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He Z.-H.,Shaoxing University | Qian C.-X.,Nanjing Southeast University | Qian G.-F.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company
Journal of Advanced Microscopy Research | Year: 2014

The influence of polyvinyl alcohol (PVA) fiber, shrinkage reducing admixture (SRA) and the combined addition of fly ash and slag on drying shrinkage of concrete with 7d same compressive strengths were studied by testing drying shrinkage, evaporable water test and scanning electron microscope (SEM). The results indicate that drying shrinkage of concrete develops rapidly, becoming stable after 100d; SRA and the combined addition of fly ash and slag can refine pore, and especially reduce the fine capillary porosity to decrease drying shrinkage, the better decrease with SRA; PVA fiber deceases the total porosity and the pore and coarse capillary porosity, but increases the fine capillary porosity to increase drying shrinkage. Copyright © 2014 American Scientific Publishers All rights reserved. Source


He Z.,Nanjing Southeast University | Qian C.,Nanjing Southeast University | Qian G.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company | Meng F.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company | And 3 more authors.
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2010

The influence law of shrinkage reducing admixture(SRA), the mixing amount of polyvinyl alcohol(PVA) fiber and the double-mixture technology on creep characteristics of concrete with 7-day same strength C50 were studied by the self-made creep loading device and the influence mechanism were analyzed by testing chemically combined water of net paste in natural state and loading state. The results indicate that the loading age 7 d, the creep coefficients become stable after 60 days' loading; the loading state facilitates the hydration of concrete with SRA, which decreases greatly the creep coefficient, compared with the reference concrete and the proper amount of PVA fiber(0.6 kg/m 3) does not influence the creep coefficient, but the loading state delays significantly the hydration of concrete with excess amount of PVA fiber(1.2 kg/m 3), which increases the creep coefficient; double-mixture technology with SRA and proper amount of PVA fiber decreases the creep coefficient of concrete, while double-mixture technology with SRA and excess amount of PVA fiber increases the creep coefficient. Source


He Z.-H.,Nanjing Southeast University | Qian C.-X.,Nanjing Southeast University | Qian G.-F.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company | Meng F.-L.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company | And 3 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2011

The influence law of polyvinyl alcohol (PVA) fiber, shrinkage reducing admixture (SRA) and the combined addition of fly ash and slag on creep characteristics of concrete with 7d same compressive strengths were studied by the self-made creep loading device and the influence mechanism were analyzed by testing chemically combined water of paste with same water-binder ratio with concrete. The results indicate that creep coefficients develop rapidly, becoming stable after 100 d' loading; SRA and the combined addition of fly ash and slag significantly reduce creep coefficients of concrete, the better effect with SRA, the value of 450 d only being 0.63, but PVA fiber increases creep coefficient, not suitable to produce concrete for high speed railway; creep coefficients of concrete decrease with the rise of chemically combined water of paste, and hydration at 60 d early ages is in favor of reducing creep coefficients but hydrated products at 450 d later ages can not make contribution to reducing creep coefficients. Source


He Z.-H.,Nanjing Southeast University | Qian C.-X.,Nanjing Southeast University | Qian G.-F.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company | Meng F.-L.,Shanghai Hangzhou Passenger Dedicated Line Ltd Company | And 3 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2011

The influence law and mechanism as well as the relationships of polyvinyl alcohol (PVA) fiber, shrinkage reducing admixture (SRA) and the combined addition of fly ash and slag on autogenous shrinkage and interior relative humidity of concrete with 7d same compressive strengths at early ages were studied by the self-made test device. The results indicate that PVA fiber, SRA and the combined addition of fly ash and slag significantly reduce autogenous shrinkage of concrete, the best effect with SRA; the development speed of autogenous shrinkage is very fast before 72 h(3d), more than 80% of the 672 h(28d) value, but the development speed of autogenous shrinkage of concrete with SRA is relatively slow, showing some lag effect; interior relative humidity of concrete at early ages has undergone the initial vapor saturated stage and the subsequent reduction stage, the concrete with SRA showing a strong moisturizing capacity; autogenous shrinkage of concrete also shows 2 distinct stages, corresponding with interior relative humidity, both showing significant linear correlation; the measured autogenous shrinkage of the vapor saturated stage mainly is chemical shrinkage and small amount of settlement shrinkage, depending on the moisturizing capacity of PVA fiber, SRA and mineral admixtures on concrete and autogenous shrinkage of the reduction stage mainly is self-desiccation shrinkage, depending on the hydration degree and rate of cementitious materials. Source

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