: 99-107
Lviv Polytechnic National University, Department of building рroduction

There were analyzed the ways of reduction of СО2 emissions in the cement industry. It was shown that a significant reduction of СО2 emissions in construction is achieved through the using of composite cements with a lower clinker factor that meets the requirements of the low carbon strategy for the cement industry. In this case, the replacement of part of Portland cement clinker with mineral additives in such cements leads decreasing of their strength, especially at early age. The influence of nano-SiO2 additives, alkaline activator (Na2SO4) and polycarboxylate type superplasticizer (PCE) on the structure formation and on the strength of Portland composite cement CEM II/B-M (S-P-L) 32.5R with additives of granular blast furnace slag, natural zeolite and limestone in early age. It was shown that the synergetic combination of mineral additives with a reduction of the clinker factor up to 65 % and the using of the complex of nano-SiO2-Na2SO4-PCE in Рortland composite cements due to the “accelerating effect”, provides a significant increase in strength at an early age (after 10 and 24 h). The methods of X-ray diffraction analysis and electron microscopy revealed that the introduction of high-surface reactivity particles of nano-SiO2 provides the intensive bіnding of
calcium hydroxide to form a denser CSH-gel at an early age of hardening of composite cement and compaction of its microstructure with fine crystals of ettringitе. Creating eco-efficient Portland composite cements with high early strength would provide the technical, ecological and economic effects in building constructions.

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