超高性能轻质混凝土的力学性能及微观结构

The mechanical property and microstructure of ultra-high performance lightweight concrete

摘要:

超高性能轻质混凝土（ultra-high performance lightweight concrete ,UHPLC）是一种由高强水泥浆体、漂珠和纤维组成的密度低于1 950 kg/m³的新型水泥基结构材料。本文研究了不同养护制度及养护龄期对UHPLC抗压强度、轴拉力学性能和弯曲性能的影响,最后利用扫描电镜观察了UHPLC中漂珠的微观形貌。结果表明:随着龄期增长,UHPLC的抗压强度、轴拉性能和弯曲性能均提高,并出现明显的应变强化现象,说明养护龄期对UHPLC基体强度和纤维-UHPLC基体的界面黏结强度均有显著提高作用；高温蒸汽养护3 d可促进UHPLC基体早期强度发展,使UHPLC的抗压强度和弯曲性能迅速达到标准养护28 d时的水平,显著缩短养护龄期,但对纤维-基体界面黏结强度的贡献不大,黏结强度仍主要受龄期影响；UHPLC实测密度为1 815.2 kg/m³,0 mm立方体抗压强度达103.1 MPa,极限抗拉强度达7.60 MPa,极限拉应变达0.431%,出现明显的应变强化现象,弯曲峰值强度达22.43 MPa,满足了RPC160的抗折强度要求,实现了水泥基结构材料轻质高强的目标。

Abstract:

Ultra-high performance lightweight concrete (UHPLC) is a new type of cement-based structural material with a density of less than 1 950 kg/m³ and is composed of high-strength cement paste,cenospheres, and fibers.This study investigated the effects of different curing systems and curing ages on the mechanical properties of UHPLC, which includes compressive strength, tensile performance, and flexural performance.Besides, the microscopic morphology of the cenospheres was also observed by scanning electron microscopy (SEM).Results show that, the compressive strength, tensile strength and bending peak strength increased obviously as the curing age increased, and UHPLC exhibited strain-hardening behavior.It indicates that curing age has a significant effect on the strength of UHPLC matrix and the interfacial bond strength between fiber and UHPLC matrix.High-temperature steam curing for 3 days, which can make the compressive strength and bending properties of the UHPLC matrix to the level of standard of curing for 28 days,can promote early strength development and shorten the curing age. However, it contributed less to the bond strength, which is still mainly affected by age.The actual density of UHPLC was 1 815.2 kg/m³ and its cubic compressive strength reached 103.1 MPa. During direct tensile test, its ultimate tensile strength and ultimate tensile strain was 7.60 MPa and 0.431% respectively, and it exhibited strain-hardening behavior. Moreover, its bending strength reached 22.43 MPa, meeting the strength demand of RPC160.The required lightweight and high-strength cement based structural materials has been achieved.