Effectiveness of Ternary Blends in Mitigating ASR Demonstrated on the Modified Mortar-Bar Test

Book excerpt: Supplementary cementitious materials (SCMs) are the effective means of improving concrete durability. Combining two SCMs with ordinary Portland cement helps overcome the probable drawbacks of using single SCM. Ternary cementitious systems have become popular in the construction industry, particularly for use in high-performance concrete. In this study, the effectiveness of ternary blends in controlling alkali-silica-reaction (ASR) deterioration was tested in the comparison of a modified mortar-bar method and ASTM C1260-14/C1567-13. Our experiment included the evaluation of 22 binary or ternary combinations of five cementitious materials (Portland cement, metakaolin, low-calcium fly ash, high-calcium fly ash, and slag) tested with two different reactive aggregates. In addition to standard ASTM C1260-14/C1567-13, the mortar mixes were assessed on a modified mortar-bar method of short bars (25 x 25 x 150 mm3) stored at 60°C and >95 % relative humidity. Ternary cementitious blends containing metakaolin and low-lime fly ash proved to be very effective at controlling ASR. In the proposed modified test, a pass/fail criterion of 0.03 % expansion over 60 days was found to be in agreement with the expansion at 14 days of ASTM C1260-14/C1567-13 at 0.10 %.