Modifications to Laboratory Test Methods to Evaluate the Beneficial Effects of Low-Alkali Binders on the Alkali-Silica Reaction

Since alkali-silica reaction (ASR) was identified in the 1940â s by Thomas Stanton, thousands of research papers have been published on identification and mitigation of the reaction. Laboratory test methods have been created, modified, and their results compared to the performance of concrete in the field. Current standardized test methods do not allow for testing of low-alkali cements, due to their storage conditions. This has been found to be a severe limitation on assessment of ASR mitigation options. The objective of this research is to adapt current standardized test methods (the concrete prism test and the accelerated mortar bar test) so they can detect the beneficial effects of low-alkali cementing systems, with or without supplementary cementing materials. The alkali leaching and the alkali boosting in the concrete prism test make it unable to evaluate concrete mixtures with low-alkali cement. The effect of cement alkali content and binder combination on the expansion and leaching was investigated, as well as ways to minimize the alkali leaching. Leaching from concrete prisms ranged from 25-50% but covering each prism with a plastic bag reduced the leaching to only about 10%, without reducing the expansion measured. By modifying the alkali boosting procedure, and with the use of improved storage conditions to minimize alkali leaching, it is possible to use the concrete prism test for evaluating the benefits of concrete mixtures made with low-alkali cements. The storage solution for the accelerated mortar bar test provides an abundance of alkali ions to cause ASR, making it unfit to evaluate low-alkali cement mixtures. Therefore, samples were also tested in a storage solution with alkalinity similar to the pore solution of the samples tested. Lowering the concentration of the storage solution to 0.7 times the alkali content of the cement used, greatly improves the correlation between the two test methods.Ph.D