Abstract. Durability of hardened cement paste depends on chemical and mineralogical composition of Portland cement. The main factor for hardened cement paste is higher content of calcium aluminate and free calcium hydroxide, binding of which into water-insoluble compounds causes increase in resistance to water, frost and corrosion. The purpose of this research is to develop modifying admixtures to cement compositions based on local raw material -rock sand. Chemical and mineralogical properties of the source materials were studied using X-ray spectroscopy and X-ray diffraction analysis. Standard methods were used for defining physico-mechanical properties of sand and binder. Influence of the degree of mechanochemical activation of modifying admixture on the properties of binder and hardened cement paste made on its basis was studied. Research methods of scanning electron microscopy and spectral measurements were applied. The possibility of using admixture based on rock sand as a modifier was determined, its usage providing increase of strength, sulphate and frost resistance, which causes higher durability of cement concrete.
The paper substantiates the effectiveness and prospects of research in the direction of developing an active mineral additive based on mountain sand of Yakutia for general construction cements in order to increase its sulfate resistance. This will expand the range of application of Portland cements operating in conditions of sulfate aggression. The Republic of Sakha (Yakutia) has many deposits of natural sands of aluminosilicate composition or the so-called "mountain sands". One of the large and developed quarries of mountain sands in Yakutia is the Kildyamskoye deposit. Today it is used for foundations and underlying road surfaces. The paper shows the possibility of obtaining an active mineral additive based on this sand. The influence of the dosage and dispersion level of the additive on the strength characteristics of cements and on the coefficient of sulfate resistance is studied in the range of 5±2 % while maintaining brand strength. The introduction of an additive of more than 15 % reduces the strength of cement by an average of 20%, the grade strength is no longer observed, while hydration processes slow down and over time in a sulfate environment, the strength of the samples first increases and then falls again. As a result of the work, an active mineral additive based on the sand of the Kildyamskoe deposit in cement is proposed. This gives a stable sulfate resistance coefficient equal to 0.95 while maintaining brand strength and hydration processes.
Abstract. Durability of hardened cement paste depends on chemical and mineralogical composition of Portland cement. The main factor for hardened cement paste is higher content of calcium aluminate and free calcium hydroxide, binding of which into water-insoluble compounds causes increase in resistance to water, frost and corrosion. The purpose of this research is to develop modifying admixtures to cement compositions based on local raw material -rock sand. Chemical and mineralogical properties of the source materials were studied using X-ray spectroscopy and X-ray diffraction analysis. Standard methods were used for defining physico-mechanical properties of sand and binder. Influence of the degree of mechanochemical activation of modifying admixture on the properties of binder and hardened cement paste made on its basis was studied. Research methods of scanning electron microscopy and spectral measurements were applied. The possibility of using admixture based on rock sand as a modifier was determined, its usage providing increase of strength, sulphate and frost resistance, which causes higher durability of cement concrete.
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