Curing methods are one of the most important factors in determining the quality and compactness of cover concrete. The effect of curing methods on the water absorption and sorptivity coefficient of cover concrete with the substitution ratio of fly ash (FA) and ground granulated blast slag (GGBS) for cement between 30 and 40 wt % was studied by capillary water absorption test. The vacuum saturation test and mercury intrusion test were employed to characterize these differences in the pore structure of cover concrete under different curing methods. With further analysis of the compactness of microstructure by SEM, the mechanism of the impact of curing methods on the permeability of cover concrete was revealed. The results obtained indicate that the effect of curing methods on the water absorption, sorptivity coefficient and porosity of cover concrete shows the trend of natural curing > cover curing > water curing > standard curing. It is also shown that reasonable curing is advantageous to reduce the porosity and permeability of cover concrete. In natural curing conditions, the appearance of porosity increasing and pore structure coarsening is more critical for cover concrete with mineral admixtures than for pure cement concrete. Therefore, the permeability of cover concrete with mineral admixtures is more sensitive to the early-age curing methods.

It is an outstanding solution for protecting the environment using manufactured sand instead of natural river sand in concrete. In this paper, tunnel granite muck was processed into low carbon, coarse and fine aggregates, and low carbon aggregates were used to prepare bridge concrete. Meanwhile, the mechanical properties, anti-permeability, and frost resistance of concrete were investigated. The results demonstrated that the concrete prepared using low carbon aggregate had higher mechanical properties than concrete prepared using river sand. The chloride ion penetration resistance of concrete using low carbon aggregate is better than that of concrete using river sand, and frost resistance has been improved.