Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned ...Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles, the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.展开更多
By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanw...By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanwhile, the single sodium sulfate solution attack （SA） was also done as comparison. Micro-observations included the analysis of attack products by thermal analysis method and the determination of sulfate-ion content from surface to interior by chemical titrating method （modified barium sulfate gravimetric method）. Macro-observations mainly included the mechanical behaviors such as compressive strength, splitting strength. The experimental results indicate, in both cases, the main attack product is ettringite, only in the first layer of case SA some gypsum is checked; in case SA, the sulfate ions mainly concentrate in the surface layer, so the attack is relatively mild; but in case TW-SA, the repeated sub-high temperature/cooling by water promotes the sulfate ions diffusing inwards, which leads to obvious strength degradation.展开更多
基金Funded by Outstanding Youth Science Foundation of Henan Province of China (No. 04120002300)
文摘Tests were carried out to study the strength deterioration of concrete cooled in air or by water after sub-high temperature at different level and varying with cycles. It is proved that the cross-shaped cracks turned up and extended little by little on the surface of specimen subjected to repeat sub-high temperature, the splitting failure is characterized by cross-shaped cracks after 30 cycles, the concrete strengths decrease rapidly at early stage and to be steady subsequently with the increase of the temperature cycles, the splitting-tensile strength is more sensitive to temperature cycles than the compressive strength, the decline of concrete strength is mainly controlled by the maximum temperature having reached, the ultrasonic velocity in concrete is also declined. On the basis of test results, the mechanisms of sub-high temperature to the strength deterioration of concrete are analyzed.The formulas for calculating the compressive and splitting-tensile strength of concrete relating to the variation of temperature are proposed.
基金Funded by the National Natural Science Foundation of China(No. 90715041)Outstanding Youth Science Fund of Henan Province(No.04120002300)
文摘By micro- and macro-observations, the deterioration mechanisms of concrete under alternate action between repeated sub-high temperature/cooling by water and sodium sulfate solution attack （TW-SA） were studied; meanwhile, the single sodium sulfate solution attack （SA） was also done as comparison. Micro-observations included the analysis of attack products by thermal analysis method and the determination of sulfate-ion content from surface to interior by chemical titrating method （modified barium sulfate gravimetric method）. Macro-observations mainly included the mechanical behaviors such as compressive strength, splitting strength. The experimental results indicate, in both cases, the main attack product is ettringite, only in the first layer of case SA some gypsum is checked; in case SA, the sulfate ions mainly concentrate in the surface layer, so the attack is relatively mild; but in case TW-SA, the repeated sub-high temperature/cooling by water promotes the sulfate ions diffusing inwards, which leads to obvious strength degradation.
