冲击荷载下高强混凝土动力特性及破碎特征研究

Dynamic characteristics and crushing features of high-strength concrete under impact load

为探究粉煤灰替代率和细集料类型对高强混凝土冲击压缩性能的影响,以粉煤灰替代水泥比例为0、10%、15%、20%、25%为胶凝材料,玄武岩机制砂和天然砂为细集料配制C80高强混凝土,利用分离式霍普金森杆对其开展冲击压缩试验,计算破碎体分形维数量化混凝土破碎特征,并借助扫描电镜(SEM)分析混凝土微观形貌。结果表明:机制砂混凝土(MSC)的峰值应力和韧性均高于天然砂混凝土(NSC);随着粉煤灰替代率增加,混凝土峰值应变逐渐降低;当粉煤灰替代率10%时,混凝土的峰值应力和韧性均达到最高值,且破碎体分形维数最小、平均块径最大、综合表现的破碎特征最简单;与未掺粉煤灰组混凝土相比,粉煤灰替代率10%时混凝土的微观形貌致密,孔隙数量减少,整体密实度提升。

Here,to investigate effects of fly ash replacement rate and fine aggregate type on impact compression performance of high-strength concrete,C80 high-strength concrete was prepared by using fly ash to replace cement with proportions of 0,10%,15%,20%and 25%,respectively as cementitious material,and using basalt mechanism sand and natural sand as fine aggregates.Impact compression tests were conducted for C80 high-strength concrete using a split Hopkinson pressure bar(SHPB),and fractal dimension of broken body was calculated to quantify concrete crushing features.The scanning electron microscopy(SEM)was used to analyze micro-morphology of concrete.The results showed that peak stress and toughness of mechanism sand concrete(MSC)are higher than those of natural sand concrete(NSC);with increase in fly ash replacement rate,peak strain of concrete gradually decreases;when fly ash replacement rate is 10%,peak stress and toughness of concrete reach their highest values and fractal dimension of broken body is the smallest,average block size is the largest and comprehensive crushing features are the simplest;compared to concrete without fly ash,when fly ash replacement rate is 10%,concrete micro morphology is dense,number of pores decreases,and the overall compactness is improved.