Papers by Author: Li Tian

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Authors: Wei Qun Cao, Li Tian, Tie Jun Zhao
Abstract: Strain-hardening cement-based composites (SHCC) resist increased tensile stress after first crack formation, over a significant range of tensile strain. This increased strength and strain capacity is achieved by effective crack bridging by fibres, across multiple cracks of widths in the micro-range. Whether the crack width limitation translates into increased durability through retardation of ingress of moisture, gas and other deleterious matter, is scrutinised in this paper. The potential of the comparatively new composite material becomes obvious, yet it is clearly outlined that further research is necessary before we fully understand the basic mechanisms underlying durability of SHCC.
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Authors: Li Tian, Jing Ru Chen, Tie Jun Zhao, Zhu Ding
Abstract: The high brittleness of cement-based materials is the dominant reason that causes cracking, corrosion, and even losing the load bearing capacity of the structure. PVA fiber reinforced Strain-hardening Cement-based Materials (SHCC) which is characterized by strain-hardening and multi-micro cracking significantly improves the mechanics performance of cement-based materials. In this paper, 3-point-bending and direct tensile tests were conducted to contrast influence of the material mechanics on SHCC by aggregate gradation. Tests results demonstrate that appropriate particle gradation may improve the strain hardening section in the stress-strain curve. Therefore, the maximum diameter of aggregate can be enlarged from 110μm to 1.25mm. Comparatively large aggregate will be convenient for such materials in the practical application and popularization.
207
Authors: Li Tian, Yu E Zhang, Feng Mei Li, Hong Yuan Zhang
Abstract: Anti-permeability, durability even strength of cement-based composites are closely related with the material pore structure. Polyvinyl alcohol (PVA) fiber reinforced strain hardening cement-based composites (SHCC) are provided with high ductility and multi- micro-crack propagation mode. Due to fibers adding, much more interface and tiny fracture had been drawn into SHCC, although it has some advantages such as high tensile strength, ductility and energy consumption under seismic load or other cyclic force. Water repellent treatment can improve the anti-permeability of SHCC. Investigations have been made through Mercury injection experiment to reveal influence on microstructure of PVA-SHCC by silane water repellence. Results show that, the pore structure of SHCC can be fined by inside water repellent agent. That is, water repellent infiltrate through the relative big hole or defect of cement paste and react with the alkali substance. Then the resultant colloids reduce the big hole, pore or fracture and reform the pore structure of the cement paste. Because the fine pore structure can prevent air, water and ions defuse into interior of cement-based composites, water repellent treatment is benefit to increase anti-permeability of high ductile SHCC.
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