Effects of Fly Ash and Superplasticizers on the Rheology of Cement Slurries

Abstract

AbstractCementitious slurries composed of an oil well cement, a high calcium fly ash, a low calcium fly ash, and three commercially available superplasticizers (two different sulfonated naphthalene formaldehyde condensates and a sulfonated melamine formaldehyde condensate)were mixed to contrast the two fly ashes and to determine the effectiveness of each of the superplasticizing agents. Most commercial superplasticizers and cements are relatively expansive; therefore a partial substitution by fly ash and other by-products represents a substantial savings in both quantity of chemical admixture required and energy consumption for the manufacture of cement. In the cement/fly ash mixtures of 100/0, 90/10, 60/40, 40/60, and 10/90, with both high calcium fly ash and low calcium fly ash, the mixture containing the low calcium fly ash was consistently less workable. The rheological properties of the high vs. low calcium fly ash mixtures were controlled by the differences in fly ash particle size and the presence of irregular large particles, rather than by the differences in chemistry between the two. The low calcium fly ash was the coarser material.