Title : REVISED TESTS FOR POTENTIAL REACTIVITY OF SLOWLY REACTIVE AGGREGATE IN INDIA
Authors : Dr. A K Mullick
Publication : 8 - 10, October 2015
Volume : 2
Pages :
Price : 250
Abstract : This paper describes the revised test methods for assessing ASR potential of ‘slowly reactive’ concrete aggregate. Instances of distress during service due to ASR in hydraulic structures in India (and Pakistan) have been reported earlier, even when metastable silica minerals were not present in the siliceous aggregate. Prior evaluation of the aggregate with conventional tests like ASTM C229 or ASTM C285 failed to detect reactivity. Appropriate test methods were, therefore, needed. Revised test methods adopted higher temperature (60 OC or 80 OC, in place of 38 OC) for mortar bar expansion tests. Threshold values of mortar bar expansion at 60 OC were worked out by tests with cements of low and high alkali contents, in the manner described in the paper. Tests for undulose extinction angle were added in IS Specification. The research led to revisions in IS: 2386, part VII (tests for reactivity) and Part VIII (petrographic examination).