Papers by Author: Chang Hui Yang

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Authors: Chong Wang, Chang Hui Yang, Chao Jun Wan, Yan Feng Tian
Abstract: Aiming at preparing the high performance concrete with metakaolin (MK) replacing silica fume (SF), comparison of fluidity between MK concrete and SF concrete was investigated in this paper. Slump, spread, and slump loss with time of fresh concrete under the condition of superplasticizer adding were tested, which containing with 5 to 15 wt. % replacement of MK, SF, combination of MK and ground granulated blastfurnace slag (GGBS), or combination of SF and GGBS, respectively. The mechanism for exploring fluidity difference of MK concrete and SF concrete were researched by measuring ζ potential and superplasticizer adsorption. The results indicate that concretes containing with 5 to 15 % MK were provided with better workability than concretes with SF. Fluidity of MK concretes incorporating with 5 to 15 % GGBS was better than that of SF concretes. Incorporating with 5 to 15% replacement, MK-cement-superplasticizer system present higher ζ potential, and lower superplasticizer adsorption than SF-cement-superplasticizer, which is an answer to why MK concrete has better fluidity than SF concrete. Physical filling effect of mineral additives is also is helpful to concrete fluidity.
Authors: Kui Yang, Chang Hui Yang, Zhen Li
Abstract: Porous PVA/MMT nanocomposites, which included a great deal of macroporous, mesoporous and a few micorporous were fabricated by directional freezing and freeze-drying. X-ray diffraction (XRD), Scan Electric Microscope (SEM), Fourier Transform Infrared (FT-IR) spectroscopy, and Thermo gravimetric-differential scanning calorimeter analysis (TG-DSC) were used characterize the samples. Results showed that the morphology and the interactions between MMT and PVA of the obtained porous nanocomposites were influenced by nanoparticle size, colloid concentration , aging time etc.O-H bond in PVA and Si-O bond in MMT, "acetate" in PVA and O-H bond in particle flat of MMT which occurred coupling constituted hydrogen bonding which enhanced the driving power to help PVA molecules insert into interlayer spaces of MMT.
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