Experimental Study on Early-Age Crack of Mass Concrete under the Controlled Temperature History

Abstract

Thermal deformation under restrained conditions often leads to early-age cracking and durability problems in mass concrete structures. It is crucial to monitor accurately the evolution of temperature and thermal stresses. In this paper, experimental studies using temperature stress testing machine (TSTM) are carried out to monitor the generated thermal cracking in mass concrete. Firstly, components and working principle of TSTM were introduced. Cracking temperatures and stress reserves are selected as the main cracking evaluation indicators of TSTM. Furthermore, effects of temperature controlling measures on concrete cracking were quantitatively studied, which consider the concrete placing temperature (before cooling) and cooling rates (after cooling). Moreover, the influence of reinforcement on early-age cracking has been quantitatively analyzed using the TSTM. The experimental results indicate that the crack probability of reinforced concrete (RC) is overestimated. Theoretical calculations proved that the internal stress can transfer from concrete to reinforcement due to creep effect. Finally, the experimental results indicate that the reinforcement can improve the crack resistance of concrete by nearly 30% in the TSTM tests, and the ultimate tensile strain of RC is approximately 105% higher than that of plain concrete with the same mix proportions.

Temperature control and crack prevention during construction in steep slope dams and stilling basins in high-altitude areas

“…Engineering experience indicates that the difficulty in avoiding cracks is due to insufficient understanding of the mechanism of crack formation, the randomness of hydrometeorological conditions, and the failure of material parameters in reflecting actual engineering conditions; in addition, crack formation occurs because of the absence of timely and reasonable measures for temperature control that are tailored to the actual conditions of specific projects. [8][9][10][11][12][13] Therefore, in the current condition in which a major breakthrough in the theory of temperature control is difficult to achieve, [14][15][16][17][18][19][20][21][22][23][24] crack prevention should still be focused on the selection of timely and reasonable measures for temperature control.…”

Experimental and numerical analysis of early age behavior in non-reinforced concrete

“…The phenomena of autogenous shrinkage induced cracking are considered in [8] for high-performance concrete, in [9] for slag cement concretes, and in [10][11][12][13] for fiber reinforced concrete. More recently, the research contribution in this field often focuses on early-age hygro-thermo-chemo-mechanical behaviors [14][15][16][17][18][19][20][21][22]. The state-of-the-art numerical models studying early-age behavior in concrete is mainly based on the hygro-thermo-chemo-mechanical coupled framework [23][24][25][26][27].…”

Causes of Early-Age Thermal Cracking of Concrete Foundation Slabs and their Reinforcement to Control the Cracking

“…Both the calculations and experiments show that reinforcement can postpone the occurrence of the appearance of the first major crack and can enhance the ultimate tensile strain of the structure (Shi et al, 2014;Sule, 2003). In terms of temperature strains, this would mean that an additional temperature difference of up to 10.8 K could be accommodated (Sule and van Breugel, 2004).…”

“…It has been shown that controlling the temperature is an effective way to prevent or reduce the risk of crack formation in concrete. Under slow cooling conditions, concrete can undergo a 20 K drop in temperature without cracking (Neville, 2011;Shi et al, 2014;Bobko et al, 2015). Early-age cracking occurs when the tensile strain that arises either from restrained thermal contractions or temperature differentials within a concrete section exceeds the actual tensile strain capacity of the concrete (Bamforth, 2007;Carino and Clifton, 1995;Mihashi and Leite, 2004).…”