Papers by Author: Zhong He Shui

Abstract: The effect of mineral admixture and curing condition in pore structure of concrete was studied in this paper. Concrete samples with different component were prepared firstly, and then they were put into standard condition, fresh water and salt environment that produced artificially respectively at 20 °C. After the experiments of curing at 3, 28 and 180 days pore structure were tested by mercury intrusion porosimetry (MIP). The results obtained reveal that with the increase of the age, the pore structure degradation impact in salt environment of concrete increase dramatically. When at 28 days, total pore volume and porosity of concretes in fresh water is lower by 20% and 5% respectively than the ones with larger mean pore size and critical aperture in salt environment, which represents pore refinement in fresh water had a good effect. Compared to the salt environment erosion, it can be found that the impact of pore refinement in fresh water is more significant.

Abstract: Concrete with a compressive strength of 100MPa was produced with metakaolin(MK), and the effect of MK replacement levels on compressive strength of concrete with a water to binder ratio of 0.25 was studied in this paper. XRD, microhardness tests, SEM and MIP were used to investigate the influences of MK on the phase composition, microhardness of interfacial transition zone(ITZ), microstructural morphology and pore structure of the high-strength concrete (HSC). The results showed that the incorporation of MK promoted the hydration process and decreased the amount of Ca(OH)2 crystals. Furthermore, MK increased the ITZ microhardness of HSC, enhanced the hydrates and improved the bond performance of aggregate and paste. The weak zone between aggregate and paste became almost disappeared when 10% MK was blended. Meanwhile, refinement of the concrete pore structure was obtained in the presence of MK. The improvement of strength and microstructure became more obvious as the MK replacement level increased to 15%.

Abstract: One of the main reasons for the damage of reinforced concrete is the expansion caused by corrosion of steel bar in concrete. In this paper, the equivalent circuit that inflects corrosion process of steel bars in reinforced concrete was analyzed, with the A.C.Impedance Spectrum method. And the effects of surface treatment of the bars on corrosion resistance of the reinforced concrete were investigated. Study results show that the surface coating (plating) on the built-in reinforcement can effectively prevent corrosion of steel bar, thereby enhancing the durability of concrete structures.

Abstract: The effects of carbonation on the microstructure of concrete containing fly ash and expansive admixture are investigated in this paper. Eight mix proportions of the concrete are designed in the experiment with the different replacement levels of the Portland cement with the fly ash and the expansive admixture. The specimens cured in accelerated carbonation condition for 3 days, 7 days and 28 days are used for macro and micro tests. MIP test is used to analyze the influence on internal pore structure of concrete by carbonation reacts. The changes of Ca(OH)₂ and CaCO₃ contents are measured with TG/DSC analysis. The results indicate that carbonation reaction can make concrete denser. Replacing Portland cement with fly ash and expansive admixture increases the carbonation rate of concrete and fly ash blended in concrete can improve the pore structure of concrete. Apart from the reaction of Ca(OH)₂ and CO₂, the carbonation reaction of other hydration product also exit in the accelerated carbonation process.