Papers by Author: Zi Yun Wen

Abstract: Using XRD and SEM analysis, the types and morphology of autoclaved aerated concrete (AAC) hydration products in different water-to-binder ratio (w/b) and different autoclaved system were studied. Strength test shows that, Using w/b=0.25 and autoclaved curing 190°C for 8h, AAC with dry density 765kg/m3 and compressive strength 7.5MPa was made. XRD and SEM analysis indicate that, the higher the autoclaved temperature is, the smaller the size of hydration products (most of them are tobermorite and hydrogamet) is, and the crystallinity has a little increase; with the extension of autoclaved time, the size of products is smaller, the crystallinity is first increased and then decreased, the crystal form of tobermorite turns 1.1nm into 1.4nm; the less the w/b is, the smaller the size of products is, and the higher the crystallinity is, and tobermorite turns 1.1nm into 1.4nm.

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: At present, masonry and plaster of AAC blocks are still carried out by traditional construction methods which often lead to some quality defects such as cracking and leaking in the wall and hollowing and spalling in the plaster layer, etc. and hinder greatly the popularization and application of AAC blocks. On the basis of the characteristics of AAC blocks and the dry masonry thin-bed mortar, a kind of high performance dry-mixed Mortar for dry masonry process of AAC blocks was developed. The mortar has excellent workability, high water-retention, property, good mechanical properties and good construction properties. It solves the problems caused by traditional construction methods. The mechanism for these is discussed.

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.