高温作用对大掺量粉煤灰混凝土力学性能影响

研究了高温作用对大掺量粉煤灰混凝土(HFCC)立方体力学性能的影响,探讨了不同加热温度、不同粉煤灰掺量与HFCC残余强度的关系.将粉煤灰掺量30%、40%和50%的混凝土立方体试块加热至250,450,550和650℃进行强度测试,并与素混凝土(不掺粉煤灰)试块进行对比.研究结果表明,随着温度升高,HFCC残余抗压、劈裂抗拉强度均出现明显退化,劈裂抗拉强度退化尤为明显;随着粉煤灰的掺入,粉煤灰掺量对强度退化率的影响具有复杂性:高温后HFCC抗压强度退化率均低于普通混凝土强度退化率;劈裂抗拉强度退化率除粉煤灰掺量30%外均低于普通混凝土退化率.在试验基础上建立HFCC高温后立方体残余抗压强度、残余劈裂抗拉强度与温度、粉煤灰掺量的定量关系,为高温后HFCC材料强度评估及修复提供依据.

Effects of elevated temperatures on the mechanical properties of high fly ash content concrete

In this paper,the effects of elevated temperatures on the mechanical properties of high fly ash content concrete(HFCC) are presented.The specimens were prepared with three different replacements of cement by fly ash 30%,40% and 50% and were tested after exposure to elevated temperature 250,450,550 and 650℃ respectively,compared with plain Portland concrete.The results showed that as the elevated temperature increases,the residual compressive strength and the residual tensile strength both apparently decrease and the deterioration of tensile strength was much quicker than the deterioration in compressive strength.The results also showed the influence of fly ash replacement on the degraded ratio of strength is complicated.After an exposure to the elevated temperatures,the degraded ratio of compressive strength is less than plain ordinary Portland concrete(PC) and one of tensile strength,except 30% fly ash replacement,remains the same.Based on the experiments,the alternating simulation formula for determining the relationship between residual strength ratio,elevated temperature and fly ash,the replacement is developed by using regression of results,which provide the theoretical basis for the evaluation and repair of HFCC after elevated temperature.