Study of low-emission multi-component cements with a high content of supplementary cementitious materials

Abstract

The studies have established the influence of various types of supplementary cementitious materials on physical and mechanical properties and structure formation of low-emission multi-component cements. The results of the granulometric composition examination of main components of multi-component cements were obtained and a comprehensive estimation of their particle size distribution relative to volume and specific surface was performed. It was proved that increase in dispersity of supplementary cementitious materials leads to decrease in their bleeding and increase in activity but simultaneously increases water demand and power consumption for mechanical activation. Efficiency of mechanical activation of main non-clinker components having different characters of activity was compared. Experimental studies have confirmed that the problem of increasing hydraulic activity of granulated blast-furnace slag is solved by increasing content of fractions up to 10 μm in size. However, when preparing highly active granulated blast-furnace slag, energy inputs for grinding significantly grow, especially in ball mills. It should be noted that a shortage of quality slag in the cement industry is expected in the coming years. This necessitates the search for new combinations of supplementary cementitious materials, namely natural zeolites and fly ash which possess excellent pozzolanic properties. Studies of partial and complete replacement of granulated blast-furnace slags in the composition of low-emission cements with clinker factor of 0.50 have shown that necessary indices of early and standard strength are ensured due to optimization of granulometric composition of pozzolanic additives. At the same time, binder strength increases significantly with the age of hardening and exceeds standard strength by 30 % in 90 days. This makes it possible to state that due to the pozzolanic reaction between superfine zeolite, fly ash and calcium hydroxide, the processes of formation of hydrate phases in the intergranular space are stimulated and microstructure of the cement matrix is compacted. It was shown that the use of low-emission multi-component cements modified with superplasticizers of polycarboxylate type provides technological, technical, economic and environmental effects. Thus, there are grounds to state feasibility of obtaining clinker-efficient low-emission multi-component cements by optimizing granulometric composition of supplementary cementitious materials of various kinds in order to reduce power inputs in the technological processes of their production.