持续荷载作用对粉煤灰混凝土冻融性能的影响

在不施加和施加持续荷载条件下,进行不掺和掺20%,40%粉煤灰的混凝土冻融试验,研究持续荷载作用对粉煤灰混凝土抗冻性能的影响。试验结果表明:与不施加持续荷载试件对比,施加持续荷载作用后粉煤灰混凝土的抗冻性能降低;粉煤灰掺量存在一临界值,对于C40混凝土,该临界值在20%～40%之间,低于该临界值,粉煤灰混凝土的抗冻性能随着粉煤灰掺量的增大而提高,超过该临界值,粉煤灰混凝土的抗冻性能随着粉煤灰掺量的增大而降低,且持续荷载作用会使该临界值变小;混凝土的抗冻性能存在陡劣点,持续荷载作用会使该陡劣点提前出现。根据试验结果,以陡劣点为阶段分界点,采用回归方法给出能够考虑粉煤灰掺量的混凝土冻融损伤两阶段模型。

Influence of Sustainable Loading on the Freezing and Thawing Performance of Fly Ash Concrete

The influence of sustainable loading on the frost resistance of fly ash concrete was investigated by freezing and thawing tests of concrete with fly ash contents of 0%,20% and 40% respectively under both non-loading and sustainable loading conditions.Results show that sustainable loading will decrease the frost resistance of fly ash concrete,compared with the test specimen non-loading condition.There is a critical value in fly ash content.For C40 concrete,the critical value is between 20% and 40%.When fly ash content is lower than the critical value,the frost resistance of fly ash concrete will increase with the increase of fly ash content.When fly ash content is greater than the critical value,the frost resistance of fly ash concrete will decrease with the increase of fly ash content.The sustainable loading will diminish the critical value.Additionally,there is sharp degradation point in the frost resistance of concrete,and the sustainable loading induces the sharp degradation point appearing in advance.According to test results and taking the sharp degradation point as cut-off point,a two-phase model for predicting the freezing and thawing damage of fly ash concrete considering fly ash content is proposed by adopting regression method.