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Michael D A Thomas - One of the best experts on this subject based on the ideXlab platform.
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the use of lithium to prevent or mitigate alkali silica Reaction in Concrete pavements and structures
2007Co-Authors: Michael D A Thomas, Jason H Ideker, Kevin J Folliard, Benoit Fournier, Y A ResendezAbstract: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 recently been increased interest in using lithium technologies to both control ASR in new Concrete and to retard the Reaction in existing ASR-affected structures. This facts book provides information on lithium, its origin and properties, and on its applications. The mechanism of alkali-silica Reaction is discussed together with methods of testing to identify potentially alkali-silica reactive aggregates. Traditional methods for minimizing the risk of damaging ASR are presented; these include the avoidance of reactive aggregates, controlling the levels of alkali in Concrete and using supplementary cementing materials such as fly ash, slag and silica fume. The final two sections of the facts book discuss the use of lithium, first as an admixture for new Concrete construction and second as a treatment for existing Concrete structures affected by ASR.
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test methods for evaluating preventive measures for controlling expansion due to alkali silica Reaction in Concrete
Cement and Concrete Research, 2006Co-Authors: Michael D A Thomas, Jason H Ideker, Kevin J Folliard, Benoit Fournier, Medhat H ShehataAbstract:Abstract This paper provides a critical evaluation of the various methods available for testing the efficacy of measures for preventing expansion due to alkali–silica Reaction (ASR) in Concrete containing deleteriously reactive aggregate. The ideal test method should be rapid, reliable and capable of determining the influence of aggregate reactivity, alkali availability and exposure conditions. None of the currently available or commonly used methods meet all of these criteria. The shortcomings of the different test methods are discussed and suggestions are made for modifying the Concrete prism test and accelerated mortar bar test to make these tests more acceptable.
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use of ternary blends containing silica fume and fly ash to suppress expansion due to alkali silica Reaction in Concrete
Cement and Concrete Research, 2002Co-Authors: Medhat H Shehata, Michael D A ThomasAbstract:Abstract This paper investigates the effects of cementitious systems containing Portland cement (PC), silica fume (SF) and fly ash (FA) on the expansion due to alkali–silica Reaction (ASR). Concrete prisms were prepared and tested in accordance with the Canadian Standards Association (CSA A23.2-14A). Paste samples were cast using the same or similar cementitious materials and proportions that were used in the Concrete prism test. Pore solution chemistry and portlandite content of the paste samples are reported. It was found that practical levels of SF with low-, moderate- or high-calcium FA are effective in maintaining the expansion below 0.04% after 2 years. Pore solution chemistry shows that while pastes containing SF yield pore solutions of increasing alkalinity at ages beyond 28 days, pastes containing ternary blends maintain the low alkalinity of the pore solution throughout the testing period (3 years).
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the effect of metakaolin on alkali silica Reaction in Concrete
Cement and Concrete Research, 2000Co-Authors: Terrence Ramlochan, Michael D A Thomas, Karen Ann GruberAbstract:This article reports on a study to evaluate the efficacy of high-reactivity metakaolin (HRM) in controlling expansion due to alkali–silica Reaction (ASR). The expansion of Concretes and mortars containing 0–20% HRM as a partial replacement for OPC was studied. Concrete prisms were prepared according to the CAN/CSA A23.2-14A Concrete prism method with two alkali–silica reactive aggregates: a siliceous limestone (Spratt) and a greywacke-argillite gravel (Sudbury). The amount of HRM required to control the expansion to <0.04% at 2 years was found to be between 10% and 15% depending on the aggregate. A modified version of the accelerated mortar bar method (CAN/CSA A23.2-25A) was also conducted with HRM and both reactive aggregates. in addition to expansion testing, the chemistry of expressed pore solutions from cement pastes containing 0%, 10%, and 20% metakaolin was determined over a 2-year period. incorporation of 20% metakaolin was found to significantly reduce the long-term OH−, Na+, and K+ ion concentrations in pore solutions. The reduction in the pH and the alkalinity of pore solutions correlate well with the observed reduction in expansion of the Concrete prisms and mortar bars.
Mda Thomas - One of the best experts on this subject based on the ideXlab platform.
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effect of slag on expansion due to alkali aggregate Reaction in Concrete
Materials, 1998Co-Authors: Mda Thomas, F A InnisAbstract:The efficacy of ground granulated blast furnace slag in controlling expansion caused by alkali-aggregate Reaction was evaluated using both Concrete prism and accelerated mortar bar testing. Six aggregates were included in the program; four of these were classified as alkali-silica reactive (siliceous limestone, sandstone, greywacke, and granite), one as alkali-carbonate reactive (dolomitic limestone), and one as nonreactive (dolostone). The partial replacement portland cement with slag in the range of 25-65% was effective in retarding the rate of expansion and limiting the ultimate expansion at 2 years in Concrete prisms cast with all four alkali-silica reactive aggregates. However, the minimum level of slag required to control expansion to an acceptable level, (for example, 0.04% at 2 years) was found to vary depending on the nature of the aggregate and the amount of alkali present in the Concrete. There appears to be a reliable correlation between the expansion of mortar bars after 14 days storage in 1M NaOH at 80 deg C and the expansion of Concrete prisms after 2 years storage over water at 38 deg C. The accelerated mortar bar test appears to be an appropriate tool for determining the minimum "safe" level of slag required for a particular reactive aggregate source. The use of slag also reduced the initial rate of expansion of Concrete prisms containing the alkali-carbonate reactive (ACR) aggregate. However, the expansion at 2 years exceeded 0.20% for all slag levels tested (25-65%), and this final expansion was actually greater for Concretes with 25-50% slag than for the control Concrete. The expansion of mortar bars was less than 0.10% at 14 days for all the mixes tested, which confirms the unsuitability of this test for detecting ACR aggregates.
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the effect of pulverised fuel ash with a high total alkali content on alkali silica Reaction in Concrete containing natural uk aggregate in durability of Concrete second international conference august 4 9 1991 montreal canada volume ii
DURABILITY OF CONCRETE. SECOND INTERNATIONAL CONFERENCE., 1991Co-Authors: Mda Thomas, P J Nixon, K PettiferAbstract:A number of seven-year-old, externally-stored 500 x 100 x 100 mm Concrete beams, some of which had suffered severe cracking due to alkali silica Reaction, have been examined. The Concretes were produced using pfa at a range of addition levels and contained a fixed proportion of a known reactive sand. Following seven years exposure, severe cracking was observed in the specimens without pfa or with 5 percent pfa. Surface crack widths were often in excess of 1 mm and examination of sawn surfaces indicated that the depth of visible cracks was up to 20 mm. Specimens containing 20 percent or more pfa did not exhibit any visible cracking. The lower quantity of available calcium in pfa Concrete and the increased absorption of potassium by its hydrates are discussed with respect to their possible contributions to the suppression of damaging alkali silica Reaction.
Farshad Rajabipour - One of the best experts on this subject based on the ideXlab platform.
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novel admixtures for mitigation of alkali silica Reaction in Concrete
Cement & Concrete Composites, 2021Co-Authors: Gopakumar Kaladharan, Tiffany Szeles, Shelley M Stoffels, Farshad RajabipourAbstract:Abstract The objective of this study is to develop a new generation of alkali-silica Reaction (ASR) inhibiting powder additives or liquid chemical admixtures for Concrete. Throughout the paper, the word additive primarily refers to a powder while admixture primarily refers to liquid (pre-dissolved powder); otherwise, the two terms are used interchangeably. These additives are cheaper and more abundant than lithium admixtures, yet provide more consistency in terms of quality, supply, and performance in comparison with supplementary cementitious materials (SCMs). A methodical approach was developed to identify such additives that primarily mitigate ASR by reducing the pH of Concrete pore solution. The mechanism of pH reduction was identified and the set of criteria that a potential additive must meet were developed. The suitable additives were screened using ASTM C1293 as well as mortar tests to estimate their impact on the performance of Concrete. A final list of seven promising additives was identified.
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an extended chemical index model to predict the fly ash dosage necessary for mitigating alkali silica Reaction in Concrete
Cement and Concrete Research, 2016Co-Authors: Asghar Gholizadeh Vayghan, Jared Wright, Farshad RajabipourAbstract:Abstract Currently, the Concrete prism test per ASTM C1293 or RILEM AAR-3 is considered the most reliable accelerated test to determine the dosage of pozzolans to suppress alkali–silica Reaction (ASR) in Concrete. However, the test takes 2 years, which makes it impractical as a mixture design tool for new Concrete construction. in the present work, a multiple nonlinear regression model is developed for predicting the fly ash dosage necessary to mitigate ASR per CPT. The model uses the oxide compositions of Portland cement and fly ash as well as the reactivity of the aggregates. Seventy-six experimental data points on CPT expansion results for plain Portland cement and fly ash-blended Concrete mixtures were used to develop and evaluate the model. The model successfully predicts the fly ash required to mitigate ASR for different aggregates, cement, and fly ash combinations. The prediction errors in most cases meet ASTM C1293 multi-laboratory precision criterion.
Andreas Leemann - One of the best experts on this subject based on the ideXlab platform.
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application of micro x ray diffraction to investigate the Reaction products formed by the alkali silica Reaction in Concrete structures
Cement and Concrete Research, 2016Co-Authors: Rainer Dahn, Alla Arakcheeva, Ph Schaub, Philip Pattison, G Chapuis, Daniel Grolimund, Erich Wieland, Andreas LeemannAbstract:Alkali-silica Reaction (ASR) is one of the most important deterioration mechanisms in Concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was employed to characterize the mineral phases formed in micro-cracks of Concrete aggregates as a consequence of ASR. This high spatial resolution technique enables to directly gain structural information on ASR products formed in a 40-year old motorway bridge damaged due to ASR. Micro-X-ray-fluorescence was applied on thin sections to locate the Reaction products formed in veins within Concrete aggregates. Micro-XRD pattern were collected at selected points of interest along a vein by rotating the sample. Rietveld refinement determined the structure of the ASR product consisting of a new layered framework similar to mountainite and rhodesite. It is conceivable that understanding the structure of the ASR product may help developing new technical treatments inhibiting ASR. (C) 2015 Elsevier Ltd. All rights reserved.
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application of micro x ray diffraction to investigate the Reaction products formed by the alkali silica Reaction in Concrete structures
Cement and Concrete Research, 2016Co-Authors: Rainer Dahn, Alla Arakcheeva, Ph Schaub, Philip Pattison, G Chapuis, Daniel Grolimund, Erich Wieland, Andreas LeemannAbstract:Alkali-silica Reaction (ASR) is one of the most important deterioration mechanisms in Concrete leading to substantial damages of structures worldwide. Synchrotron-based micro-X-ray diffraction (micro-XRD) was employed to characterize the mineral phases formed in micro-cracks of Concrete aggregates as a consequence of ASR. This high spatial resolution technique enables to directly gain structural information on ASR products formed in a 40-year old motorway bridge damaged due to ASR. Micro-X-ray-fluorescence was applied on thin sections to locate the Reaction products formed in veins within Concrete aggregates. Micro-XRD pattern were collected at selected points of interest along a vein by rotating the sample. Rietveld refinement determined the structure of the ASR product consisting of a new layered framework similar to mountainite and rhodesite. It is conceivable that understanding the structure of the ASR product may help developing new technical treatments inhibiting ASR. (C) 2015 Elsevier Ltd. All rights reserved.
Benoit Fournier - One of the best experts on this subject based on the ideXlab platform.
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the use of lithium to prevent or mitigate alkali silica Reaction in Concrete pavements and structures
2007Co-Authors: Michael D A Thomas, Jason H Ideker, Kevin J Folliard, Benoit Fournier, Y A ResendezAbstract: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 recently been increased interest in using lithium technologies to both control ASR in new Concrete and to retard the Reaction in existing ASR-affected structures. This facts book provides information on lithium, its origin and properties, and on its applications. The mechanism of alkali-silica Reaction is discussed together with methods of testing to identify potentially alkali-silica reactive aggregates. Traditional methods for minimizing the risk of damaging ASR are presented; these include the avoidance of reactive aggregates, controlling the levels of alkali in Concrete and using supplementary cementing materials such as fly ash, slag and silica fume. The final two sections of the facts book discuss the use of lithium, first as an admixture for new Concrete construction and second as a treatment for existing Concrete structures affected by ASR.
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test methods for evaluating preventive measures for controlling expansion due to alkali silica Reaction in Concrete
Cement and Concrete Research, 2006Co-Authors: Michael D A Thomas, Jason H Ideker, Kevin J Folliard, Benoit Fournier, Medhat H ShehataAbstract:Abstract This paper provides a critical evaluation of the various methods available for testing the efficacy of measures for preventing expansion due to alkali–silica Reaction (ASR) in Concrete containing deleteriously reactive aggregate. The ideal test method should be rapid, reliable and capable of determining the influence of aggregate reactivity, alkali availability and exposure conditions. None of the currently available or commonly used methods meet all of these criteria. The shortcomings of the different test methods are discussed and suggestions are made for modifying the Concrete prism test and accelerated mortar bar test to make these tests more acceptable.
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alteration of alkali reactive aggregates autoclaved in different alkali solutions and application to alkali aggregate Reaction in Concrete i alteration of alkali reactive aggregates in alkali solutions
Cement and Concrete Research, 2006Co-Authors: Laibao Mei, Mingshu Tang, Benoit FournierAbstract:Surface alteration of typical aggregates with alkali–silica reactivity and alkali–carbonate reactivity, i.e. Spratt limestone (SL) and Pittsburg dolomitic limestone (PL), were studied by XRD and SEM/EDS after autoclaving in KOH, NaOH and LiOH solutions at 150 °C for 150 h. The results indicate that: (1) NaOH shows the strongest attack on both ASR and ACR aggregates, the weakest attack is with LiOH. For both aggregates autoclaved in different alkali media, the crystalline degree, morphology and distribution of products are quite different. More crystalline products are formed on rock surfaces in KOH than that in NaOH solution, while almost no amorphous product is formed in LiOH solution; (2) in addition to dedolomitization of PL in KOH, NaOH and LiOH solutions, cryptocrystalline quartz in PL involves in Reaction with alkaline solution and forms typical alkali–silica product in NaOH and KOH solutions, but forms lithium silicate (Li2SiO3) in LiOH solution; (3) in addition to massive alkali–silica product formed in SL autoclaved in different alkaline solutions, a small amount of dolomite existing in SL may simultaneously dedolomitize and possibly contribute to expansion; (4) it is promising to use the duplex effect of LiOH on ASR and ACR to distinguish the alkali–silica reactivity and alkali–carbonate reactivity of aggregate when both ASR and ACR might coexist.
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alkali aggregate Reaction in Concrete a review of basic concepts and engineering implications
Canadian Journal of Civil Engineering, 2000Co-Authors: Benoit Fournier, Marcandre BerubeAbstract:This paper presents theoretical and applied state-of-the-art information in the field of alkali-aggregate reactivity (AAR) in Concrete. The aspects discussed include basic concepts of the Reaction and expansion mechanisms, conditions conducive to the development and the sustainability of AAR in Concrete, field and laboratory investigation programs for evaluating the potential alkali-reactivity of Concrete aggregates, selection of preventive measures against AAR, and the management of structures affected by AAR. The management section includes the diagnosis of AAR in existing Concrete structures, evaluation of the potential for future distress due to AAR, and mitigation and repair approaches used on such structures. This is an introductory paper and sets the stage for a special review of the current AAR situation in the various regions of Canada that is presented in seven papers as part of this issue.Key words: alkali-aggregate Reaction, alkali-silica Reaction, alkali-carbonate Reaction, petrography, testi...
