and the service life of concrete. According to our findings, eco-efficiency increased as the compressive strength of concrete increased from 21 MPa to 40 MPa. The eco-efficiency of 40 MPa concrete was about 50% higher than the eco-efficiency of 24 MPa concrete. Thus eco-efficiency is found to increase with an increasing compressive strength of concrete because the rate of increase in the service life of concrete is larger than the rate of increase in the costs. In addition, eco-efficiency (KRW/year was shown to increase for all concrete strengths as mixing rates of admixtures (Ground Granulated Blast furnace Slag increased to 30% during concrete mix design. However, when the mixing rate of admixtures increased to 40% and 60%, the eco-efficiency dropped due to rapid reduction in the service life values of concrete to 74 (year/m3 and 44 (year/m3, respectively.

  19. Online Corrosion and Force Monitoring for Inner Containment Concrete Structures

    Directory of Open Access Journals (Sweden)

    K. Kumar

    2008-05-01

    Full Text Available Corrosion of steel in concrete reduces the service life and durability of concrete structures. It is a worldwide problem, which causes heavy losses to the economy of the country. The durability of concrete structures primarily depends on the condition of the embedded steel in concrete, apart from any deterioration that concrete may undergo. In general potential surveys are carried out on concrete structures to know about the condition of steel. Most of these measurements in the field are carried out manually and the data obtained are analyzed. This offline measurements leads to an error in the data collected, time consuming and involvement of huge man power. Online corrosion monitoring eliminates such errors in the measurements and improves the accuracy of the data collected from humanly inaccessible regions of a structure. To mitigate corrosion prior to significant degradation and optimize the performance of such concrete structures, various sensors have been used to detect the corrosion and to provide early warning. To assess the condition of the embedded steel, the sensors of the probe are connected to a computer through specialized data acquisition hardware. The computer controls the data acquisition using suitable user friendly software that calculates the corrosion rate at prescribed intervals for continuous monitoring. New types of corrosion sensors and its mechanism in real time measurements are described. Online analysis of data for corrosion and force monitoring is described in this paper.

  20. Review of Concrete Biodeterioration in Relation to Buried Nuclear Waste

    Energy Technology Data Exchange (ETDEWEB)

    Turick, C; Berry, C.

    2012-10-15

    Long-term storage of low level radioactive material in below ground concrete disposal units (DUs) (Saltstone Disposal Facility) is a means of depositing wastes generated from nuclear operations of the U.S. Department of Energy. Based on the currently modeled degradation mechanisms, possible microbial induced effects on the structural integrity of buried low level wastes must be addressed. Previous international efforts related to microbial impacts on concrete structures that house low level radioactive waste showed that microbial activity can play a significant role in the process of concrete degradation and ultimately structural deterioration. This literature review examines the recent research in this field and is focused on specific parameters that are applicable to modeling and prediction of the fate of concrete vaults housing stored wastes and the wastes themselves. Rates of concrete biodegradation vary with the environmental conditions, illustrating a need to understand the bioavailability of key compounds involved in microbial activity. Specific parameters require pH and osmotic pressure to be within a certain range to allow for microbial growth as well as the availability and abundance of energy sources like components involved in sulfur, iron and nitrogen oxidation. Carbon flow and availability are also factors to consider in predicting concrete biodegradation. The results of this review suggest that microbial activity in Saltstone, (grouted low level radioactive waste) is unlikely due to very high pH and osmotic pressure. Biodegradation of the concrete vaults housing the radioactive waste however, is a possibility. The rate and degree of concrete biodegradation is dependent on numerous physical, chemical and biological parameters. Results from this review point to parameters to focus on for modeling activities and also, possible options for mitigation that would minimize concrete biodegradation. In addition, key chemical components that drive microbial

  1. Concrete decontamination by Electro-Hydraulic Scabbling (EHS). Topical report

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1996-03-30

    Electro-Hydraulic Scabbling (EHS) technology and equipment for decontaminating concrete structures from radionuclides, organic substances, and hazardous metals is being developed by Textron Systems Division (TSD). This wet scabbling technique involves the generation of powerful shock waves and intense cavitation by a strong pulsed electric discharge in a water layer at the concrete surface. The high pressure impulse results in stresses which crack and peel off a concrete layer of a controllable thickness. Scabbling produces contaminated debris of relatively small volume which can be easily removed, leaving clean bulk concrete. This new technology is being developed under Contract No. DE-AC21-93MC30164. The project objective is to develop and demonstrate a cost-efficient, rapid, controllable process to remove the surface layer of contaminated concrete while generating minimal secondary waste. The primary target of this program is uranium-contaminated concrete floors which constitute a substantial part of the contaminated area at DOE weapon facilities.

  2. Nanostructured silicate polymer concrete

    Directory of Open Access Journals (Sweden)

    Figovskiy Oleg L'vovich

    2014-03-01

    Full Text Available It has been known that acid-resistant concretes on the liquid glass basis have high porosity (up to 18~20 %, low strength and insufficient water resistance. Significant increasing of silicate matrix strength and density was carried out by incorporation of special liquid organic alkali-soluble silicate additives, which block superficial pores and reduce concrete shrinkage deformation. It was demonstrated that introduction of tetrafurfuryloxisilane additive sharply increases strength, durability and shock resistance of silicate polymer concrete in aggressive media. The experiments showed, that the strength and density of silicate polymer concrete increase in case of decreasing liquid glass content. The authors obtained optimal content of silicate polymer concrete, which possesses increased strength, durability, density and crack-resistance. Diffusive permeability of concrete and its chemical resistance has been investigated in various corroding media.

  3. Monitoring corrosion of steel bars in reinforced concrete structures.

    Science.gov (United States)

    Verma, Sanjeev Kumar; Bhadauria, Sudhir Singh; Akhtar, Saleem

    2014-01-01

    Corrosion of steel bars embedded in reinforced concrete (RC) structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP) method. This paper also presents few techniques to protect concrete from corrosion.

  4. Waterproofing Underground Concrete Structures

    Science.gov (United States)

    1990-01-01

    their explosive potential, were required to be hardened earth covered concrete structures . Because the water table was located only one foot below the... concrete structures such as utility tunnels, communication vaults, I basements, elevator pits, missile silos, and control rooms. *|2 1.2 Reasons for...underground concrete structures which are usually surrounded by moisture the need to keep the water out is critical. Probably the most common example of

  5. POLYMER CONCRETE CREEP

    OpenAIRE

    Yu. М. Borisov; I. S. Surovtsev; Yu. B. Potapov

    2012-01-01

    Problem statement. It is well known that creep is the tendency of a solid material to move slowly or deform permanently under the influence of stresses. The aim of the paper is to study the process of creep in polymer concretes. Results and conclusions. It is shown that creep in polymer concrete occurs according to the same pattern as in many other polymer composites with the elastic core. Equations which indirectly es-tablish the relation between complete deformations of polymer concrete, in...

  6. Evaluation of recycled concrete as aggregate in new concrete pavements.

    Science.gov (United States)

    2014-04-01

    This study evaluated the use of recycled concrete as coarse aggregate in new concrete pavements. : Recycled concrete aggregate (RCA) produced from demolished pavements in three geographically dispersed locations in Washington state were used to perfo...

  7. Comminution and sizing processes of concrete block waste as recycled aggregates.

    Science.gov (United States)

    Gomes, P C C; Ulsen, C; Pereira, F A; Quattrone, M; Angulo, S C

    2015-11-01

    Due to the environmental impact of construction and demolition waste (CDW), recycling is mandatory. It is also important that recycled concrete aggregates (RCA) are used in concrete to meet market demands. In the literature, the influence of RCAs on concrete has been investigated, but very limited studies have been conducted on how the origin of concrete waste and comminution processes influence RCA characteristics. This paper aims to investigate the influence of three different comminution and sizing processes (simple screening, crushing and grinding) on the composition, shape and porosity characteristics of RCA obtained from concrete block waste. Crushing and grinding implies a reduction of RCA porosity. However, due to the presence of coarse quartz rounded river pebbles in the original concrete block mixtures, the shape characteristics deteriorated. A large amount of powder (<0.15 mm) without detectable anhydrous cement was also generated. Copyright © 2015 Elsevier Ltd. All rights reserved.

  8. Concrete portable handbook

    CERN Document Server

    Woodson, R Dodge

    2011-01-01

    Whether or not, you are on the job site or back in the office, this book will help you to avoid mistakes, code violations, and wasted time and money. The book's four part treatment begins with constituent materials followed by self contained parts on Concrete Properties, Processes, and Concrete Repair and Rehabilitation. Designed to be an ""all in one"" reference, the author includes a wealth information for the most popular types of testing. This includes: Analysis of Fresh Concrete; Testing Machines; Accelerated Testing Methods; Analysis of Hardened Concrete and Mortar; Core Sampl

  9. Using biological and physico-chemical test methods to assess the role of concrete mixture design in resistance to microbially induced corrosion

    Science.gov (United States)

    House, Mitchell Wayne

    to evaluate performance of concrete specimens under conditions designed to accelerate MIC. Concrete specimens representing 12 mixture designs were inoculated with 5 species of Thiobacillus bacteria and placed in a biological growth chamber designed to encourage bacterial growth and sulfuric acid production by optimizing temperature, delivering necessary nutrients, and providing hydrogen sulfide gas. Results indicate that using supplementary cementitious materials, limestone aggregates, and sulfate resistant cement can improve resistance to MIC. It is interesting to note that this study showed that unlike many other durability problems the role of water to cement ratio was unclear. The second method presented is a sulfuric acid immersion study designed to evaluate the resistance of 12 concrete mixture designs to 5 concentrations of sulfuric acid. Experimental protocols (like those in ASTM) previously considered trivial were found to have a dramatic effect on experimental results. It was found that using supplementary cementitious materials, limestone coarse aggregate, and sulfate resistant cement can increase concrete resistance to moderate sulfuric acid concentrations. The primary damage mechanism was observed to change depending on sulfuric acid concentration. Rapid deterioration of specimens exposed to aggressive sulfuric acid solutions indicates that degradation of concrete under the most severe MIC conditions (i.e., a pH < 1.0) cannot be prevented by strictly manipulating concrete mixture proportions. A holistic approach is needed for these situations that considers environmental conditions as well.

  10. LIGHTWEIGHT CONCRETE BASED GRANSHLAK

    Directory of Open Access Journals (Sweden)

    NETESA M. I.

    2016-02-01

    Full Text Available Raising of problem. Concrete advisable to obtain a low strength with local secondary resources for recycling and reduce the environmental burden on the environment. But it is important to design such concrete compositions with a reduced flow of cement. It is known that the coefficient of efficiency of use of cement in the concrete of the heavy and B10 is less than about 0.5, which is almost two times smaller than in class B15 concrete and above. Even lower coefficient of efficiency in light concrete cement low strength. Therefore, it is important to find patterns determining the composition of lightweight concrete based on local-products industry with more efficient use of cement in them. Purpose.. Based on the analysis of earlier research results, including with the use of methods of mathematical planning of experiments to determine the concrete contents, which can provide the requirements for the underlying layers of the floor, the compressive strength of which should correspond to the class B5. It is important to provide the required strength at minimum flow of the cement, which is the most expensive and energy-intensive part of concrete. Conclusion. Analysis of the test results of control samples of concrete in 28-day-old, the following laws. The required tensile strength of concrete compressive strength of 7.0 MPa can be obtained in the test range when used in formulations as a filler as the Dnieper hydroelectric power station fly ash and tailings Krivoy Rog iron ore YuGOK. To ensure providing the required characteristic strength of the concrete in the underlying layers of the floor is advisable to use a nominal composition per cubic meter of concrete: cement 160 kg granshlaka Plant named after Petrovsky, 675 kg of fly ash Dnieper HPP 390 kg, 400 kg of sand, 230 liters of water. Thus, while ensuring rational grain composition components can obtain the desired strength lightweight concrete based granshlaka plant Petrovsky, using as fillers

  11. STUDY ON TEMPERATURE DISTRIBUTION DUE TO FREEZING AND THAWING AT THE FENGMAN CONCRETE GRAVITY DAM

    Directory of Open Access Journals (Sweden)

    He Yu

    2011-01-01

    Full Text Available Freezing and thawing damage is one of the major problems of the Fengman concrete dam. Based on the temperature records of the dam, appropriate heat transfer boundary conditions in the dam body are suggested. A three-dimensional finite element model is used to determine annual variation of temperature field of the dam as a case study. The deterioration problem of concrete dam owing to freezing and thawing effect is investigated.

  12. Rapid Set Materials for Advanced Spall Repair

    Science.gov (United States)

    2010-08-01

    compressive strength, tensile strength, modulus of rupture, and the coefficient of thermal expansion. pavement , spall repair, airfield damage repair...expediency and quality. Rapid repairs extend the life of a pavement using more forgiving methods than those used in traditional repairs, but...cement-based polymer -cement mortar and concrete • Magnesium-ammonium-phosphate-cement mortar and concrete • Polymer -based mortar and concrete

  13. Concrete, hardened: Self desiccation

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard; Persson, Bertil

    1999-01-01

    The test method covers the determination of internal relative humidity (RH) in hardened concrete and cement mortar using RH instruments. The determination of RH is done on crushed samples of concrete or cement motar. This test method is only for measuring equipment which gives off or takes up...

  14. Curing of Concrete

    African Journals Online (AJOL)

    use it economically. Curing of concrete involves the retention of sufficient free water in the cement paste so that the process of cement hydration may readily proceed. It also involves favorable temperature, humidity, and wind speed. No part of the process of making good concrete is more important than thorough curing.

  15. Concrete deck material properties.

    Science.gov (United States)

    2009-01-01

    The two-fold focus of this study was (a) to develop an understanding of the mechanisms responsible for causing : cracking in the concrete; and (b) to study the influence of the local materials on the performance of NYSDOTs HP : concrete mixture. R...

  16. Environmental Impact of Concrete

    Directory of Open Access Journals (Sweden)

    Dan Babor

    2009-01-01

    Full Text Available The cement and concrete industries are huge. What does this mean in terms of the environment? Concrete and other cementitious materials have both environmental advantages and disadvantages. This paper takes a look at how these materials are made, then reviews a number of environmental considerations relating to their production and use.

  17. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    The durability of MOC concrete compositions against extreme environmental conditions viz. heating–cooling, freezing–thawing, wetting–drying and penetration and deposition of salts etc were investigated. The results reveal that MOC concrete has high compressive strength associated with high flexural strength and the ...

  18. Concrete-Design

    Directory of Open Access Journals (Sweden)

    Leczovics Péter

    2014-12-01

    Full Text Available Present paper introduces a new interpretation of concrete, demonstrating some extreme possibilities of this rigid material such as a design element. In the first part a brief overview of the previous achievements are shown. The second part of this paper focuses on the relationship between concrete and fashion.

  19. concrete5 Beginner's Guide

    CERN Document Server

    Laubacher, Remo

    2011-01-01

    This book is part of Packt's Beginner's Guide series. You will be guided through the set up of a Concrete5 site with step-by-step practical examples. This book is ideal for developers who would like to build their first site with Concrete5. Some k

  20. Identification of the sources of organic compounds that decalcify cement concrete and generate alcohols and ammonia gases

    Energy Technology Data Exchange (ETDEWEB)

    Tomoto, Takashi [Technical Research Institute, Obayashi Road Corporation, 4-640 Shimokiyoto, Kiyose, Tokyo, 204-0011 (Japan); Moriyoshi, Akihiro [Material Science Laboratory, Hokkaido University, 2-1-9-10 Kiyota, Kiyota-ku, Sapporo, 004-0842 (Japan); Sakai, Kiyoshi [Department of Environmental Health, Nagoya City Public Health Research Institute, 1-11 Hagiyama-cho, Mizuho-ku, Nagoya, 467-8615 (Japan); Shibata, Eiji [Department of Health and Psychosocial Medicine, Aichi Medical University School of Medicine, Nagakute-cho, Aichi, 480-1195 (Japan); Kamijima, Michihiro [Department of Occupational and Environmental Health, Nagoya University Graduate School of Medicine, 65 Tsurumai-cho, Showa-ku, Nagoya, 466-8550 (Japan)

    2009-09-15

    This study identifies the emission sources of various types of airborne organic compounds, which deteriorate cement concrete by penetrating into the concrete together with moisture. The study used high-performance liquid chromatography and gas chromatograph mass spectrometry. The results show that the types of organic compounds contained in decalcified cement concrete were very similar to those found in the total suspended compounds in the air, and that the source of the emissions was particles of exhaust from diesel vehicles and radial tires used in summer. Such organic compounds include substances suspected of having endocrine disrupting properties. Hydrolysis occurs when these substances penetrate into highly alkaline cement concrete, and leads to deterioration of the cement concrete and the release of alcohols and ammonia gases which pollute indoor air and may be a cause of the sick building syndrome. (author)

  1. Use of Macro Basalt Fibre Concrete for Marine Applications

    OpenAIRE

    Mohammadi Mohaghegh, Ali

    2016-01-01

    Deterioration of concrete structures due to the corrosion of embedded steel is a well-known universal problem. Norway with its numerous bridges, ports, offshore and floating structures along its coastline, is also encountered with corrosion degradation. The harsh environment of the Norwegian Sea regarding its low temperature, wind, and waves, makes the design and construction of marine structures more demanding. In recent years, usage of sustainable composite materials in the field of structu...

  2. Concrete quality assurance

    Energy Technology Data Exchange (ETDEWEB)

    Holz, N. [Harza Engineering Company, Chicago, IL (United States)

    2000-08-01

    This short article reports on progress at the world's largest civil construction project, namely China's Three Gorges hydro project. Work goes on around the clock to put in place nearly 28 M m{sup 3} of concrete. At every stage of the work there is strong emphasis on quality assurance (QA) and concrete is no exception. The US company Harza Engineering has been providing QA since the mid-1980s and concrete QA has been based on international standards. Harza personnel work in the field with supervisors developing educational tools for supervising concrete construction and quality, as well as providing training courses in concrete technology. Some details on flood control, capacity, water quality and environmental aspects are given..

  3. Multi-physical and multi-scale deterioration modelling of re-inforced concrete: modelling corrosion-induced concrete damage

    DEFF Research Database (Denmark)

    Michel, Alexander; Lepech, Michael; Stang, Henrik

    2016-01-01

    of corrosion products along the circumference of the reinforcement. Final-ly, results of numerical simulations in terms of corrosion-induced deformations and cracking are compared to experimental data obtained by digital image correlation and published in the literature....

  4. Repairing design and construction of wastewater storage tank, which is exposed to high temperature, with self-compacting concrete; Koon ni sarasareru haisui choso no koryudo concrete ni yoru hoshu sekkei / seko

    Energy Technology Data Exchange (ETDEWEB)

    Maruya, T.; Sakamoto, J.; Shimada, M. [Taisei Construction Co. Ltd., Tokyo (Japan)

    1998-09-01

    The Anesaki Thermal power Plant of Tokyo Electric Power Co., Inc. at Ichihara, Chiba Prefecture is installed with an outside blow tank, a reinforced concrete structure as a facility to store temporarily surplus high temperature water at starting and suspension of the boiler. This tank is applied with a lining material of acid-resisting epoxy resin on the ceiling, walls and bottom in order to prevent deterioration of reinforced concrete, however, it requires repair due to exfoliation of bonded surface and deterioration of the lining material after a long period exposure to high temperature. The condition of the deterioration was surveyed and the repairing method and the cost were examined. The repair works were conducted with additional concrete casting using self-compacting concrete. This paper describes the survey of the deterioration, the examination of the repair works and the outline of the execution of the works. The features of this works include the use of a Vickers hardness meter for the determination of the deterioration near the surface of the body in addition to the conventional survey and the application self-compacting concrete. 3 refs., 4 figs., 3 tabs.

  5. Concrete sample point: 304 Concretion Facility

    Energy Technology Data Exchange (ETDEWEB)

    Rollison, M.D.

    1995-03-10

    This report contains information concerning the analysis of concretes for volatile organic compounds. Included are the raw data for these analysis and the quality control data, the standards data, and all of the accompanying chains-of-custody records and requests for special analysis.

  6. Microbial healing of cracks in concrete: a review.

    Science.gov (United States)

    Joshi, Sumit; Goyal, Shweta; Mukherjee, Abhijit; Reddy, M Sudhakara

    2017-11-01

    Concrete is the most widely used construction material of the world and maintaining concrete structures from premature deterioration is proving to be a great challenge. Early age formation of micro-cracking in concrete structure severely affects the serviceability leading to high cost of maintenance. Apart from conventional methods of repairing cracks with sealants or treating the concrete with adhesive chemicals to prevent the cracks from widening, a microbial crack-healing approach has shown promising results. The unique feature of the microbial system is that it enables self-healing of concrete. The effectiveness of microbially induced calcium carbonate precipitation (MICCP) in improving durability of cementitious building materials, restoration of stone monuments and soil bioclogging is discussed. Main emphasis has been laid on the potential of bacteria-based crack repair in concrete structure and the applications of different bacterial treatments to self-healing cracks. Furthermore, recommendations to employ the MICCP technology at commercial scale and reduction in the cost of application are provided in this review.

  7. Nonlinear fracture of concrete and ceramics

    Science.gov (United States)

    Kobayashi, Albert S.; Du, Jia-Ji; Hawkins, Niel M.; Bradt, Richard C.

    1989-01-01

    The nonlinear fracture process zones in an impacted unnotched concrete bend specimen, a prenotched ceramic bend specimen, and an unnotched ceramic/ceramic composite bend specimen were estimated through hybrid experimental numerical analysis. Aggregate bridging in concrete, particulate bridging in ceramics, and fiber bridging in ceramic/ceramic composite are modeled by Barenblatt-type cohesive zones which are incorporated into the finite-element models of the bend specimens. Both generation and propagation analyses are used to estimate the distribution of crack closure stresses in the nonlinear fracture process zones. The finite-element models are then used to simulate fracture tests consisting of rapid crack propagation in an impacted concrete bend specimen, and stable crack growth and strain softening in a ceramic and ceramic/ceramic composite bend specimens.

  8. Assessment of the Reliability of Concrete Bridges

    DEFF Research Database (Denmark)

    Middleton, C. R.; Thoft-Christensen, Palle

    Although there has been a considerable amount of research into different aspects of concrete bridge reliability, it has still not been widely adopted in professional practice other than in the development and calibration of codes. This situation appears to be changing as there has been a signific......Although there has been a considerable amount of research into different aspects of concrete bridge reliability, it has still not been widely adopted in professional practice other than in the development and calibration of codes. This situation appears to be changing as there has been...... in the wake of ever increasing traffic loads and volumes, and an ageing population of bridges subject to various mechanisms of deterioration. The goal is to optimise the allocation of limited resources whilst maintaining their bridges in a safe and serviceable condition. Reliability analysis is one tool being...... adopted to assist in achieving this goal. Rather than review the specific research on this subject this paper examines a number of key issues related to the practical application of reliability analysis to the assessment of concrete bridges....

  9. Development of Flexible Link Slabs using Ductile Fiber Reinforced Concrete

    DEFF Research Database (Denmark)

    Lárusson, Lárus Helgi

    -induced deflections of adjacent spans. Mechanical expansion joints, commonly used between simply supported spans in bridge structures, tend to deteriorate and require significant maintenance activities. Deterioration is often caused by ingress of water and chlorides into the joints, which leads to corrosion......Civil engineering structures with large dimensions, such as multi-span bridges, overpasses and viaducts, are typically equipped with mechanical expansion joints. These joints allow the individual spans of the structure to undergo unrestrained deformations due to thermal expansions and load...... of the joint and spalling of the surrounding concrete, and more importantly to corrosion of the bridge substructure including girders and bearings. Deterioration and the resulting rehabilitation and maintenance needs of such structures constitute a significant infrastructure deficiency. In this study...

  10. Performance of Waterless Concrete

    Science.gov (United States)

    Toutanji, Houssam; Evans, Steve; Grugel, Richard N.

    2010-01-01

    The development of permanent lunar bases is constrained by performance of construction materials and availability of in-situ resources. Concrete seems a suitable construction material for the lunar environment, but water, one of its major components, is an extremely scarce resource on the Moon. This study explores an alternative to hydraulic concrete by replacing the binding mix of concrete (cement and water) with sulfur. Sulfur is a volatile element on the lunar surface that can be extracted from lunar soils by heating. Sulfur concrete mixes were prepared to investigate the effect of extreme environmental conditions on the properties of sulfur concrete. A hypervelocity impact test was conducted, having as its target a 5-cm cubic sample of sulfur concrete. This item consisted of JSC-1 lunar regolith simulant (65%) and sulfur (35%). The sample was placed in the MSFC Impact Test Facility s Micro Light Gas Gun target chamber, and was struck by a 1-mm diameter (1.4e-03 g) aluminum projectile at 5.85 km/s. In addition, HZTERN code, provided by NASA was used to study the effectiveness of sulfur concrete when subjected to space radiation.

  11. Concrete bridge deck early problem detection and mitigation using robotics

    Science.gov (United States)

    Gucunski, Nenad; Yi, Jingang; Basily, Basily; Duong, Trung; Kim, Jinyoung; Balaguru, Perumalsamy; Parvardeh, Hooman; Maher, Ali; Najm, Husam

    2015-04-01

    More economical management of bridges can be achieved through early problem detection and mitigation. The paper describes development and implementation of two fully automated (robotic) systems for nondestructive evaluation (NDE) and minimally invasive rehabilitation of concrete bridge decks. The NDE system named RABIT was developed with the support from Federal Highway Administration (FHWA). It implements multiple NDE technologies, namely: electrical resistivity (ER), impact echo (IE), ground-penetrating radar (GPR), and ultrasonic surface waves (USW). In addition, the system utilizes advanced vision to substitute traditional visual inspection. The RABIT system collects data at significantly higher speeds than it is done using traditional NDE equipment. The associated platform for the enhanced interpretation of condition assessment in concrete bridge decks utilizes data integration, fusion, and deterioration and defect visualization. The interpretation and visualization platform specifically addresses data integration and fusion from the four NDE technologies. The data visualization platform facilitates an intuitive presentation of the main deterioration due to: corrosion, delamination, and concrete degradation, by integrating NDE survey results and high resolution deck surface imaging. The rehabilitation robotic system was developed with the support from National Institute of Standards and Technology-Technology Innovation Program (NIST-TIP). The system utilizes advanced robotics and novel materials to repair problems in concrete decks, primarily early stage delamination and internal cracking, using a minimally invasive approach. Since both systems use global positioning systems for navigation, some of the current efforts concentrate on their coordination for the most effective joint evaluation and rehabilitation.

  12. Behaviour of a Sustainable Concrete in Acidic Environment

    Directory of Open Access Journals (Sweden)

    Salim Barbhuiya

    2017-09-01

    Full Text Available Sustainability has become one of the most important considerations in building design and construction in recent years. Concrete is susceptible to acid attack because of its alkaline nature. The socioeconomic losses associated with infrastructure deterioration due to acid attack exceed billions of dollars all around the world. An experimental investigation was carried out to study the behaviour of sustainable concrete in 3% sulphuric acid and 1.5% nitric acid environment in which cement was replaced by a combination of fly ash and ultra fine fly ash. It was found that the compressive strength loss of concrete in these acid environments was the minimum in which cement was replaced by 30% fly ash and 10% ultra fine fly ash. This mix also showed the lowest mass loss when exposed to these acids.

  13. Transcriptional profiling of trait deterioration in the insect pathogenic nematode Heterorhabditis bacteriophora

    Directory of Open Access Journals (Sweden)

    Shapiro-Ilan David I

    2009-12-01

    Full Text Available Abstract Background The success of a biological control agent depends on key traits, particularly reproductive potential, environmental tolerance, and ability to be cultured. These traits can deteriorate rapidly when the biological control agent is reared in culture. Trait deterioration under laboratory conditions has been widely documented in the entomopathogenic nematode (EPN Heterorhabditis bacteriophora (Hb but the specific mechanisms behind these genetic processes remain unclear. This research investigates the molecular mechanisms of trait deterioration of two experimental lines of Hb, an inbred line (L5M and its original parental line (OHB. We generated transcriptional profiles of two experimental lines of Hb, identified the differentially expressed genes (DEGs and validated their differential expression in the deteriorated line. Results An expression profiling study was performed between experimental lines L5M and OHB of Hb with probes for 15,220 ESTs from the Hb transcriptome. Microarray analysis showed 1,185 DEGs comprising of 469 down- and 716 up-regulated genes in trait deteriorated nematodes. Analysis of the DEGs showed that trait deterioration involves massive changes of the transcripts encoding enzymes involved in metabolism, signal transduction, virulence and longevity. We observed a pattern of reduced expression of enzymes related to primary metabolic processes and induced secondary metabolism. Expression of sixteen DEGs in trait deteriorated nematodes was validated by quantitative reverse transcription-PCR (qRT-PCR which revealed similar expression kinetics for all the genes tested as shown by microarray. Conclusion As the most closely related major entomopathogen to C. elegans, Hb provides an attractive near-term application for using a model organism to better understand interspecies interactions and to enhance our understanding of the mechanisms underlying trait deterioration in biological control agents. This information

  14. concrete5 cookbook

    CERN Document Server

    Strack, David

    2013-01-01

    The Cookbook-style recipes allow you to go both directly to your topic of interest or follow topics throughout a chapter to gain in-depth knowledge. This practical Cookbook will cater to the needs of both intermediate and advanced concrete5 developers.This book is geared towards intermediate to advanced PHP developers who would like to learn more about the concrete5 content management system. Developers already familiar with concrete5 will learn new time-saving tricks and will find the book to be a great reference tool.

  15. The connection of hydronephrosis and microcirculation deterioration

    Directory of Open Access Journals (Sweden)

    Vorobets Dmytro

    2016-09-01

    Full Text Available In this study, we have analyzed the influence of hydronephrosis upon the microcirculation system, in situations of pyeloureteral junction obstruction. Herein, bulbar conjunctiva has been chosen as the object of this biomicroscopic study because of its simplicity and the method availability in clinic practice. In fulfilling this work, we ascertained the connections between extravascular, intravascular, vascular and general conjunctival indices of the patients before radical and paliatic correction of the pyeloureteral junction obstruction (i.e. by open and laparoscopic pyeloplasty, endopyelotomy, laser resection and balloon dilatation. We concluded that, apart from the proved deterioration of kidney function, systemic deteriorations of microcirculation may be observed in situations of clinically marked hydronephrosis, according to the results of radioisotope renography and excretory urography.

  16. Deterioration of gait and balance over time

    DEFF Research Database (Denmark)

    Kreisel, Stefan H; Blahak, Christian; Bäzner, Hansjörg

    2013-01-01

    Cross-sectional studies have shown an association between the severity of age-related white matter change (ARWMC) and lower body motor function. However, the association between prevalent ARWMC and incident deterioration of balance and gait remains insufficiently investigated. This study...... relevance: given the increasing use of neuroimaging, incidental white matter pathology is common; being able to delineate natural trajectories of balance and gait function given ARWMC may improve patient advice and help optimize allocation of care....... investigates if the degree of prevalent ARWMC has a differential effect on lower body motor function as it changes over time, hypothesizing that individuals with more severe baseline white matter pathology experience greater clinical deterioration independent of potential confounders. This is of clinical...

  17. Analysis of time-dependent reliability of degenerated reinforced concrete structure

    Directory of Open Access Journals (Sweden)

    Zhang Hongping

    2016-07-01

    Full Text Available Durability deterioration of structure is a highly random process. The maintenance of degenerated structure involves the calculation of the reliability of time-dependent structure. This study introduced reinforced concrete structure resistance decrease model and related statistical parameters of uncertainty, analyzed resistance decrease rules of corroded bending element of reinforced concrete structure, and finally calculated timedependent reliability of the corroded bending element of reinforced concrete structure, aiming to provide a specific theoretical basis for the application of time-dependent reliability theory.

  18. Influence of alkali-silica reaction on the physical, mechanical, and structural behaviour of reinforced concrete

    DEFF Research Database (Denmark)

    Barbosa, Ricardo Antonio

    Alkali-silica reaction (ASR) is one of the major concrete deterioration mechanisms in the world. Cracking in concrete structures due to ASR has been observed worldwide. In Denmark numerous concrete structures have been built with a critical amount of ASR-reactive aggregate, mostly as porous opaline...... and porous calcareous opaline flint in the fine aggregate fraction. During the last few decades, an increasing number of bridges in Denmark have been severely damaged due to ASR. In the most severe cases, the ASR-damaged bridges have been demolished and reconstructed due to uncertainty about their residual...

  19. Electrokenitic Corrosion Treatment of Concrete

    Science.gov (United States)

    Cardenas, Henry E (Inventor)

    2015-01-01

    A method and apparatus for strengthening cementitious concrete by placing a nanoparticle carrier liquid in contact with a first surface of a concrete section and inducing a current across the concrete section at sufficient magnitude and for sufficient time that nanoparticles in the nanoparticle carrier liquid migrate through a significant depth of the concrete section.

  20. Electrokinetic Strength Enhancement of Concrete

    Science.gov (United States)

    Cardenas, Henry E. (Inventor)

    2016-01-01

    A method and apparatus for strengthening cementitious concrete by placing a nanoparticle carrier liquid in contact with a first surface of a concrete section and inducing a current across the concrete section at sufficient magnitude and for sufficient time that nanoparticles in the nanoparticle carrier liquid migrate through a significant depth of the concrete section.

  1. Damage Detection and Deteriorating Structural Systems

    DEFF Research Database (Denmark)

    Long, Lijia; Thöns, Sebastian; Döhler, Michael

    2017-01-01

    . The approach of the quantification the value of damage detection information builds upon the Bayesian decision theory facilitating the utilization of damage detection performance models, which describe the information and its precision on structural system level, facilitating actions to ensure the structural...... integrity and facilitating to describe the structural system performance and its functionality throughout the service life. The structural system performance is described with its functionality, its deterioration and its behavior under extreme loading. The structural system reliability given the damage...

  2. Fatigue Strain and Damage Analysis of Concrete in Reinforced Concrete Beams under Constant Amplitude Fatigue Loading

    Directory of Open Access Journals (Sweden)

    Fangping Liu

    2016-01-01

    Full Text Available Concrete fatigue strain evolution plays a very important role in the evaluation of the material properties of concrete. To study fatigue strain and fatigue damage of concrete in reinforced concrete beams under constant amplitude bending fatigue loading, constant amplitude bending fatigue experiments with reinforced concrete beams with rectangular sections were first carried out in the laboratory. Then, by analyzing the shortcomings and limitations of existing fatigue strain evolution equations, the level-S nonlinear evolution model of fatigue strain was constructed, and the physical meaning of the parameters was discussed. Finally, the evolution of fatigue strain and fatigue damage of concrete in the compression zone of the experimental beam was analyzed based on the level-S nonlinear evolution model. The results show that, initially, fatigue strain grows rapidly. In the middle stages, fatigue strain is nearly a linear change. Because the experimental data for the third stage are relatively scarce, the evolution of the strain therefore degenerated into two phases. The model has strong adaptability and high accuracy and can reflect the evolution of fatigue strain. The fatigue damage evolution expression based on fatigue strain shows that fatigue strain and fatigue damage have similar variations, and, with the same load cycles, the greater the load level, the larger the damage, in line with the general rules of damage.

  3. Anchorage in concrete construction

    CERN Document Server

    Eligehausen, Rolf; Silva, John F

    2013-01-01

    A comprehensive treatment of current fastening technology using inserts (anchor channels, headed stud), anchors (metal expansion anchor, undercut anchor, bonded anchor, concrete screw and plastic anchor) as well as power actuated fasteners in concrete. It describes in detail the fastening elements as well as their effects and load-bearing capacities in cracked and non-cracked concrete. It further focuses on corrosion behaviour, fire resistance and characteristics with earthquakes and shocks. It finishes off with the design of fastenings according to the European Technical Approval Guideline (ETAG 001), the Final Draft of the CEN Technical Specification 'Design of fastenings for use in concrete' and the American Standards ACI 318-05, Appendix D and ACI 349-01, Appendix B.

  4. Prestressed concrete design

    CERN Document Server

    Hurst, MK

    1998-01-01

    This edition provides up-to-date guidance on the detailed design of prestressed concrete structures. All major topics are dealt with, including prestressed flat slabs, an important and growing application in the design of buildings.

  5. INORGANIC CEMENT CONCRETE

    Directory of Open Access Journals (Sweden)

    Alisson Clay Rios Silva

    2014-07-01

    Full Text Available In this work, a Geopolymeric Cement Concrete (GCC was developed through adequate portions of geopolymer components. Its characteristics were compared with Portland Cement Concrete (PCC, through of the establishment of some parameters of design, as consumption of binders, water/aggregates ratio and mortar content. The concrete mechanical performance was evaluated with emphasis to the fatigue behavior. Were tested the effects of different tensile strength maximum (increasing and decreasing. The results of fatigue tests had shown that GCC presents a better performance when compared to PCC. Its fatigue strength was 15% higher than that of PCC, when 70% of rupture tension of the concrete in static bending (SR, was applied. Tensions of about 80% SR resulted in 96% of increase, when compared to GCC. The SEM microstructural analysis showed that the GCC has a matrix/aggregate bonding very strong, when compared to PCC, probably due to the massive nature of the geopolymeric matrix.

  6. Concrete Research Facility

    Data.gov (United States)

    Federal Laboratory Consortium — This is a 20,000-sq ft laboratory that supports research on all aspects of concrete and materials technology. The staff of this facility offer wide-ranging expertise...

  7. Modeling reinforced concrete durability.

    Science.gov (United States)

    2014-06-01

    This project developed a next-generation modeling approach for projecting the extent of : reinforced concrete corrosion-related damage, customized for new and existing Florida Department of : Transportation bridges and suitable for adapting to broade...

  8. Improving concrete overlay construction.

    Science.gov (United States)

    2010-03-01

    Several road construction projects involving concrete overlays at the state and county levels in Iowa in 2009 were studied for : construction techniques and methods. The projects that were evaluated consisted of sites in four Iowa counties: Osceola, ...

  9. Asphaltic concrete pavement survey.

    Science.gov (United States)

    1963-04-01

    The ever increasing problem of wheel path rutting and excessive desification of asphaltic concrete pavement has been the subject of asphalt technology for quite sometime. It is known that the density of the pavement, which is significant for several ...

  10. Concrete Block Pavements

    Science.gov (United States)

    1983-03-01

    intersections, bus loading areas, and pedestrian crosswalks. The change in surface texture between conven- tional and block pavements has been successful...blocks polished under traffic within a few weeks, providing a pavement surface with unsatisfactory skid resistance. U. K. Cement and Concrete Association...further problems of this type. Kellersman (1980) reports that although many brick pavements have become polished and slippery under traffic, no concrete

  11. Drying of Porous Asphalt Concrete Investigated by X-Ray Computed Tomography

    Science.gov (United States)

    Jerjen, I.; Poulikakos, L. D.; Plamondon, M.; Schuetz, Ph.; Luethi, Th.; Flisch, A.

    Porous asphalt concrete is composed of aggregates, a bituminous binder and air voids which can form a complex network. Because rain water can easily drain through this network of voids, porous asphalt concrete is often used for improving the security of highways. However, porous asphalt concrete is often deteriorating fast due to its large contact area with environmental agents. A quantitative determination of the influence of rain water on the aging of porous asphalt concrete requires an understanding of water drainage and evaporation in the material. In this paper, the water evaporation rate in a sample of porous asphalt concrete was investigated by means of X-ray micro computed tomography. Discontinuities in the evaporation rate were observed. A qualitative inspection of the pore network allowed tentatively linking sudden acceleration of evaporation to the disappearance of water lids which were clogging pores.

  12. Characterization of acoustic wave propagation in a concrete member after fire exposure

    Science.gov (United States)

    Chiang, Chih-Hung; Huang, Chin-Ting

    2001-04-01

    The acoustic wave propagation in a concrete member with embedded reinforcing bars was analyzed. Fire exposure was applied to two batches of concrete specimens prior to acoustic wave characterization. The fire duration and maximum temperature were simulated for experimental studies using a custom-built electric oven. A standard ultrasonic pulse velocity testing system for concrete was used to provide the through-transmission wave propagation. Multiple peaks were found in the frequency domain based on the fast Fourier transform of the waveform. This could be due to cracks induced by the incompatibility of thermal deformation of the constituents of concrete. Further study showed bond deterioration between reinforcing bars and concrete would also contribute to the variation in frequency content of the recorded waveform.

  13. A STUDY ON DEF-RELATED EXPANSION IN HEAT-CURED CONCRETE

    Science.gov (United States)

    Kawabata, Yuichiro; Matsushita, Hiromichi

    This paper reports the requirements for deleterious expansion due to delayed ettringite formation (DEF) based on field experience. In recent years, the delete rious expansion of concrete have been reported. The concrete have been characterized by expansion and cracking after several years of service in environments exposed in wet conditions. In many cases, the concrete consists of white cement, limestone and copper slag and it has been manufactured at elevated temperatures for early shipment. From detailed analysis, it was made clear that the cause of deleterious expansion was DEF. The gaps which are featured in DEF-damaged concrete were observed around limest one aggregate. There was a possibility that use of limestone aggregate affects DEF-related expansion while the condition of steam curing was the most effective factor for DEF-related expansion. Based on experimental data, the mechanism of DEF-related expansion and the methodology of diagnosing DEF-deterior ated concrete structures were discussed in this paper.

  14. Shear Resistance between Concrete-Concrete Surfaces

    Science.gov (United States)

    Kovačovic, Marek

    2013-12-01

    The application of precast beams and cast-in-situ structural members cast at different times has been typical of bridges and buildings for many years. A load-bearing frame consists of a set of prestressed precast beams supported by columns and diaphragms joined with an additionally cast slab deck. This article is focused on the theoretical and experimental analyses of the shear resistance at an interface. The first part of the paper deals with the state-of-art knowledge of the composite behaviour of concrete-concrete structures and a comparison of the numerical methods introduced in the relevant standards. In the experimental part, a set of specimens with different interface treatments was tested until failure in order to predict the composite behaviour of coupled beams. The experimental part was compared to the numerical analysis performed by means of FEM basis nonlinear software.

  15. Performance of "Waterless Concrete"

    Science.gov (United States)

    Toutanji, H. A.; Grugel, R. N.

    2009-01-01

    Waterless concrete consists of molten elementary sulfur and aggregate. The aggregates in a lunar environment will be lunar rocks and soil. Sulfur is present on the Moon in Troilite soil (FeS) and, by oxidation of the soil, iron and sulfur can be produced. Sulfur concrete specimens were cycled between liquid nitrogen (approx.]91 C) and room temperature (^21 C) to simulate exposure to a lunar environment. Cycled and control specimens were subsequently tested in compression at room temperatures (^21 C) and ^-101 C. Test results showed that due to temperature cycling, the compressive strength of cycled specimens was 20% of those non-cycled. This reduction in strength can be attributed to the large differences in thermal coefficients of expansion of the materials constituting the concrete which promoted cracking. Similar sulfur concrete mixtures were strengthened with short and long glass fibres. The lunar regolith simulant was melted in a 25 cc Pt- Rh crucible in a Sybron Thermoline high temperature MoSi2 furnace at melting temperatures of 1450 to 1600 C for times of 30 min to i hour. Glass fibres and small rods were pulled from the melt. The glass fibres were used to reinforce sulfur concrete plated to improve the flexural strength of the sulfur concrete. Beams strengthened with glass fibres showed to exhibit an increase in the flexural strength by as much as 45%.

  16. Recycled Concrete as Aggregate for Structural Concrete Production

    Directory of Open Access Journals (Sweden)

    Mirjana Malešev

    2010-04-01

    Full Text Available A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC as a control concrete and two types of concrete made with natural fine and recycled coarse aggregate (50% and 100% replacement of coarse recycled aggregate. Ninety-nine specimens were made for the testing of the basic properties of hardened concrete. Load testing of reinforced concrete beams made of the investigated concrete types is also presented in the paper. Regardless of the replacement ratio, recycled aggregate concrete (RAC had a satisfactory performance, which did not differ significantly from the performance of control concrete in this experimental research. However, for this to be fulfilled, it is necessary to use quality recycled concrete coarse aggregate and to follow the specific rules for design and production of this new concrete type.

  17. New generation concretes including reactive powder concretes

    Directory of Open Access Journals (Sweden)

    Stefania Grzeszczyk

    2015-09-01

    Full Text Available Based on a broad literature review, this paper presents characteristics of new generation composites on the basis of cements which are applied in engineering structures and in rehabilitation of structures. The role of cement, microfillers, superplasticizers and fibers in the above stated composites i.e. factors which allow for the maximum packing of particles in the cement matrix and a minimum pore volume, and the increase in composite bending strength, have been discussed. Special attention was paid to Reactive Powder Concrete in which coarse aggregate was replaced by ground quartz and sand. Such composites contain active microfillers and the applied new-generation superplasticizers allow us to decrease the water-cement ratio in the composite up to 0.2. Whereas, steel fibre additive allows us to significantly improve the bending strength.The paper presents the properties of the excellent Ductal — a composite from Reactive Powder Concrete, which at compressive strength from 180 to 230 MPa achieves the tensile strength of 30 to 50 MPa. Its application allows us to create slim profiles and tall light and slender, and simultaneously durable and corrosion-resistant structural elements of considerable span. This paper gives a few examples of Ductal application in practice.[b]Keywords[/b]: civil engineering, composite materials, reactive powder concrete

  18. Deterioration and Repair of Concrete in the Lower Monumental Navigation Lock Wall.

    Science.gov (United States)

    1981-06-01

    ions. 83. OIRUTLCTIUN U WRAILN MLSOuliCLS. 6.1 fi"ZJ the Contractor Shell not pollute streevis, lakes or reservoirs w.ith fuels, oil*, bitumens , calcium...thorough initial mixing and periodic stirring afterwards, the solids Portion and anti- foaming agent may @operate from tha weter in the Haend. If

  19. Effect of Wheel/Rail Loads on Concrete Tie Stresses and Rail Rollover.

    Science.gov (United States)

    2011-09-21

    As a result of vertical and lateral wheel/rail forces, high contact stresses can develop at the interface between the rail base and tie. Under certain conditions, these stresses can exceed the strength of the concrete tie and result in deterioration ...

  20. Electrochemical lithium migration to mitigate alkali-silica reaction in existing concrete structures

    NARCIS (Netherlands)

    Silva De Souza, L.M.

    2016-01-01

    Alkali-silica reaction (ASR) is a deterioration process that affects the durability of concrete structures worldwide. During the reaction, hydroxyl and alkali ions present in the pore solution react with reactive silica from the aggregate, forming a hygroscopic ASR gel. Alternatively, the silica

  1. Investigation of mechanistic deterioration modeling for bridge design and management.

    Science.gov (United States)

    2017-04-01

    The ongoing deterioration of highway bridges in Colorado dictates that an effective method for allocating limited management resources be developed. In order to predict bridge deterioration in advance, mechanistic models that analyze the physical pro...

  2. Deterioration of J-bar reinforcement in abutments and piers.

    Science.gov (United States)

    2011-12-31

    Deterioration and necking of J-bars has been reportedly observed at the interface of the footing and stem wall during the demolition : of older retaining walls and bridge abutments. Similar deterioration has been reportedly observed between the pier ...

  3. Going green with geopolymer concrete

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2008-05-15

    Getting a low CO{sub 2} concrete from the lab to streets and buildings around Australia was quite challenging, but the increased emphasis on climate change and environmentally friendly solutions helped achieve this outcome by University of Melbourne researchers John Provis, Peter Duxson and Jannie van Deventer from the Department of Chemical and Biomolecular Engineering. The use of fly ash in geopolymers does not give raw materials- derived CO{sub 2} emissions. The ash cools rapidly as it leaves the furnace, so contains reactive glassy phases without the need for energy-intensive treatment in a cement kiln. These glasses are generally not quite as reactive as Portland cement, so 'activation' is needed to make them react quickly enough to give acceptable strength development in a concrete. In the geopolymer process, an alkaline activating solution - usually an alkali metal hydroxide or silicate - is mixed with the ash to initiate and accelerate formation of a hardened binder phase. The commercial development of geopolymers in Australia is being led by Melbourne-based company Zeobond Pty Ltd, who are marketing fly ash-based geopolymer technology under the trade name 'E-Crete'. In addition to large slabs, ready-mix E-Crete has been used to construct footpaths in the northern suburbs of Melbourne, and also in precasting of large panels. 5 refs., 5 figs.

  4. Dataset of producing and curing concrete using domestic treated wastewater

    Directory of Open Access Journals (Sweden)

    Gholamreza Asadollahfardi

    2016-03-01

    Full Text Available We tested the setting time of cement, slump and compressive and tensile strength of 54 triplicate cubic samples and 9 cylindrical samples of concrete with and without a Super plasticizer admixture. We produced concrete samples made with drinking water and treated domestic wastewater containing 300, 400 kg/m3 of cement before chlorination and then cured concrete samples made with drinking water and treated wastewater. Second, concrete samples made with 350 kg/m3 of cement with a Superplasticizer admixture made with drinking water and treated wastewater and then cured with treated wastewater. The compressive strength of all the concrete samples made with treated wastewater had a high coefficient of determination with the control concrete samples. A 28-day tensile strength of all the samples was 96–100% of the tensile strength of the control samples and the setting time was reduced by 30 min which was consistent with a ASTMC191 standard. All samples produced and cured with treated waste water did not have a significant effect on water absorption, slump and surface electrical resistivity tests. However, compressive strength at 21 days of concrete samples using 300 kg/m3 of cement in rapid freezing and thawing conditions was about 11% lower than concrete samples made with drinking water.

  5. Analysis of Pitch Gear Deterioration using Indicators

    DEFF Research Database (Denmark)

    Nielsen, Jannie Jessen; Sørensen, John Dalsgaard

    . This deterioration is expected to cause larger loads, because increased play causes dynamic loads. At some point, the increased loads can be expected to cause a failure somewhere in the pitch system. If the loads increase with the size of the damage, the loads can be used as indicators of the size of the damage....... This hypothesis was supported by results from a measurement campaign where measurements were available both before and after maintenance was performed. The loads dramatically decreased after the maintenance. However, after a few more months of measurements, and by including data from the SCADA system, it became...

  6. 40 CFR 52.2729 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2729 Section 52.2729 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  7. 40 CFR 52.2827 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2827 Section 52.2827 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  8. 40 CFR 52.2451 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2451 Section 52.2451 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... Quality Deterioration. (b) Regulations for preventing significant deterioration of air quality. The...

  9. 40 CFR 52.1689 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1689 Section 52.1689 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  10. 40 CFR 52.2497 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2497 Section 52.2497 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  11. 40 CFR 52.1603 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1603 Section 52.1603 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  12. 40 CFR 52.1234 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1234 Section 52.1234 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  13. 40 CFR 52.499 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.499 Section 52.499 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  14. 40 CFR 52.1180 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1180 Section 52.1180 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  15. 40 CFR 52.1884 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1884 Section 52.1884 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  16. 40 CFR 52.2779 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2779 Section 52.2779 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  17. 40 CFR 52.2528 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2528 Section 52.2528 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of Sections 160 through 165 of the Clean Air... Quality Deterioration. (b) Regulations for Preventing Significant Deterioration of Air Quality, the...

  18. 40 CFR 52.1165 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1165 Section 52.1165 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulation for preventing significant deterioration of air quality. The...

  19. 40 CFR 52.2676 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2676 Section 52.2676 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) Regulations for preventing significant deterioration of air quality. The...

  20. Damage Detection in Railway Prestressed Concrete Sleepers using Acoustic Emission

    Science.gov (United States)

    Clark, A.; Kaewunruen, S.; Janeliukstis, R.; Papaelias, M.

    2017-10-01

    Prestressed concrete sleepers (or railroad ties) are safety-critical elements in railway tracks that distribute the wheel loads from the rails to the track support system. Over a period of time, the concrete sleepers age and deteriorate in addition to experiencing various types of static and dynamic loading conditions, which are attributable to train operations. In many cases, structural cracks can develop within the sleepers due to high intensity impact loads or due to poor track maintenance. Often, cracks of sleepers develop and present at the midspan due to excessive negative bending. These cracks can cause broken sleepers and sometimes called ‘center bound’ problem in railway lines. This paper is the world first to present an application of non-destructive acoustic emission technology for damage detection in railway concrete sleepers. It presents experimental investigations in order to detect center-bound cracks in railway prestressed concrete sleepers. Experimental laboratory testing involves three-point bending tests of four concrete sleepers. Three-point bending tests correspond to a real failure mode, when the loads are not transferred uniformly to the ballast support. It is observed that AE sensing provides an accurate means for detecting the location and magnitude of cracks in sleepers. Sensor location criticality is also highlighted in the paper to demonstrate the reliability-based damage detection of the sleepers.

  1. Freeze-Thaw Durability of Air-Entrained Concrete

    Directory of Open Access Journals (Sweden)

    Huai-Shuai Shang

    2013-01-01

    Full Text Available One of the most damaging actions affecting concrete is the abrupt temperature change (freeze-thaw cycles. The types of deterioration of concrete structures by cyclic freeze-thaw can be largely classified into surface scaling (characterized by the weight loss and internal crack growth (characterized by the loss of dynamic modulus of elasticity. The present study explored the durability of concrete made with air-entraining agent subjected to 0, 100, 200, 300, and 400 cycles of freeze-thaw. The experimental study of C20, C25, C30, C40, and C50 air-entrained concrete specimens was completed according to “the test method of long-term and durability on ordinary concrete” GB/T 50082-2009. The dynamic modulus of elasticity and weight loss of specimens were measured after different cycles of freeze-thaw. The influence of freeze-thaw cycles on the relative dynamic modulus of elasticity and weight loss was analyzed. The findings showed that the dynamic modulus of elasticity and weight decreased as the freeze-thaw cycles were repeated. They revealed that the C30, C40, and C50 air-entrained concrete was still durable after 300 cycles of freeze-thaw according to the experimental results.

  2. Fracture Mechanics of Concrete

    DEFF Research Database (Denmark)

    Ulfkjær, Jens Peder

    Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high-strength......Chapter 1 Chapter l contains the introduction to this thesis. The scope of the thesis is partly to investigate different numerical and analytical models based on fracture mechanical ideas, which are able to predict size effects, and partly to perform an experimental investigation on high......-strength concrete. Chapter 2 A description of the factors which influence the strength and cracking of concrete and high strength concrete is made. Then basic linear fracture mechanics is outlined followed by a description and evaluation of the models used to describe concrete fracture in tension. The chapter ends...... to describe fracture in concrete are presented. Two of the methods are combined into a power method which is stable for all brittleness numbers and which is able of calculating the entire load-displacement curve even for very ductile beams. This method is used extensively in the rest of the thesis. Chapter 4...

  3. Concrete with onyx waste aggregate as aesthetically valued structural concrete

    Science.gov (United States)

    Setyowati E., W.; Soehardjono, A.; Wisnumurti

    2017-09-01

    The utillization of Tulungagung onyx stone waste as an aggregate of concrete mixture will improve the economic value of the concrete due to the brighter color and high aesthetic level of the products. We conducted the research of 75 samples as a test objects to measure the compression stress, splits tensile stress, flexural tensile stress, elasticity modulus, porosity modulus and also studied 15 test objects to identify the concrete micro structures using XRD test, EDAX test and SEM test. The test objects were made from mix designed concrete, having ratio cement : fine aggregate : coarse aggregate ratio = 1 : 1.5 : 2.1, and W/C ratio = 0.4. The 28 days examination results showed that the micro structure of Tulungagung onyx waste concrete is similar with normal concrete. Moreover, the mechanical test results proved that Tulungagung onyx waste concretes also have a qualified level of strength to be used as a structural concrete with higher aesthetic level.

  4. An Expert System for Concrete Bridge Management

    DEFF Research Database (Denmark)

    Brito, J. de; Branco, F. A.; Thoft-Christensen, Palle

    1997-01-01

    The importance of bridge repair versus new bridge construction has risen in recent decades due to high deterioration rates that have been observed in these structures. Budgets both for building new bridges and keeping the existing ones are always limited. To help rational decision-making, bridge...... management systems are presently being implemented by bridge authorities in several countries. The prototype of an expert system for concrete bridge management is presented in this paper, with its functionality relying on two modules. The inspection module relies on a periodic acquisition of field...... information complemented by a knowledge-based interactive system, BRIDGE-1. To optimize management strategies at the headquarters, the BRIDGE-2 module was implemented, including three submodules: inspection strategy, maintenance and repair....

  5. Contact Loss beneath Track Slab Caused by Deteriorated Cement Emulsified Asphalt Mortar: Dynamic Characteristics of Vehicle-Slab Track System and Prototype Experiment

    Directory of Open Access Journals (Sweden)

    Dan Liu

    2016-01-01

    Full Text Available The contact loss beneath track slab caused by deteriorated cement emulsified asphalt mortar (CA mortar has been one of the main diseases occurring in the CRTS- (China Railway Track System- I Slab Track of high-speed railway in China. Based on the slab track design theory and the vehicle-track coupling vibration theory, a vehicle-track vertical coupling dynamic FEM model was established to analyze the influence of the contact loss length on the dynamic characteristics of vehicle and track subsystems at different train speeds. A prototype dynamic characteristic experimental test of CRTS-I Slab Track with CA mortar contact loss was conducted to verify the FEM model results. The train load was generated by the customized ZSS50 excitation car. The results showed that when the operation speed is less than 300 km/h, the contact loss with length smaller than 2.0 m barely affects the running smoothness ride safety of vehicle. The contact loss length effect on the dynamic characteristics of track subsystem is pronounced, especially on the track slab. Once the contact loss beneath the track slab occurs, the vibration displacement and the acceleration of the track slab increase rapidly, while it has little influence on the displacement and acceleration of the concrete roadbed.

  6. Environmental Impact Analysis of Acidification and Eutrophication Due to Emissions from the Production of Concrete

    Directory of Open Access Journals (Sweden)

    Tae Hyoung Kim

    2016-06-01

    Full Text Available Concrete is a major material used in the construction industry that emits a large amount of substances with environmental impacts during its life cycle. Accordingly, technologies for the reduction in and assessment of the environmental impact of concrete from the perspective of a life cycle assessment (LCA must be developed. At present, the studies on LCA in relation to greenhouse gas emission from concrete are being carried out globally as a countermeasure against climate change. However, the studies on the impact of the substances emitted in the concrete production process on acidification and eutrophication are insufficient. As such, assessing only a single category of environmental impact may cause a misunderstanding about the environmental friendliness of concrete. The substances emitted in the concrete production process have an impact not only on global warming but also on acidification and eutrophication. Acidification and eutrophication are the main causes of air pollution, forest destruction, red tide phenomena, and deterioration of reinforced concrete structures. For this reason, the main substances among those emitted in the concrete production process that have an impact on acidification and eutrophication were deduced. In addition, an LCA technique through which to determine the major emissions from concrete was proposed and a case analysis was carried out. The substances among those emitted in the concrete production process that are related to eutrophication were deduced to be NOx, NH3, NH4+, COD, NO3−, and PO43−. The substances among those emitted in the concrete production process that are related to acidification, were found to be NOx, SO2, H2S, and H2SO4. The materials and energy sources among those input into the concrete production process, which have the biggest impact on acidification and eutrophication, were found to be coarse aggregate and fine aggregate.

  7. Drying of Concrete

    DEFF Research Database (Denmark)

    Hansen, Kurt Kielsgaard; Geiker, Mette Rica; Nygaard, Peter Vagn

    2002-01-01

    Estimated and measured relative humidity (RH) change during drying are compared for two concretes, 1: w/c=0.46 and 2: w/(c+0.5fa+2sf)=0.50. The estimations were undertaken by means of the Swedish program TorkaS 1.0. Measurements were performed by RH-sensors type Humi-Guard. Drying of 150 mm thick...... samples from sides at 60% RH and 22 °C took place from 4 to 56 days after casting. At the end of the drying period the measured RH was about 4% lower than the estimated RH at 1/5th depth from the exposed surface for both concretes. In the middle of the samples, the measured RH of concretes 1 and 2 were 2...

  8. Water Entrainment in Concrete

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede; Hansen, Per Freiesleben

    This report gives a survey of different techniques for incorporation of designed, water-filled cavities in concrete: Water entrainment. Also an estimate of the optimum size of the water inclusions is given. Water entrainment can be used to avoid self-desiccation and self-desiccation shrinkage...... during hydration [1,26]. What is needed is some sort of container which retains the shape of the water when mixed into the concrete. The container may function based on several different physical or chemical principles. Cells and gels are examples of containers found in nature. A cell membrane provides...... a boundary to water, whereas a polymer network incorporates water in its intersticious space with its affinity due to interaction energy and polymer entropy. Such containers allow water to be stored as an entity. In relation to concrete the water encapsulation may be accomplished either before or after start...

  9. The influence of concrete joints on the structural behavior

    Directory of Open Access Journals (Sweden)

    Koyankin Aleksandr Aleksandrovich

    2014-03-01

    Full Text Available The buildings made of monolithic reinforced concrete currently enjoy great popularity. Along with a great number of advantages of monolithic building, which are repeatedly listed in the works of many authors, there are many unexplored issues which require detailed consideration. The technological concrete joints are among them. The joints are inevitable in the process of construction of almost any monolithic building and their quality affects the reliability of buildings and structures. Despite regular use of the concept of cold joint and clear instructions in building standards on the technology of joint production, most organizations do not follow the correct technology of concreting the elements. As a result, the strength and stiffness characteristics of the construction deteriorate, because the linkage value of new concrete with the old one is significantly lower than in monolith. In order to conduct experimental studies the reinforced concrete beams of rectangular section were produced. As a result of testing, it was determined that the presence of a concrete joint significantly reduces the stiffness and carrying capacity of the structures. It is confirmed by the fact that the received deflections of solid beams without joint are significantly lower than the deflections of beams with cold joint. It also noted that the deflections of the beams manufactured following the normative technology are lower, than the deflections of the beams, manufactured with violation of the rules. Basing on the obtained results, it was concluded, that more detailed study of the work of a construction with cold joints in concrete is required. The reason for it is in the changing for the worse of the strength and stiffness characteristics of structural element, which is made produced with a joint, while in the process of real designing, the monolith buildings are calculated as solid monolithic, without joints.

  10. Use of fiber reinforced concrete for concrete pavement slab replacement.

    Science.gov (United States)

    2014-03-01

    Unlike ordinary concrete pavement, replacement concrete slabs need to be open to traffic within 24 hours (sooner in : some cases). Thus, high early-strength concrete is used; however, it frequently cracks prematurely as a result of high : heat of hyd...

  11. Accelerated Gray and White Matter Deterioration With Age in Schizophrenia.

    Science.gov (United States)

    Cropley, Vanessa L; Klauser, Paul; Lenroot, Rhoshel K; Bruggemann, Jason; Sundram, Suresh; Bousman, Chad; Pereira, Avril; Di Biase, Maria A; Weickert, Thomas W; Weickert, Cynthia Shannon; Pantelis, Christos; Zalesky, Andrew

    2017-03-01

    Although brain changes in schizophrenia have been proposed to mirror those found with advancing age, the trajectory of gray matter and white matter changes during the disease course remains unclear. The authors sought to measure whether these changes in individuals with schizophrenia remain stable, are accelerated, or are diminished with age. Gray matter volume and fractional anisotropy were mapped in 326 individuals diagnosed with schizophrenia or schizoaffective disorder and in 197 healthy comparison subjects aged 20-65 years. Polynomial regression was used to model the influence of age on gray matter volume and fractional anisotropy at a whole-brain and voxel level. Between-group differences in gray matter volume and fractional anisotropy were regionally localized across the lifespan using permutation testing and cluster-based inference. Significant loss of gray matter volume was evident in schizophrenia, progressively worsening with age to a maximal loss of 8% in the seventh decade of life. The inferred rate of gray matter volume loss was significantly accelerated in schizophrenia up to middle age and plateaued thereafter. In contrast, significant reductions in fractional anisotropy emerged in schizophrenia only after age 35, and the rate of fractional anisotropy deterioration with age was constant and best modeled with a straight line. The slope of this line was 60% steeper in schizophrenia relative to comparison subjects, indicating a significantly faster rate of white matter deterioration with age. The rates of reduction of gray matter volume and fractional anisotropy were significantly faster in males than in females, but an interaction between sex and diagnosis was not evident. The findings suggest that schizophrenia is characterized by an initial, rapid rate of gray matter loss that slows in middle life, followed by the emergence of a deficit in white matter that progressively worsens with age at a constant rate.

  12. Electrokinetic decontamination of concrete

    Energy Technology Data Exchange (ETDEWEB)

    Lomasney, H. [ISOTRON Corp., New Orleans, LA (United States)

    1995-10-01

    The U.S. Department of Energy has assigned a priority to the advancement of technology for decontaminating concrete surfaces which have become contaminated with radionuclides, heavy metals, and toxic organics. This agency is responsible for decontamination and decommissioning of thousands of buildings. Electrokinetic extraction is one of the several innovative technologies which emerged in response to this initiative. This technique utilizes an electropotential gradient and the subsequent electrical transport mechanism to cause the controlled movement of ionics species, whereby the contaminants exit the recesses deep within the concrete. This report discusses the technology and use at the Oak Ridge k-25 plant.

  13. Concentrated loads on concrete

    DEFF Research Database (Denmark)

    Lorenzen, Karen Grøndahl; Nielsen, Mogens Peter

    1997-01-01

    This report deals with concentrated loads on concrete.A new upper bound solution in the axisymmetrical case of a point load in the center of the end face of a cylinder is developed.Based on previous work dealing with failure mechanisms and upper bound solutions, new approximate formulas are devel......This report deals with concentrated loads on concrete.A new upper bound solution in the axisymmetrical case of a point load in the center of the end face of a cylinder is developed.Based on previous work dealing with failure mechanisms and upper bound solutions, new approximate formulas...

  14. Recycled aggregate concrete; an overview

    OpenAIRE

    Sorato, Renan

    2016-01-01

    The aim of this Bachelor’s thesis was to investigate whether recycled materials can be incorporated into the production of concrete without compromising the compressive strength of the concrete produced. In order to shed light on the compressive strength of concrete made from recycled materials, the thesis reviewed studies in which waste materials are utilised as recycled aggregates in the composition of concrete and presented the results of this synthesis and analysis. It was found that som...

  15. Concrete produced with recycled aggregates

    OpenAIRE

    Tenório,J. J. L.; Gomes,P. C. C.; Rodrigues,C. C.; Alencar,T. F. F. de

    2012-01-01

    This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC) for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW), which were d...

  16. Damage Detection and Deteriorating Structural Systems

    DEFF Research Database (Denmark)

    Long, Lijia; Thöns, Sebastian; Döhler, Michael

    2017-01-01

    integrity and facilitating to describe the structural system performance and its functionality throughout the service life. The structural system performance is described with its functionality, its deterioration and its behavior under extreme loading. The structural system reliability given the damage...... detection information is determined utilizing Bayesian updating. The damage detection performance is described with the probability of indication for different component and system damage states taking into account type 1 and type 2 errors. The value of damage detection information is then calculated......This paper addresses the quantification of the value of damage detection system and algorithm information on the basis of Value of Information (VoI) analysis to enhance the benefit of damage detection information by providing the basis for its optimization before it is performed and implemented...

  17. Tree mineral nutrition is deteriorating in Europe

    DEFF Research Database (Denmark)

    Jonard, Mathieu; Fürst, Alfred; Verstraeten, Arne

    2015-01-01

    The response of forest ecosystems to increased atmospheric CO2 is constrained by nutrient availability. It is thus crucial to account for nutrient limitation when studying the forest response to climate change. The objectives of this study were to describe the nutritional status of the main...... European tree species, to identify growth-limiting nutrients and to assess changes in tree nutrition during the past two decades. We analysed the foliar nutrition data collected during 1992–2009 on the intensive forest monitoring plots of the ICP Forests programme. Of the 22 significant temporal trends...... to higher nutrient demand by trees. As the soil nutrient supply was not always sufficient to meet the demands of faster growing trees, this could partly explain the deterioration of tree mineral nutrition. The results suggest that when evaluating forest carbon storage capacity and when planning to reduce CO...

  18. The effect of measuring procedure on the apparent rheological properties of self-compacting concrete

    DEFF Research Database (Denmark)

    Geiker, Mette Rica; Bradl, M.; Thrane, L.N.

    2002-01-01

    Torque versus time during testing of the rheological properties of fresh concrete has been investigated. The testing was performed in a BML viscometer and on a self-compacting concrete (w/c = 0.45, 70% rapid hardening Portland cement, 3% silica fume, 27% fly ash, third generation superplasticizer......, lack of steady state may explain the apparent shear-thickening behaviour of self-compacting concrete reported elsewhere. (C) 2002 Elsevier Science Ltd. All rights reserved....

  19. An inventory model of instantaneous deteriorating items with controllable deterioration rate for time dependent demand and holding cost

    Directory of Open Access Journals (Sweden)

    Vinod Kumar Mishra

    2013-06-01

    Full Text Available Purpose: The purpose of this paper to develop an inventory model for instantaneous deteriorating items with the consideration of the facts that the deterioration rate can be controlled by using the preservation technology (PT and the holding cost & demand rate both are linear function of time which was treated as constant in most of the deteriorating inventory model. Design/methodology/approach: Developed the mathematical equation of deterministic deteriorating inventory model in which demand rate and holding cost both is linear function of time, deterioration rate is constant, backlogging rate is variable and depend on the length of the next replenishment, shortages are allowed and partially backlogged and obtain an analytical solution which optimizes the total cost of the proposed inventory model. Findings: The model can be applied for optimizing the total inventory cost of deteriorating items inventory for such business enterprises where they use the preservation technology to control the deterioration rate under other assumptions of the model. Originality/value: The inventory system for deteriorating items has been an object of study for a long time, but little is known about the effect of investing in reducing the rate of product deterioration and their significant impact in the business. The proposed model is effective as well as efficient for the business organization that uses the preservation technology to reduce the deterioration rate of the instantaneous deteriorating items of the inventory.

  20. Structural Concrete, Science into Practice

    NARCIS (Netherlands)

    Bruggeling, A.S.G.

    1987-01-01

    There is a need for a more rational and unified approach to all types of concrete structure, reinforced of prestressed. The first chapter explains in a historical review why the approach of reinforced concrete and that of prestressed concrete have hitherto been very different. In outlining the

  1. Concrete produced with recycled aggregates

    Directory of Open Access Journals (Sweden)

    J. J. L. Tenório

    Full Text Available This paper presents the analysis of the mechanical and durable properties of recycled aggregate concrete (RAC for using in concrete. The porosity of recycled coarse aggregates is known to influence the fresh and hardened concrete properties and these properties are related to the specific mass of the recycled coarse aggregates, which directly influences the mechanical properties of the concrete. The recycled aggregates were obtained from construction and demolition wastes (CDW, which were divided into recycled sand (fine and coarse aggregates. Besides this, a recycled coarse aggregate of a specific mass with a greater density was obtained by mixing the recycled aggregates of the CDW with the recycled aggregates of concrete wastes (CW. The concrete was produced in laboratory by combining three water-cement ratios, the ratios were used in agreement with NBR 6118 for structural concretes, with each recycled coarse aggregates and recycled sand or river sand, and the reference concrete was produced with natural aggregates. It was observed that recycled aggregates can be used in concrete with properties for structural concrete. In general, the use of recycled coarse aggregate in combination with recycled sand did not provide good results; but when the less porous was used, or the recycled coarse aggregate of a specific mass with a greater density, the properties of the concrete showed better results. Some RAC reached bigger strengths than the reference concrete.

  2. Multiscale Concrete Modeling of Aging Degradation

    Energy Technology Data Exchange (ETDEWEB)

    Hammi, Yousseff [Mississippi State Univ., Mississippi State, MS (United States); Gullett, Philipp [Mississippi State Univ., Mississippi State, MS (United States); Horstemeyer, Mark F. [Mississippi State Univ., Mississippi State, MS (United States)

    2015-07-31

    In this work a numerical finite element framework is implemented to enable the integration of coupled multiscale and multiphysics transport processes. A User Element subroutine (UEL) in Abaqus is used to simultaneously solve stress equilibrium, heat conduction, and multiple diffusion equations for 2D and 3D linear and quadratic elements. Transport processes in concrete structures and their degradation mechanisms are presented along with the discretization of the governing equations. The multiphysics modeling framework is theoretically extended to the linear elastic fracture mechanics (LEFM) by introducing the eXtended Finite Element Method (XFEM) and based on the XFEM user element implementation of Giner et al. [2009]. A damage model that takes into account the damage contribution from the different degradation mechanisms is theoretically developed. The total contribution of damage is forwarded to a Multi-Stage Fatigue (MSF) model to enable the assessment of the fatigue life and the deterioration of reinforced concrete structures in a nuclear power plant. Finally, two examples are presented to illustrate the developed multiphysics user element implementation and the XFEM implementation of Giner et al. [2009].

  3. From concrete repair to concrete conservation: How to preserve the heritage values of historic concrete

    NARCIS (Netherlands)

    Heinemann, H.A.; Zijlstra, H.; Hees, R.P.J. van; Nijland, T.G.

    2012-01-01

    The conservation of historic concrete is an increasing task, challenging both concrete repair specialists and conservation specialists. In practice, too often repair strategies are followed where conservation strategies would have been necessary. The application of repair techniques poses two

  4. Review of Cement Concrete Pavement of Noise Reduction Method

    Directory of Open Access Journals (Sweden)

    Tao Hongliang

    2017-01-01

    Full Text Available In recent years, with the rapid development of the economy, a sharp increase in car ownership in China, the rapid increase in cities traffic volume. Meanwhile, the effect on the normal life, work, study, rest and environment of residents along grows increasingly fierce both in extent and scope. Cement Concrete Pavement noise reduction measures seem more urgent. In this paper, introducing the current commonly used cement pavement noise reduction measures, and discussing the research and development direction of cement concrete pavement noise reduction measures.

  5. Danish High Performance Concretes

    DEFF Research Database (Denmark)

    Nielsen, M. P.; Christoffersen, J.; Frederiksen, J.

    1994-01-01

    In this paper the main results obtained in the research program High Performance Concretes in the 90's are presented. This program was financed by the Danish government and was carried out in cooperation between The Technical University of Denmark, several private companies, and Aalborg University...

  6. Teaching concrete structures

    DEFF Research Database (Denmark)

    Goltermann, Per

    2014-01-01

    The teaching of concrete structures has been revised and a number of new approaches have been developed, implemented and evaluated. Inductive teaching, E-learning and “patches” have been found to be improvements and may be an inspiration and help for others development of the teaching and learning...

  7. Polyester polymer concrete overlay.

    Science.gov (United States)

    2013-01-01

    Polyester polymer concrete (PPC) was used in a trial application on a section of pavement that suffers from extensive studded tire wear. The purpose of the trial section is to determine if PPC is a possible repair strategy for this type of pavement d...

  8. Anisotropic Concrete Compressive Strength

    DEFF Research Database (Denmark)

    Gustenhoff Hansen, Søren; Jørgensen, Henrik Brøner; Hoang, Linh Cao

    2017-01-01

    When the load carrying capacity of existing concrete structures is (re-)assessed it is often based on compressive strength of cores drilled out from the structure. Existing studies show that the core compressive strength is anisotropic; i.e. it depends on whether the cores are drilled parallel...

  9. Forterra Concrete Products, Inc.

    Science.gov (United States)

    The EPA is providing notice of a proposed Administrative Penalty Assessment against Forterra Concrete Products, Inc., a business located at 511 E. John Carpenter Freeway, Irving, TX, 75062, for alleged violations at its facility located at 23600 W. 40th St

  10. Fracture Mechanics of Concrete

    Indian Academy of Sciences (India)

    R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

    there was a workshop on the size effect in concrete structures, organized by H Mihashi,. H Okamura and Z P Ba˘zant, at Sendai, Japan in 1993. Various international committees were formed, the earliest one being the RILEM Committee chaired by F H Wittmann. Several other important meetings took place at different ...

  11. Continuous Reinforced Concrete Beams

    DEFF Research Database (Denmark)

    Hoang, Cao Linh; Nielsen, Mogens Peter

    1996-01-01

    This report deals with stress and stiffness estimates of continuous reinforced concrete beams with different stiffnesses for negative and positive moments e.g. corresponding to different reinforcement areas in top and bottom. Such conditions are often met in practice.The moment distribution...

  12. Magnesium oxychloride cement concrete

    Indian Academy of Sciences (India)

    TECS

    ting. It is used in industrial floorings, ship decks, railway passenger coach floorings, hospital floors, ammunition factory floors, missile silos and underground armament factories and bunkers. Recently, concrete of high compres- sive and tensile strength prepared with magnesium oxy- chloride cement and recycled rubber ...

  13. Electrical pulses protect concrete

    NARCIS (Netherlands)

    Koleva, D.; Fraaij, A.; Van Kasteren, J.

    2006-01-01

    Even concrete is not as hard as it looks. Sea water, salt on icy roads, and indirectly even carbon dioxide from the air can corrode the steel of the reinforcing bars and so threaten the strength and integrity of a bridge pier, jetty, or viaduct. Dessi Koleva, a chemical engineer from Bulgaria, spent

  14. Shell concrete pavement.

    Science.gov (United States)

    1966-10-01

    This report describes the testing performed with reef shell, clam shell and a combination of reef and clam shell used as coarse aggregate to determine if a low modulus concrete could be developed for use as a base material as an alternate to the pres...

  15. A Parameter Sensitivity Analysis of the Effect of Rebar Corrosion on the Stress Field in the Surrounding Concrete

    Directory of Open Access Journals (Sweden)

    Fangyuan Li

    2017-01-01

    Full Text Available Rebar corrosion results in a change in the stress field in the surrounding concrete, which in turn accelerates the deterioration of the concrete structure. In addition to the protective layer, the compressive stress under which concrete is prestressed also affects the effect of corrosion-induced rebar expansion on the stress field in the concrete. The present study simulates the effect of corrosion-induced rebar expansion on the stress field in the concrete using the finite element method (FEM by applying a virtual radial displacement to the product of corrosion-induced rebar expansion. Based on an analysis of the effect of multiple rebars on the stress field in ordinary concrete, stress distribution in the protective layer of the concrete is determined. Afterward, the locations where there is damage to the surface concrete caused by rebar corrosion are determined. After verifying the feasibility of the FEM analysis, the effect of corrosion-induced ordinary rebar expansion in a typical prestressed concrete segment is determined by analyzing the characteristics of corrosion-induced rebar expansion occurring in various prestressed concrete specimens.

  16. Potential polymer concrete heat exchanger tubes for corrosive environments

    Energy Technology Data Exchange (ETDEWEB)

    Fontana, J.J.; Reams, W.; Cheng, H.C.

    1986-11-01

    It has long been known that carbon steel exposed to some geothermal brines is aggressively attacked, and large corrosion allowances must be made in the design of piping used in such environments. In addition, scaling of the pipes reduces the flow through within a short period of time. Several high temperature polymer concretes have been developed which can be used as non-corrosive liner materials. In addition, polymer concretes with high thermal conductivities have been developed which may be used as heat exchanger tubes for geothermal brines. Studies have indicated that polymer concretes will not scale as rapidly as carbon steel does, thus making them attractive alternatives for heat exchanger tubes. Thin walled, thermally conductive polymer concrete tubes have been made that can withstand pressures >4.1 MPa at 150/sup 0/C without leaking. Continuing studies are being made to characterize these materials and evaluate them for heat exchanger applications.

  17. Transport and Corrosion Behavior of Cracked Reinforced Concrete

    DEFF Research Database (Denmark)

    Pease, Bradley Justin

    to enter the concrete. This is, among others, important in the corrosion of reinforcing steel. When cracks protrude to the depth of reinforcing steel, liquids containing aggressive ions (i.e. chlorides associated with salts and sea water) may rapidly access and initiate corrosion of the reinforcing...... structures. These models currently lack some of the scientific validity to fully represent actual field structures, i.e. structures containing cracks. Further understanding, therefore is needed on the effect cracks have on transport and corrosion in reinforced concrete. The fundamental mechanisms...... of transport and corrosion in cracked, reinforced concrete are not yet fully understood. The scope of this study therefore is to develop a link between concrete cracks and the relevant transport mechanism(s) under particular environmental conditions. It is envisioned that a finite element model...

  18. Self-compacting concrete (SCC)

    DEFF Research Database (Denmark)

    Geiker, Mette Rica

    2008-01-01

    In many aspects Self-Compacting Concrete (SCC, “Self-Consolidating Concrete” in North America) can be considered the concrete of the future. SCC is a family of tailored concretes with special engineered properties in the fresh state. SCC flows into the formwork and around even complicated...... reinforcement arrangements under its own weight. Thus, SCC is not vibrated like conventional concrete. This drastically improves the working environment during construction, the productivity, and potentially improves the homogeneity and quality of the concrete. In addition SCC provides larger architectural...

  19. MAIN MODIFICATIONS OF READY MIX CONCRETE STATIONS HAVING MODULAR-BLOCK LINE-UP

    Directory of Open Access Journals (Sweden)

    S. N. Leonovich

    2015-01-01

    Full Text Available The paper considers a new BNTU development that is concrete complexes having modular-block design. The modular-block approach presupposes to divide the whole technological chain for production of concrete and mortar mixes into separate sections (modules, each of which performs specific functions and can be used separately and independently of others. Then it is necessary to select such set of modules that ensure production of concrete and mortars. The paper presents designs of main modules in the technological chain for preparation of concrete mixes: a concrete mixing module, a storage and supply module of inert materials, a storage and supply module of cement and a number of additional auxiliary modules (a concrete supply module, a module for preparation of chemical additives, an operator module and a module for preparation and supply of air.Two main modifications of ready mix concrete stations developed on the basis of modular-block principle using basic modules are given in the paper. The first modification is a stationary concrete-mortar complex characterized by high productivity, large reserves of aggregates and cement, ability to be operated in winter due to heat insulation and water heating system and inert materials. The second modification is a transportable option that permits to transport the station from place to place due to reduction of time required for its installation and removal and execute production of concrete mixtures in the vicinity of the object construction. This options provides the possibility to reduce expenses on concrete transportation to the place of its deposit and decrease the probability of deterioration of consumer properties of the concrete mix that in its turn entails reduction in final cost of the object construction and improves quality of the construction.

  20. Chloride Resistance Behavior on Nano-Metaclayed Ultra-High Performance Concrete

    Directory of Open Access Journals (Sweden)

    Jaafar Mohd Faizal Md

    2017-01-01

    Full Text Available Nowadays, the application of nano materials is getting attention to enhance the conventional concrete properties. The ultrafine particles of nano material also will help reducing the formation of micro pores by acting as a filler agent, produce a very dense concrete and will reduce the growth of micro pores in the UHPC structures. The introduction of nano materials in concrete is to increase the strength and durability of concrete. One of the most important factor affecting concrete durability is chloride penetrability. The purpose of this study was to evaluate the chloride permeability and chloride penetration depth by using rapid chloride permeability test (RCPT and colorimetric method, respectively. The study was conducted for normal performance concrete (NPC, high performance concrete (HPC, ultra-high performance concrete (UHPC and a series of UHPC (nano metaclayed-UHPC incorporating different replacement levels of nano metaclay. All the tests were performed at ages of concretes from 3 up to 365 days. The results showed that the presence of silica fume in HPC and nano metaclay in UHPC reducing the Coulombs passed on the 56-days up to 365-days. The experimental results also revealed the depth of chloride ion penetration for nano metaclayed-UHPC concretes are much lesser than those concretes. As regards to the results, nano metaclay led to noticeable benefit in term of chloride resistance.

  1. Life Cycle Assessment of Concrete

    Energy Technology Data Exchange (ETDEWEB)

    Sjunnesson, Jeannette

    2005-09-15

    This is an environmental study on concrete that follows the standard protocol of life cycle assessment (LCA). The study is done for two types of concrete, ordinary and frost-resistant concrete, and has an extra focus on the superplasticizers used as admixtures. The utilization phase is not included in this study since the type of construction for which the concrete is used is not defined and the concrete is assumed to be inert during this phase. The results show that it is the production of the raw material and the transports involved in the life cycle of concrete that are the main contributors to the total environmental load. The one single step in the raw material production that has the highest impact is the production of cement. Within the transportation operations the transportation of concrete is the largest contributor, followed by the transportation of the cement. The environmental impact of frost-resistant concrete is between 24-41 % higher than that of ordinary concrete due to its higher content of cement. Superplasticizers contribute with approximately 0.4-10.4 % of the total environmental impact of concrete, the least to the global warming potential (GWP) and the most to the photochemical ozone creation potential (POCP). Also the toxicity of the superplasticizers is investigated and the conclusion is that the low amount of leakage of superplasticizers from concrete leads to a low risk for the environment and for humans.

  2. Biocalcification by halophilic bacteria for remediation of concrete structures in marine environment.

    Science.gov (United States)

    Bansal, Roohi; Dhami, Navdeep Kaur; Mukherjee, Abhijit; Reddy, M Sudhakara

    2016-11-01

    Microbial carbonate precipitation has emerged as a promising technology for remediation and restoration of concrete structures. Deterioration of reinforced concrete structures in marine environments is a major concern due to chloride-induced corrosion. In the current study, halophilic bacteria Exiguobacterium mexicanum was isolated from sea water and tested for biomineralization potential under different salt stress conditions. The growth, urease and carbonic anhydrase production significantly increased under salt stress conditions. Maximum calcium carbonate precipitation was recorded at 5 % NaCl concentration. Application of E. mexicanum on concrete specimens significantly increased the compressive strength (23.5 %) and reduced water absorption about five times under 5 % salt stress conditions compared to control specimens. SEM and XRD analysis of bacterial-treated concrete specimens confirmed the precipitation of calcite. The present study results support the potential of this technology for improving the strength and durability properties of building structures in marine environments.

  3. Effect of hot-dry environment on fiber-reinforced self-compacting concrete

    Science.gov (United States)

    Tioua, Tahar; Kriker, Abdelouahed; Salhi, Aimad; Barluenga, Gonzalo

    2016-07-01

    Drying shrinkage can be a major reason for the deterioration of concrete structures. Variation in ambient temperature and relative humidity cause changes in the properties of hardened concrete which can affect their mechanical and drying shrinkage characteristics. The present study investigated mechanical strength and particularly drying shrinkage properties of self-compacting concretes (SCC) reinforced with date palm fiber exposed to hot and dry environment. In this study a total of nine different fibers reinforced self compacting concrete (FRSCC) mixtures and one mixture without fiber were prepared. The volume fraction and the length of fibers reinforcement were 0.1-0.2-0.3% and 10-20-30 mm. It was observed that drying shrinkage lessened with adding low volumetric fraction and short length of fibers in curing condition (T = 20 °C and RH = 50 ± 5 %), but increased in hot and dry environment.

  4. A simple model for fatigue crack growth in concrete applied to a hinge beam model

    DEFF Research Database (Denmark)

    Skar, Asmus; Poulsen, Peter Noe; Olesen, John Forbes

    2017-01-01

    In concrete structures, fatigue is one of the major causes of material deterioration. Repeated loads result in formation of cracks. Propagation of these cracks cause internal progressive damage within the concrete material which ultimately leads to failure. This paper presents a simplified general...... concept for non-linear analysis of concrete subjected to cyclic loading. The model is based on the fracture mechanics concepts of the fictitious crack model, considering a fiber of concrete material, and a simple energy based approach for estimating the bridging stress under cyclic loading. Further......, the uni-axial fiber response is incorporated in a numerical hinge model for beam analysis. Finally, the hinge model is implemented into a finite element beam element on a constitutive level. The proposed model is compared to experimental results on both fiber-and beam level. The proposed model shows good...

  5. Concrete casting robustness improvement due to active rheology

    Directory of Open Access Journals (Sweden)

    Schmidt Wolfram

    2018-01-01

    Full Text Available With ongoing innovation in process technology, the challenges of concrete technology are more and more focused on the rheological optimisation for these processes, since improper mixture stability or poor compaction ability negatively affect the concrete homogeneity and quality. However, along with the increasing complexity of today’s concrete mixture compositions, concrete becomes more prone to failure regarding the casting process. Variable properties of the raw materials typically cause changing workability. The reasons can be found among others in scattering water contents, physical or chemical properties of the cement or varying environmental temperatures. Robustness in the delicately adjusted rheology, however, is of utmost importance for modern and future process technology, from sprayed concrete over pumpable concrete towards 3D-printing, with regard to the long-term strength, the function and the durability. Typically, material induced changes cannot be identified easily due to the complex interactions of concrete constituents. Therefore, a precise and prompt counteraction is impossible. However, it is known that the yield stress can be controlled by addition of supplementary superplasticizer or stabilising agent. In combination with computerized process observation tools that can rapidly interpret and react on changes in the rheology, it is therefore thinkable, that only these two admixture types can adjust the rheology steadily and permanently, regardless of the actual root cause for observed macroscopic rheology change. The presentation will firstly give a comprehensive overview of effects at the interface between pore solution, particles and hydrates, which affect the rheology of fresh concrete. Secondly, ways are recommended how the rheology can be actively manipulated before eventually computerized methods are demonstrated that help to actively and rapidly assess and counteract performance scatter during steady casting processes.

  6. Reliability analysis and updating of deteriorating systems with subset simulation

    DEFF Research Database (Denmark)

    Schneider, Ronald; Thöns, Sebastian; Straub, Daniel

    2017-01-01

    An efficient approach to reliability analysis of deteriorating structural systems is presented, which considers stochastic dependence among element deterioration. Information on a deteriorating structure obtained through inspection or monitoring is included in the reliability assessment through B...... is an efficient and robust sampling-based algorithm suitable for such analyses. The approach is demonstrated in two case studies considering a steel frame structure and a Daniels system subjected to high-cycle fatigue....

  7. Comparative environmental assessment of natural and recycled aggregate concrete.

    Science.gov (United States)

    Marinković, S; Radonjanin, V; Malešev, M; Ignjatović, I

    2010-11-01

    Constant and rapid increase in construction and demolition (C&D) waste generation and consumption of natural aggregate for concrete production became one of the biggest environmental problems in the construction industry. Recycling of C&D waste represents one way to convert a waste product into a resource but the environment benefits through energy consumption, emissions and fallouts reductions are not certain. The main purpose of this study is to determine the potentials of recycled aggregate concrete (concrete made with recycled concrete aggregate) for structural applications and to compare the environmental impact of the production of two types of ready-mixed concrete: natural aggregate concrete (NAC) made entirely with river aggregate and recycled aggregate concrete (RAC) made with natural fine and recycled coarse aggregate. Based on the analysis of up-to-date experimental evidence, including own tests results, it is concluded that utilization of RAC for low-to-middle strength structural concrete and non-aggressive exposure conditions is technically feasible. The Life Cycle Assessment (LCA) is performed for raw material extraction and material production part of the concrete life cycle including transport. Assessment is based on local LCI data and on typical conditions in Serbia. Results of this specific case study show that impacts of aggregate and cement production phases are slightly larger for RAC than for NAC but the total environmental impacts depend on the natural and recycled aggregates transport distances and on transport types. Limit natural aggregate transport distances above which the environmental impacts of RAC can be equal or even lower than the impacts of NAC are calculated for the specific case study. Copyright © 2010 Elsevier Ltd. All rights reserved.

  8. Early deterioration of coarse woody debris.

    Energy Technology Data Exchange (ETDEWEB)

    Tainter, Frank, H.; McMinn, James, W.

    1999-02-16

    Tainter, F.H., and J.W. McMinn. 1999. Early deterioration of coarse woody debris. In: Proc. Tenth Bien. South. Silv. Res. Conf. Shreveport, LA, February 16-18, 1999. Pp. 232-237 Abstract - Coarse woody debris (CWD) is an important structural component of southern forest ecosystems. CWD loading may be affected by different decomposition rates on sites of varying quality. Bolts of red oak and loblolly pine were placed on plots at each of three (hydric, mesic. and xerlc) sites at the Savannah River Site and sampled over a I6-week period. Major changes were in moisture content and nonstructural carbohydrate content (total carbohydrates, reducing sugars, and starch) of sapwood. Early changes in nonstructural carbohydrate levels following placement of the bolts were likely due to reallocation of these materials by sapwood parenchyma cells. These carbohydrates later formed pools increasingly metabolized by bacteria and invading fungi. Most prevalent fungi in sapwood were Ceratocysfis spp. in pine and Hypoxy/on spp. in oak. Although pine sapwood became blue stained and oak sapwood exhibited yellow soft decay with black zone lines, estimators of decay (specific gravity, sodium hydroxide solubility, and holocellulose content) were unchanged during the 16-week study period. A small effect of site was detected for starch content of sapwood of both species. Fungal biomass in sapwood of both species, as measured by ergosterol content, was detectable at week zero, increased somewhat by week three and increased significantly by week 16.

  9. Interim Report on Concrete Degradation Mechanisms and Online Monitoring Techniques

    Energy Technology Data Exchange (ETDEWEB)

    Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States); Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States); Neal, Kyle [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kosson, David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Adams, Douglas [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2014-09-01

    The existing nuclear power plants in the United States have initial operating licenses of 40 years, though most of these plants have applied for and received license extensions. As plant structures, systems, and components age, their useful life—considering both structural integrity and performance—is reduced as a result of deterioration of the materials. The research on online monitoring of concrete structures conducted under the Advanced Instrumentation, Information, and Control Systems Technologies Pathway of the Light Water Reactor Sustainability Program at Idaho National Laboratory will develop and demonstrate concrete structures health monitoring capabilities. Assessment and management of aging concrete structures in nuclear plants require a more systematic approach than simple reliance on existing code margins of safety. Therefore, structural health monitoring is required to produce actionable information regarding structural integrity that supports operational and maintenance decisions. Through this research project, several national laboratories and Vanderbilt University propose to develop a framework of research activities for the health monitoring of nuclear power plant concrete structures that includes the integration of four elements—damage modeling, monitoring, data analytics, and uncertainty quantification. This report briefly discusses available techniques and ongoing challenges in each of the four elements of the proposed framework with emphasis on degradation mechanisms and online monitoring techniques.

  10. Damaged Concrete Viaduct in an Italian Highway: Concrete Characterization and Possible Strengthening Techniques by FRP Applications in Comparison

    Science.gov (United States)

    Tittarelli, Francesca; Ruello, Maria Letizia; Capuani, Domenico; Aprile, Alessandra

    2017-10-01

    The “Fornello” viaduct in the Italian Orte-Ravenna highway (E45) is seriously damaged. In this paper, the concrete of the reinforced slab has been widely characterized to evaluate the level of damage and to identify the causes of degradation. No-destructive tests, as those based on ultrasonic waves, as well as chemical, physical and mechanical destructive tests have been carried out on specimens drawn from deteriorated and not deteriorated zones of the R/C bridge decks. Into the slab thickness, the concentration distribution of main anions has been quantified by ion chromatography. Porosimetry tests have been carried out to detect the resistance to freeze-thaw cycles of cement paste. Possible strengthening techniques by FRP applications have been compared.

  11. Permeability, porosity and compressive strength of self-compacting concrete

    Directory of Open Access Journals (Sweden)

    Valcuende, M.O.

    2005-12-01

    Full Text Available Most deterioration affecting the durability of self-compacting concrete structures is mediated by water penetration in the concrete, a condition related to its porous structure. The present study analyzes these two factors. To this end, two types of concrete were prepared, a self-compacting and a traditional vibrated concrete, with different W/C ratios and different types of cement. The results of low-pressure water testing to evaluate permeability and analyses to determine compressive strength and pore size distribution showed that self-compacting concrete has lower capillary porosity than traditional concrete, which would explain its greater resistance to water penetration. Such concrete likewise reached higher strength values, except where large proportions of lime powder with low sand equivalents were used in its manufacture, when lower strength was recorded. Lastly, the depth of water penetration and compressive strength were found to be linearly correlated. That correlation was seen to depend, in turn, on the type of concrete, since for any given strength level, self-compacting concrete was less permeable than the traditional material.

    En este trabajo experimental se estudia la penetración de agua en hormigones autocompactables, analizando al mismo tiempo su estructura porosa, pues gran parte de los procesos de deterioro que afectan a la durabilidad de las estructuras están condicionados por estos dos aspectos. Para ello se han fabricado dos tipos de hormigones, uno autocompactable y otro tradicional vibrado, con diferentes relaciones A/C y distintos tipos de cemento. Tras determinar la permeabilidad al agua bajo presión, la resistencia a compresión y las distribuciones de tamaño de poro, los resultados obtenidos ponen de manifiesto que los hormigones autocompactables presentan menor porosidad capilar que los tradicionales, lo que les confiere mejores prestaciones frente a la penetración de agua. Asimismo, dichos hormigones

  12. Micro Environmental Concrete

    Science.gov (United States)

    Lanez, M.; Oudjit, M. N.; Zenati, A.; Arroudj, K.; Bali, A.

    Reactive powder concretes (RPC) are characterized by a particle diameter not exceeding 600 μm and having very high compressive and tensile strengths. This paper describes a new generation of micro concrete, which has an initial as well as a final high physicomechanical performance. To achieve this, 15% by weight of the Portland cement have been substituted by materials rich in Silica (Slag and Dune Sand). The results obtained from the tests carried out on the RPC show that compressive and tensile strengths increase when incorporating the addition, thus improving the compactness of mixtures through filler and pozzolanic effects. With a reduction in the aggregate phase in the RPC and the abundance of the dune sand (southern of Algeria) and slag (industrial by-product of the blast furnace), the use of the RPC will allow Algeria to fulfil economical as well as ecological requirements.

  13. Laser ablation of concrete.

    Energy Technology Data Exchange (ETDEWEB)

    Savina, M.

    1998-10-05

    Laser ablation is effective both as an analytical tool and as a means of removing surface coatings. The elemental composition of surfaces can be determined by either mass spectrometry or atomic emission spectroscopy of the atomized effluent. Paint can be removed from aircraft without damage to the underlying aluminum substrate, and environmentally damaged buildings and sculptures can be restored by ablating away deposited grime. A recent application of laser ablation is the removal of radioactive contaminants from the surface and near-surface regions of concrete. We present the results of ablation tests on concrete samples using a high power pulsed Nd:YAG laser with fiber optic beam delivery. The laser-surface interaction was studied on various model systems consisting of Type I Portland cement with varying amounts of either fine silica or sand in an effort to understand the effect of substrate composition on ablation rates and mechanisms. A sample of non-contaminated concrete from a nuclear power plant was also studied. In addition, cement and concrete samples were doped with non-radioactive isotopes of elements representative of cooling waterspills, such as cesium and strontium, and analyzed by laser-resorption mass spectrometry to determine the contamination pathways. These samples were also ablated at high power to determine the efficiency with which surface contaminants are removed and captured. The results show that the neat cement matrix melts and vaporizes when little or no sand or aggregate is present. Surface flows of liquid material are readily apparent on the ablated surface and the captured aerosol takes the form of glassy beads up to a few tens of microns in diameter. The presence of sand and aggregate particles causes the material to disaggregate on ablation, with intact particles on the millimeter size scale leaving the surface. Laser resorption mass spectrometric analysis showed that cesium and potassium have similar chemical environments in the

  14. Concrete containment aging study

    Energy Technology Data Exchange (ETDEWEB)

    Pachner, J. [International Atomic Energy Agency, Vienna (Austria); Tai, T.M. [Bechtel National, Inc., Oak Ridge, TN (United States); Naus, D. [Oak Ridge National Lab., TN (United States)

    1994-04-01

    In 1989, IAEA initiated a pilot study on the management of aging of nuclear power plant components. The Phase I and II studies of concrete containment are discussed. With the data base, plant owners will be able to review and enhance their existing programs. IAEA will analyze data provided by participating plants and the report is scheduled to be released by late 1994 (final report release mid-1995).

  15. New era for concrete

    OpenAIRE

    Petra Novotna; Federico Meneghello

    2016-01-01

    The article presentes the Eco-Binder project, the scope of the project is to demonstrate the fasibility of replacing Ordinary Portland Cement (OPC) and OPC based concrete (products) with new products based on the innovative Belite-Ye’elimite-Ferrite (BYF) class of low-CO2 binders. ECO-Binder aims to address the vast market for envelope retrofitting and new construction with a new generation of prefabricated building envelope components with: -30% carbon footprints +20% insulating pr...

  16. Nondestructive Concrete Characterization System

    Science.gov (United States)

    2013-05-20

    blocks to establish the mechanical properties of the concrete material. The destructive tests were undertaken according to the relevant ASTM standards...The large blocks were cast for Non Destructive Testing ( NDT ) along with the cylinders and small beams for destructive testing with the following...NCSU performed the destructive testing in accordance with the following standards: ASTM C39 for compressive strength, ASTM C469 for modulus of

  17. Design of ultra-lightweight concrete: towards monolithic concrete structures

    Directory of Open Access Journals (Sweden)

    Yu Qing Liang

    2014-04-01

    Full Text Available This study addresses the development of ultra-lightweight concrete. A moderate strength and an excellent thermal conductivity of the lightweight concrete are set as the design targets. The designed lightweight aggregates concrete is targeted to be used in monolithic concrete façade structure, performing as both load bearing element and thermal insulator. The developed lightweight concrete shows excellent thermal properties, with a low thermal conductivity of about 0.12 W/(m·K; and moderate mechanical properties, with 28-day compressive strengths of about 10-12 N/mm . This combination of values exceeds, to the researchers’ knowledge, the performance of all other lightweight building materials. Furthermore, the developed lightweight concrete possesses excellent durability properties.

  18. Surface resistivity test evaluation as an indicator of the chloride permeability of concrete.

    Science.gov (United States)

    2012-12-01

    Many agencies have adopted the standard tests for electrical : indication of concretes ability to resist chloride ion penetration : (AASHTO T 277 and ASTM C1202), commonly known as the rapid : chloride permeability test (RCPT), in their specificat...

  19. The use of lithium to prevent or mitigate alkali-silica reaction in concrete pavements and structures.

    Science.gov (United States)

    2007-03-01

    Alkali-silica reaction (ASR) was first identified as a form of concrete deterioration in the late 1930s : (Stanton 1940). Approximately 10 years later, it was discovered that lithium compounds can be used to : control expansion due to ASR. There has ...

  20. An Experimental Study on Strength and Durability for Utilization of Fly Ash in Concrete Mix

    Directory of Open Access Journals (Sweden)

    Abdulhalim Karaşin

    2014-01-01

    Full Text Available The intention of this study is to discuss the variation of concrete exposed to high sulfate environment of a specific region with respect to strength and durability. Secondly, it is aimed to discuss the possibility of reducing the cement amount in construction of concrete structures. For this purpose, laboratory tests were conducted to investigate compressive strength and sulfate resisting capacity of concrete by using 20% fly ash as mineral additives, waste materials, instead of cement. As a case study the soil samples, received from Siirt Province areas which contain high sulfate rate, have been compared with respect to sulfate standard parameters of TS 12457-4. In such regions contact of underground water seep into hardened concrete substructures poses a risk of concrete deterioration. In order to determine the variation of strength and durability for concrete exposed to such aggressive environment, the samples were rested in a solution of Na2SO4 (150 g/lt in accordance with ASTM C 1012 for the tests. As a result of this experimental study, it is noted that the use of 20% fly ash, replacement material instead of cement, has no significant effect on compressive strength of concrete over time.

  1. Numerical simulation of CFRP-repaired reinforced concrete columns.

    Science.gov (United States)

    2014-07-01

    The overarching goal of this study was to investigate the influence of repair to individual reinforced concrete bridge columns on the : post-repair seismic performance of the bridge system. A method was developed to rapidly repair an earthquake-damag...

  2. Microbial deterioration studies of military cotton and leather based ...

    African Journals Online (AJOL)

    Microbial deterioration studies on selected cotton based uniforms were carried out using test-fungi earlier isolated from the uniforms stored in the Military Warehouses. These fungi includes, Aspergillus nigar, A. fumigatus, C. gwbosum, C. thermophile, Var.coprohile, B. stolonifer and S. pulverulentum. The deteriorative ...

  3. Causes of Early Deterioration of Coastal and Marine Structures in ...

    African Journals Online (AJOL)

    Causes of Early Deterioration of Coastal and Marine Structures in Temperate African Countries and Design Approaches to Improve their Service-Lives. ... conditions and lack of routine maintenance and monitoring system has resulted in the premature deterioration and failure of a large percentage of these vital structures.

  4. Review of inventory systems with deterioration since 2001

    NARCIS (Netherlands)

    Bakker, M.; Riezebos, J.; Teunter, R.H.

    2012-01-01

    This paper presents an up-to-date review of the advances made in the field of inventory control of perishable items (deteriorating inventory). The last extensive review on this topic dates back to 2001 (Goyal S.K. and Giri B.C., Recent trends in modeling of deteriorating inventory, European Journal

  5. microbial deterioration studies of military cotton and leather based ...

    African Journals Online (AJOL)

    BSN

    The implications of the findings are discussed. INTRODUCTION. Microbial deterioration is the study of any undesirable change in the properties of a material caused by the activities of microorganisms. Any investigation on materials deterioration would inevitably involve the estimation or precise measurement of the extent.

  6. 40 CFR 52.1987 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1987 Section 52.1987 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The Oregon Department of Environmental Quality rules for the prevention of significant deterioration of air quality (provisions of OAR chapter 340, Divisions 200, 202...

  7. 40 CFR 52.1029 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.1029 Section 52.1029 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. The program to review operation and construction of new and modified...

  8. 40 CFR 52.931 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.931 Section 52.931 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) Regulations for preventing significant deterioration of air quality. The..., the Kentucky Division for Air Quality has determined that the application complies with the applicable...

  9. 40 CFR 52.96 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.96 Section 52.96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The State of Alaska Department of Environmental Conservation Air Quality... deterioration of air quality. (b) The requirements of sections 160 through 165 of the Clean Air Act are not met...

  10. 40 CFR 52.738 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.738 Section 52.738 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air Act are not met... air quality. (b) Regulations for preventing significant deterioration of air quality. The provisions...

  11. 40 CFR 52.2083 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.2083 Section 52.2083 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The Rhode Island plan, as submitted, is approved as meeting the...

  12. 40 CFR 52.793 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.793 Section 52.793 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air Act are not met... air quality. (b) Regulations for preventing significant deterioration of air quality. The provisions...

  13. 40 CFR 52.581 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.581 Section 52.581 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) All applications and other information required pursuant to § 52.21 of this...

  14. 40 CFR 52.632 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.632 Section 52.632 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air Act are not met... air quality. (b) Regulations for preventing significant deterioration of air quality. The provisions...

  15. 40 CFR 52.1485 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1485 Section 52.1485 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... include approvable procedures for preventing the significant deterioration of air quality. (b) Regulation...

  16. 40 CFR 52.884 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.884 Section 52.884 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of section 160 through 165 of the Clean Air Act, as amended...

  17. 40 CFR 52.2303 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2303 Section 52.2303 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The plan submitted by Texas is approved as meeting the requirements of part C, Clean Air Act for preventing significant deterioration of air quality. The plan...

  18. 40 CFR 52.2131 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.2131 Section 52.2131 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a)-(b) (c) All applications and other information required pursuant...

  19. 40 CFR 52.986 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.986 Section 52.986 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The plan submitted by the Governor of Louisiana on August 14, 1984 (as adopted... preventing significant deterioration of air quality. (b) The requirements of sections 160 through 165 of the...

  20. 40 CFR 52.1436 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.1436 Section 52.1436 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. The requirements of sections 160 through 165 of the Clean Air Act...

  1. 40 CFR 52.833 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.833 Section 52.833 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air Act are met... for preventing significant deterioration of air quality. The provisions of § 52.21 except paragraph (a...

  2. 40 CFR 52.2380 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.2380 Section 52.2380 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. The program to review the construction and operation of new and...

  3. 40 CFR 52.343 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.343 Section 52.343 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air Act are not met for the following categories of sources for preventing the significant deterioration of air quality...

  4. 40 CFR 52.1116 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.1116 Section 52.1116 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air... deterioration of air quality. (b) The following provisions of 40 CFR 52.21 are hereby incorporated and made a...

  5. 40 CFR 52.2581 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2581 Section 52.2581 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a)-(c) (d) The requirements of sections 160 through 165 of the... of Wisconsin. (e) Regulations for the prevention of the significant deterioration of air quality. The...

  6. 40 CFR 52.1529 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.1529 Section 52.1529 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. New Hampshire's Part Env-A 623, “Requirements for Prevention of...

  7. 40 CFR 52.2178 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2178 Section 52.2178 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The South Dakota plan, as submitted, is approved as meeting the... on Indian reservations; (b) Regulations for preventing significant deterioration of air quality. The...

  8. 40 CFR 52.382 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.382 Section 52.382 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Air Act are not met...

  9. 40 CFR 52.2346 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.2346 Section 52.2346 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) The Utah plan, as submitted, is approved as meeting the... construct on Indian Reservations. (b) Regulation for prevention of significant deterioration of air quality...

  10. 40 CFR 52.144 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... quality. 52.144 Section 52.144 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... deterioration of air quality. (a) The requirements of sections 160 through 165 of the Clean Act are not met... lands does not include approvable procedures for preventing the significant deterioration of air quality...

  11. 40 CFR 52.1280 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... 40 Protection of Environment 4 2010-07-01 2010-07-01 false Significant deterioration of air quality. 52.1280 Section 52.1280 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Significant deterioration of air quality. (a) All applications and other information required pursuant to § 52...

  12. Concern With Environmental Deterioration and Attitudes Toward Population Limitation

    Science.gov (United States)

    Barnett, Larry D.

    1970-01-01

    Analysis of Gallup Poll data of Junuary 1969 reveals weak association between concern about environmental deterioration and the recognition of need for eventual limitation of human population. Suggests that to increase favorable attitudes to population control, role of overpopulation in causing environmental deterioration needs to be presented to…

  13. 40 CFR 52.530 - Significant deterioration of air quality.

    Science.gov (United States)

    2010-07-01

    ... deterioration of air quality. (a) EPA approves the Florida Prevention of Significant Deterioration program, as... applications and other information required pursuant to § 52.21 of this part from sources located in the State... Act are not met since the Florida plan, as submitted, does not apply to certain sources. Therefore...

  14. A study on the effects of seawater on the durable life of concrete structures(II)

    Energy Technology Data Exchange (ETDEWEB)

    Oh, Byung Hwan; Jang, Bong Suk; Jang, Seung Yeop; Jeon, Se Jin; Yu, Yeong; Park, Dae Gyun; Hyeong, Sang Soo [Seoul National Univ., Seoul (Korea, Republic of)

    1999-02-15

    Recently, large scale concrete structures such as nuclear power plants and offshore structures are actively being built in this country. These structures are subject to heavy attack due to seawater environment. A reasonable consideration for corrosion has not been paid to the structures in the past decades due to insufficient research data and guidelines. The durability is emerging as one of the most important factors. In the design and construction of concrete structures. The purpose of the present study is, therefore, to explore the corrosion mechanism and penetration mechanism of chloride ion, and to establish the evaluation procedure of durability life of concrete structures. In this study, the chloride ion concentration of seawater around our country have been analyzed and the deterioration mechanism of concrete structures have been also analyzed. The penetration mechanism of seawater into the concrete has been also studied. To this end, a comprehensive experimental program has been setup. The major test variables include the type of cement and the type of mineral admixture. The strength test as well as corrosion test have been conducted to explore the effects of chloride ion penetration on the properties of concrete. The corrosion mechanism and the penetration of chloride ion into concrete structures have been studied. These results will allow the estimation of durable life of concrete structures in nuclear power plants. The experimental results and the developed theory in the present study can be efficiently used to analyze the chloride ion penetration and to estimate the durability of concrete structures In nuclear power plants. The present study may also provide strong basis to evaluate the remaining service life of concrete structures in nuclear power plants.

  15. Chapter K: Progress in the Evaluation of Alkali-Aggregate Reaction in Concrete Construction in the Pacific Northwest, United States and Canada

    Science.gov (United States)

    Shrimer, Fred H.

    2005-01-01

    The supply of aggregates suitable for use in construction and maintenance of infrastructure in western North America is a continuing concern to the engineering and resources-management community. Steady population growth throughout the region has fueled demand for high-quality aggregates, in the face of rapid depletion of existing aggregate resources and slow and difficult permitting of new sources of traditional aggregate types. In addition to these challenges, the requirement for aggregates to meet various engineering standards continues to increase. In addition to their physical-mechanical properties, other performance characteristics of construction aggregates specifically depend on their mineralogy and texture. These properties can result in deleterious chemical reactions when aggregate is used in concrete mixes. When this chemical reaction-termed 'alkali-aggregate reaction' (AAR)-occurs, it can pose a major problem for concrete structures, reducing their service life and requiring expensive repair or even replacement of the concrete. AAR is thus to be avoided in order to promote the longevity of concrete structures and to ensure that public moneys invested in infrastructure are well spent. Because the AAR phenomenon is directly related to the mineral composition, texture, and petrogenesis of the rock particles that make up aggregates, an understanding of the relation between the geology and the performance of aggregates in concrete is important. In the Pacific Northwest, some aggregates have a moderate to high AAR potential, but many others have no or only a low AAR potential. Overall, AAR is not as widespread or serious a problem in the Pacific Northwest as in other regions of North America. The identification of reactive aggregates in the Pacific Northwest and the accurate prediction of their behavior in concrete continue to present challenges for the assessment and management of geologic resources to the owners and operators of pits and quarries and to the

  16. Experimental research on durability of recycled aggregate concrete under freeze- thaw cycles

    Science.gov (United States)

    Cheng, Yanqiu; Shang, Xiaoyu; Zhang, Youjia

    2017-07-01

    The freeze-thaw durability of recycled aggregate concrete has significance for the concrete buildings in the cold region. In this paper, the rapid freezing and thawing cycles experience on recycle aggregate concrete was conducted to study on the effects of recycle aggregate amount, water-binder ratio and fly ash on freeze-thaw durability of recycle aggregate concrete. The results indicates that recycle aggregate amount makes the significant influence on the freeze-thaw durability. With the increase of recycled aggregates amount, the freeze-thaw resistance for recycled aggregate concrete decreases. Recycled aggregate concrete with lower water cement ratio demonstrates better performance of freeze-thaw durability. It is advised that the amount of fly ash is less than 30% for admixture of recycled aggregates in the cold region.

  17. Chloride Transport in OPC Concrete Subjected to the Freeze and Thaw Damage

    Directory of Open Access Journals (Sweden)

    Ki Yong Ann

    2017-01-01

    Full Text Available To predict the durability of a concrete structure under the coupling degradation consisting of the frosting and chloride attack, microstructural analysis of the concrete pore structure should be accompanied. In this study, the correlation between the pore structure and chloride migration for OPC concrete was evaluated at the different cement content in the concrete mix accounting for 300, 350, and 400 kg/m3 at 0.45 of a free water cement ratio. The influence of frosting damage on the rate of chloride transport was assessed by testing with concrete specimens subjected to a rapid freezing and thawing cyclic environment. As a result, it was found that chloride transport was accelerated by frost damage, which was more influential at the lower cement content. The microscopic examination of the pore structure showed that the freezing environment increased the volume of the large capillary pore in the concrete matrix.

  18. Let’s Get Concrete!

    DEFF Research Database (Denmark)

    Jones, Candace; Boxenbaum, Eva

    Scholars emphasize the cognitive or ideational aspects of institutional logics. Less clear is the role of materiality, which is a key aspect of institutional logics, and aesthetic responses to material objects. This study focuses on the introduction of a new building material—concrete— during 1890...... to 1939 in the architectural profession. Our findings reveal that how professional logics were enacted drove different process for incorporating concrete as a legitimate building material: in France professional and state logics combined to create regulations that governed architects’ use of concrete......-legitimated not only concrete but also stone. Concrete was perceived as merely imitative and thus inauthentic. For concrete to become a legitimate and widely adopted material, architects had to theorize concrete as unique material with distinctive aesthetic possibilities, which led to new kinds of buildings and new...

  19. Investigation of the Precipitates on the Concrete Surface due to Sulphate Exposure

    Science.gov (United States)

    Kovalčíková, Martina; Eštoková, Adriana; Oravec, Jozef; Luptáková, Alena

    2016-12-01

    The aim of this study is to investigate the durability of cement-based materials subjected to the effects of sulphuric acid in terms of surface deterioration. Damaged concrete surfaces and the samples' mass changes were studied during 270-day simulation of both chemical and biological attacks. Chemical corrosion was simulated by sulphuric acid with pH of 3.0 and 4.0, respectively, while biological corrosion was simulated by activity of bacteria Acidithiobacillus thiooxidans. XRD and SEM analyses confirmed a massive sulphate precipitate formation on the concrete surface due to chemical and biological sulphate corrosion.

  20. Resistance of biofilm-covered mortars to microbiologically influenced deterioration simulated by sulfuric acid exposure

    Energy Technology Data Exchange (ETDEWEB)

    Soleimani, Sahar, E-mail: ssoleima@connect.carleton.ca; Isgor, O. Burkan, E-mail: burkan_isgor@carleton.ca; Ormeci, Banu, E-mail: banu_ormeci@carleton.ca

    2013-11-15

    Following the reported success of biofilm applications on metal surfaces to inhibit microbiologically influenced corrosion, effectiveness and sustainability of E. coli DH5α biofilm on mortar surface to prevent microbiologically influenced concrete deterioration (MICD) are investigated. Experiments simulating microbial attack were carried out by exposing incrementally biofilm-covered mortar specimens to sulfuric acid solutions with pH ranging from 3 to 6. Results showed that calcium concentration in control reactors without biofilm was 23–47% higher than the reactors with biofilm-covered mortar. Formation of amorphous silica gel as an indication of early stages of acid attack was observed only on the control mortar specimens without biofilm. During acidification, the biofilm continued to grow and its thickness almost doubled from ∼ 30 μm before acidification to ∼ 60 μm after acidification. These results demonstrated that E. coli DH5α biofilm was able to provide a protective and sustainable barrier on mortar surfaces against medium to strong sulfuric acid attack. -- Highlights: •Effectiveness of E.coli DH5α biofilm to prevent MICD was studied. •Conditions that lead to MICD were simulated by chemical acidification. •Biofilm-covered mortar specimens were exposed to sulfuric acid solutions. •The presence of biofilm helped reduce the chemically-induced mortar deterioration. •Biofilm remained alive and continued to grow during the acidification process.

  1. Acute functional deterioration in a child with cerebral palsy.

    LENUS (Irish Health Repository)

    Smyth, Elizabeth

    2012-01-01

    We describe a case of acute functional deterioration in a 13-year-old girl with severe spastic diplegia (GMFCS III) and a new diagnosis of diffuse intrinsic pontine glioma (DIPG). She presented with acute deterioration in mobility and motor function over 1 month, which was associated with dysarthria, dysphagia and behavioural change. Her mother had noticed subtle functional deterioration over the 2 months prior to this. Her physiotherapist who was concerned about her acute functional deterioration referred her for emergency review. Neurological imaging revealed a diffuse pontine lesion consistent with DIPG. She was subsequently referred to oncology. She deteriorated further, clinically, over the next few days and following discussion with the team; her family opted for palliative treatment, given the poor prognosis associated with DIPG.

  2. Delirium and high fever are associated with subacute motor deterioration in Parkinson disease: a nested case-control study.

    Directory of Open Access Journals (Sweden)

    Atsushi Umemura

    Full Text Available BACKGROUND: In Parkinson disease (PD, systemic inflammation caused by respiratory infections such as pneumonia frequently occurs, often resulting in delirium in the advanced stages of this disease. Delirium can lead to cognitive and functional decline, institutionalization, and mortality, especially in the elderly. Inflammation causes rapid worsening of PD motor symptoms and signs, sometimes irreversibly in some, but not all, patients. PURPOSE: To identify factors associated with subacute motor deterioration in PD patients with systemic inflammation. METHODS: The association of clinical factors with subacute motor deterioration was analyzed by a case-control study. Subacute motor deterioration was defined as sustained worsening by one or more modified Hoehn and Yahr (H-Y stages. Using multivariable logistic regression incorporating baseline characteristics (age, sex, PD duration, modified H-Y stage, dementia, and psychosis history and statistically selected possible predictors (peak body temperature, duration of leukocytosis, and presence of delirium, the odds ratios for these factors were estimated as relative risks. RESULTS: Of 80 PD patients with systemic inflammation, 26 with associated subacute motor deterioration were designated as cases and the remainder as controls. In the 26 cases, 6 months after its onset the motor deterioration had persisted in 19 patients and resolved in four (three were lost for follow-up. Multivariable logistic regression analysis showed that delirium and body temperature are significantly associated with motor deterioration after systemic inflammation (P = 0.001 for delirium and P = 0.026 for body temperature, the adjusted odds ratios being 15.89 (95% confidence interval [CI]: 3.23-78.14 and 2.78 (95% CI: 1.13-6.83, respectively. CONCLUSIONS: In patients with PD and systemic inflammation, delirium and high body temperature are strong risk factors for subsequent subacute motor deterioration and such deterioration

  3. Spall Damage of Concrete Structures

    Science.gov (United States)

    1988-06-01

    C1 APPENDIX D DATA ON DAMAGE OF REINFORCED CONCRETE STRUCTURES CAUSED BY’ NEARBY BOMB DETONATIONS ..................... D1 LIST OF...27.6799 grams/centimeters 3 xiii SPALL DAMAGE TO CONCRETE STRUCTURES PART I: INTRODUCTION Backaround Spall is defined as the ejection of fragments of a...of the walls. Additional data from other tests with detonations of bombs near concrete structures were also collected in a literature search. The data

  4. Inspection Strategies for Concrete Bridges

    DEFF Research Database (Denmark)

    Sørensen, John Dalsgaard; Thoft-Christensen, Palle

    1989-01-01

    In this paper an optimal inspection strategy for concrete bridges based on periodic routine and detailed inspections is presented. The failure mode considered is corrosion of the reinforcement due to chlorides. A simple modelling of the corrosion and of the inspection strategy is presented....... The optimal inspection strategy is determined from an optimization problem, where the design variables are time intervals between detailed inspections and the concrete cover. The strategy is illustrated on a simple structure, namely a reinforced concrete beam....

  5. Markets: Ready-Mixed Concrete

    OpenAIRE

    Chad Syverson

    2008-01-01

    Concrete's natural color is gray. Its favored uses are utilitarian. Its very ubiquity causes it to blend into the background. But ready-mix concrete does have one remarkable characteristic: other than manufactured ice, perhaps no other manufacturing industry faces greater transport barriers. The transportation problem arises because ready-mix concrete both has a low value-to-weight ratio and is highly perishable -- it absolutely must be discharged from the truck before it hardens. These trans...

  6. Concreteness effects in single-meaning, multi-meaning and newly acquired words.

    Science.gov (United States)

    Palmer, Shekeila D; Macgregor, Lucy J; Havelka, Jelena

    2013-11-13

    This study examined the extent to which concreteness influences the acquisition and subsequent processing of novel (low frequency) concepts. Participants were trained on 70 rare English words (35 concrete, 35 abstract) paired with definitions. ERPs were then recorded while participants performed a semantic categorisation (concrete vs. abstract) and a lexical decision task on single-meaning, multi-meaning and the newly acquired words. During training there was a significant effect of concreteness, in that participants were more successful at acquiring concrete concepts. In both the semantic categorisation and the lexical decision task, concreteness effects were evident in the behavioural and in the ERP data for all word types, with concrete words eliciting more negative waveforms than abstract words in the N400 time window. Behaviourally, participants experienced greater difficulty in judging the concreteness of multi-meaning words, yet concreteness effects in the N400 were equally strong for all three word types across both tasks. These findings indicate that concreteness represents a fundamental distinction in the way that items are represented in memory, which is independent of the participant's perceived judgement. They further demonstrate that novel concepts can be acquired rapidly after minimal training, and that the neurophysiological correlates associated with processing novel words are modulated by the specific nature of the conceptual characteristics assigned to the word. © 2013 Published by Elsevier B.V.

  7. Photogrammetric Assessment of Flexure Induced Cracking of Reinforced Concrete Beams under Service Loads

    DEFF Research Database (Denmark)

    Pease, Bradley Justin; Geiker, Mette Rica; Stang, Henrik

    2006-01-01

    Reinforced concrete structures are known to crack due to restrained shrinkage, temperature gradients, application of load, and expansive reactions. Cracks provide paths for rapid ingress of moisture, chlorides, and other aggressive substances, which may affect the long-term durability...... of the structure. For example, concrete cracks located at the reinforcing steel may contribute to a rapid corrosion initiation and propagation. Previous research has shown that cracked reinforced concrete under static flexural loading may have an increased ingress of chloride ions along the reinforcement....../concrete interface. The aim of this paper is to provide a detailed description of the development of cracks in reinforced concrete under flexural load. Cracking at both realistic service load levels (1.0-1.8 times estimated cracking load) and unrealistically high service load levels (> 0.5 times beam capacity) has...

  8. Design of Reinforced Concrete Elements Under Fire

    Directory of Open Access Journals (Sweden)

    P. Mihai

    2008-01-01

    Full Text Available Fire safety regulations can have a major impact on many aspects of the overall design of a building, including layout, aesthetics, function, and cost. Rapid developments in modern building technology in the last decades often have resulted in unconventional structures and design solutions. Because the world is developed continuously, the physical size of buildings increases continually; there is a tendency to build large underground car parks, warehouses, and shopping complexes. As a result, we have a worldwide movement to replace prescriptive building codes with ones based on performance. The paper presents the basic principles for the designing process of reinforced concrete elements under fire.

  9. Mechanical and durability aspects of concrete incorporating secondary aluminium slag

    Directory of Open Access Journals (Sweden)

    M. Satish Reddy

    2016-12-01

    Full Text Available The environmental impact can be minimised by making use of many industrial wastes in a sustainable manner. Recycling and reutilisation of industrial waste and by-products is of paramount importance in cement and concrete industry. In view of rapid infrastructure growth, there is an emerging need for development of cementitious materials or fillers either to replace cement or fine aggregate for stable growth. One of the industrial wastes is secondary aluminium dross. In this paper, an attempt has been made to study the mechanical and durability aspects of concrete incorporated with secondary aluminium dross. Cement has been partially replaced by secondary aluminium dross in different proportions to study the mechanical and durability aspects. Various properties such as compressive strength, split tensile strength, flexural strength, sorptivity, water absorption, rapid chloride penetration have been studied for the usefulness of secondary aluminium dross as construction material. It is observed that up to 15% replacement of cement by secondary aluminium dross, the responses are comparable with the conventional concrete. Studies have also been carried out by adding other supplementary cementitious materials such as fly ash and silica fume in various proportions along with secondary aluminium dross and found the improved mechanical and durability properties. From the overall study, it can be concluded that the concrete incorporated with secondary aluminium dross can be used for making paver blocks, refractory bricks and for normal concrete strength applications.

  10. Effects of gamma irradiation on deteriorated paper

    Science.gov (United States)

    Bicchieri, Marina; Monti, Michela; Piantanida, Giovanna; Sodo, Armida

    2016-08-01

    Even though gamma radiation application, also at the minimum dosage required for disinfection, causes depolymerization and degradation of the paper substrate, recently published papers seemed, instead, to suggest that γ-rays application could be envisaged in some conditions for Cultural Heritage original documents and books. In some of the published papers, the possible application of γ-rays was evaluated mainly by using mechanical tests that scarcely reflect the chemical modifications induced in the cellulosic support. In the present article the effect of low dosage γ-irradiation on cellulosic substrates was studied and monitored applying different techniques: colorimetry, spectroscopic measurements, carbonyl content and average viscometric degree of polymerization. Two different papers were investigated, a non-sized, non-filled cotton paper, and a commercial permanent paper. To simulate a real deteriorated document, which could need γ-rays irradiation, some samples were submitted to a hydrolysis treatment. We developed a treatment based on the exposition of paper to hydrochloric acid vapors, avoiding any contact of the samples with water. This method induces a degradation similar to that observed on original documents. The samples were then irradiated with 3 kGy γ-rays at a 5258 Gy/h rate. The aforementioned analyses were performed on the samples just irradiated and after artificial ageing. All tests showed negative effects of gamma irradiation on paper. Non-irradiated paper preserves better its appearance and chemical properties both in the short term and after ageing, while the irradiated samples show appreciable color change and higher oxidation extent. Since the Istituto centrale restauro e conservazione patrimonio archivistico e librario is responsible for the choice of all restoration treatments that could be applied on library and archival materials under the protection of the Italian State (http://www.icpal.beniculturali.it/allegati/DM-7

  11. Experimental analysis of reinforced concrete columns strengthened with self-compacting concrete and connectors

    Directory of Open Access Journals (Sweden)

    P. P. Nascimento

    Full Text Available There are many problems involving cases of destruction of buildings and other structures. The columns can deteriorate for several reasons such as the evolution and changing habits of the loads. The experimental phase of this work was based on a test involving nine reinforced concrete columns under combined bending and axial compression, at an initial eccentricity of 60 mm. Two columns were used as reference, one having the original dimensions of the column and the other, monolithic, had been cast along the thickness of the strengthened piece. The remaining columns received a 35 mm thick layer of self-compacting concrete on their compressed face. For the preparation of the interface between the two materials, this surface was scarified and furrowed and connectors were inserted onto the columns' shear reinforcement in various positions and amounts.As connectors, 5 mm diameter steel bars were used (the same as for stirrups, bent in the shape of a "C" with 25 mm coatings. >As a conclusion, not only the quantity, but mainly, the location of the connectors used in the link between substrate and reinforcement is crucial to increase strength and to change failure mode.

  12. Evaluating the Carbonation Resistance of Self Compacting Concrete made with Recycled Concrete Aggregates

    Directory of Open Access Journals (Sweden)

    S P Singh

    2016-07-01

    Full Text Available The paper presents the results of an investigation conducted to examine carbonation resistance of Self Compacting Concrete (SCC made with coarse Recycled Concrete Aggregates (RCA. In total, five SCC mixes were prepared by systematically replacing coarse Natural Aggregates (NA by RCA at 0, 25, 50, 75 and 100%. In order to measure the carbonation resistance of SCC made with RCA, accelerated carbonation tests were performed for 4 and 12 weeks of exposure to carbon dioxide. The carbonation resistance has been evaluated after curing periods of 28 and 90 days. In addition to this, the compressive strength of all the mixes was also obtained after 7, 28 and 90 days of curing and ultra-sonic pulse velocity tests (UPV were also conducted. The results indicate that with the increase in the content of RCA as replacement of NA, decrease in the carbonation resistance, compressive strength and UPV was observed for all SCC mixes. It has been observed that the SCC mixes containing low percentages of RCA (i.e. 25% as replacement of NA do not impart detrimental behaviour in the overall performance but higher replacement levels (>50% have been found to deteriorate the performance in terms of carbonation resistance, compressive strength and UPV.

  13. Alkali-silica reaction resistant concrete using pumice blended cement

    Science.gov (United States)

    Ramasamy, Uma

    Durability of structures is a major challenge for the building industry. One of the many types of concrete deterioration that can affect durability is alkali-silica reaction (ASR). ASR has been found in most types of concrete structures, including dams, bridges, pavements, and other structures that are 20 to 50 years old. The degradation mechanism of ASR produces a gel that significantly expands in the presence of water as supplied from the surrounding environment. This expansion gel product can create high stresses and cracking of the concrete, which can lead to other forms of degradation and expensive structural replacement costs. The four essential factors that produce an expansive ASR gel in concrete are the presence of alkalis, siliceous aggregate, moisture, and free calcium hydroxide (CH). If concrete is starved of any one of these essential components, the expansion can be prevented. Reducing CH through the use of a supplementary cementitious material (SCM) such as natural pozzolan pumice is the focus of this research. By using a pozzolan, the amount of CH is reduced with time based on the effectiveness of the pozzolan. Many pozzolans exist, but one such naturally occurring pozzolanic material is pumice. This research focuses on determining the effect of a finely ground pumice as a SCM in terms of its resistance to ASR expansion, as well as improving resistance to other potential concrete durability mechanisms. In spite of having high alkali contents in the pumice, mixtures containing the SCM pumice more effectively mitigated the ASR expansion reaction than other degradation mechanisms. Depending on the reactivity of the aggregates and fineness of the pumice, 10-15% replacement of cement with the pumice was found to reduce the ASR expansion to the acceptable limits. The amount of CH remaining in the concrete was compared to the ASR expansion in order to improve understanding of the role of CH in the ASR reaction. Thermo-gravimetric analysis (TGA) and X

  14. Properties of Low Strength Concrete made with Recycled Concrete ...

    African Journals Online (AJOL)

    Conventional concrete aggregate consists of sand and various sizes of stones. In recent years, there has been a growing interest in substituting conventional aggregates with recycled materials. The present investigation has been carried out to study the effect of fly ash on the mechanical properties of low strength concrete ...

  15. TECHNOLOGICAL PROPERTIES OF CONCRETES AND MORTARS FOR UNDERWATER CONCRETING

    Directory of Open Access Journals (Sweden)

    O. V. Anufrieva

    2009-03-01

    Full Text Available The article is about the results of experimental-and-theoretical research of usefulness of mortar and concrete mixes for underwater repair works. It is shown that the developed compositions of hydraulic engineering concretes are characterized by high effectiveness in the corrosive medium.

  16. Anisotropic Concrete Compressive Strength

    DEFF Research Database (Denmark)

    Gustenhoff Hansen, Søren; Jørgensen, Henrik Brøner; Hoang, Linh Cao

    2017-01-01

    When the load carrying capacity of existing concrete structures is (re-)assessed it is often based on compressive strength of cores drilled out from the structure. Existing studies show that the core compressive strength is anisotropic; i.e. it depends on whether the cores are drilled parallel...... correlation to the curing time. The experiments show no correlation between the anisotropy and the curing time and a small strength difference between the two drilling directions. The literature shows variations on which drilling direction that is strongest. Based on a Monto Carlo simulation of the expected...

  17. Characterisation and management of concrete grinding residuals.

    Science.gov (United States)

    Kluge, Matt; Gupta, Nautasha; Watts, Ben; Chadik, Paul A; Ferraro, Christopher; Townsend, Timothy G

    2018-02-01

    Concrete grinding residue is the waste product resulting from the grinding, cutting, and resurfacing of concrete pavement. Potential beneficial applications for concrete grinding residue include use as a soil amendment and as a construction material, including as an additive to Portland cement concrete. Concrete grinding residue exhibits a high pH, and though not hazardous, it is sufficiently elevated that precautions need to be taken around aquatic ecosystems. Best management practices and state regulations focus on reducing the impact on such aquatic environment. Heavy metals are present in concrete grinding residue, but concentrations are of the same magnitude as typically recycled concrete residuals. The chemical composition of concrete grinding residue makes it a useful product for some soil amendment purposes at appropriate land application rates. The presence of unreacted concrete in concrete grinding residue was examined for potential use as partial replacement of cement in new concrete. Testing of Florida concrete grinding residue revealed no dramatic reactivity or improvement in mortar strength.

  18. The influence of recycled concrete aggregates in pervious concrete

    Directory of Open Access Journals (Sweden)

    L. M. TAVARES

    Full Text Available The expansion of urban areas under constant changes in the hydrological cycle directly affects the drainage of rainwater. The problems of urban drainage become major engineering problems to be solved in order to avoid negative consequences for local populations. Another urban problem is the excessive production of construction and demolition waste (CDW, in which , even with a increasingly policy of waste management , have been an end up being thrown in inappropriate disposal sites. Alternatively aiming to a minimization of the problems presented, we propose the study of permeable concrete using recycled concrete aggregate. In this study, there were evaluated the performance of concrete by means of permeability, consistency, strength, and interface conditions of the materials . Satisfactory relationships of resistance/permeability of concrete with recycled aggregate in relation to the concrete with natural aggregates was obtained, showing their best potential.

  19. Influence of High Temperatures on the Workability of Fresh Ready-Mixed Concrete

    Directory of Open Access Journals (Sweden)

    Victor Sampebulu'

    2012-04-01

    Full Text Available Properties of fresh concrete made in tropical countries, which is mixed, transported (with agitation, placed and initially cured in places where the temperature ranges from about 20oC to 40oC and relative humidity above 60%, are not completely understood. Applicable requirements also differ from country to country and government agencies and private enterprises have their own specifications. Assuming such temperature and relative humidity conditions, the present study is an attempt at evaluating the properties of hot weather concrete in fresh state with using a method of ready–mixed concrete. The fresh concrete was mixed and agitated at varying concrete and ambient temperatures. Three groups of the component materials, each material having such temperature as to bring resulting temperature of the fresh concrete to about 20oC, 30oC, 35oC, were chosen. The temperature of cement was conditioned to about20o, 40oC and 60oC for each of groups respectively. The aggregate was made warm enough to simulate the condition of outdoor pile in ready-mixed concrete plant. The temperature of tap water was always 20oC as it was easily controlled and unlikely affected by outdoor temperature. With the fresh concrete prevented from evaporation, slump loss is caused solely by increased temperature of concrete. During agitation, the slump loss increases rapidly during the first 30 minutes but moderately during the remaining period. Concrete-placing temperature (upon arrival at the work site could be estimated by a proposed formula derived from this study. Besides the freshly mixed concrete temperature, this formula also takes into consideration the ambient temperature, agitating time in transit and hydration heat. The achievement as described in this study may be useful to control concrete quality in terms of strength, shrinkage and other properties of concrete to be placed in hot-humid environment.

  20. Comparison of standardized patients with high-fidelity simulators for managing stress and improving performance in clinical deterioration: A mixed methods study.

    Science.gov (United States)

    Ignacio, Jeanette; Dolmans, Diana; Scherpbier, Albert; Rethans, Jan-Joost; Chan, Sally; Liaw, Sok Ying

    2015-12-01

    The use of standardized patients in deteriorating patient simulations adds realism that can be valuable for preparing nurse trainees for stress and enhancing their performance during actual patient deterioration. Emotional engagement resulting from increased fidelity can provide additional stress for student nurses with limited exposure to real patients. To determine the presence of increased stress with the standardized patient modality, this study compared the use of standardized patients (SP) with the use of high-fidelity simulators (HFS) during deteriorating patient simulations. Performance in managing deteriorating patients was also compared. It also explored student nurses' insights on the use of standardized patients and patient simulators in deteriorating patient simulations as preparation for clinical placement. Fifty-seven student nurses participated in a randomized controlled design study with pre- and post-tests to evaluate stress and performance in deteriorating patient simulations. Performance was assessed using the Rescuing A Patient in Deteriorating Situations (RAPIDS) rating tool. Stress was measured using salivary alpha-amylase levels. Fourteen participants who joined the randomized controlled component then participated in focus group discussions that elicited their insights on SP use in patient deterioration simulations. Analysis of covariance (ANCOVA) results showed no significant difference (p=0.744) between the performance scores of the SP and HFS groups in managing deteriorating patients. Amylase levels were also not significantly different (p=0.317) between the two groups. Stress in simulation, awareness of patient interactions, and realism were the main themes that resulted from the thematic analysis. Performance and stress in deteriorating patient simulations with standardized patients did not vary from similar simulations using high-fidelity patient simulators. Data from focus group interviews, however, suggested that the use of

  1. ANALYSIS AND APPLICATION PROSPECTS OF EFFECTIVE RESOURCES-SAVING TECHNOLOGIES IN CONCRETE MANUFACTURE

    Directory of Open Access Journals (Sweden)

    H. P. Ivanova

    2014-10-01

    Full Text Available Purpose. Prospectivity assessments of the nano-materials usage in construction technologies at the same time meeting the requirements of environmental safety and rational use of the natural resources. Methodology. During the study the building composites, in particular concretes, which are obtained on the base of the raw materials, which are introduced in the array of micro- and nanolevels were researched and analyzed. The deformation and deterioration processes of nanostructured concrete depending on their composition and manufacture parameters were simulated. Findings. Concrete manufacture is in the direct dependence on its components. Due to the extraction and processing of these components land degradation occurs because of soil destruction with oversize pits, which threatens the ecology of the environment. In this connection there is a need for another concept of building materials receiving for concrete manufacture. The new branch of science based on nanotechnologies, nanomaterials and nanostructuring is a key to its foundation. The special features of nanostructured concretes are the nanoagents in their composition (carbon nanotubes, mechanoactivated slags of blast furnace production. The study of deformation patterns and concrete deterioration based on the mechanoactivated material will purposefully affect the structure, physical and chemical properties, as well as the mechanical and deformational ones. Originality. The researches have shown that nano-structured concrete had high fluidity. The strength of such compositions is enhanced up to 13 % without reduction of concrete consumption and up to 8.8% at 10% reduced concrete consumption. Practical value. The application of the structured concretes based on the mechanoactivated material will increase the efficiency of the industrial wastes recycling and improve the physical, mechanical and technological properties of the produced composites. From the standpoint of the economic benefits

  2. Structural evaluation of a prestressed concrete bridge under an alkali-silica reaction; Evaluacion estructural de un puente de hormigon pretensado afectado por una reaccion alcali-silice

    Energy Technology Data Exchange (ETDEWEB)

    Carpintero Garcia, I.; Bermudez Adriozola, B.

    2010-07-01

    The Central Laboratory of Structures and Materials (CEDEX) was commissioned by the National Department of Highways to evaluate the safety conditions of one bridge built on 1997, which is part of the net of the Spanish National Highways. Even at the first inspection many cracks were detected in the concrete deck, associated with expansion concrete processes. This examination revealed that concrete deterioration was not associated with any reinforcement corrosion process; in fact, there were no symptoms of this pathology all along the bridge. for that reason the internal chemical reactions were considered as the most probable cause for the expansion of concrete, as no symptoms of deterioration due to external attack were found. In order to check the origin of concrete expansion, some tests were carried out on concrete samples drilled on the decks. Results of these tests show that there had been internal reactions in concrete mass which explains its expansion and the appearance of those cracks observed. Further more, some other activities were also carried out on site to estimate the importance of the structural damages, as topographic levelling and dynamic testing of the decks. Also the mechanical properties of concrete probes were tested at laboratory. This article shows the main results obtained on the study carried on to determine the cause and significance of the structural damages of the bridge. (Author) 3 refs.

  3. Influence of metakaolin on chemical resistance of concrete

    Science.gov (United States)

    Mlinárik, L.; Kopecskó, K.

    2013-12-01

    Nowadays the most suitable and widely used construction material is concrete. We could develop concrete for every request in connection with the properties of fresh concrete and the quality of hardened concrete, too. The demand is rising in application of special concretes, like high performance and ultra high performance concretes (HPC, UHPC). These are usable in extreme natural circumstances or in very corrosive surroundings (for example: sewage farm, sewer, cooling tower, biogas factories). The pH value of the commercial sewage is between 7-8, but this value is often around 4 or less. The concrete pipes, which transport the sewage, are under corrosion, because above the liquid level sulphuric acid occurs due to microbes. Acidic surroundings could start the corrosion of concrete. When the pH value reduces, the influence of the acids will increase. The most significant influence has the sulphuric acid. The pH value of sulphuric acid is about 1, or less. Earlier in the cooling towers of coal thermal power stations used special coating on the concrete wall. Recently application of high performance concrete without polymeric coating is more general. Cementitious supplementary materials are widely used to protect the concrete from these corrosive surroundings. Usually used cementitious supplementary materials are ground granulated blastfurnace slag (GGBS), flying ash (FA) or silica fume (SF). In the last years there has been a growing interest in the application of metakaolin. Metakaolin is made by heat treatment, calcinations of a natural clay mineral, kaolinite. In our present research the chemical resistance of mortars in different corrosive surroundings (pH=1 sulphuric acid; pH=3 acetic acid) and the chloride ion migration were studied on series of mortar samples using rapid chloride migration test. Cement paste and mortar samples were made with 17% metakaolin replacement or without metakaolin. The following cements were used: CEM II/A-S 42.5 N, CEM I 42.5 N-S. We

  4. Interface Microstructures in Concrete

    Directory of Open Access Journals (Sweden)

    Puertas, Francisca

    1991-03-01

    Full Text Available This paper constitutes a compilation as well as an interpretation of the present state of knowledge about the different microstructures developed in the interface areas of concrete, that is, the cement paste-aggregates, the cement paste-reinforcement, the cement paste-fiber, etc. The Chemical reactions taking place in interface areas, the development and morphology of such areas and their strength ^since interfaces are taken as the weakest points of concrete are the aspects dealt with in some detail in this work.

    El presente trabajo constituye un resumen y también una interpretación del estado actual del conocimiento respecto de las diferentes microestructuras que se desarrollan en las zonas interfaciales de los hormigones, es decir: pasta de cemento-áridos, pasta de cemento-armaduras, pasta de cemento-fibras, etc. Las reacciones químicas que tienen lugar en la zona interfacial, el desarrollo y morfología de dicha zona y su resistencia (las interfases se consideran como uno de los puntos débiles del hormigón son los aspectos que con cierto detalle se tratan en el trabajo.

  5. of reinforced concrete columns

    Directory of Open Access Journals (Sweden)

    Anna Szcześniak

    2015-09-01

    Full Text Available The paper presents the modification of the dynamic relaxation method in order to increase its effectiveness in the range of the post-critical analysis. For this purpose, the arc-length parameter on the equilibrium path was introduced into the computational procedure. The additional constraints equation that combines increment of load parameter and the vector of displacement increments with the arc-length increment on the solution path was incorporated to analysis of the equations of motion. Solution of nonlinear equilibrium equations is obtained recursively in subsequent pseudo-time instants. The proposed method allows for tracking the global softening phenomenon of the structural element in the post-critical range, which leads to failure. We ran numerical experiments for the reinforced concrete eccentrically loaded column. Our comparative analysis with previously published numerical results demonstrated that the proposed computational method is effective.[b]Keywords[/b]: reinforced concrete columns, dynamic relaxation method, arc-length method, load-carrying capacity

  6. Molded Concrete Center Mine Wall

    Science.gov (United States)

    Lewis, E. V.

    1987-01-01

    Proposed semiautomatic system forms concrete-foam wall along middle of coal-mine passage. Wall helps support roof and divides passage into two conduits needed for ventilation of coal face. Mobile mold and concrete-foam generator form sections of wall in place.

  7. Concrete Operations and Attentional Capacity.

    Science.gov (United States)

    Chapman, Michael; Lindenberger, Ulman

    1989-01-01

    To test predictions regarding the attentional capacity requirements of Piaget's stage of concrete operations, a battery of concrete operational tasks and two measures of attentional capacity were administered to 120 first-, second-, and third-graders. Findings concern class inclusion, transitivity of length and weight, and multiplication of…

  8. Revised Rules for Concrete Bridges

    DEFF Research Database (Denmark)

    Thoft-Christensen, Palle; Jensen, F. M.; Middleton, C.

    This paper is based on research performed for the Highway Agency, London, UK under the project DPU/9/44 "Revision of Bridge Assessment Rules Based on Whole Life Performance: Concrete Bridges" It contains details of a methodology which can be used to generate Whole Life (WL) reliability profiles....... These WL reliability profiles may be used to establish revised rules for Concrete Bridges....

  9. Fatigue of Concrete Armour Units

    DEFF Research Database (Denmark)

    Sørensen, N. B.; Burcharth, H. F.; Liu, Z.

    1995-01-01

    In the present article fatigue as a possible reason for failure of Dolosse armour units made of plain concrete is discussed.......In the present article fatigue as a possible reason for failure of Dolosse armour units made of plain concrete is discussed....

  10. Urban heritage, building maintenance : Concrete

    NARCIS (Netherlands)

    Verhoef, L.G.W.

    1999-01-01

    Concrete as a conglomerate of sand, stone and a binder, is a very old material indeed. In the Roman period earth from Puozzoli, together with lime and water could bind the sand and the stones to form a conglomerate that has an affmity to our modem concrete. Later, in the more northem areas of

  11. The steel–concrete interface

    DEFF Research Database (Denmark)

    Angst, Ueli M.; Geiker, Mette Rica; Michel, Alexander

    2017-01-01

    Although the steel–concrete interface (SCI) is widely recognized to influence the durability of reinforced concrete, a systematic overview and detailed documentation of the various aspects of the SCI are lacking. In this paper, we compiled a comprehensive list of possible local characteristics at...

  12. Proportioning of light weight concrete

    DEFF Research Database (Denmark)

    Palmus, Lars

    1996-01-01

    Development of a method to determine the proportions of the raw materials in light weight concrete made with leight expanded clay aggregate. The method is based on composite theory......Development of a method to determine the proportions of the raw materials in light weight concrete made with leight expanded clay aggregate. The method is based on composite theory...

  13. Novel techniques for concrete curing

    DEFF Research Database (Denmark)

    Kovler, Konstantin; Jensen, Ole Mejlhede

    2005-01-01

    It is known that some high-strength/high-performance concretes (HSC/HPC) are prone to cracking at an early age unless special precautions are taken. The paper deals with the methods of curing as one of the main strategies to ensure good performance of concrete. Curing by both external (convention...

  14. The Concrete and Pavement Challenge

    Science.gov (United States)

    Roman, Harry T.

    2012-01-01

    The modern world is characterized by the extensive use of concrete and asphalt pavement. Periodically, these materials are replaced and the old materials disposed of. In this challenge, students will be asked to develop ways to reuse the old materials. It is important for students to understand how concrete and asphalt are made and applied, as…

  15. Numerical Simulation of GFRP Reinforced Concrete Beams

    National Research Council Canada - National Science Library

    Xia Zhao; Xiong-Jun He; Yong-Chao Yang

    2017-01-01

    .... The finite element numerical simulation of GFRP fiber reinforced concrete beam was carried out, and the load deflection nephogram of fiber reinforced concrete beam, strain nephogram, crack nephogram...

  16. Structural health and dynamic behavior of residential buildings: field challenges in the rehab of damaged reinforced concrete

    Directory of Open Access Journals (Sweden)

    Chalhoub M. S.

    2014-01-01

    Full Text Available Reinforced concrete buildings require special consideration under dynamic excitations due to their anisotropic material properties. Strain compatibility equations are used in concrete analysis and design with assumptions about the stress and strain field across member section and member length. However, these assumptions fall short of describing real life behavior when concrete elements deteriorate, age or undergo cyclic loading. This paper addresses the structural health of reinforced concrete buildings and proposes an analytical model to account for concrete damage through loss of bond. The proposed model relates steel loading that causes bond distress to design parameters such as development length and bar properties, and therefore could be complemented by field measurement. The paper proposes a diagnosis method and discusses the sustainability of the structure by assisting in a simplistic decision rule as to whether to perform minor fixes, major rehabilitation, or disposal. Emphasis is placed on the difference between reversible and irreversible effects of cyclic loading on structural behaviour, and draws a distinction between damage to the girder and damage to the column in the overall structural system. The model is compared to empirical results to address field challenges faced when the structure is subjected to severe conditions in its ambient environment, or to unusual loading. Deterioration in concrete causes alteration in its composite behavior with the reinforcing steel. This affects the fundamental period of the structure, and its response to seismic loading.

  17. Why is it so difficult to prove that rapid response systems improve patient outcome? : Directions for further research

    NARCIS (Netherlands)

    H.G. van der Hoeven; Joke Mintjes; Lisette Schoonhoven; Friede Simmes; B.G. Fikkers

    2012-01-01

    The implementation of rapid response systems (RRS) is based on the knowledge that deteriorating physiological processes are frequently present for hours or days before clear clinical deterioration is recognized [1,2]. It is assumed that this physiological deterioration is often treatable and that

  18. Clinical deterioration after sildenafil cessation in patients with pulmonary hypertension

    Directory of Open Access Journals (Sweden)

    Anne M Keogh

    2008-10-01

    Full Text Available Anne M Keogh, Andrew Jabbour, Christopher S Hayward, Peter S MacdonaldHeart Lung Transplant Unit, St Vincent’s Hospital, Sydney, New South Wales, AustraliaAbstract: Sildenafil is a selective inhibitor of phosphodiesterase type 5 (PDE-5. Its chronic administration has been shown to improve exercise capacity, World Health Organization functional class, and haemodynamics in patients with symptomatic pulmonary arterial hypertension (PAH. There is however, no data describing the clinical consequences of sudden cessation of sildenafil treatment. In this series, 9 patients with NYHA Class II–IV PAH who were stable on 2 months of sildenafil monotherapy, had their sildenafil ceased to accommodate a 2-week washout period, required for enrollment in research involving an endothelin receptor antagonist. Six minute walk distance (SMWD and clinical assessments were performed before cessation of sildenafil, and again 2 weeks later. Over the course of this 2-week washout period, 6 of the 9 patients reported increased breathlessness and fatigue, 1 of these was hospitalized with worsening right heart failure. The SMWD fell in 6 patients, with falls of greater than 100 m recorded in 4 patients. This was accompanied by a worsening of NYHA Class from 2.5 ± 0.2 to 3.1 ± 0.1 (mean ± SEM, p = 0.01. These data indicate that sudden cessation of sildenafil monotherapy, in patients with PAH, carries with it a significant and unpredictable risk of rapid clinical deterioration. We recommend that if sildenafil needs to be ceased, it would be more prudent to consider concurrent vasodilator therapy before the gradual cessation of sildenafil.Keywords: sildenafil, pulmonary hypertension, phosphodiesterase inhibitor

  19. Diffusion of ultrasound in concrete.

    Science.gov (United States)

    Anugonda, P; Wiehn, J S; Turner, J A

    2001-10-01

    The propagation and scattering of ultrasound in concrete is discussed. The heterogeneous composition of concrete causes the ultrasound to scatter considerably. In the limit of many scattering events, the ultrasonic energy density in circular cylinders of concrete is shown to evolve in accordance with a one-dimensional diffusion equation. The ultrasonic diffusivity and dissipation are measured experimentally over the frequency range of 100-900 kHz. Theoretical descriptions of the diffusivity are in accord with the experimental values. Such frequencies are well above typical frequencies used for concrete inspection. Thus, it is anticipated that the use of these higher frequencies will result in new techniques for characterizing material properties and damage in concrete structures.

  20. Basic principles of concrete structures

    CERN Document Server

    Gu, Xianglin; Zhou, Yong

    2016-01-01

    Based on the latest version of designing codes both for buildings and bridges (GB50010-2010 and JTG D62-2004), this book starts from steel and concrete materials, whose properties are very important to the mechanical behavior of concrete structural members. Step by step, analysis of reinforced and prestressed concrete members under basic loading types (tension, compression, flexure, shearing and torsion) and environmental actions are introduced. The characteristic of the book that distinguishes it from other textbooks on concrete structures is that more emphasis has been laid on the basic theories of reinforced concrete and the application of the basic theories in design of new structures and analysis of existing structures. Examples and problems in each chapter are carefully designed to cover every important knowledge point. As a basic course for undergraduates majoring in civil engineering, this course is different from either the previously learnt mechanics courses or the design courses to be learnt. Compa...

  1. Durability of visitable concrete sewer gallery under the effect of domestic wastewater

    Science.gov (United States)

    Salhi, Aimed; Kriker, Abdelouahed; Tioua, Tahar; Abimiloud, Youcef; Barluenga, Gonzalo

    2016-07-01

    The durability of concrete structures for the disposal of wastewater depends on their behavior when faced to different aggressions such as mechanics, chemical and biological, causing a deterioration often cementing matrix. The deterioration of recent evacuations wastewater infrastructure, made of reinforced concrete less than 15 years ago, has become an important concern. The aim of this study was to investigate the degradation and the factors responsible for the deterioration of the concrete visitable gallery of sewage from the town of Touggourt (south-east of Algeria). Thus, samples from different parts of the gallery were extracted and unaltered samples were selected as a reference. A degraded sample exposed to H2S gas and another sample of the gallery submerged into wastewater were analyzed to characterize the internal and external damage to the gallery as well as the chemical and mineralogical changes. These tests were complemented by a physical and mechanical characterization of the samples. The experimental results showed the strong anisotropy of both internal and external damage.

  2. Permeability and pore structure connectivity of basic concrete formulations to use in near-surface repositories for radioactive wastes

    Energy Technology Data Exchange (ETDEWEB)

    Tolentino, Evandro; Santos, Carlos Eduardo de Oliveira [Centro Federal de Educação Tecnológica de Minas Gerais (CEFET-MG), Timóteo, MG (Brazil); Tello, Clédola Cássia Oliveira de, E-mail: tolentino@timoteo.cefetmg.br, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2017-07-01

    The main concern of engineers who prepare concrete specifications for a particular application is to predict the deteriorative exposures that could cause concrete degradation over its intended service life. A durable concrete is able to resist destructive environmental conditions, without requiring excessive maintenance. Durability of cementitious materials largely depends on the possibilities of penetration of hazardous ions into the porous material with water as medium. Therefore, the water permeability of cementitious materials is related to its durability. Permeability and porosity should not instinctively be regarded as manifestations of the same phenomenon. Usually, when permeability increases, porosity increases as well. The connectivity of pore network exerts an important control on preferential flow into cementitious materials. This work presents results of quantitative evaluation of permeability and pore connectivity of Portland cement concretes. Two concrete mixture proportions with limestone and gneiss as coarse aggregate were produced. A modified polycarboxyl ether plasticizer GLENIUM 51 was added to one of the concrete mixtures in order to reduce the water content. Permeability tests were performed on all the specimens and a geometric modeling considering pore with cylindrical shape was applied in order to evaluate the pore network connectivity. The results showed that pore structure connectivity of concrete with plasticizer admixture decreased. The purpose of this research is to expand the knowledge concerning concrete durability and to provide the technical requirements related to the production the Brazilian near-surface repository of radioactive wastes. (author)

  3. Repair systems for deteriorated bridge piles : final report.

    Science.gov (United States)

    2017-04-01

    The objective of this research project is to develop a durable repair system for deteriorated steel bridge piles that : can be implemented without the need for dewatering. A rigorous survey of the relevant practice nationwide was : conducted to infor...

  4. Functioning of Philippine seagrass species under deteriorating light conditions

    NARCIS (Netherlands)

    Uy, W.H.

    2001-01-01

    Industrialization, urbanization and agricultural intensification result in increased sediment loading and eutrophication of S.E.Asian coastal waters and associated deterioration of light availability to seagrasses inhabiting coastal waters. In the present study, different (internal and external)

  5. Natural history of hearing deterioration in intracanalicular vestibular schwannoma

    NARCIS (Netherlands)

    Pennings, R.J.E.; Morris, D.P.; Clarke, L.; Allen, S.; Walling, S.; Bance, M.L.

    2011-01-01

    BACKGROUND: Intracanalicular vestibular schwannomas have a range of treatment options that can preserve hearing: microsurgery, stereotactic radiotherapy, and conservative observation. OBJECTIVE: To evaluate the natural course of hearing deterioration during a period of conservative observation.

  6. From concrete repair to concrete conservation: how to preserve the heritage values of historic concrete

    NARCIS (Netherlands)

    Nijland, T.G.; Hees, R.P.J. van; Heinemann, H.A.; Zijlstra, H.

    2011-01-01

    ABSTRACT: The conservation of historic concrete is an increasing task, challenging both concrete repair specialists and conservation specialists. In practice, too often repair strategies are followed where conserva-tion strategies would have been necessary. The application of repair techniques poses

  7. High performance polymer concrete

    Directory of Open Access Journals (Sweden)

    Frías, M.

    2007-06-01

    Full Text Available This paper studies the performance of concrete whose chief components are natural aggregate and an organic binder —a thermosetting polyester resin— denominated polymer concrete or PC. The material was examined macro- and microscopically and its basic physical and mechanical properties were determined using mercury porosimetry, scanning electron microscopy (SEM-EDAX, X-ray diffraction (XRD and strength tests (modulus of elasticity, stress-strain curves and ultimate strengths. According to the results of these experimental studies, the PC exhibited a low density (4.8%, closed pore system and a concomitantly continuous internal microstructure. This would at least partially explain its mechanical out-performance of traditional concrete, with average compressive and flexural strength values of 100 MPa and over 20 MPa, respectively. In the absence of standard criteria, the bending test was found to be a useful supplement to compressive strength tests for establishing PC strength classes.Este trabajo de investigación aborda el estudio de un hormigón de altas prestaciones, formado por áridos naturales y un aglomerante orgánico constituido por una resina termoestable poliéster, denominado hormigón polimérico HP. Se describe el material a nivel microscópico y macroscópico, presentando sus propiedades físicas y mecánicas fundamentales, mediante diferentes técnicas experimentales, tales como: porosimetría de mercurio, microscopía electrónica (SEM-EDAX, difracción de rayos X (DRX y ensayos mecánicos (módulo de elasticidad, curvas tensión- deformación y resistencias últimas. Como consecuencia del estudio experimental llevado a cabo, se ha podido apreciar cómo el HP está formado por porosidad cerrada del 4,8%, proporcionando una elevada continuidad a su microestructura interna, lo que justifica, en parte, la mejora de propiedades mecánicas respecto al hormigón tradicional, con unos valores medios de resistencia a compresión de 100

  8. Response of an isolated structure with deteriorating hysteretic isolator model

    OpenAIRE

    Özdemir, Gökhan; Bayhan, Beyhan

    2015-01-01

    Cyclic motion of lead rubber bearings (LRBs) leads to increasing temperature in lead core initiating the reduction in strength of LRB. This reduction results in a deteriorating bi-linear force deformation relation for LRB. In this study, response of LRBs (with deteriorating hysteresis loops due to temperature change) subjected to near-field ground motions with distinct pulse-type behavior is studied. Ground motions are applied bi-directionally and LRBs are modeled with due consideration of co...

  9. Host genetics predict clinical deterioration in HCV-related cirrhosis.

    Directory of Open Access Journals (Sweden)

    Lindsay Y King

    Full Text Available Single nucleotide polymorphisms (SNPs in the epidermal growth factor (EGF, rs4444903, patatin-like phospholipase domain-containing protein 3 (PNPLA3, rs738409 genes, and near the interleukin-28B (IL28B, rs12979860 gene are linked to treatment response, fibrosis, and hepatocellular carcinoma (HCC in chronic hepatitis C. Whether these SNPs independently or in combination predict clinical deterioration in hepatitis C virus (HCV-related cirrhosis is unknown. We genotyped SNPs in EGF, PNPLA3, and IL28B from liver tissue from 169 patients with biopsy-proven HCV cirrhosis. We estimated risk of clinical deterioration, defined as development of ascites, encephalopathy, variceal hemorrhage, HCC, or liver-related death using Cox proportional hazards modeling. During a median follow-up of 6.6 years, 66 of 169 patients experienced clinical deterioration. EGF non-AA, PNPLA3 non-CC, and IL28B non-CC genotypes were each associated with increased risk of clinical deterioration in age, sex, and race-adjusted analysis. Only EGF non-AA genotype was independently associated with increased risk of clinical deterioration (hazard ratio [HR] 2.87; 95% confidence interval [CI] 1.31-6.25 after additionally adjusting for bilirubin, albumin, and platelets. Compared to subjects who had 0-1 unfavorable genotypes, the HR for clinical deterioration was 1.79 (95%CI 0.96-3.35 for 2 unfavorable genotypes and 4.03 (95%CI 2.13-7.62 for unfavorable genotypes for all three loci (Ptrend<0.0001. In conclusion, among HCV cirrhotics, EGF non-AA genotype is independently associated with increased risk for clinical deterioration. Specific PNPLA3 and IL28B genotypes also appear to be associated with clinical deterioration. These SNPs have potential to identify patients with HCV-related cirrhosis who require more intensive monitoring for decompensation or future therapies preventing disease progression.

  10. Effectiveness of respiratory rates in determining clinical deterioration

    DEFF Research Database (Denmark)

    Mølgaard, Rikke Rishøj; Larsen, Palle; Håkonsen, Sasa Jul

    2016-01-01

    Review question/objective: The objective of this systematic review is to identify, appraise and synthesize the best available evidence on the effectiveness of manually measuring respiratory rates for 60 s or less in detecting clinical deterioration of inpatients. More specifically, the review...... question is: Is measurement of respiratory rates for 60 s more effective in detecting clinical deterioration than a shorter duration of measurement?...

  11. Integrated Monitoring System for Durability Assessment of Concrete Bridges

    Directory of Open Access Journals (Sweden)

    Cristian-Claudiu Comisu

    2005-01-01

    Full Text Available An ageing and deteriorating bridge stock presents the bridge owners with the growing challenge of maintaining the structures at a satisfactory level of safety, performance and aesthetic appearance within the allocated budgets. This task calls for optimized bridge management based on efficient methods of selecting technical and economical optimal maintenance and rehabilitation strategies. One of the crucial points in the assessment of the current condition and future development and performance. Selecting the optimal maintenance and rehabilitation strategy within the actual budget is a key point in bridge management for which an accurate assessment of performance and deterioration rate is necessary. For this assessment, the use of integrated monitoring system has several advantages compared to the traditional approach of scattered visual inspections combined with occasional on site testing with portable equipment and laboratory testing of collected samples. For this reason, attention is more focusing on the development of permanent integrated monitoring system for durability assessment of concrete bridges. It is estimated that with the implementation of such integrated monitoring systems, it should be possible to reduce the operating costs of inspections and maintenance by 25% and the operator of the structures will be able to take protective actions before damaging processes start. This paper indentifies the main bridge owner requirements to integrated monitoring systems and outlines how monitoring systems may be used for performance and deterioration rate assessment to establish a better basis for selecting the optimal maintenance and rehabilitation strategy.

  12. Evaluating portland cement concrete degradation by sulphate exposure through artificial neural networks modeling

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Douglas Nunes de; Bourguignon, Lucas Gabriel Garcia; Tolentino, Evandro, E-mail: tolentino@timoteo.cefetmg.br [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Timoteo, MG (Brazil); Costa, Rodrigo Moyses, E-mail: rodrigo@moyses.com.br [Universidade de Itauna, Itauna, MG (Brazil); Tello, Cledola Cassia Oliveira de, E-mail: tellocc@cdtn.br [Centro de Desenvolvimento da Tecnologia Nucelar (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)

    2015-07-01

    A concrete is durable if it has accomplished the desired service life in the environment in which it is exposed. The durability of concrete materials can be limited as a result of adverse performance of its cement-paste matrix or aggregate constituents under either chemical or physical attack. Among other aggressive chemical exposures, the sulphate attack is an important concern. Water, soils and gases, which contain sulphate, represent a potential threat to the durability of concrete structures. Sulphate attack in concrete leads to the conversion of the hydration products of cement to ettringite, gypsum, and other phases, and also it leads to the destabilization of the primary strength generating calcium silicate hydrate (C-S-H) gel. The formation of ettringite and gypsum is common in cementitious systems exposed to most types of sulphate solutions. The present work presents the application of the neural networks for estimating deterioration of various concrete mixtures due to exposure to sulphate solutions. A neural networks model was constructed, trained and tested using the available database. In general, artificial neural networks could be successfully used in function approximation problems in order to approach the data generation function. Once data generation function is known, artificial neural network structure is tested using data not presented to the network during training. This paper is intent to provide the technical requirements related to the production of a durable concrete to be used in the structures of the Brazilian near-surface repository of radioactive wastes. (author)

  13. Testing of High Thermal Cycling Stability of Low Strength Concrete as a Thermal Energy Storage Material

    Directory of Open Access Journals (Sweden)

    Chao Wu

    2016-09-01

    Full Text Available Concrete has the potential to become a solution for thermal energy storage (TES integrated in concentrating solar power (CSP systems due to its good thermal and mechanical properties and low cost of material. In this study, a low strength concrete (C20 is tested at high temperatures up to 600 °C. Specimens are thermally cycled at temperatures in the range of 400–300 °C, 500–300 °C, and 600–300 °C, which TES can reach in operation. For comparison, specimens also cycled at temperature in the range of 400–25 °C (room temperature, 500–25 °C, and 600–25 °C. It is found from the test results that cracks are not observed on the surfaces of concrete specimens until the temperature is elevated up to 500 °C. There is mechanical deterioration of concrete after exposure to high temperature, especially to high thermal cycles. The residual compressive strength of concrete after 10 thermal cycles between 600 °C and 300 °C is about 58.3%, but the specimens remain stable without spalling, indicating possible use of low strength concrete as a TES material.

  14. Mechanisms of Phosphorus Removal by Recycled Crushed Concrete.

    Science.gov (United States)

    Deng, Yihuan; Wheatley, Andrew

    2018-02-17

    Due to urbanisation, there are large amounts of waste concrete, particularly in rapidly industrialising countries. Currently, demolished concrete is mainly recycled as aggregate for reconstruction. This study has shown that larger sizes (2-5 mm) of recycled concrete aggregate (RCA) removed more than 90% of P from effluent when at pH 5. Analysis of the data, using equilibrium models, indicated a best fit with the Langmuir which predicated an adsorption capacity of 6.88 mg/g. Kinetic analysis indicated the equilibrium adsorption time was 12 h, with pseudo second-order as the best fit. The thermal dynamic tests showed that the adsorption was spontaneous and, together with the evidence from the sequential extraction and desorption experiments, indicated the initial mechanism was physical attraction to the surface followed by chemical reactions which prevented re-release. These results suggested that RCA could be used for both wastewater treatment and P recovery.

  15. Failure Modes in Concrete Repair Systems due to Ongoing Corrosion

    Directory of Open Access Journals (Sweden)

    Mladena Luković

    2017-01-01

    Full Text Available Corrosion of steel reinforcement is the main cause of deterioration in reinforced concrete structures. It can result in cracking and spalling of the concrete cover. After the damaged cover is repaired, reinforcement corrosion might continue and even accelerate. While the development of the corrosion cell is difficult to control, the damage can be possibly delayed and controlled by use of a suitable repair material. The lattice fracture model is used in this paper to investigate the performance of strain hardening cementitious composite (SHCC in concrete repair systems exposed to ongoing corrosion. Numerical results were verified by experimental tests when SHCC, nonreinforced material (repair mortar, and commercial repair mortar are used as repair materials. In experiments, reinforcement bars (surrounded by a repair material were exposed to accelerated corrosion tests. The influence of the substrate surface preparation, the type of repair material, the interface, and the substrate strength on the resulting damage and failure mode of repair systems are discussed. In general, SHCC repair enables distributed cracking with small crack widths, up to several times smaller compared to repair mortar. Furthermore, more warning signs prior to the final failure are present in the SHCC repair system.

  16. Deterioration of bioplastic carrier bags in the environment and assessment of a new recycling alternative.

    Science.gov (United States)

    Accinelli, Cesare; Saccà, Maria Ludovica; Mencarelli, Mariangela; Vicari, Alberto

    2012-09-01

    Increasing environmental concerns and the introduction of technologies based on renewable resources have stimulated the replacement of persistent petroleum-derived plastics with biodegradable plastics from biopolymers. As a consequence, a variety of products are currently manufactured from bioplastic, including carrier bags. This series of studies investigated the deterioration of carrier bags made with Mater-Bi (MB), a starch-based bioplastic, in soil, compost and two aquatic ecosystems, a littoral marsh and seawater. Results from the laboratory study indicated that bioplastic carrier bags were rapidly deteriorated in soil and compost. After three months of incubation, weight loss of specimens was of 37% and 43% in soil and compost, respectively. Conversely, little deterioration was observed in specimens buried in soil under field conditions or exposed to water of a littoral marsh and of the Adriatic Sea. These findings were consistent with the greater number of bacteria and especially fungi capable of degrading MB that were recovered from soil and compost with respect to the two aquatic ecosystems. Considering that a variety of microbial isolates are capable of using MB as a source of carbon, a new alternative to recycle these MB-based carrier bags was explored. More specifically, starchy residues from bags were fermented by the fungus Rhizopus oryzae to produce up to 35 mg of lactic acid per g of bag residues. Copyright © 2012 Elsevier Ltd. All rights reserved.

  17. Experimental Study on Tensile Properties of GFRP Bars Embedded in Concrete Beams with Working Cracks

    Directory of Open Access Journals (Sweden)

    Dai Li

    2017-01-01

    Full Text Available This paper presents the test results of an experimental study carried out to investigate the tensile properties of GFRP bars embedded in concrete beams with working cracks. The specimens were conditioned with sustained loading in 50°C alkaline solution and tap water for 6, 12, 18 months. The tensile test results show that the degradation rate of GFRP bars embedded in the concrete specimens with work cracks is larger than that of non-work cracks, while the effect of working cracks on the elastic modulus is not significant. The microstructure of GFRP bar surface before and after the test was observed by scanning electron microscopy (SEM, combined with Fourier-transform infrared spectroscopy (FTIR and differential-scanning calorimetry (DSC, the degree of hydrolysis reaction and glass transition temperature is also analyzed. Compared with the hydrolysis of resin matrix, it can be found that the deterioration of glass fiber and the delamination at the interfacial is more pronounced for the GFRP bars embedded in concrete beams. As a result, the mainly reason that caused the degradation of GFRP bars embedded in concrete environments are the deterioration of glass fiber and the delamination at the interfacial.

  18. Application of Interfacial Propagation and Kinking Crack Concept to ECC/Concrete Overlay Repair System

    Directory of Open Access Journals (Sweden)

    Yaw ChiaHwan

    2014-01-01

    Full Text Available Research on the application of ultraductile engineered cementitious composite (ECC as overlay in the repair of deteriorated concrete structures is performed in this paper. Also, interfacial crack kinking and trapping mechanism experimentally observed in ECC/concrete overlay repair system are described by comparison of toughness and energy release rate. The mechanism involves cycles of extension, kinking, and arrest of interfacial crack into the overlay. Experimental testing of overlay repair system reveals significant improvements in load carrying capacity and ductility over conventional concrete overlay. The commonly observed overlay system failure mode of delamination or spalling is eliminated when ECC is applied. These failure modes are suppressed when ECC is used as an ideal and durable candidate overlay repair material.

  19. Investigation and Rehabilitation to Extend Service Life of DSS-13 Antenna Concrete Foundation

    Science.gov (United States)

    Riewe, A. A., Jr.

    1984-01-01

    An investigation to establish the cause and, devise a repair technique to maintain the serviceability of the DSS-13 26 meter antenna is described. Core samples are obtained from the concrete and various laboratory tests conducted. In-place nondestructive type tests are also performed. The tests established that the concrete is deteriorating because of alkali aggregate reactivity. This is a phenomenon wherein certain siliceous constituents present in some aggregates react with alkalies in the portland cement to produce a silica gel which, in turn, imbibes water, swells, and cracks the concrete. The scheme consists of a supplemental steel frame friction pile anchored grade beam encircling the existing foundation. This system provides adequate bracing against base shear and overturning due to seismic loading. Larger cracks are sealed using a pressure injected two-component epoxy.

  20. Valuation of the 12 year old Concrete in the Ulkebugt Bridge, Sisimiut, Greenland

    DEFF Research Database (Denmark)

    Gottlieb, Christian; Olsen, Idar; Henningsen, Jesper Frej

    2011-01-01

    The Ulkebugt bridge is a vital connection for the town Sisimiut, as it is the only link between the airport and the town. The bridge is a box girder bridge with one central pillar. Most of the pillar’s concrete surface is exposed to seawater, with a tide variation around 4 meters. In addition...... to the seawater the bridge is exposed to the rough arctic climate. Furthermore, the mean temperature is below 0 °C for two thirds of the year with many freeze-thaw passages in late autumn and early spring, which increases the opportunity for severe frost damages. The focus has been to evaluate the quality...... and condition of the concrete pillar in terms of composition and the extent of the present deterioration mechanisms, best represented by frost damage and chloride ingress. Results show critical chloride content in the concrete will be reached in approximately 10 years at the depth of the reinforcement bars...

  1. Comparison of policies for recognising and responding to clinical deterioration across five Victorian health services.

    Science.gov (United States)

    Considine, Julie; Hutchison, Anastasia F; Rawson, Helen; Hutchinson, Alison M; Bucknall, Tracey; Dunning, Trisha; Botti, Mari; Duke, Maxine M; Street, Maryann

    2017-05-25

    Objectives The aim of the present study was to describe and compare organisational guidance documents related to recognising and responding to clinical deterioration across five health services in Victoria, Australia.Methods Guidance documents were obtained from five health services, comprising 13 acute care hospitals, eight subacute care hospitals and approximately 5500 beds. Analysis was guided by a specific policy analysis framework and a priori themes.Results In all, 22 guidance documents and five graphic observation and response charts were reviewed. Variation was observed in terminology, content and recommendations between the health services. Most health services' definitions of physiological observations fulfilled national standards in terms of minimum parameters and frequency of assessment. All health services had three-tier rapid response systems (RRS) in place at both acute and subacute care sites, consisting of activation criteria and an expected response. RRS activation criteria varied between sites, with all sites requiring modifications to RRS activation criteria to be made by medical staff. All sites had processes for patient and family escalation of care.Conclusions Current guidance documents related to the frequency of observations and escalation of care omit the vital role of nurses in these processes. Inconsistencies between health services may lead to confusion in a mobile workforce and may reduce system dependability.What is known about the topic? Recognising and responding to clinical deterioration is a major patient safety priority. To comply with national standards, health services must have systems in place for recognising and responding to clinical deterioration.What does this paper add? There is some variability in terminology, definitions and specifications of physiological observations and medical emergency team (MET) activation criteria between health services. Although nurses are largely responsible for physiological observations and

  2. Evaluation of repeatability of Kansas test method KT-73, "density, absorption and voids in hardened concrete," boil test.

    Science.gov (United States)

    2015-06-01

    For years, the Kansas Department of Transportation (KDOT) and concrete producers in the state have used a : Rapid Chloride Test for concrete cylinders, AASHTO T277. This test has been thought of as an appropriate quality : control test to evaluate pe...

  3. Porosity of Concrete - Morphological Study of Model Concrete

    NARCIS (Netherlands)

    Hu, J.

    2004-01-01

    This study has developed a comprehensive methodological framework for characterizing geometrical and morphological aspects of pore space in cementitious materials and explored its application to actual cement pastes and model concretes for the purpose of predicting mechanical and transport

  4. Long-life concrete : how long will my concrete last?

    Science.gov (United States)

    2013-10-01

    There is an ongoing discussion about moving toward performance-based specifications for concrete pavements. This document seeks to : move the discussion forward by outlining the needs and the challenges, and proposing some immediate actions. However,...

  5. PCM Concrete. [Phase Change Materials

    Energy Technology Data Exchange (ETDEWEB)

    Juul Andersen, T. [Danish Technological Institute, Taastrup (Denmark); Poulsen, H.-H. [BASF A/S, Roedekro (Denmark); Passov, F. [Spaencom A/S, Hedehusene (Denmark); Heiselberg, P. [Aalborg Univ..Aalborg (Denmark)

    2013-04-01

    PCM-Concrete was a research and development project launched in 2009 and finished in 2012. The project, which was funded by The Danish National Advanced Technology Foundation, had a total budget of 1.7 million Euros and included 4 partners: Danish Technological Institute (project manager), Aalborg University, BASF A/S and Spaencom A/S. The overall vision of the project was to reduce energy consumption for heating and cooling in buildings by developing high-performance concrete structures microencapsulated Phase Change Materials (PCM). The PCM used in the project was Micronal produced by BASF A/S. Micronal is small capsules with an acrylic shell and inside a wax with a melting point at approx. 23 deg. C equal to a comfortable indoor temperature. During the melting process thermal energy is transferred to chemical reaction (melting/solidification) depending on PCM being heated up or cooled down. Adding Micronal to concrete would theoretically increase the thermal mass of the concrete and improve the diurnal heat capacity which is the amount of energy that can be stored and released during 24 hours. Nevertheless, it is a relatively new technology that has not received much attention, yet. In the PCM-Concrete project 5 main investigations were carried out: 1) Development of concrete mix design with PCM. 2) Investigation of thermal properties of the PCM concrete: thermal conductivity, specific heat capacity, density. 3) Up-scaling the research to industrial production of PCM-concrete structures. 4) Testing energy efficiency in full scale. 5) Confronting aesthetic and acoustic barriers to full exploitation of the potential of PCM-concrete structures. The results from the test program showed: 1) That the diurnal heat storage capacity is higher for all 4 hollow core decks with tiles attached compared to the reference hollow core deck. 2) The hollow core decks with concrete tiles without PCM performs slightly better than the tiles with PCM. 3) That is was impossible to

  6. Characteristics of Concrete with Admixtures

    Directory of Open Access Journals (Sweden)

    Bogdan Roşca

    2008-01-01

    Full Text Available In recent decades, tremendous success has been achieved in the advancement of chemical admixtures for Portland cement concrete. Most efforts have centered on improving the properties of concrete with minimal investments by ready-mix suppliers and contractors in the way of specialized equipment or special skills and education of their labor forces. This approach has resulted in construction cost reductions and universally accepted ready-made remedies for unexpected problems during construction. The behavior of concrete improved with superplasticizers additives is studied.

  7. Mechanical Properties of Polymer Concrete

    Directory of Open Access Journals (Sweden)

    Raman Bedi

    2013-01-01

    Full Text Available Polymer concrete was introduced in the late 1950s and became well known in the 1970s for its use in repair, thin overlays and floors, and precast components. Because of its properties like high compressive strength, fast curing, high specific strength, and resistance to chemical attacks polymer concrete has found application in very specialized domains. Simultaneously these materials have been used in machine construction also where the vibration damping property of polymer concrete has been exploited. This review deals with the efforts of various researchers in selection of ingredients, processing parameters, curing conditions, and their effects on the mechanical properties of the resulting material.

  8. Investigation on Wall Panel Sandwiched With Lightweight Concrete

    Science.gov (United States)

    Lakshmikandhan, K. N.; Harshavardhan, B. S.; Prabakar, J.; Saibabu, S.

    2017-08-01

    The rapid population growth and urbanization have made a massive demand for the shelter and construction materials. Masonry walls are the major component in the housing sector and it has brittle characteristics and exhibit poor performance against the uncertain loads. Further, the structure requires heavier sections for carrying the dead weight of masonry walls. The present investigations are carried out to develop a simple, lightweight and cost effective technology for replacing the existing wall systems. The lightweight concrete is developed for the construction of sandwich wall panel. The EPS (Expanded Polystyrene) beads of 3 mm diameter size are mixed with concrete and developed a lightweight concrete with a density 9 kN/m3. The lightweight sandwich panel is cast with a lightweight concrete inner core and ferrocement outer skins. This lightweight wall panel is tested for in-plane compression loading. A nonlinear finite element analysis with damaged plasticity model is carried out with both material and geometrical nonlinearities. The experimental and analytical results were compared. The finite element study predicted the ultimate load carrying capacity of the sandwich panel with reasonable accuracy. The present study showed that the lightweight concrete is well suitable for the lightweight sandwich wall panels.

  9. Durability of recycled aggregate concrete using pozzolanic materials.

    Science.gov (United States)

    Ann, K Y; Moon, H Y; Kim, Y B; Ryou, J

    2008-01-01

    In this study, pulverized fuel ash (PFA) and ground granulated blast furnace slag (GGBS) were used to compensate for the loss of strength and durability of concrete containing recycled aggregate. As a result, 30% PFA and 65% GGBS concretes increased the compressive strength to the level of control specimens cast with natural granite gravel, but the tensile strength was still lowered at 28 days. Replacement with PFA and GGBS was effective in raising the resistance to chloride ion penetrability into the concrete body, measured by a rapid chloride ion penetration test based on ASTM C 1202-91. It was found that the corrosion rate of 30% PFA and 65% GGBS concretes was kept at a lower level after corrosion initiation, compared to the control specimens, presumably due to the restriction of oxygen and water access. However, it was less effective in increasing the chloride threshold level for steel corrosion. Hence, it is expected that the corrosion time for 30% PFA and 65% GGBS concrete containing recycled aggregate mostly equates to the corrosion-free life of control specimens.

  10. Performance of concrete blended with pozzolanic materials in marine environment

    Directory of Open Access Journals (Sweden)

    Khan Asad-ur-Rehman

    2017-01-01

    Full Text Available Reinforced concretes structures located at or near the coast line needs to be repaired more frequently when compared to structures located elsewhere. This study is continuation of previous studies carried out at the Department of Civil Engineering, NED University of Engineering and Technology, Karachi, Pakistan to study the performance of concrete made up of cements blended by pozzolonic materials. Different pozzolanic materials (blast furnace slag, fly ash and silica fume were used in the study. Tests conducted during the study to compare the performance of samples cast from concrete of different mix designs were Compressive Strength Test (ASTM C 39, Flexural Strength Test (ASTM C 293, Rapid Migration Test (NT Build 492, Absorptivity of the oven-dried samples (ASTM C 642 and Half Cell Potential (ASTM C 876. Use of cements blended with pozzolanic materials, used during the study, proved to be effective in enhancing the performance of the concrete exposed to marine environment. Use of pozzolans in concrete not only provides a sustainable and feasible solution to the durability problems in coastal areas, it also helps in conservation of natural resources and reduction of pollution and energy leading to a green environment.

  11. Durability of fibre reinforced concrete structures

    DEFF Research Database (Denmark)

    Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard

    1996-01-01

    The planned research will indicate, whether fibre reinforced concrete has better or worse durability than normal concrete. Durability specimens will be measured on cracked as well as uncracked specimens. Also the pore structure in the concrete will be characterized.Keywords: Fibre reinforced...... concrete, durability, pore structure, mechanical load...

  12. Betonreparationers holdbarhed (Durability of Concrete Repairs)

    DEFF Research Database (Denmark)

    Brimnes, Eydbjørn; Dali, Bogi í; Larsen, Erik Stoklund

    1999-01-01

    Concrete repairs on 11 pillars on bridges built in the sixties and repaired 8 to 9 years ago have been examined. Especially the chloride penetration in the repair concrete have been measured. Chloride penetration in the repair concrete is much lower than in the original concrete....

  13. Deliberate deformation of concrete after casting

    NARCIS (Netherlands)

    Grunewald, S.; Janssen, B.; Schipper, H.R.; Vollers, K.J.; Walraven, J.C.

    2012-01-01

    This paper discusses the effect of intentional deformation of a flexible formwork after casting of the concrete and the influence of the characteristics of concrete in the fresh state on the quality of a concrete element. This deformation is intended to bring the concrete element in its desired

  14. Shear reinforced beams in autoclaved aerated concrete

    DEFF Research Database (Denmark)

    Cornelius, Thomas

    2010-01-01

    Shear behaviour in concrete materials is very well documented, for normal density concrete materials. In this paper results of various tests on low density concrete materials like aerated autoclaved concrete (in the following denoted aircrete) will be presented and analyzed for different combinat...

  15. 75 FR 52916 - Action To Ensure Authority To Issue Permits Under the Prevention of Significant Deterioration...

    Science.gov (United States)

    2010-08-30

    ... Prevention of Significant Deterioration Program to Sources of Greenhouse Gas Emissions: Federal... Ensure Authority to Issue Permits under the Prevention of Significant Deterioration Program to Sources of... Review Prevention of Significant Deterioration program for sources of greenhouse gases. Public hearing...

  16. Influence of treated recycled concrete aggregate on concrete properties

    OpenAIRE

    Galindo, Anna; Etxeberria Larrañaga, Miren

    2017-01-01

    The amount and the quality of the old cement mortar attached to the aggregates influence the quality of the recycled concrete aggregate (RCA) produced. The characteristics of RCA adversely affect the physical, mechanical and durability properties of concretes. Due to these adverse effects, it is necessary to improve the RCA properties, not only changing their surface but also their internal microstructure. The main objective of this research work was to analyse the influence of chemically tre...

  17. Review of concrete properties for prestressed concrete pressure vesssels

    Energy Technology Data Exchange (ETDEWEB)

    Nanstad, R.K.

    1976-10-01

    The desire for increasing power output along with safety requirements has resulted in consideration of the prestressed concrete pressure vessel (PCPV) for most current nuclear reactor systems, as well as for the very-high-temperature reactor for process heat and as primary pressure vessels for coal conversion systems. Results are presented of a literature review to ascertain current knowledge regarding plain concrete properties under conditions imposed by a mass concrete structure such as PCRV. The effects of high temperature on such properties as strength, elasticity, and creep are discussed, as well as changes in thermal properties, multiaxial behavior, and the mechanisms thought to be responsible for the observed behavior. In addition, the effects of radiation and moisture migration are discussed. It is concluded that testing results found in the technical literature show much disagreement as to the effects of temperature on concrete properties. The variations in concrete mixtures, curing and testing procedures, age at loading, and moisture conditions during exposure and testing are some of the reasons for such disagreement. Test results must be limited, in most cases, to the materials and conditions of a given test rather than applied to such a general class of materials such as concrete. It is also concluded that sustained exposure of normal concretes to current PCRV operating conditions will not result in any significant loss of properties. However, lack of knowledge regarding effects of temperatures exceeding 100/sup 0/C (212/sup 0/F), moisture migration, and multiaxial behavior precludes a statement advocating operation beyond current design limits. The report includes recommendations for future research on concrete for PCPVs.

  18. Online Monitoring of Concrete Structures in Nuclear Power Plants: Interim Report

    Energy Technology Data Exchange (ETDEWEB)

    Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Idaho National Lab. (INL), Idaho Falls, ID (United States); Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-03-01

    The existing fleet of nuclear power plants in the United States have initial operating licenses of 40 years, and many of these plants have applied for and received license extensions. As plant structures, systems, and components age, their useful life—considering both structural integrity and performance—is reduced as a result of deterioration of the materials. Assessment and management of aging concrete structures in nuclear plants require a more systematic approach than simple reliance on existing code-based design margins of safety. Structural health monitoring is required to produce actionable information regarding structural integrity that supports operational and maintenance decisions. The online monitoring of concrete structures project conducted under the Advanced Instrumentation, Information, and Control Technologies Pathway of the Light Water Reactor Sustainability program at Idaho National Laboratory is seeking to develop and demonstrate capabilities for concrete structures health monitoring. Through this research project, several national laboratories and Vanderbilt University propose to develop a framework of research activities for the health monitoring of nuclear power plant concrete structures that includes the integration of four elements—damage modeling, monitoring, data analytics, and uncertainty quantification. This report briefly discusses activities in this project during October-December, 2014. The most significant activity during this period was the organizing of a two-day workshop on research needs in online monitoring of concrete structures, hosted by Vanderbilt University in November 2014. Thirty invitees from academia, industry and government participated in the workshop. The presentations and discussions at the workshop surveyed current activities related to concrete structures deterioration modeling and monitoring, and identified the challenges, knowledge gaps, and opportunities for advancing the state of the art; these

  19. Concrete density estimation by rebound hammer method

    Energy Technology Data Exchange (ETDEWEB)

    Ismail, Mohamad Pauzi bin, E-mail: pauzi@nm.gov.my; Masenwat, Noor Azreen bin; Sani, Suhairy bin; Mohd, Shukri [NDT Group, Nuclear Malaysia, Bangi, Kajang, Selangor (Malaysia); Jefri, Muhamad Hafizie Bin; Abdullah, Mahadzir Bin [Material Technology Program, Faculty of Applied Sciences, UiTM, Shah Alam, Selangor (Malaysia); Isa, Nasharuddin bin; Mahmud, Mohamad Haniza bin [Pusat Penyelidikan Mineral, Jabatan Mineral dan Geosains, Ipoh, Perak (Malaysia)

    2016-01-22

    Concrete is the most common and cheap material for radiation shielding. Compressive strength is the main parameter checked for determining concrete quality. However, for shielding purposes density is the parameter that needs to be considered. X- and -gamma radiations are effectively absorbed by a material with high atomic number and high density such as concrete. The high strength normally implies to higher density in concrete but this is not always true. This paper explains and discusses the correlation between rebound hammer testing and density for concrete containing hematite aggregates. A comparison is also made with normal concrete i.e. concrete containing crushed granite.

  20. Towards Better Understanding of Concrete Containing Recycled Concrete Aggregate

    Directory of Open Access Journals (Sweden)

    Hisham Qasrawi

    2013-01-01

    Full Text Available The effect of using recycled concrete aggregates (RCA on the basic properties of normal concrete is studied. First, recycled aggregate properties have been determined and compared to those of normal aggregates. Except for absorption, there was not a significant difference between the two. Later, recycled aggregates were introduced in concrete mixes. In these mixes, natural coarse aggregate was partly or totally replaced by recycled aggregates. Results show that the use of recycled aggregates has an adverse effect on the workability and air content of fresh concrete. Depending on the water/cement ratio and on the percent of the normal aggregate replaced by RCA, the concrete strength is reduced by 5% to 25%, while the tensile strength is reduced by 4% to 14%. All results are compared with previous research. As new in this research, the paper introduces a simple formula for the prediction of the modulus of elasticity of RCA concrete. Furthermore, the paper shows the variation of the air content of RAC.

  1. Impact of the distribution of calcite concretions on performance of SAGD

    Energy Technology Data Exchange (ETDEWEB)

    Gates, Ian [University of Calgary (Canada)

    2011-07-01

    In the heavy oil industry, the steam assisted gravity drainage (SAGD) process is often used to enhance oil recovery. In Grand Rapids oil sands reservoirs, carbonate cemented concretions can be found. In terms of SAGD process, these concretions can have an impact on the growth of steam chambers and thus on the method's performance. Calcite concretions are non productive rock but this can also enhance heat transfer through thermal dispersion depending on the length scales of its spatial distribution, sizes and shapes. The aim of this paper is then to study the effects of the concretion's spatial distributions and size on the performance of SAGD. Tests were conducted to assess several parameters of the steam chamber and results showed that steam chamber conformance depends on the heterogeneity of the concretions. This paper highlighted that SAGD performance can be optimized by deciding length scales for placement of well pairs and provided a means to do it.

  2. Experimental Investigation of the Optimal Design of the Ultrahigh Early Strength Concrete

    Science.gov (United States)

    Dai, Mingzhi; Qin, Longfei; Liu, Yang

    2017-10-01

    Comparing with the common concrete, the ultrahigh early strength concrete can form in an extremely short time, which can be effectively applied in the field of the fast repair engineering. Based on this point, the design of the optimal mix proportion of ultrahigh early strength concrete was investigated in this study. First, the optimal water-cement ratio was determined through the experiment. Second, the relationship between water reducing agent and concrete strength was investigated, and then the optimal dosage of admixture was determined. The experimental results show that the prepared ultrahigh early strength concrete can obtain the high strength in the early time, which is beneficial for the practical application. Additionally, some other performances are acquired, such as the rapid condensation properties, the permeability resistance and workability etc.

  3. Electrically conductive polymer concrete overlays

    Science.gov (United States)

    Fontana, J. J.; Webster, R. P.

    1984-08-01

    The use of cathodic protection to prevent the corrosion of reinforcing steel in concrete structures has been well established. Application of a durable, skid-resistant electrically conductive polymer concrete overlay would advance the use of cathodic protection for the highway industry. Laboratory studies indicate that electrically conductive polymer concrete overlays using conductive fillers, such as calcined coke breeze, in conjunction with polyester or vinyl ester resins have resistivities of 1 to 10 ohm-cm. Both multiple-layer and premixed mortar-type overlays were made. Shear bond strengths of the conductive overlays to concrete substrates vary from 600 to 1300 psi, with the premixed overlays having bond strengths 50 to 100% higher than the multiple-layer overlays.

  4. GFRP reinforced concrete bridge decks.

    Science.gov (United States)

    2000-07-01

    This report investigates the application of glass fiber reinforced polymer (GFRP) rebars in concrete bridge decks as a potential replacement or supplement to conventional steel rebars. Tests were conducted to determine the material properties of the ...

  5. Uncontrolled concrete bridge parapet cracking.

    Science.gov (United States)

    2013-06-01

    The Ohio Department of Transportation has recently identified the problem of wide-spread premature cracking of concrete bridge : parapets throughout its District 12 region (Northeast Ohio). Many of the bridge decks that contain these prematurely crac...

  6. Premature asphalt concrete pavement cracking.

    Science.gov (United States)

    2015-06-01

    Recently, the Oregon Department of Transportation (ODOT) has identified hot mix asphalt concrete : (HMAC) pavements that have displayed top-down cracking within three years of construction. The objective of : the study was to evaluate the top-down cr...

  7. Tests on standard concrete samples

    CERN Multimedia

    CERN PhotoLab

    1973-01-01

    Compression and tensile tests on standard concrete samples. The use of centrifugal force in tensile testing has been developed by the SB Division and the instruments were built in the Central workshops.

  8. Self-healing of polymer modified concrete

    OpenAIRE

    Abd_Elmoaty M. Abd_Elmoaty

    2011-01-01

    Self healing phenomenon of concrete has been observed in traditional, fibrous, self compacting concrete. This phenomenon occurred mainly due to the presence of unhydrated cement particles in the presence of water. Mechanism of polymer in concrete depends on creating a layer and net of polymer around cement particles which enhances the properties of polymer modified concrete. This mechanism may affect the self healing of this type of concrete. This work aims to study the presence of the self h...

  9. Monitoring water loss form fresh concrete

    DEFF Research Database (Denmark)

    Jensen, Ole Mejlhede

    2006-01-01

    Desiccation of concrete before or during setting may lead to detrimental plastic shrinkage cracking in the concrete surface zone. Cracking due to plastic shrinkage is a major technological problem for any concrete, however, modern high-performance concretes are especially susceptible to this. Thi...... determination of the evaporation loss from hardening concrete and thus better possibility for preventing curing problems, including detrimental crack damage due to plastic shrinkage....

  10. Adaptive Control of a Reverse Logistic Inventory Model with Uncertain Deteriorations and Disposal Rates

    National Research Council Canada - National Science Library

    Alshamrani, Ahmad

    2012-01-01

    ... to an inventory system with ameliorating and deteriorating items. They derived the optimal inventory level and optimal production rate for different cases of both amelioration and deterioration ra...

  11. 75 FR 54292 - Action To Ensure Authority To Issue Permits Under the Prevention of Significant Deterioration...

    Science.gov (United States)

    2010-09-07

    ... the Prevention of Significant Deterioration Program to Sources of Greenhouse Gas Emissions: Federal... Under the Prevention of Significant Deterioration Program to Sources of Greenhouse Gas Emissions...

  12. Concrete Durability in Harsh Environmental Conditions Exposed to Freeze Thaw Cycles

    Science.gov (United States)

    Hamze, Youssef

    Under line Pathology of Materials; one of the environmental causes of damage effects on concrete is freeze thaw cycles, which deteriorate the concrete exposed to water in cold weather. An example of old concrete is a dam project that was built in Canada, in the early 1909-1913. This project was reconstructed in 1932, 1934 and 1972, and required renovation due to the ice abrasion with the freeze/thaw cycles. Before completing any renovation, it is required to analyze the structural stability and the concrete failures of this dam. An investigation was conducted to determine the quality of the concrete in the Piers and in the Bridge Deck Slab. It was also required to determine the basic materials' properties that constitute this project. This will improve the analysis of its stability [10]. Core samples were examined and used as test samples, for the Alkali-Silica reactivity test samples, as well as the compressive strength test, the Chloride Ion test, and the freeze thaw testing which was performed on two sets of 12 concrete core samples that were taken from different locations in the project. These locations are the representations of the age of the concrete. Thus, the age difference between the samples' two sets is four decades. Testing was performed on prisms cut from cores. ASTM C-666 procedure (A) was applied using an automatic test system [6]. It was suggested that a plan for renovation of this project should be performed after the analysis is undertaken to assess the conditions estimating the remaining life of the concrete in this project [15].

  13. Characteristics of Concrete with Admixtures

    OpenAIRE

    Bogdan Roşca; P. Mihai

    2008-01-01

    In recent decades, tremendous success has been achieved in the advancement of chemical admixtures for Portland cement concrete. Most efforts have centered on improving the properties of concrete with minimal investments by ready-mix suppliers and contractors in the way of specialized equipment or special skills and education of their labor forces. This approach has resulted in construction cost reductions and universally accepted ready-made remedies for unexpected problems during construction...

  14. Electrically conductive polymer concrete coatings

    Science.gov (United States)

    Fontana, Jack J.; Elling, David; Reams, Walter

    1990-01-01

    A sprayable electrically conductive polymer concrete coating for vertical d overhead applications is described. The coating is permeable yet has low electrical resistivity (strength to concrete substrates, and good weatherability. A preferred formulation contains about 60 wt % calcined coke breeze, 40 wt % vinyl ester with 3.5 wt % modified bentonite clay. Such formulations apply evenly and provide enough rigidity for vertical or overhead structures so there is no drip or sag.

  15. Annotated Bibliography: Polymers in Concrete.

    Science.gov (United States)

    1982-10-01

    sulfur within 20 hr. Limonene, myrcene , alloocimene, dicyclopentadiene, cyclododeca- 1,5,9-triene, cycloocta-1,3-diene, styrene, and the polymeric poly...saturated into hardened concrete and subsequently polymerized . Section C covers latex-modified concretes and has 256 abstracts on articles dating back... polymerization led by the associated crystals. A44 Franke, W., "The Employment of Epoxy Resin in the Sanitation of Prefabricated Bridge Members Made of

  16. Does renal function deteriorate more rapidly in diabetic cardiac transplant recipients?

    Science.gov (United States)

    Almuti, Khalid; Haythe, Jennifer; Tsao, Lana; Naka, Yoshifumi; Mancini, Donna

    2007-03-15

    Selection criteria for cardiac transplant candidates with diabetes mellitus (DM) have been liberalized resulting in increased numbers of diabetic patients receiving organs. Calcineurin inhibition results in nephrotoxicity. Whether this nephrotoxicity is accelerated in diabetic heart transplant recipients is unknown. To investigate this question, we derived the glomerular filtration rate (GFR) at transplant and at multiple time intervals thereafter for adult heart transplants performed from January 1, 2000 to January 1, 2005. GFR was estimated using the Modification of Diet in Renal Disease Study equation (GFRMDRD) and the Cockcroft-Gault (GFRCG) formula. In all, 257 patients were nondiabetic and 102 patients were diabetic before and after transplant. The diabetic patients were older (57+/-8 vs. 53+/-13 years; Pcyclosporine or tacrolimus posttransplant. The change in the GFRMDRD in nondiabetic and diabetic patients was constant and comparable at 1, 2, and 3 years posttransplant. In normal subjects, GFRMDRD declined from baseline by 7+/-26, 5+/-23, and 7+/-23 mL/min(2) and in the diabetic patients was 13+/-22, 9+/-26, 10+/-22 ml/min(2) at 1, 2, and 3 years, respectively (P=NS). This data suggests that nephrotoxicity posttransplant is not accelerated in diabetic recipients.

  17. Rapid deterioration of preexisting renal insufficiency after autologous mesenchymal stem cell therapy

    OpenAIRE

    Jun-Seop Kim; Jong-Hak Lee; Owen Kwon; Jang-Hee Cho; Ji-Young Choi; Sun-Hee Park; Chan-Duck Kim; Yong-Jin Kim; Yong-Lim Kim

    2017-01-01

    Administration of autologous mesenchymal stem cells (MSCs) has been shown to improve renal function and histological findings in acute kidney injury (AKI) models. However, its effects in chronic kidney disease (CKD) are unclear, particularly in the clinical setting. Here, we report our experience with a CKD patient who was treated by intravenous infusion of autologous MSCs derived from adipose tissue in an unknown clinic outside of Korea. The renal function of the patient had been stable for ...

  18. Rapidly deteriorating course in Dutch hereditary spastic paraplegia type 11 patients

    NARCIS (Netherlands)

    de Bot, Susanne T.; Burggraaff, Rogier C.; Herkert, Johanna C.; Schelhaas, Helenius J.; Post, Bart; Diekstra, Adinda; van Vliet, Reinout O.; van der Knaap, Marjo S.; Kamsteeg, Erik-Jan; Scheffer, Hans; van de Warrenburg, Bart P.; Verschuuren - Bemelmans, Corien C.; Kremer, Hubertus P. H.

    2013-01-01

    Although SPG11 is the most common complicated hereditary spastic paraplegia, our knowledge of the long-term prognosis and life expectancy is limited. We therefore studied the disease course of all patients with a proven SPG11 mutation as tested in our laboratory, the single Dutch laboratory

  19. Concrete waterproofing in nuclear industry.

    Science.gov (United States)

    Scherbyna, Alexander N; Urusov, Sergei V

    2005-01-01

    One of the main points of aggregate safety during the transportation and storage of radioactive materials is to supply waterproofing for all constructions having direct contact with radiating substances and providing strength, seismic shielding etc. This is the problem with all waterside structures in nuclear industry and concrete installations in the treatment and storage of radioactive materials. In this connection, the problem of developing efficient techniques both for the repair of operating constructions and the waterproofing of new objects of the specified assignment is genuine. Various techniques of concrete waterproofing are widely applied in the world today. However, in conditions of radiation many of these techniques can bring not a profit but irreparable damage of durability and reliability of a concrete construction; for instance, when waterproofing materials contain organic constituents, polymers etc. Application of new technology or materials in basic construction elements requires in-depth analysis and thorough testing. The price of an error might be very large. A comparative analysis shows that one of the most promising types of waterproofing materials for radiation loaded concrete constructions is "integral capillary systems" (ICS). The tests on radiation, thermal and strength stability of ICS and ICS-treated concrete samples were initiated and fulfilled in RFNC-VNIITF. The main result is--ICS applying is increasing of waterproofing and strength properties of concrete in conditions of readiation The paper is devoted to describing the research strategy, the tests and their results and also to planning of new tests.

  20. Self Healing in Concrete Materials

    Science.gov (United States)

    Li, Victor C.; Yang, En-Hua

    The phenomenon of self healing in concrete has been known for many years. It has been observed that some cracks in old concrete structures are lined with white crystalline material suggesting the ability of concrete to self-seal the cracks with chemical products by itself, perhaps with the aid of rainwater and carbon dioxide in air. Later, a number of researchers [1, 2] in the study of water flow through cracked concrete under a hydraulic gradient, noted a gradual reduction of permeability over time, again suggesting the ability of the cracked concrete to self-seal itself and slow the rate of water flow. The main cause of self-sealing was attributed to the formation of calcium carbonate, a result of reaction between unhydrated cement and carbon dioxide dissolved in water [1]. Thus, under limited conditions, the phenomenon of self-sealing in concrete is well established. Self-sealing is important to watertight structures and to prolonging service life of infrastructure.

  1. Chlorine signal attenuation in concrete.

    Science.gov (United States)

    Naqvi, A A; Maslehuddin, M; ur-Rehman, Khateeb; Al-Amoudi, O S B

    2015-11-01

    The intensity of prompt gamma-ray was measured at various depths from chlorine-contaminated silica fume (SF) concrete slab concrete specimens using portable neutron generator-based prompt gamma-ray setup. The intensity of 6.11MeV chloride gamma-rays was measured from the chloride contaminated slab at distance of 15.25, 20.25, 25.25, 30.25 and 35.25cm from neutron target in a SF cement concrete slab specimens. Due to attenuation of thermal neutron flux and emitted gamma-ray intensity in SF cement concrete at various depths, the measured intensity of chlorine gamma-rays decreases non-linearly with increasing depth in concrete. A good agreement was noted between the experimental results and the results of Monte Carlo simulation. This study has provided useful experimental data for evaluating the chloride contamination in the SF concrete utilizing gamma-ray attenuation method. Copyright © 2015 Elsevier Ltd. All rights reserved.

  2. Modification of ASTM C666 for testing resistance of concrete to freezing and thawing in sodium chloride solution.

    Science.gov (United States)

    1978-01-01

    Since 1961 the Research Council has used equipment manufactured by Conrad, Inc. for exposing concrete specimens to rapid cycles of freezing and thawing. In addition, the Materials Division of the Virginia Department of Highways and Transportation sen...

  3. Nondestructive inspection of corrosion and delamination at the concrete-steel reinforcement interface

    Science.gov (United States)

    Miller, Tri Huu

    The proposed study explores the feasibility of detecting and quantifying corrosion and delamination (physical separation) at the interface between reinforcing steel bars and concrete using ultrasonic guided waves. The problem of corrosion of the reinforcing steel in structures has increased significantly in recent years. The emergence of this type of concrete deterioration, which was first observed in marine structures and chemical manufacturing plants, coincided with the increased applications of deicing salts (sodium and calcium chlorides) to roads and bridges during winter months in those states where ice and snow are of major concern. Concrete is strengthened by the inclusion of the reinforcement steel such as deformed or corrugated steel bars. Bonding between the two materials plays a vital role in maximizing performance capacity of the structural members. Durability of the structure is of concern when it is exposed to aggressive environments. Corrosion of reinforcing steel has led to premature deterioration of many concrete members before their design life is attained. It is therefore, important to be able to detect and measure the level of corrosion in reinforcing steel or delamination at the interface. The development and implementation of damage detection strategies, and the continuous health assessment of concrete structures then become a matter of utmost importance. The ultimate goal of this research is to develop a nondestructive testing technique to quantify the amount of corrosion in the reinforcing steel. The guided mechanical wave approach has been explored towards the development of such methodology. The use of an embedded ultrasonic network for monitoring corrosion in real structures is feasible due to its simplicity. The ultrasonic waves, specifically cylindrical guided waves can p ropagate a long distance along the reinforcing steel bars and are found to be sensitive to the interface conditions between steel bars and concrete. Ultrasonic

  4. Optimal pricing and marketing planning for deteriorating items.

    Directory of Open Access Journals (Sweden)

    Seyed Reza Moosavi Tabatabaei

    Full Text Available Optimal pricing and marketing planning plays an essential role in production decisions on deteriorating items. This paper presents a mathematical model for a three-level supply chain, which includes one producer, one distributor and one retailer. The proposed study considers the production of a deteriorating item where demand is influenced by price, marketing expenditure, quality of product and after-sales service expenditures. The proposed model is formulated as a geometric programming with 5 degrees of difficulty and the problem is solved using the recent advances in optimization techniques. The study is supported by several numerical examples and sensitivity analysis is performed to analyze the effects of the changes in different parameters on the optimal solution. The preliminary results indicate that with the change in parameters influencing on demand, inventory holding, inventory deteriorating and set-up costs change and also significantly affect total revenue.

  5. Optimal dynamic pricing and replenishment policies for deteriorating items

    Directory of Open Access Journals (Sweden)

    Masoud Rabbani

    2014-08-01

    Full Text Available Marketing strategies and proper inventory replenishment policies are often incorporated by enterprises to stimulate demand and maximize profit. The aim of this paper is to represent an integrated model for dynamic pricing and inventory control of deteriorating items. To reflect the dynamic characteristic of the problem, the selling price is defined as a time-dependent function of the initial selling price and the discount rate. In this regard, the price is exponentially discounted to compensate negative impact of the deterioration. The planning horizon is assumed to be infinite and the deterioration rate is time-dependent. In addition to price, the demand rate is dependent on advertisement as a powerful marketing tool. Several theoretical results and an iterative solution algorithm are developed to provide the optimal solution. Finally, to show validity of the model and illustrate the solution procedure, numerical results are presented.

  6. Application of Artificial Intelligence for Bridge Deterioration Model

    Directory of Open Access Journals (Sweden)

    Zhang Chen

    2015-01-01

    Full Text Available The deterministic bridge deterioration model updating problem is well established in bridge management, while the traditional methods and approaches for this problem require manual intervention. An artificial-intelligence-based approach was presented to self-updated parameters of the bridge deterioration model in this paper. When new information and data are collected, a posterior distribution was constructed to describe the integrated result of historical information and the new gained information according to Bayesian theorem, which was used to update model parameters. This AI-based approach is applied to the case of updating parameters of bridge deterioration model, which is the data collected from bridges of 12 districts in Shanghai from 2004 to 2013, and the results showed that it is an accurate, effective, and satisfactory approach to deal with the problem of the parameter updating without manual intervention.

  7. Increased Durability of Concrete Made with Fine Recycled Concrete Aggregates Using Superplasticizers

    OpenAIRE

    Francisco Cartuxo; Jorge de Brito; Luis Evangelista; José Ramón Jiménez; Enrique F. Ledesma

    2016-01-01

    This paper evaluates the influence of two superplasticizers (SP) on the durability properties of concrete made with fine recycled concrete aggregate (FRCA). For this purpose, three families of concrete were tested: concrete without SP, concrete made with a regular superplasticizer and concrete made with a high-performance superplasticizer. Five volumetric replacement ratios of natural sand by FRCA were tested: 0%, 10%, 30%, 50% and 100%. Two natural gravels were used as coarse aggregates. All...

  8. Performance under sulfate attack of concrete additioned with fluid catalytic cracking catalyst residue (FCC and metakaolin (MK

    Directory of Open Access Journals (Sweden)

    Nancy Torres Castellanos

    2013-04-01

    Full Text Available In this work the evaluation of the performance of concrete added with Fluid Catalytic Cracking Catalyst residue (FCC from a Colombian petroleum company, under sulfate attack, is presented. The results of this concrete are compared with the results of Metakaolin (MK added concrete. The analysis of the pozzolanic materials included the determination of the particle size, the pozzolanic activity and the chemical and mineralogical composition. Different percentages of FCC were used as Portland cement replacement in proportions of 0, 10, 20 and 30%; similarly concrete added with 20% of MK as replacement was elaborated. Compressive strength and performance under sulfate attack were evaluated. Results showed that concrete with FCC and MK as well as control concrete had similar behavior; however its expansion was higher. In addition, the performance of the two types of concrete (FCC y MK under sulfate attack was comparable; this could be due to fact that FCC and MK showed similarities regarding of their chemical and mineralogical composition. Importantly, after 360 days of exposure the specimens with MK and FCC showed no significant deterioration.

  9. Performance under sulfate attack of concrete additioned with fluid catalytic cracking catalyst residue (FCC and metakaolin (MK

    Directory of Open Access Journals (Sweden)

    Nancy Torres Castellanos

    2013-01-01

    Full Text Available In this work the evaluation of the performance of concrete added with Fluid Catalytic Cracking Catalyst residue (FCC from a Colombian petroleum company, under sulfate attack, is presented. The results of this concrete are compared with the results of Metakaolin (MK added concrete. The analysis of the pozzolanic materials included the determination of the particle size, the pozzolanic activity and the chemical and mineralogical composition. Different percentages of FCC were used as Portland cement replacement in proportions of 0, 10, 20 and 30%; similarly concrete added with 20% of MK as replacement was elaborated. Compressive strength and performance under sulfate attack were evaluated. Results showed that concrete with FCC and MK as well as control concrete had similar behavior; however its expansion was higher. In addition, the performance of the two types of concrete (FCC y MK under sulfate attack was comparable; this could be due to fact that FCC and MK showed similarities regarding of their chemical and mineralogical composition. Importantly, after 360 days of exposure the specimens with MK and FCC showed no significant deterioration.

  10. Network condition simulator for benchmarking sewer deterioration models.

    Science.gov (United States)

    Scheidegger, A; Hug, T; Rieckermann, J; Maurer, M

    2011-10-15

    An accurate description of aging and deterioration of urban drainage systems is necessary for optimal investment and rehabilitation planning. Due to a general lack of suitable datasets, network condition models are rarely validated, and if so with varying levels of success. We therefore propose a novel network condition simulator (NetCoS) that produces a synthetic population of sewer sections with a given condition-class distribution. NetCoS can be used to benchmark deterioration models and guide utilities in the selection of appropriate models and data management strategies. The underlying probabilistic model considers three main processes: a) deterioration, b) replacement policy, and c) expansions of the sewer network. The deterioration model features a semi-Markov chain that uses transition probabilities based on user-defined survival functions. The replacement policy is approximated with a condition-class dependent probability of replacing a sewer pipe. The model then simulates the course of the sewer sections from the installation of the first line to the present, adding new pipes based on the defined replacement and expansion program. We demonstrate the usefulness of NetCoS in two examples where we quantify the influence of incomplete data and inspection frequency on the parameter estimation of a cohort survival model and a Markov deterioration model. Our results show that typical available sewer inventory data with discarded historical data overestimate the average life expectancy by up to 200 years. Although NetCoS cannot prove the validity of a particular deterioration model, it is useful to reveal its possible limitations and shortcomings and quantifies the effects of missing or uncertain data. Future developments should include additional processes, for example to investigate the long-term effect of pipe rehabilitation measures, such as inliners. Copyright © 2011 Elsevier Ltd. All rights reserved.

  11. Mechanical properties of structural lightweight concrete reinforced with waste steel wires

    OpenAIRE

    Aghaee, K; Yazdi, MA; Tsavdaridis, KD

    2014-01-01

    The study of concrete incorporating different waste fibres has started to increase rapidly due to economic reasons and positive environmental effects. In the study reported here, waste steel wires from steel reinforcement and used formworks were blended with structural lightweight concrete, with the aim of replacing commercial steel fibres of controlled quality with recycled fibres. Compression, tensile, flexural and impact tests were performed to assess the mechanical properties of 28 d old ...

  12. Pre-Cast Concrete Panels for Contingency Rigid Airfield Pavement Damage Repairs

    Science.gov (United States)

    2010-06-01

    Micro- texture of the particle plays an important role in aggregate interlock. Therefore, mixes consisting of less polished aggregates are expected to...AFRL-RX-TY-TR-2010-0095 PRECAST CONCRETE PANELS FOR CONTINGENCY RIGID AIRFIELD PAVEMENT DAMAGE REPAIRS Reza S. Ashtiani, Christopher J...Final Technical Report 01-JAN-2008 -- 30-APR-2010 Pre-Cast Concrete Panels for Rapid Repair of Airfield Rigid Pavements FA4819-09-C-0028 62102F 4915 D1

  13. Safety in ready mixed concrete industry: descriptive analysis of injuries and development of preventive measures

    OpenAIRE

    AKBO?A, ?zge; BARADAN, Selim

    2016-01-01

    Ready mixed concrete (RMC) industry, one of the barebones of construction sector, has its distinctive occupational safety and health (OSH) risks. Employees experience risks that emerge during the fabrication of concrete, as well as its delivery to the construction site. Statistics show that usage and demand of RMC have been increasing along with the number of producers and workers. Unfortunately, adequate OSH measures to meet this rapid growth are not in place even in top RMC producing countr...

  14. Utilization of Construction Waste Composite Powder Materials as Cementitious Materials in Small-Scale Prefabricated Concrete

    Directory of Open Access Journals (Sweden)

    Cuizhen Xue

    2016-01-01

    Full Text Available The construction and demolition wastes have increased rapidly due to the prosperity of infrastructure construction. For the sake of effectively reusing construction wastes, this paper studied the potential use of construction waste composite powder material (CWCPM as cementitious materials in small-scale prefabricated concretes. Three types of such concretes, namely, C20, C25, and C30, were selected to investigate the influences of CWCPM on their working performances, mechanical properties, and antipermeability and antifrost performances. Also the effects of CWCPM on the morphology, hydration products, and pore structure characteristics of the cement-based materials were analyzed. The results are encouraging. Although CWCPM slightly decreases the mechanical properties of the C20 concrete and the 7 d compressive strengths of the C25 and C30 concretes, the 28 d compressive strength and the 90 d flexural strength of the C25 and C30 concretes are improved when CWCPM has a dosage less than 30%; CWCPM improves the antipermeability and antifrost performances of the concretes due to its filling and pozzolanic effects; the best improvement is obtained at CWCPM dosage of 30%; CWCPM optimizes cement hydration products, refines concrete pore structure, and gives rise to reasonable pore size distribution, therefore significantly improving the durability of the concretes.

  15. Green Concrete from Sustainable Recycled Coarse Aggregates: Mechanical and Durability Properties

    Directory of Open Access Journals (Sweden)

    Neeraj Jain

    2015-01-01

    Full Text Available Present investigations deal with the development of green concrete (M 30 grade using recycled coarse aggregates for sustainable development. Characterization of recycled coarse aggregates showed that physical and mechanical properties are of inferior quality and improvement in properties was observed after washing due to removal of old weak mortar adhered on its surface. The influence of natural coarse aggregates replacement (50 and 100% with recycled coarse aggregate on various mechanical and durability properties of hardened concrete were discussed and compared with controls at different w/c ratio. Improvements in all the engineering properties of hardened concrete were observed using washed recycled coarse aggregates. The compressive strength of 28-day hardened concrete containing 100% washed recycled aggregate was slightly lower (7% than concrete prepared with natural aggregates. Water absorption, carbonation, and rapid chloride penetration test were conducted to assess the durability of the concrete. Concrete was found moderately permeable for chloride ions penetration and no carbonation was observed in all the concrete mixes studied.

  16. The enhancement of the deteriorated South African bond options market

    Directory of Open Access Journals (Sweden)

    Coert Frederik Erasmus

    2015-06-01

    Full Text Available nvestments, especially those in the bond market, carry a level of risk. Risks in the bond market can be mitigated by transacting in option contracts. In the developing South African economy, trading activity of over-the-counter (OTC bond options decreased significantly. Possible deteriorating factors and interventions to enhance OTC bond options were investigated in this research. Experts in the OTC bond option market were surveyed and the quantitative data collected was analysed with descriptive statistical methods. Results indicated that three factors were positively identified as deteriorating factors in the OTC bond option market and that five different interventions were possible to possible enhance this market.

  17. A production inventory model with deteriorating items and shortages

    Directory of Open Access Journals (Sweden)

    Samanta G.P.

    2004-01-01

    Full Text Available A continuous production control inventory model for deteriorating items with shortages is developed. A number of structural properties of the inventory system are studied analytically. The formulae for the optimal average system cost, stock level, backlog level and production cycle time are derived when the deterioration rate is very small. Numerical examples are taken to illustrate the procedure of finding the optimal total inventory cost, stock level, backlog level and production cycle time. Sensitivity analysis is carried out to demonstrate the effects of changing parameter values on the optimal solution of the system.

  18. Anterior cruciate ligament deterioration correlates with patella osteoarthritis.

    Science.gov (United States)

    Iriuchishima, Takanori; Ryu, Keinosuke; Aizawa, Shin; Yorifuji, Hiroshi; Ohyama, Tetsuji; Fu, Freddie H

    2014-04-01

    The correlation between anterior cruciate ligament (ACL) condition and patella osteoarthritic (OA) changes has not been well reported. The aim of this study was to reveal the correlation between ACL deterioration and the morphology of OA changes in the patella. The hypothesis was that significant correlation between ACL deterioration and patella OA morphology would be revealed in this study. Two hundred ninety-one cadaveric knees from 151 cadavers were included in this study with a median age of 83 years (54-98). Knees were opened with a sub-vastus approach and the ACL condition was classified as intact or deteriorated. Patella OA lesions were classified using Han's method: type 1, no or minimal lesion; type 2, medial facet lesion without involvement of the ridge; type 3, lateral facet lesion without involvement of the ridge; type 4, lesion involving the ridge only; type 5, medial facet lesion with involvement of the ridge; type 6, lateral facet lesion with involvement of the ridge; and type 7, global lesion. OA depth evaluation was performed following Outerbridge's classification. Statistical analysis of the collected data was performed using generalized estimating equations (GEE). The ACL was intact in 277 knees and deteriorated in 14 knees. Patella OA lesions were observed as follows: type 1, 29%; type 2, 15%; type 3, 2%; type 4, 12%; type 5, 18%; type 6, 2%; and type 7, 22%. Outerbridge's classification of over grade 2 OA depth was observed in 73.5% of subjects. When patella OA was divided into types 1-4 and types 5-7, ACL deterioration was correlated with the occurrence of type 5-7 patella OA [OR 6.44, 95%CI 2.27-18.25, p = 0.000]. When patella OA was divided into types 1-6 and type 7, ACL deterioration was correlated with the occurrence of type 7 patella OA [OR 6.02, 95%CI 2.57-14.09, p = 0.000]. When patella OA depth was divided into grades 1-3 and grade 4, ACL deterioration was highly correlated with the occurrence of grade 4 patella OA [OR 9.31, 95

  19. Drying of concrete. Part II: The drying time of concrete structures

    DEFF Research Database (Denmark)

    Hansen, Kurt Kielsgaard; Christensen, Søren Lolk

    1998-01-01

    The composition of a concrete mix has a significant influence on the drying time to reach a given relative humidity in the concrete pores. Knowledge of the influence on the drying of a specific component in the concrete makes it possible to design a concrete mix having a predetermined drying time....... In the paper the effects of the air content and the silica fume content on the drying time are investigated on two concrete mixes having different water/cement ratios. One concrete represents a normal concrete and the other represents a selfdesiccation concrete....

  20. Retrofitting of Reinforced Concrete Beams using Reactive Powder Concrete (RPC)

    Science.gov (United States)

    Karthik, S.; Sundaravadivelu, Karthik

    2017-07-01

    Strengthening of existing damaged structures is one of the leading studies in civil engineering. The purpose of retrofitting is to structurally treat the member with an aim to restore the structure to its original strength. The focus of this project is to study the behaviour of damaged Reinforced Concrete beam retrofitted with Reactive Powder Concrete (RPC) Overlay. Reinforced concrete beams of length 1200 mm, width 100 mm and depth 200 mm were casted with M30 grade of concrete in the laboratory and cured for 28 days. One beam is taken as control and are tested under two point loading to find out ultimate load. Remaining beams are subjected to 90 % ultimate load of control beams. The partially damaged beams are retrofitted with Reactive Powder Concrete Overlay at the full tension face of the beam and side overlay depends upon the respectable retrofitting techniques with 10 mm and 20 mm thick layer to find optimum. Materials like steel fibres are added to enhance the ductility by eliminating coarse particle for homogeneity of the structure. Finally, the modes of failure for retrofitted beams are analysed experimentally under two point loading & compared the results with Control beam.