基于楔入劈拉法的湿态混凝土双K断裂特性试验研究

摘要/Abstract

摘要： 采用楔入劈拉法,针对浸泡在自由水环境中0 h、2 h、5 h、24 h、120 h的3种强度等级(C20、C30、C40)混凝土开展含水率及双K断裂力学特性变化规律研究,为服役于水环境下的混凝土结构安全度评估提供支撑。研究表明:混凝土强度等级越高,吸水速度越慢,含水率越低,达到饱和状态所需浸泡时间越长;混凝土起裂断裂韧度与失稳断裂韧度均随含水率的增大呈近似线性降低。C20、C30、C40混凝土饱和状态的起裂断裂韧度较干燥状态分别降低了29.6%、23.2%、33.4%,失稳断裂韧度较干燥状态分别降低了22.7%、23.9%、33.8%。相同含水率条件下,混凝土起裂断裂韧度与失稳断裂韧度降低幅度基本相似。P-CMOD曲线均明显存在线弹性未起裂阶段、稳定扩展阶段、失稳扩展阶段。随含水率增大,线弹性及稳定扩展阶段斜率均逐渐降低,失稳扩展阶段下降趋势越来越平缓。临界裂缝口张开位移随含水率增大而逐渐降低,混凝土变形能力降低,韧性逐渐减弱。

关键词: 混凝土, 含水率, 楔入劈拉法, 双K断裂特性, 起裂断裂韧度, 失稳断裂韧度

Abstract: Using wedge-splitting method, the changes of moisture content and double K fracture mechanical properties of three strength grades (C20, C30 and C40) concrete immersed in free water environment for 0 h, 2 h, 5 h, 24 h and 120 h were studied, so as to provide support for the safety evaluation of concrete structure in water environment. The results show that the higher the concrete strength grade is, the slower the water absorption rate is, the lower the moisture content is, and the longer soaking time it takes to reach saturation state. The initial cracking fracture toughness and unstable fracture toughness of concrete decrease linearly with the increase of moisture content. The initial cracking fracture toughness of C20, C30 and C40 concrete in saturated state is 29.6%, 23.2% and 33.4% lower than that in dry state, and the unstable fracture toughness of C20, C30 and C40 concrete in saturated state is 22.7%, 23.9% and 33.8% lower than that in dry state, respectively. Under the same moisture content, the initial cracking fracture toughness and unstable fracture toughness of C20, C30 and C40 concrete decrease similar basically. The P-CMOD curves obviously have a linear elastic non-crack initial stage, a stable expansion stage and an unstable expansion stage. With the increase of moisture content, the slope of linear elastic stage and stable expansion stage gradually decreases, and the curve of unstable expansion stage drops more and more gently. The critical crack opening displacement decreases gradually with the increase of moisture content, the deformation capacity and toughness of concrete decrease gradually.

Key words: concrete, moisture content, wedge-splitting method, double K fracture characteristic, initial cracking fracture toughness, unstable fracture toughness

中图分类号:

TU528

楼建敏, 张国辉, 杨振东, 孙俊崇, 李虎. 基于楔入劈拉法的湿态混凝土双K断裂特性试验研究[J]. 硅酸盐通报, 2022, 41(9): 3107-3114.

LOU Jianmin, ZHANG Guohui, YANG Zhendong, SUN Junchong, LI Hu. Experimental Study on Double K Fracture Characteristics of Wet Concrete Based on Wedge-Splitting Method[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(9): 3107-3114.

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