Volume 5, Issue 8 (September 2008)
Use of the Accelerated Mortar Bar Test to Evaluate the Effectiveness of LiNO3 Against Alkali-Silica Reaction—Part 1: Pore Solution Chemistry and Influence of Various Parameters
For the time being, the only reliable test method to evaluate the effectiveness of lithium nitrate against alkali-silica reaction (ASR) in concrete is the concrete prism test (CPT) CSA A23.2-14A or ASTM C1293, extended to two years. In its actual form, the more commonly used accelerated mortar bar test (AMBT) CSA A23.2-25A or ASTM C1260 is not able to predict this effectiveness and needs to be modified to improve it’s reliability. Part I of this study, which involves a large variety of reactive aggregates from Canada and the United States, aims to evaluate the partition of various ions (OH−, Na+, K+, Li+, and silica species) between the mortar pore solution and the soak solution in the AMBT, and the effect of a number of experimental parameters on the expansion of mortar bars with/without lithium nitrate, e.g., the presence of lithium in the original mortar bars, the Li concentration in the soak solution, the concentration and the composition (NaOH versus KOH) of the soak solution, the cement alkali content, the water-to-cement ratio, and the initial 24-h soaking in pure water. The second part of this study (Part II) compares the above AMBT results with the CPT results for the same aggregates and aims to propose modifications to the AMBT when testing lithium nitrate against ASR to better correlate with the most realistic CPT results.