钢纤维混凝土抗冲击性能及其阻裂增韧机理

摘要

采用自制落锤冲击试验装置,以韧性系数和延性比来评价钢纤维混凝土(SFRC)的韧性,研究了钢纤维对混凝土抗冲击性能的影响.以纤维分散系数表征钢纤维分布的均匀程度,对冲击面裂缝进行观测,并对冲击断面纤维分布进行了统计计算,分析了冲击荷载作用下钢纤维混凝土的阻裂效应及增韧机理.结果表明:钢纤维的掺入可显著提高混凝土的抗冲击性能;在钢纤维掺量(体积分数,下同)为0.8％时,钢纤维混凝土的延性比超过15％,其韧性系数随钢纤维掺量的提高而增大,在钢纤维掺量为1.0％时达到最大值,接近基准混凝土的10倍;钢纤维的掺入降低了基体脆性,改善了其塑性特征,从而延缓了钢纤维混凝土的裂缝开展,并改善了其主裂缝形状、减少了裂缝条数;钢纤维混凝土的抗冲击韧性与钢纤维掺量及其在冲击断面上的分布均匀程度密切相关.%Using self-made drop hammer impact test device,the effect of steel fiber on the impact resistance of concrete was investigated by analyzing the toughness and ductility ratio.The uniformity of the distribution of steel fiber was characterized by fiber dispersion coefficient.Besides,the fractures of the impact surface were observed and the fiber distribution of the impact section was calculated to analyze the toughening mechanism and crack impact resistance properties of steel fiber reinforced concrete.Results show that the addition of steel fiber could increase the impact performance effectively.The ductility ratio is more than 15％ when the steel fiber content(by volume) is 0.8％.The toughness coefficient increases with the increase of the fiber volume fraction.When the steel fiber content is 1.0％,the toughness reaches the maximum value,which is close to 10 times of the standard concrete.The addition of steel fiber could decrease the brittleness of the matrix and improve its plasticity,which delays the crack development,and changes the shape and the number of main cracks as well.Both of the amount of steel fiber and its distribution on the impact section are closely related to the impact toughness of concrete.