Creep Behavior of High-Strength Concrete Subjected to Elevated Temperatures

Abstract

Strain is generated in concrete subjected to elevated temperatures owing to the influence of factors such as thermal expansion and design load. Such strains resulting from elevated temperatures and load can significantly influence the stability of a structure during and after a fire. In addition, the lower the water-to-binder (W–B) ratio and the smaller the quantity of aggregates in high-strength concrete, the more likely it is for unstable strain to occur. Hence, in this study, the compressive strength, elastic modulus, and creep behavior were evaluated at target temperatures of 100, 200, 300, 500, and 800 °C for high-strength concretes with W–B ratios of 30%, 26%, and 23%. The loading conditions were set as non-loading and 0.33fcu. It was found that as the compressive strength of the concrete increased, the mechanical characteristics deteriorated and transient creep increased. Furthermore, when the point at which creep strain occurred at elevated temperatures after the occurrence of transient creep was considered, greater shrinkage strain occurred as the compressive strength of the concrete increased. At a heating temperature of 800 °C, the 80 and 100 MPa test specimens showed creep failure within a shrinkage strain range similar to the strain at the maximum load.

Investigation of the Residual Mechanical and Porosity Properties of Cement Mortar under Axial Stress during Heating

“…Under the unstressed conditions, due to the dehydration of the ettringite and the loss of physically bound water, there was a slight increase of porosity after the mortar was heated at 200 °C [ 7 , 30 ]. However, when heated at 400 °C and the temperature after that temperature, the porosity of mortar increases significantly.…”

“…Many factors lead to the decrease of compressive strength as concrete exposure to high temperature [ 7 ]. As we have known, the thermal expansion of cement paste and aggregate were different.…”

“…Many researchers have conducted experiments on the compressive strength of concrete [ 4 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. The investigations indicate that temperature has a great influence on the compressive strength of concrete, and the compressive strength decreases with the increase of temperature.…”

“…The same conclusion was reached by Tao et al [ 25 ], when a preload at a pre-stress ratio of 0.2 was applied on self-compacting concrete cylinder specimens. Kim et al did a series of experiments on the stressed concrete [ 7 , 16 , 26 ], and carried out experiments on the compressive strengths of light-weight and normal concrete at high temperature at different pre-stress ratios [ 16 ]. The results showed that the light weight concrete had a higher compressive strength, and Kim suggested that the stress applied to the concrete during heating should be controlled at less than 40% of the concrete strength at room temperature.…”

Investigation of the Impacts of Thermal Shock on Carbon Composite Materials

“…Research has shown that thermal shock damage can have serious adverse effects on the static performance parameters of granite [8,9]. It was proved that high-strength concrete would begin to crack when suffering from a temperature step frequently changing from 18 to 20 °C [10,11]. It was suggested that the different thermal expansion coefficients of the material components would lead to intergranular compression and tensile force, which might result in a specific microcrack network [12,13,14,15,16,17,18,19,20,21].…”