Effect of Some Novel Polymers on the Physico-Chemical Properties of Blended Cement Pastes

Abstract

In this study, the mechanical, physico-chemical, fire resistance and rheological properties of blended cement pastes were improved using three different admixtures namely; phenol formaldehyde sulfonilate (SI), and low phenol content phenol formaldehyde sulfonilate (SII) and sikament-TG (TG). The mechanical properties for all cement pastes containing different doses of these admixtures at various curing time were investigated by using compressive strength test. The hydration kinetics was studied by determining chemically combined water, degree of hydration and gel/space ratio. The fire resistance tests were studied by measuring the weight loss percentages and compressive strength values for some selected pastes (optimum dose) at each firing temperature. The phase composition and microstructure of the formed hydrates were examined using scanning electron microscopy (SEM), X-ray diffraction (XRD) and different thermal analysis techniques. The rheological properties were performed by using Mini-slump and Rheometer test. The results showed that, the decreasing in the water of consistency caused by adding these admixtures, leads to the decreasing in the total porosity, which enhancing the mechanical properties. The doses of 0.25% TG, 0.50% SI and 1.00% SII were the optimum doses. Moreover, in case of air cooling, the compressive strength of the hardened pastes admixed with the optimum doses increased by firing the specimens up to 500oC, then decreased by firing the specimens at temperatures up to 700oC, but still higher than the compressive strength at room temperature. The compressive strength in case of water cooling is lower than air cooling due to formation of microcracks. The repulsion and steric hindrance effect of these admixtures improve the rheological behavior of the cement slurries. Keywords: Blended cement pastes, Mechanical, Physico-chemical, Rheology, Chemical admixtures, Compressive strength, Combined water, Degree of hydration, Gel/space ratio, Fire resistance, Thermal Analysis, X-ray diffraction (XRD), Scanning electron microscopy (SEM), Mini-slump test and Rheometer test.