Papers by Author: Juan Hong Liu

Abstract: Based on the rapid determination of chloride diffusion coefficient with NEL method and pore structure analysis, the influence of HCSA expansive agent on chloride diffusion coefficient of concrete has been investigated. Besides, the effects of chloride diffusion coefficient of Water-Cement ratio on HCSA expansive concrete have been also analyzed. The results show that on the condition of 55% mixing amount of fly ash, the chloride diffusion coefficient of concrete of no HCSA is 1.96×10－8cm2/s, which is classified moderate. While the concrete mixing HCSA is about 0.62×10－8cm2/s, the permeability belongs to inferior. The effects of permeability of HCSA mixing amount on concrete is not obviously. The Water-Cement ratio affects the concrete permeability. Under the experimental conditions, the water-cement ratio of 0.4 can achieve better effect of the HCSA expansion; Furthermore, the mercury intrusion further verified that incorporating proper amount of HCSA can make the internal structure dense and improve the density and impermeability of concrete.

Abstract: The effects of ground limestone powder on the fluidity, strength and viscosity of reactive powder concrete(RPC) were studied. The results show that, the flexural strength of RPC greatly increases with the increase of the content of ground limestone powder at the W/B of 0.16, 0.18 and 0.20 when ground limestone powder content is less than 30%; for fresh RPC, the maximum compressive strength is 160MPa and the maximum flexural strength is 36.9MPa when the limestone powder content is 158kg/m3 at the W/B of 0.20, with 20cm good fluidity and very compact microstructure; the viscosity of RPC greatly decreases with the addition amount of ground limestone powder, the viscosity of RPC mixture changes from 60,000MPa•S to 18,000MPa•S when cement content decreases from 388kg/m3 to 150kg/m3 and the addition amount of limestone powder increases from 0 to 238kg/m3.

Abstract: The combined admixture of limestone powder and substandard fly ash for the preparation of C40 machine-made sand concrete were studied. The results show that the C40 machine-made sand concrete prepared with the combined admixture of limestone powder and substandard fly ash has very good workability, with a 60min slump loss of less than 15mm. The combined admixture of limestone powder and substandard fly ash has very good filling effect and crystal nucleus effect, which makes hardened cement paste structure and interface structure more compact. The chloride ion permeability coefficient of machine-made sand concrete at 28d are less than 182×10-14m2/s, showing that the C40 machine-made sand concrete has good resistance to chloride ion permeation. It can be seen from SEM and energy spectrum technique that the structure of machine-made sand concrete is compact, and the C-S-H gel in the concrete has low calcium-silicate ratio.

Abstract: In this article, the effects of different content and compound ratio of low-grade fly ash and limestone powder on the strength, water requirement and adaptability with admixture of green complex binder were studied, and the influence of particle size distribution and particle morphology on its performance was analyzed. The results indicated that the strength decreased obviously with the increase of mineral content. There was an optimum ratio of fly ash and limestone powder (6:4) at a certain mineral content. Water requirement decreased, and the saturated content of admixture points became small with the increasing of limestone powder. The effects of content on the strength were much more than that of particle size distribution for composite cement with high volume of mineral admixtures.