细集料对超高性能混凝土的性能影响

为探寻出一种低成本、可替代石英砂的细集料来制备超高性能混凝土(UHPC),研究了不同种类、级配的细集料对超高性能混凝土的工作性能、力学性能和收缩性能影响规律,通过XRD、SEM等测试方法对其微结构进行分析。研究结果表明:在相同胶凝材料体系、水胶比、钢纤维掺量、标准养护条件下,河砂制备的UHPC的流动性略低于石英砂制备的UHPC;河砂制备的UHPC与石英砂制备的UHPC的抗压/抗折强度均可达140 MPa/20 MPa以上;粒径小于1. 18 mm河砂制备的UHPC的收缩率最低,可至600×10^-6。分析XRD、SEM等表征结果发现石英砂和河砂制备的UHPC中砂与胶凝浆体连接更紧密,而机制砂制备的UHPC中界面较为明显。粒径小于1. 18 mm河砂制备的UHPC的流动性、力学性能和收缩率综合最佳,并且河砂的价格较低,可降低UHPC的成本,良好的替代传统UHPC中的石英砂。

Effect of Fine Aggregate on Performance of Ultra High Performance Concrete

To develop a UHPC with a low-cost fine aggregate replacing quartz sand,the effect of different types and gradations of fine aggregates on the working performance,mechanical properties and shrinkage properties of ultra-high performance concrete were studied.And its microstructures were investigated by XRD,SEM,and other test methods.The results show:in the same cementitious material composition,water-cement ratio,steel fiber content,and standard curing conditions,flowability of UHPC prepared from river sand is slightly lower than UHPC prepared from quartz sand.Pressure/flexural strength of UHPC made from river sand and quartz sand can reach 140 MPa/20 MPa.UHPC with river sand particle size of less than 1.18 mm has the lowest shrinkage,up to 600×10^-6.Analysis of XRD,SEM,and other test results show that sand and cement paste are combined more closely in UHPC prepared from quartz sand and river sand.The interface between UHPC prepared by machine-made sand is more obvious.The UHPC with a particle size of less than 1.18 mm has the best flowability,mechanical properties and shrinkage properties.And the low price of river sand can reduce cost of UHPC,and it is a good alternative to quartz sand in traditional UHPC.