Papers by Author: Dong Lin

Abstract: The comparison experiments are carried out at different silica fume dosage between the silica fume with pre-treatment and the silica fume without pre-treatment. The results show that the pre-treatment of silica fume improved the strength greatly and the silica fume dosage corresponding to the strength peak somewhat moved forward from 0.20 for the cement-based materials with pre-treatment of silica fume to 0.21 for the cement-based materials without pre-treatment of silica fume. The particles distribution experiment results indicate that after the pre-treatment of silica fume, the average particle diameter of silica fume reduced from 2.865μｍto 0.151μｍ. Based on Aim-Goff model, it is concluded that the increase in the compressive strength and flextural strength of cement-based materials with pre-treatment of silica fume, are attributed to the dispersion of silica fume agglomeration and the increase in the packing density of the cement-based materials.

Abstract: In order to discuss the action mechanism of polyvinyl alcohol (PVA) polymers in high performance cement-based composites(HPCBC), the effect of PVA on the strength of HPCBC with different ratio of polymer to binding material (P/B) was studied,and action mechanism of PVA polymers in HPCBC were also studied by SEM and X ray diffraction(XRD). Results show that the strength of HPCBC with addition of PVA polymers can be improved greatly,and there exists an optimal P/B with which the strength were upmost; In this experiment, the optimal P/B is 2.5%,and at this point the strength attain extremity with compressive strength and flexural strength of 113.6MPa, 23.0MPa respectively.By using SEM and XRD, it is found that the interface zone structure is improved and so it was of high-density, low-porosity and high adhere-strength, and PVA polymers chemical action works in the course of cement hydration and hardening.

Abstract: In ordinary processing condition, using small amount (2%) of polymer to modify reactive powder concrete (RPC), the performance of modified and unmodified RPC was studied for their corrosion resistance with water-dip-in, acid-dip-in and sulphate solution-dip-in tests and was verified by the strength loss rate. The results show that not only the corrosion resistance but also the strength, especially the flexural strength, has been improved obviously after the polymer modification. The mechanism has been studied with SEM and EDS analysis.

Abstract: The strength and shrinkage properties of mortars with different superplasticizer were studied. The results indicated that the saturation point was the best dosage of superplasticizer, at which it not only helped to reach highest paste fluidity with minimum superplasticizer dosage, but also reach the highest mortar strength and comparatively lower shrinkage rate.

Abstract: This paper studied rheological properties of fresh cement pastes and adsorption behavior of superplasticizers which are FDN-5R, a type of naphthalene sulfonic acid based condensate, 3350, a type of polycarboxylate superplasticizer, by R/S-SST rheometer and UV Visible Spectrometer. Results show that superplasticizers can reduce the flocculation structure of fresh cement paste obviously and reduce the yield stress and apparent viscosity. The turn of thixotropic property is: blank sample > FDN-5R > 3350, especially the sample with 3350’s curve of upward and downward almost match together and the thixotropic property drives to zero. Shearing stress, apparent viscosity and thixotropic property are decreased, adsorption capacity is higher by the superplasticizer adding. The bigger effectual adsorption, the better dispersive action of flocculation and rheological properties of fresh cement pastes. Therefore, we can understand the effect mechanism and properties of superplasticizer much better by combining the molecular structure, adsorption capacity, dispersive action and rheological properties.

Abstract: Feasibility study of partially replacement of cement and ground sand by ground steel slag (GSS) and ground granulated blast furnace slag (GGBFS) in producing prestressed high strength concrete pile (PHC) was conducted. The results showed that under normal curing（20oC, 95% RH）and the steam curing condition (80oC), GSS possessed less reactivity than GGBFS. However, under autoclave curing condition (180 °C, 1.0MPa), the reactivity of GSS can be effectively activated. The autoclaving strength of the concrete made from 20% GSS with Blaine 550m2/kg, 55% cement and 25% ground sand could reach 89.0 MPa which is not only higher than that of GGBFS (82.8MPa), but also higher than that of traditional PHC concrete (83.9Mpa, 70% cement and 30% ground sand). It’s feasible to produce PHC concrete by GSS with high fineness and optimized dosage.