Papers by Author: Hui Xu

Abstract: This paper studies on the relative denseness of fresh cement pastes compounded with multi-cementitious materials and the performances of their harden concretes. Results show that with the dense packing of several ultra-fine particles, higher the relative denseness of different cementitious material system, higher the compressive strength and lower the air permeability of the harden concrete. The multi-cementitious material compounded by 37% cement、20% fly ash、40% pulverized slag and 3% silica fume has the higher relative denseness of fresh cement paste, and its compressive strength and air permeation of harden concrete composite is also improved.

Abstract: Performing the superposition effect of multi-elements mineral admixtures, high performance concrete (HPC) with 3% of silicon fume, 20% of fly ash and 40% of ground granulated blast-furnace slag (GGBS) was prepared, and its physical and mechanical properties and durability were studied systematically. The compressive strength and tensile strength of HPC are better than those of ordinary concrete. HPC has high compactness with smaller gas diffusion coefficient and relative permeability coefficient. Adding volume stabilizer and controlling the contents of SO3 in the GGBS and volume stabilizer at 3%, can reduce dry shrinkages effectively. Large mount of mineral admixture was used to make the concentrations of K+ and Na+ in the pore solution and the expansion caused by alkali-silica reaction depress greatly. So the alkali-silica reaction gets controlled markedly. The effective diffusion coefficient of chloride ion is 1.96×10-12 m2/s, which means HPC has a favorable chloride ion penetration resistance. After 15 times of wet-dry cycle, the rates of the rust area and quality loss of the reinforcing steel bars in HPC are only 4.1% and 0.05% respectively, so HPC has better performance of steel protection. The mortar bar did not expand in corrosive sodium sulfate solution, and it means HPC has better performance of sulfate resistance. The performances of frost resistance and carbonation resistance of HPC are also favorable. It’s proved in tests that the superposition effect of multi-elements mineral admixtures can enhance the physical and mechanical properties and durability of concrete greatly.