The effect of the blaine fineness on the mechanical properties of the alkali-activated slag cement

Abstract

If slag is activated by an alkaline solution, it can be used as a binder. This product is known as the alkali-activated slag cement (AASC). In order to reduce the cost of production and operation, it is more appropriate to have a composite binder that can be made only by adding water. This issue, however, has not been considered in the previous studies adequately. For this reason, in the present study, sodium hydroxide and sodium metasilicate were blended in the solid form with the slag and only water was added to the mixture to make the “just add water” AASC paste. In the “two-part” AASC, the slag was mixed with sodium silicate and sodium hydroxide solution. The effect of the Blaine fineness (Bf) of the slag is one of the most important parameters investigated in the present study. So two different types of Bf including 2900 cm2/g and 4200 cm2/g were considered. The purpose of the present study was, therefore, to investigate the effect of the Bf of the slag on such mechanical properties as setting time, compressive strength, flexural strength and autoclave expansion of the “just add water” and “two-part” alkali-activated slag cement. Based on the results, a suitable combination for the production of the “just add water” AASC with the Bf of 4200 cm2/g was obtained with higher mechanical properties, in comparison to those of the ordinary Portland cement (OPC). In the following, SEM images were used to compare the microstructure of these two combinations.