轻骨料对砂浆力学与毛细吸水性能的影响

摘要/Abstract

摘要： 采用等体积取代法制备了5种不同体积取代率的轻骨料水泥砂浆,借助抗压、抗折试验和称重法,研究了内掺轻骨料对水泥砂浆力学和毛细吸水性能的影响规律,并基于低场核磁共振技术和扫描电镜技术分析了内掺轻骨料砂浆微观结构特征。结果表明:内掺力学强度较低的轻骨料可对水泥砂浆整体力学性能产生影响,随着轻骨料取代率的增加,砂浆抗压、抗折强度相应降低;毛细吸水率随轻骨料取代率、养护龄期的增加而降低。核磁共振试验数据表明:小孔孔隙体积占比随着轻骨料取代率的增多而降低,中孔和大孔孔隙体积占比则与取代率呈正相关;随着龄期的增长,小孔信号弛豫幅值降低。利用扫描电镜对轻骨料砂浆界面过渡区观察,发现轻骨料砂浆界面区结构较致密。同时,由于水化产物堵塞轻骨料表面微孔,形成不透水边界和内部封闭孔,在毛细吸水过程中内掺轻骨料砂浆表现出高孔隙度低渗透性的特征。

关键词: 轻骨料, 低场核磁共振, 抗压强度, 毛细吸水, 孔隙结构

Abstract: Five kinds of lightweight aggregate (LWA) cement mortars with different volume replacement ratios were prepared by the equal volume replacement method. The influence of LWA on the mechanical properties and capillary water absorption of cement mortar was tested using compressive, flexural strength test and weighing method. Based on the low-field nuclear magnetic resonance (LF-NMR) and scanning electron microscopy (SEM), the microstructure characteristics of LWA were analyzed. The results show that the weak mechanical strength of LWA affects the overall mechanical properties of cement mortar. As the replacement ratio of LWA increases, the compressive strength of the mortar decreases correspondingly. The capillary water absorption decreases with the increase of the replacement ratio and the age of LWA mortar. LF-NMR test data shows that the volume fraction of small pores decreases with the increase in the replacement ratio of LWA, and the volume fraction of medium and large pores is positively correlated with the replacement ratio. As the age increases, the amplitude of the signal amplitude representing the small pores decreases. The analysis of the interface transition zone (ITZ) of LWA mortar with SEM images indicates that the structure of the LWA mortar ITZ is relatively dense. At the same time, because the hydration product blockes the microporous surface of LWA, the impermeable boundary and internal closed pores are formed. The mortar mixed with LWA exhibits the characteristics of high porosity and low permeability during the capillary water absorption process.

Key words: lightweight aggregate, low-field nuclear magnetic resonance, compressive strength, capillary water absorption, pore structure

中图分类号:

TU528

李春云, 薛善彬, 张鹏, 王俊洁, 高世壮. 轻骨料对砂浆力学与毛细吸水性能的影响[J]. 硅酸盐通报, 2022, 41(1): 41-50.

LI Chunyun, XUE Shanbin, ZHANG Peng, WANG Junjie, GAO Shizhuang. Influence of Lightweight Aggregate on Mechanical and Capillary Water Absorption Properties of Mortar[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(1): 41-50.

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