Research on the Crack Risk of Early-Age Concrete under the Temperature Stress Test Machine

Abstract

A new temperature stress test machine (TSTM) was developed to improve temperature control accuracy and efficiency. As there is no uniform standard for the threshold value of TSTM, quite different threshold values are used in the test, which results in the influences of the threshold value on the evaluation of thermal stresses and crack risk of concrete not being determined. To illustrate the importance of an appropriate threshold value, different threshold values were used to evaluate the influences on the thermal stresses and cracking resistance of concrete specimens under a complete restraint test with semi-adiabatic temperature development. The results show that the maximum compressive stress of a concrete specimen with a threshold value 3 με was slightly larger than that of 1.5 με when the growth rate of tensile stress of the concrete specimen with the threshold value 3 με was slightly greater than that of concrete specimen with the threshold value 1.5 με. Based on the combination of crack risk coefficient and restraint degree, a new system for evaluating the crack resistance of concrete was proposed, in which different threshold values were used to estimate their influences on the crack risk of concrete. Thus, an appropriate range of threshold values could be determined.

Thermal deformation and stress of alkali-activated slag concrete under semi-adiabatic condition: Experiments and simulations

“…From 9 h, the temperature increased rapidly at a rate of >1 • C/h, while the concrete started to shrink rather than to continue the expansion. This phenomenon is interesting and was also identified for some high strength OPC concrete, although OPC systems normally expands at this rate of temperature increment [24,30]. The shrinkage of AASC from 9 to 18 h was attributed to the large autogenous shrinkage in this period [31].…”

Thermal Stress Analysis for Carbon/Carbon Material Throat Lining Based on Finite Element Analysis

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Longitudinal restraining devices for the evaluation of structural behaviour of cement‐based materials: The past, present and prospective trends

“…As the above described testing system mainly allows for the effects of restrained linear shrinkage to be examined, the traditional TSTM has been recently modified and improved by numerous researchers, in order to enable thermally insulated and regulated concrete specimens to be examined. These improvements include temperature and humidity control, insulation, simultaneous measurements on restrained and unrestrained specimens, as well as the addition of a closed loop computer‐controlled system 70,82,85,88,113–122 …”