不同粗骨料粒径混凝土动态压缩强度的离散性研究

Study on the discreteness of dynamic compressive strength of concrete with different coarse aggregate particle size

为了研究粗骨料粒径差异引起的动态压缩试验离散性问题,制备了最大粒径分别为8 mm、14 mm和26 mm的混凝土与砂浆试件,通过动静态压缩试验,得到不同应变率下各试样的应力-应变曲线和应变率-动态增长因子曲线。为了更直观地分析由粗骨料粒径差异引起的试验离散性问题,定义粒径系数λ为粗骨料最大粒径d与试件直径D之比,引入变异系数CV,运用数理统计方法量化离散性,得到λ与CV关系图,直观反映试验离散性与粗骨料粒径关系。分析表明:λ=0.34为混凝土材料异质性临界点;当粒径系数λ<0.34时,混凝土材料异质性影响不明显;当λ>0.34时,粗骨料的粒径过大已经影响到了混凝土的动态响应,材料异质性明显增强。该结论的得出对今后工程与试验中粗骨料粒径的选取有指导意义。

In order to study the discreteness problem of dynamic compression test caused by the difference of coarse aggregate particle size,concrete and mortar specimens with the largest particle size of 8 mm,14 mm and 26 mm are prepared,and the stress-strain curves and strain rate-dynamic increase factor(DIF)curves of each sample under different strain rates are obtained through dynamic and static compression tests.In order to more intuitively analyze the problem of test discreteness caused by the difference in coarse aggregate particle size,the particle size coefficientλis defined as the ratio of the maximum particle size of the coarse aggregate d to the diameter of the specimen D,and the coefficient of variation CV is introduced.Using mathematical statistical methods to quantify the discreteness,obtain the relationship betweenλand CV,and intuitively reflect the relationship between the discreteness and the coarse aggregate particle size.The analysis shows that,λ=0.34 is the critial point of concrete material heterogeneity.When the particle size coefficientλ<0.34,the effect of concrete material heterogeneity is not obvious.Whenλ>0.34,the excessively large coarse aggregate particle size has affected the dynamic response of concrete,and the material heterogeneity is obviously enhanced.This conclusion has guiding significance for the selection of coarse aggregate particle size in future engineering and experiments.