Papers by Author: Bei Xing Li

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Authors: Jun Hong Shan, Ming Kai Zhou, Bei Xing Li, Ji Wei Cai, Fang Xu
Abstract: The Badong highway bridge over the Yangtze River is a grand bridge in Enshi, Hubei Province of China. Its deck pavement consists of C40 polypropylene fiber concrete, 100 millimeters thick. Experiments show that C40 concrete incorporating polypropylene fibers at dosage of 1.35 kg/m3 has the excellent properties against cracking, permeation, impact, wearing, etc. Thus polypropylene fiber concrete as deck pavement can extend service life of the deck and decrease the maintenance cost and traffic inconvenience for reparation. It can be widely applied in construction of deck pavement and road pavement.
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Authors: Bei Xing Li, Ji Liang Wang, Ming Kai Zhou
Abstract: The workability, strength and modulus of elasticity, drying shrinkage and creep, and chloride ion permeability as well as freeze-thaw resistance of the C60 high Performance concretes (HPCs) with manufactured sand (MS) containing crushed limestone dust in percents ranging from 3.5% to 14% were experimentally investigated. The results were compared with those of river sand (RS) concrete. In addition, the effect of clay amounts at 3% and 5% in MS on properties of C60 HPCs was also investigated. The results showed that expect for the creep, the other performances of C60 MS-HPCs with crushed limestone dust content of 7% to 10.5% were excellent or compared favorably with those of C60 RS-HPCs. The increment of clay content in MS obviously decreased workability, increased dry shrinkage and accelerated freeze-thaw destruction of C60 MS-HPCs, but didn’t affecting compressive strength and chloride ion permeability of the concrete. It was concluded that C60 HPC can be made with MS with a high content of crushed limestone dust but the amount of clay in MS should be controlled to a low limit.
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Authors: Ji Wei Cai, Shao Bo Zhang, Ming Kai Zhou, Bei Xing Li
Abstract: The crusher dust in Manufactured fine aggregate (MFA), e.g. limestone powder in calcareous MFA, constitutes micro gradation of the aggregate and suitable content of crusher dust in MFA can improve the properties of concretes. In this paper, early hydration processes of samples substituting limestone powder and fly ash for part of cement are analyzed, and effects of limestone powder on cement hydrates are studied through experiment of mortar prepared with MFA partially replaced by limestone powder and fly ash. The result reveals that both the dormant period and acceleration period of hydration ended earlier in the samples substituting limestone powder for part of cement, and amount of crystals of calcium hydroxide and hydrated calcium carboaluminate increases in hardened paste in the samples substituting limestone powder for part of MFA, i.e. calcareous dust (limestone powder) in MFA can stimulate and enhance hydration of cement.
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Authors: Fang Xu, Ming Kai Zhou, Wei Guo Shen, Bei Xing Li
Abstract: In order to improve the performance of polymer modified porous concrete (PMPC), the mineral admixtures (MAs) including fly ash (FA) and silicon fume (SF), are added in the concrete. In this paper, the optimum dosage of the MAs, the influence of the MAs on the strength performance, permeability performance and the surface functional performance of PMPC are studied. The microscopic test of SEM is used to explore the microscopic structure of PMPC. The test results indicate that: the dosage of 10% FA or of 6% SF is the optimum dosage, while the 28d compressive strength can reach 24MPa and 43MPa, respectively, the 28d flexural strength can reach 5.2MPa and 5.3MPa, respectively, and the permeability coefficient can reach 0.36cm/s and 0.32cm/s, respectively. The surface structural depth can reach more than 1mm and the slide resistance coefficient can reach more than 40BPN, which can conform to the standard of JTG F30-2003. The Contact Element Model is proved to conform to the structural features of PMPC. With the microscopic test, as the addition of the polymer and MAs, the internal micro-cracks and non-hydrated cement particles in the interfacial transition zone (ITZ) are covered by the cement paste and polymer films. The contact area, the mechanical property and durability of PMPC can be improved.
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Authors: Jin Zha, Bei Xing Li, Jin Hui Li, He Gao, Gong Cui
Abstract: This paper investigated the mechanical properties, workability, autogenous shrinkage, drying shrinkage and durability of the high performance combined aggregate concrete with the coarse aggregate replaced by the lightweight aggregate in the volume fraction from 0% to 50%. The results demonstrated that the fresh concrete with the lightweight aggregate volume fraction of 10% and 30% had good workability, but degrade with a high volume fraction of 50 %. The hardened concrete with 10% and 30% lightweight aggregate replacement had similar compressive strength and splitting tensile strength comparing to the reference concrete without adding lightweight aggregate. The concrete with 50% lightweight aggregate replacement showed decreased compressive strength and splitting tensile strength. The concrete adding lightweight aggregate exhibited less autogenous shrinkage and drying shrinkage than the reference concrete without adding lightweight aggregate. The autogenous shrinkage and drying shrinkage increased with the increasing lightweight aggregate volume fraction. The concrete containing lightweight aggregate showed good durability after 200 freezing and thawing cycles, but the chloride permeability efficiency of concrete decreased.
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Authors: Fang Xu, Ming Kai Zhou, Wei Guo Shen, Bei Xing Li
Abstract: In this paper, polypropylene fiber and SBR polymer latex are added into cement mortar to improve the toughness. Using two flexural toughness test methods of ASTM-C1018 and JSCE-SF4, the ratio of compressive strength to flexural strength (σC/σF for short) and flexural toughness index are used to evaluate the toughness of the cement mortar. The experimental results show that, comparing to the control cement mortar sample, when the SBR polymer mass percent of 20% and the polypropylene fiber volume percent of 1.0%, the σC/σF is 2.17, reduced by 59.2%, the ASTM toughness index I5, I10, I30 is 2.86, 2.95, 3.16 respectively, increased by 63.4%, 58.6%, 68.1% respectively, the JCI toughness index is 13.1, increased by 258%. Based on the SEM, adding SBR-polymer into cement mortar can form the polymer transition layer between the interfaces of polypropylene fibers and cement matrix, from XRD test, SBR polymer latex has no significant influence on the cement hydration after 7d curing. This research provides some useful references for the application of this new material.
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