This paper presents the effects of mineral admixtures and the water to binder ratio (W/B) on the tensile and compressive strength and micro pore structure of hardened cement pastes. The test results show that: with the water to binder ratio increasing, the tensile and compressive strength of cement paste with different mineral admixtures will decrease, air content and mean pore diameter will decrease and the cement paste with the ground blast furnace slag is the lowest. The artificial neural network based on its nonlinear mapping function can fit the relationship between strength and pore structure more accurate than an empirical formula.
Self-compacting Concrete (SCC) has many good properties such as high fluidity, good cohesiveness and resistance to segregation. Therefore, SCC should have higher durability compared to ordinary vibrated concrete in theory. At the same time, the cementitious materials and additives used in SCC are much more than that of used in ordinary concrete, which will cause SCC to generate shrinkage cracks easily and deteriorate its durability. So the durability of SCC should be studied further. In this paper, C30~C60 SCC were prepared, and then the permeability and reinforcing bar corrosion of reinforced self-compacting concrete were conducted. The results show that the permeability of SCC is lower which make sure the embedded reinforcing bars have high resistance to the corrosion.
In order to study the shrinkage characteristics of cement paste, environmental scanning electron microscope was used to observe the microstructure shrinkage of cement paste and cement mortar under different humidity. The results showed that : with the relative humidity decreased from 80% to 10%, the shrinkage cracking of paste microstructure appeared in different degree and increased continuously,also the regression analysis showed the relative humidity and shrinkage was conical relationship.
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