Abstract
<p>Many preventive measures showed improved performance of concrete against alkali-silica reaction (ASR) based on the concrete prism test (CPT) described in the Canadian and American Standards, CSA A23.2-14A and ASTM C1293. However, research has shown that preventive measures that limited the 2-year expansion in the concrete prism test produced late expansion after 7-15 years when tested in the field. The objective of this research is to understand the possible reasons for this late expansion under field conditions and to come up with modified approach to determine the level of supplementary cementing materials (SCM) needed to mitigate the long-term expansion. The research mainly focuses on studying two possible reasons to explain the late expansion. The first reason is the rate and ultimate hydration of SCM, where their capacity to bind alkalis under CPT could be higher than those under field conditions. The other reason for the late expansion could be the geometry and size of the CPT samples which might reduce the expansion due to the excessive alkali leaching. Larger samples showed less leaching compared to standard prisms. 100-mm cylinders showed higher expansion than 75-mm standard prisms; however, both sample shapes showed similar expansions for one tested aggregate when used with SCM. In addition, the capacity of SCM to bind alkalis was shown to be higher at 38ºC compared to the other two tested temperatures investigated in this study: 23ºC and 60ºC. Samples with SCM at high replacement levels expanded more at 60ºC compared to 38ºC. Due to their reduced leaching compared to prisms, testing cylinders at 60ºC showed accelerated results reducing the testing duration to one year compared to the standard test duration of two years. Moreover, a new way to predict the minimum levels of SCM required to mitigate expansion due to alkali-silica reaction is presented showing better correlation with the field. Finally, a fast and reliable test method is suggested to evaluate the reactivity of mineral fillers by adapting and adopting the current test methods available for ASR testing.</p>
Highlights
Since 1940, alkali-silica reaction (ASR) in concrete is being studied in order to find preventive measures to mitigate it
The results are based on the concrete prism test (CPT) described in the Canadian and American Standards, CSA A23.2-14A (2014) and ASTM C1293 (2018)
Effect of Sample Geometry and Aggregate Type on ASR The aim of this section is to study the effect of sample geometry and aggregate reactivity on alkali leaching and expansion due to ASR
Summary
Since 1940, alkali-silica reaction (ASR) in concrete is being studied in order to find preventive measures to mitigate it. Researchers found that the field expansion at later ages were much higher than the expansion found in the CPT at two years (Fournier et al, 2008; Ideker et al, 2012) Reasons behind this discrepancy in expansion between the field and the laboratory samples could be excessive alkali leaching from the samples and a possible higher binding capacity of the supplementary cementing materials under laboratory conditions; both factors will be investigated in this study. Another challenge that is facing the concrete prism test is the long testing duration which takes 2 years to evaluate the efficiency of the SCM in preventing expansion due to ASR. There is no unique test that was adopted to reduce the testing duration yet
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