干湿循环作用下混凝土力学性能及微观结构研究

硅酸盐通报 ›› 2021, Vol. 40 ›› Issue (9): 2948-2955.

干湿循环作用下混凝土力学性能及微观结构研究

邵化建¹, 李宗利^1,2, 肖帅鹏¹, 姚希望¹, 张宁¹

1.西北农林科技大学水利与建筑工程学院,杨凌 712100;
2.西北农林科技大学旱区农业水土工程教育部重点实验室,杨凌 712100

收稿日期:2021-03-23 修回日期:2021-04-29 出版日期:2021-09-15 发布日期:2021-10-08
通讯作者: 李宗利,博士,教授。E-mail:zongli02@163.com
作者简介:邵化建(1995—),男,硕士研究生。主要从事混凝土材料耐久性方面的研究。E-mail:1027792671@qq.com
基金资助:
“十三五”国家重点研发计划(2017YFC405101-2);国家自然科学基金(51379178)

Mechanical Properties and Microstructure of Concrete under Drying-Wetting Cycles

SHAO Huajian¹, LI Zongli^1,2, XIAO Shuaipeng¹, YAO Xiwang¹, ZHANG Ning¹

1. College of Water Resources and Architectural Engineering, Northwest A&F University, Yangling 712100, China;
2. Key Laboratory of Agricultural Soil and Water Engineering in Arid and Semiarid Areas, Ministry of Education, Northwest A&F University, Yangling 712100, China

Received:2021-03-23 Revised:2021-04-29 Online:2021-09-15 Published:2021-10-08

摘要/Abstract

摘要： 为揭示混凝土在干湿循环作用下的劣化机理,本文对不同强度等级的混凝土进行干湿循环试验,并在试验过程中测定混凝土的抗压强度、劈裂抗拉强度、超声波速、孔隙率等物理量,探究了干湿循环作用对混凝土物理力学性能的影响,并从微观尺度上分析了混凝土强度与孔结构的关系。结果表明:混凝土的强度随干湿循环次数的增加先升高后降低,干湿循环40次后,C20、C30、C40、C50混凝土的相对抗压强度分别下降了13.33%、12.47%、8.45%、6.58%,相对劈裂抗拉强度分别下降了25.93%、23.06%、20.59%、19.03%,相对劈裂抗拉强度较抗压强度衰减更为显著;超声波速和超声波幅表现出不同的变化规律,随着干湿循环次数的增加,超声波速先略有增加而后减小,超声波幅则不断增大;在干湿交替的环境中,混凝土试样的孔隙率、孔隙总体积、平均孔径、中值孔径、最可几孔径随着干湿循环次数的增多,先减小后增大,最终表现出孔径粗化特征,这也是混凝土强度后期损失的内在原因。

关键词: 混凝土, 干湿循环, 强度, 超声波, 微观结构

Abstract: To reveal the deterioration mechanism of concrete under the action of drying-wetting cycles, the drying-wetting cycles tests of different strength grades of concrete was carried out, and the compressive strength, splitting tensile strength, ultrasonic wave velocity, porosity, and other physical quantities of concrete were measured in the test process. The effect of drying-wetting cycles on the physical and mechanical properties of concrete was explored, and the relationship between concrete strength and pore structure was analyzed from the micro-scale. The results show that with the increase of drying-wetting cycles,the strength of concrete increases at the beginning, and then decreases. After 40 drying-wetting cycles, the relative compressive strength of C20, C30, C40 and C50 concrete decreased 13.33%, 12.47%, 8.45% and 6.58% respectively, and the relative splitting tensile strength decreased by 25.93%, 23.06%, 20.59% and 19.03% respectively, the relative splitting tensile strength is more obvious than the compressive strength attenuation. The ultrasonic velocity and ultrasonic amplitude show different variation laws, with the increase of drying-wetting cycles, the ultrasonic velocity increases first and then decreases, while the ultrasonic amplitude increases continuously. In drying-wetting cycle environment, with the increase of drying-wetting cycles, the porosity, total pore volume, average pore diameter, median pore diameter and most probable pore diameter of concrete samples decrease firstly and then increase. Finally, it shows the characteristics of pore coarsening,which is also the internal reason for the later loss of concrete strength.

Key words: concrete, drying-wetting cycle, strength, ultrasonic wave, microstructure

中图分类号:

TU528

邵化建, 李宗利, 肖帅鹏, 姚希望, 张宁. 干湿循环作用下混凝土力学性能及微观结构研究[J]. 硅酸盐通报, 2021, 40(9): 2948-2955.

SHAO Huajian, LI Zongli, XIAO Shuaipeng, YAO Xiwang, ZHANG Ning. Mechanical Properties and Microstructure of Concrete under Drying-Wetting Cycles[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2021, 40(9): 2948-2955.

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