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Tian Z.,Hohai University | Jing J.,Hohai University | Huang G.,Sinohydro Bureau seventh CO.
Earth and Space 2012 - Proceedings of the 13th ASCE Aerospace Division Conference and the 5th NASA/ASCE Workshop on Granular Materials in Space Exploration | Year: 2012

In order to investigate workability of fresh concrete quantitatively, a newly device for test online was invented to measure rheolgical parameters of concrete. The device consists of temperature measurement system, torque measurement system, driving system and human-computer interaction system. The working principle of this device is to adopt single-chip microcomputer auto-control system driving cross axis torquemeter operation by stepping motor and, total 6 classes different speeds of the corresponding rotating torque are obtained to calculate the rheological parameters of fresh concrete. Results of verifying test continuously with the device indicated that rheological characteristic of fresh concrete is similar to Bingham models and yield stress reduces linearly with increase of slumps, but relation between plastic viscosity and slumps is inexplicit. The device can be used to measure continuous rheological parameters for situ-pouring concrete expediently. © ASCE 2012. Source


Tian Z.,Hohai University | Liu H.,Hohai University | Wu Y.,Sinohydro Bureau seventh CO.
Earth and Space 2012 - Proceedings of the 13th ASCE Aerospace Division Conference and the 5th NASA/ASCE Workshop on Granular Materials in Space Exploration | Year: 2012

In this article, total shrinkages of early-age concrete specimens, which formed by controlled permeability formwork (CPF) liner and normal formwork, were obtained by non-contact contractometer test, and the results show that shrinkage amounts before initial setting and swelling amounts can be distinguished. Compared with ordinary specimens whose water-binder ratio dosage varied from 0.50 to 0.35, total shrinkage of specimens poured by CPF liner reduced from 76 percent to 87 percent. The study also demonstrated that evident differences on shrinkage-reducing depend on water retention of CPF liner, which can contribute researchers to understand the shrinkage-reducing working mechanism and improve of CPF liner properties. © ASCE 2012. Source


Tian Z.,Hohai University | Li X.,Hohai University | Peng Z.,Sinohydro Bureau seventh CO.
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2015

Gel medium made from 940 series Carbomer resin was selected to simulate rheological characteristics of cement paste, and the fine aggregate component of mortar was simulated by adding a proper amount of transparent glass beads in it. The similarity of simulation medium and rheological parameters of prototype material was analyzed by applying rotational viscometer. It can be proved that the rheological property of cement paste to be simulated by Carbomer gel medium is completely feasible, which may lay a foundation for visualization of experimental study of cement mortar medium rheology. ©, 2015, Tongji University. All right reserved. Source


Bian C.,Hohai University | Tian Z.,Hohai University | Mao L.,China Tiesiju Civil Engineering Group Co. | Wu J.,Sinohydro Bureau seventh CO.
Indian Journal of Engineering and Materials Sciences | Year: 2015

The influence of voltage applied for better demoulding concrete on its properties including hydration process at early age, formed pore structure, surface permeability and compressive strength is studied through a series of methods such as conductivity, non-evaporable water content and mercury intrusion porosimetry (MIP). Test results show that: (i) increasing voltage results in a drop in degree of hydration caused by assemble of cement grains on one hand and on the other hand the increase of quantity of water transported toward cathode and anode due to the effect of electro-osmosis; (ii) as the voltage increases, the porosity, critical pore radius and volume fraction of larger capillary pores decrease at first mainly due to reduction of water-cement ratio (w/c) by displacing water then increase caused by reduction of degree of hydration and water block at the concrete/mold interface, but placing filter cloth on the mold walls could slow down the adverse changes of properties; (iii) variation of surface permeability with voltage is similar with that of porosity as well as critical pore radius and the permeability has a good correlation with the two parameters while compressive strength is good correlated with volume fraction of larger capillary pores. © 2015, Indian Journal of Engineering and Materials Sciences. All rights reserved. Source


Tian Z.,Hohai University | Li X.,Hohai University | Zhu F.,Hohai University | Peng Z.,Sinohydro Bureau seventh CO.
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2016

Visual physical model experiment of aggregates motion law were carried out via transparent adhesive prepared from carbomer gel with equivalent rheological properties of fresh concrete. Based on the principle of consistency in both real-time image of flow process and real aggregate distribution from fresh mortar and transparent adhesive, the mechanism of rheological deformation of mortar and aggregate settling characteristics forced vibration was analyzed. Results indicate that visual simulation method of fresh concrete based on equivalent rheological properties is unique and feasible, and from the experiments the aggregates settlement motion law i. e., displacement fields, velocity fields and other motion morphological parameters can be directly obtained, which provide vital foundation on the analysis of constitutive relationship and grain contact model of rheological concrete. © 2016, Tongji University. All right reserved. Source

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