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Yao T.,Jiangsu Academy of Building Science | Zhang J.,Jiangsu Academy of Building Science | Liu J.,Jiangsu Academy of Building Science | Tian Q.,Jiangsu Academy of Building Science
Advanced Materials Research | Year: 2012

Structure monitoring has been increasingly valuable in recent years and has taken a leading role in the field of structural engineering. Date collected by early age monitoring represent a unique source of information for understanding the real behavior. In this paper, the temperatures evolution and concrete deformation evolution are obtained by real-time continuous monitoring of Reinforcement concrete(RC) wall. The result shows that the early age thermal cracking is one of the most important origin of several phenomena that imperil durability and shorten the lifespan of the structure. Though the wall is not considered as mass concrete, and has a big radiating surface, the maximum temperature can even reach up to 52°C due to heat generation of cement and the insulation of formwork, which can lead to shrinkage deformation when the temperature decreases. The measured experimental date can provide useful reference for early crack control and durability of RC concrete structure, and they can also be use to verify and improve the accuracy of the numerical results for RC wall, which is available in the future for basis to similar projects and research. © (2012) Trans Tech Publications, Switzerland. Source


Liu J.,Jiangsu Academy of Building Science | Wang Y.,Jiangsu Academy of Building Science | Tian Q.,Jiangsu Academy of Building Science | Zhang S.,Jiangsu Academy of Building Science
Dongnan Daxue Xuebao (Ziran Kexue Ban)/Journal of Southeast University (Natural Science Edition) | Year: 2011

To evaluate the effect of temperature on expansion of light calcined magnesia expansion agent (MEA), two typical MEA were chosen, and temperature sensitivity of hydration rate of MEA and expansive process of cement paste containing MEA were analyzed. Furthermore, the mechanism of temperature was also discussed based on hydration kinetics of MEA. The results indicate that the hydration and expansion of MEA calcined at higher temperature show stronger temperature sensitivity compared to that calcined at lower temperature. Similar to Portland cement, the hydration process of MEA can also be divided into five stages, and the activation energy difference in induction and acceleration period of hydration reaction is remarkable (75.9 and 149.8 kJ/mol, for two MEA respectively). The differences of expansive effectiveness and kinetic parameters are the main cause of the difference of temperature sensitivity. Source


Zhou D.-L.,Jiangsu Academy of Building Science | Zhou D.-L.,Jiangsu Bote New Materials Co. | Ran Q.-P.,Jiangsu Academy of Building Science | Ran Q.-P.,Jiangsu Bote New Materials Co. | And 5 more authors.
Jianzhu Cailiao Xuebao/Journal of Building Materials | Year: 2011

Effects of temperature on dispersability, adsorption behavior and chemical structural stability of acrylate-type polycarboxylate superplasticizer (PAAE) were investigated systematically and the relationships between these properties and temperature were further analyzed. The results show that the initial dispersability of PAAE increases as the temperature increases, but the time of dispersion retention gradually decrease with increasing temperature. The adsorption amount of PAAE increases as the temperature increase below 30°C but decrease significantly when the temperature up to 30°C. The ester bond in PAAE is partly broken in the alkaline environment and at higher temperature. The hydrolyzed ratio of PAAE increases with increasing temperature. This hydrolysis of acrylate-type polycarboxylate has directly an adverse effect on dispersion properties. Source


Yao T.,Jiangsu Academy of Building Science | Tian Q.,Jiangsu Academy of Building Science | Zhang S.Z.,Jiangsu Academy of Building Science | Guo F.,Jiangsu Academy of Building Science | Wang Y.J.,Jiangsu Academy of Building Science
Applied Mechanics and Materials | Year: 2013

Concrete deformation measured under a certain condition in the experiment are very different from those in practical engineering structures, therefore, it's necessary to monitor concrete properties in structures. In the paper, by real-time continuous monitoring of reinforcement concrete slab prepared with expansive agent, time-dependent temperature variations and strain variations are obtained and analyzed, and indoor test of the mechanical properties and deformation of field sampling from the slab are presented, so that this completes a transition from the specimen in experiment to the structure in engineering. The result shows that: there was no early-age crack in the four month after casting; the temperature had a certain increase due to heat generation of cement, which can lead to shrinkage deformation in cooling period; the temperature fluctuate with ambient temperature and there are obvious peak temperature rise about 15°C; There was a certain expansion at heating period, which can be considered as compensating shrinkage caused at late age in a certain extent so that minimum strain value is just about -120με which are not beyond the ultimate tensile strain. In addition, the measured experimental data can provide helpful reference for early crack control and durability of concrete structure, and they can also be use to verify and improve the accuracy of the numerical results for slab, which is available in the future for basis to similar projects and research. © (2013) Trans Tech Publications, Switzerland. Source

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