The best preventive measure against Alkali-Silica Reaction (ASR) in concrete is:
Choose the correct answer
Using high w/c ratio concrete
Using low-alkali cement (Na2O equivalent < 0.6%) and/or replacing cement with fly ash, slag or silica fume that dilutes alkalis
Using high alkali cement
Increasing water content
Correct Answer
B. Using low-alkali cement (Na2O equivalent < 0.6%) and/or replacing cement with fly ash, slag or silica fume that dilutes alkalis
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ASR: alkalis (Na2O, K2O) from cement + reactive silica in aggregate + moisture -> expansive gel -> cracking (map cracking). Prevention: (1) low-alkali cement < 0.6% Na2O eq; (2) SCMs (fly ash, slag reduce alkali availability and consume silica); (3) limit reactive aggregate; (4) lithium compounds (LiNO3). IS 2386 Part 7 for aggregate reactivity test.
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