Influence of different fractions of high-calcium fly ash on the density and strength of well Portland cement

Abstract

High calcium fly ash (HCFA) from thermal power plants is a good replacement for Portland cement, but its properties vary greatly depending on particle size and composition. The industrial HCFA fractions (Fr1-Fr4) taken from four fields of electrostatic precipitators (EP) of the ash collection unit of the Krasnoyarsk thermal power plant (TPP-2) were studied as a component of well Portland cement. The aim of work is to study the effect of different HCFA fractions on the density of the cement slurry, the density and strength of the cement paste. The study of the bulk density of the initial fractions, the pycnometric density of cement slurries and the average density of cement stone at different curing age was carried out. Trends in bulk density are shown depending on the sampling point. The pycnometric density of cement slurries containing HCFA is close to commercial well cements of normal density. The average density of cured specimens continuously increases with increasing curing time from 2 to 150 days. A significant decrease in density is observed in order Fr4 >Fr3 >Fr2 >Fr1, which is accompanied by an increase in the volume of the specimens in the reverse order, which means the presence of a different degree of expanding effect. A general dependence of compressive strength on average density is observed for all specimens, which becomes stronger with increasing curing age from 2 to 90 days. An individual linear dependence of strength on density during hardening from 2 to 90 days is observed for specimens of each of the fractions, with an increase in the angular coefficient in the linear regression equation in order from Fr1 to Fr4. The effect of particle size and phase composition components on the characteristics of specimens was analyzed.