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Xinjiang has a temperature difference of 20°C between day and night, interannual temperature difference of 50°C, the control of the temperature cracks in mass concrete becomes difficult. Although low-heat portland (P·LH) cement concrete containing fly ash (FA) can reduce hydration heat, the mismatch between its mechanical and thermal properties is still not fully resolved. An attempt to explore the effect of FA on the competitive hydration reaction of C3A and C3S at super-early ages, and how this effect changes the physical and chemical properties of hardened cement pastes by electrical resistivity and zeta potential and common microstructure test methods, and to provide a theoretical basis for optimization of mechanical and thermal properties of P·LH cement concrete with FA. Results showed that in the fast dissolution stage, a numerous {Ca6[Al(OH)6]224H2O}6+ ions and a very small amount of H3SiO4−/H2SiO42− ions were formed, and incorporating 20%, 30%, 40% FA primarily inhibited the Al(OH)63− hydration and the {Ca6[Al(OH)6]224H2O}6+ generation, resulting in the generation time of AFt in comparison with pure cement, respectively, delayed by 44%, 140%, and 524%. This phenomenon decreased the nucleation and crystallization growth rate of AFt and Ca(OH)2 in the induction stage, and reduced the consumption of gypsum in the acceleration stage. Hence, monosulfoaluminate did not exist for pastes with more than 30% FA, and the number of particles involved in the reaction for the P·LH cement stone with 20%, 30%, and 40% FA decreased by 4.0%, 46.5%, and 52.0% in the deceleration stage compared with the pure cement. The research results can provide a theoretical reference for modifying chemical properties of FA to meet the matching of mechanical strength and thermal of P·LH cement. [ABSTRACT FROM AUTHOR]

A salinized soil curing agent was prepared from calcium carbide slag, fly ash and alkali activator, and the effects of different factors on compaction performance and compressive strength of solidified saline soil were analyzed by orthogonal test, finally, the curing mechanism and hydration products of solidified saline soil in calcium carbide slag-volcanic ash cementitious system was explored. The results showed that the influence of various factors on the compressive strength of solidified saline soil was ranked as the alkali initiator, the content of cementitious materials and the ratio of calcium carbide slag to fly ash: the compressive strength and water stability of curing saline soil for 7 d meet the demand of curing saline soil strength in practical engineering: Under the dual excitation of calcium carbide slag and alkali activator, the pozzolanic reaction of fly ash occurs: the main products of pozzolanic reaction are hydrated calcium silicate gel, ettringite and dihydrate gypsum. When the curing age was 360d, Ca (OH)2 was not found obviously in the specimen, it indicated that the pozzolanic reaction was basically completed when cured soil specimen was cured for 360 d. [ABSTRACT FROM AUTHOR]