粗骨料对超高性能混凝土力学性能的影响及拟合分析

Effect of Coarse Aggregate on Mechanical Properties of Ultra-high Performance Concrete and Fitting Analysis

为探明粗骨料对超高性能混凝土(UHPC)力学性能的作用规律,分别采用河砂,河砂与4.75~9.5mm碎石配制了两个系列不同粒径骨料的UHPC,试验研究了骨胶比(骨料与胶凝材料质量比,A/B)在0.6~1.2范围与石砂比(碎石与河砂的质量比,CS/RS)在1/4~1范围对UHPC工作性能与力学性能的影响。研究结果表明:骨胶比的增加与等骨胶比时石砂比的增大均会使UHPC的扩展度减小。随骨胶比增大,UHPC的抗压强度与抗弯拉强度均呈先增后减的趋势,弹性模量则呈线性增长趋势;当石砂比为1/2时,碎石对抗压强度与轴心抗压强度的增强效应最显著,石砂比越大,UHPC弹性模量增长幅度越高。当骨胶比≤0.9、石砂比≤1/2时,碎石的骨架增强正效应高于碎石因阻隔钢纤维的均匀分布而降低钢纤维增强增韧效率的负效应,有助于提高UHPC的抗弯拉强度。

To find out the effect of coarse aggregate on the mechanical properties of ultra-high performance concrete(UHPC),two series of UHPC with different particle size aggregates were prepared by using two aggregate systems(river sand,river sand and crushed stone with the particle size from 4.75 to 9.5 mm).The effects of A/B(weight ratio of aggregate to binder)ranging from 0.6 to 1.2 and CS/RS(weight ratio of crushed stone to river sand)ranging from 1/4 to 1 on the workability and mechanical properties of UHPC were studied.The results show that both the increase of A/B and the increase of CS/RS at the same A/B reduce the slump flow of UHPC.With the increase of the A/B,the compressive strength and bending strength of UHPC increase first and then decrease,and the elastic modulus shows a linear growth trend.W hen the CS/RS is 1/2,the reinforcement effect of crushed stone to compressive strength and axial compressive strength is most significant.The larger the CS/RS,the higher the UHPC elastic modulus increases.When the A/Bis not more than0.9 and the CS/RS is not more than 1/2,the positive effect of the skeleton reinforcement deriving from the crushed stone is higher than its negative effect on reducing the reinforcing and toughening efficiency of the steel fiber,and it helps to improve the bending strength of UHPC.