Use of finely ground basalt as a mineral admixture in blended Portland cement production

Abstract

Basalt powder is an active mineral admixture used commonly in the production of mixed Portland cement in Vietnam. Addition of basalt powder may improve many important properties of cement and cement concrete: increasing compressive and flexural strength at late age, increasing sulphate sulfate resistance, increasing freeze-thaw resistance, reducing water absorption, and reducing heat of hydration. However, the use of basalt powder with the same fineness as cement currently has the disadvantage of reducing the compressive strength of cement from the initial stage up to 90 days or 180 days. The magnitude of the decrease was greater at earlier ages than at later ages. This disadvantage of basalt power limits its amount that can be added in blended Portland cement production. In theory, increasing the fineness can increase the activity of basalt powder. Therefore, the objective of this study was to evaluate the possibility of using finely ground basalt powder as a mineral admixture in the production of blended Portland cement, by determining the influence of basalt powder of different fineness (Blaine 3600 cm²/g, 4800 cm²/g and 6000 cm²/g) on some properties of Portland cement. The investigated properties of cement included water of consistency, setting time, compressive strength at 1, 3, 7, and 28 days, and soundness. The results show that, increasing the fineness of basalt increased slightly the water demand and setting time of cement. Increasing the fineness of basalt powder increased significantly the strength of cement at early ages and increased less significantly at late ages. Therefore, the use of finely ground basalt can minimize the disadvantage of basalt powder, then allow to increase its content that can be added in the production of blended Portland cement.