Multi-effect of fineness and replacement ratio of binders on thixotropic and some fresh state properties of cementitious systems, a comparative study

Abstract

Effects of cement fineness, fly ash replacement ratio and fineness changes on some fresh state and rheological properties of mixtures were investigated in this study. Two different Blaine finenesses of portland cement (4000, 5000 cm2/g) and 4 different finenesses of fly ash (4000, 5000, 6000 and 7000 cm2/g) were used. 26 different paste mixtures were prepared by substituting fly ash in 3 different ratios (10%, 20%, and 30%) by weight. Marsh-funnel flow time, mini-slump, setting time, dynamic yield stress (DYS), viscosity and thixotropic behavior of mixtures were investigated. 4 different thixotropy measurement methods were used; dynamic yield stress ratio (DYSR), viscosity ratio (VR), shear stress-structural build-up area (SBUshr) and viscosity-structural build-up area (SBUvis). There was no notable change in the initial setting time results of the mixtures with the increase in portland cement fineness. The rheological parameters and thixotropic behavior of the mixtures increased significantly. Vicat-water requirement and setting-time-value decreased with the increase of fly ash fineness in cementitious mixtures with low fineness. The structural build-up of the mixtures decrease with the rise of the F class FA replacement ratio. It was determined that the methods with the highest correlation among thixotropy measurement methods were SBUshr-SBUvis, DYSR-SBUshr and DYSR-Athix, respectively.