Influence of cement composition on expansions observed in standard and modified ASTM C1260 test procedures

This paper presents the results of a laboratory study conducted to determine the influence of cement composition on the expansions observed in standard and modified ASTM C1260 tests. Also, the effectiveness of selected mitigation measures for alkali-silica reactivity was studied by using a modified ASTM C1260 test. Two different cements with substantially different alkali levels were used in combination with a Class F fly ash and a Class C fly ash. The results obtained from tests with 89 different sources of fine aggregate were analyzed. The results from this study indicate that cement composition has a distinct influence on the expansion levels observed in the ASTM C1260 study. For a majority of the aggregates tested in this study (88%), the use of a specific cement low in alkali content resulted in higher expansion than a cement with a relatively higher alkali content, regardless of the level of reactivity of the aggregate in the standard ASTM C1260 tests. Class F fly ash was found to be more effective than Class C fly ash in reducing the expansions in the modified ASTM C1260 tests. However, the cement used in the mixture influenced the percent reduction in expansion offered by both Class F fly ash and Class C fly ash. The use of low-alkali cement with Class F and Class C fly ashes yielded larger reductions in percent expansion.