Abstract:

In this study, the effect of different permeability-reducing admixtures on the flowability performance of cement paste mixtures containing different ratios of mineral admixtures was investigated. For this purpose, the cement paste and mortar mixtures having plain, binary and ternary binder systems were prepared by partial replacement of cement with fly ash and metakaolin. Besides, the compressive strength of the mortar mixture was measured at different ages. In order to investigate the effect of utilization of permeability-reducing admixture on properties of the cementitious systems, 3 commercial permeability-reducing admixtures which produced by 2 different companies were used as 2 wt.% of cement. Three series of mineral admixture-containing mixture was prepared. In the first and second series, 10% and 20% of the cement were replaced with fly ash and metakaolin, respectively. In the third series, mixtures having ternary binder systems were produced by replacing of 10% and 20% of cement with fly ash and metakaolin, respectively. Consequently, 23 different cement paste and mortar mixtures were prepared in the scope of the study. According to the test results, it was unexpected, in spite of increase of the total amount of fine materials by utilization of metakaolin instead of cement in the mixture, the flowability of mixtures was positively affected, in the case of presence of sufficient amount of water-reducing admixture in the system. This mentioned positively effect may be attributed to the fact that the water-reducing admixture is more easily adsorbed on the finer grains.

Keywords: