"GREEN" CEMENT COMPOSITES WITH HYBRID ADDITIVES OF MICROSILICA AND ASH SLAG MIXTURE FROM THERMAL POWER PLANT

Abstract

The paper presents the results of studies on determination of composition of ultra dispersed microsilica (MS) and its derivatives in composition with active ash and slag mixture (ASM) of dry ash removal Thermal Power Plant. Their chemical and mineralogical compositions and suitability for use as an additive in cement were determined by their hydraulic activity according to the Student’s t-criterion value and CaO absorption from saturated lime solution. It has been established that according to the t-criterion value, ASM meets the requirements of the Interstate standard (ISS) 31108 - 2020 for active mineral additives for cement (t - criterion - no less than 15), but MS does not correspond. Taking these data into account, the compositions of hybrid additives (HA) were formed, including active (ASM) and passive components (ASM), providing maximum replacement of the expensive clinker part in cement with the optimal ratios of the ingredients of hybrid additives and its optimal dosage found in the composition of composite Portland cements (CPC).The rate of chemical interaction of the ratio of mineral ingredients was found to be in the composition of hybrid additives: CPC exhibits high chemical activity upon contact with water with a content of 15 % ASM + 10 % MS (HA), introduced into cement in an amount of up to 35 %. The achievement of hydraulic activity of cement composites is scientifically substantiated to be higher than that of additive-free cement, providing their belonging to the class 32.5 and 42.5 in strength due to the formation of a dense microstructure. Control tests of “green” CPC in the laboratories of two large cement plants of Uzbekistan confirmed the results of research on the  possibility of replacing up to 35 % of expensive clinker with available and cheap hybrid additives from local techno genic waste to obtain high durability composite Portland cement.