JOB MIX PARAMETERS’ EFFECTS ON ALKALI SILICA REACTIVITY RELATED EXPANSION IN CONCRETE

Abstract

Numerous test methods to assess aggregate reactivity (for ASR) have been proposed and standardized in the last couple of decades. However, all of the standard test methods can only find ASR potential of aggregates within the scope of the test (with standard test mix proportion) but none of these methods incorporate actual job mix propotions (with job mix w/c, total cement amount and total alkalinity, SCM replacement % etc.) and therefore can not predict correctly the actual concrete expansion potential due to ASR. This article focuses on the job mixture parameters’ effects on ASR expansion. Miniature Concrete Prism Test (MCPT)-a rapid ASR test method was employed to evluate the job mix parameters’ effects. The factors considered areinfluence of i) w/c ratio ii) Cement Alkalinity iii) Total Cement Content iii) Total Alkali Loading. The ASR expansions of concrete specimens (as % expansion) in different variable conditions were measured. Based on the results, it is found that the w/c ratio of concrete has minimal influence on the observed expansions of specimens due to ASR (within the scope of the research), but cement alkalinity and cement content (in terms of alkali loading) has significant effect(within the scope of the research) and there is a very good correlation (near linear) between the total alkali loading and the expansion due to ASR.