A study of alkali-silica reaction on greenstone aggregate.

This research reports on a study to evaluate the effects of greenstone aggregate on alkali-silica reaction (ASR). Greenstone aggregate is developed by University Malaysia Sabah, Malaysia (UMS). It is produced using solid waste materials like Palm Oil Fuel Ash (POFA), waste glass, recycled aggregate and natural fibre. The main purpose of this study is to develop the optimum mix design to reduce the ASR potential of the greenstone aggregate. The reactivity of the greenstone aggregate was determined using Acceleration Mortar Bar Test (AMBT) and Autoclave Test. From the results of these two tests, the greenstone is evaluated as a moderate reactive aggregate with the potential to cause a harmful crack in the concrete. Moreover, the effectiveness of Supplementary Cementing Materials (SCM) – Clay Brick Powder (CBP) was also tested. The expansion of mortars containing 0, 5, 10, 15, 20 and 25% CBP as a partial replacement for Ordinary Portland Cement was studied with autoclaving expansion test and AMBT. Results showed that the amount of CBP required to control the expansion to <0.1%, which is the harmless zone according to the ASTM C1260 standard limit, is between 15% and 25%. It proved that by the addition of the CBP, the ASR effect of greenstone would be minimized; the amount of CBP added is inversely proportional to the expansion of greenstone mortars. In addition to expansion testing, the compressive strength (ASTM C109) of the greenstone 50 mm mortar cube was determined. Results showed that a greenstone mortar cube containing 15% of CBP is the optimum mix design to reduce greenstone's reactivity and maintain its compressive strength. [ABSTRACT FROM AUTHOR]