Fly ash belite cement is a kind of low-carbon cement prepared by a two-step process involving hydrothermal synthesis and low-temperature calcination. Pozzolanic reaction pastes, as the precursors of fly ash belite cement prepared by hydrothermal synthesis, are affected mainly by reaction temperature, time, ratios of the mass of fly ash/lime (FA/CA), and the dosage of Na2O. The absorbance rate of CaO with reaction time was tested for all samples, and the reaction kinetic model and parameters of the granule-hydrothermal synthesis method were discussed. A kinetic model for the hydrothermal synthesis in the presence of Na2O was proposed based on the Kondo’s modified Jander equation and Arrhenius equation. The activation energy (Ea) of the process was determined to be 67.76 kJ/mol. In addition, with an increasing dosage of Na2O, the pre-exponential factor A of the Arrhenius equation increased. However, the hydrothermal reaction degree was accurately predicted using the kinetic model characterized by the absorption rate of CaO. The results indicated that Na2O, as an alkali activator, facilitated the diffusion of Ca2+ firstly, then partly dissolved the amorphous phase in the mixtures and, finally, accelerated the formation of poorly crystallized hydrates.

Curing techniques and curing conditions have crucial effects to the strength and durability of concrete. The objective of this experimental study is to examine the strength and resistance to chloride ion permeability of high performance concrete under various curing methods in different simulated arid and large diurnal temperature variation climates. Laboratory experiments were conducted to investigate the strength and electric flux when different curing methods were used. Three curing methods and three simulated climates were applied to concrete specimens. The results show that the difference of measured experiment data are not significant under standard curing (SC), moisture insulation curing (MIC) and thermal and moisture insulation curing (TMIC) in an arid climate. However, the compressive strength and resistance to chloride ion permeability are worse under MIC and TMIC compared with SC in an arid and large diurnal temperature variation due to frost heaving and thermal stress. Moreover, compressive strength and resistance to chloride ion permeability decrease significantly when the large diurnal temperature variation increases and the lowest temperature reduces. The insulation material can effectively reduce concrete temperature variation between near surface and core region. Therefore, TMIC is a better curing method than MIC in an arid and large diurnal temperature variation climate.