基于低场核磁共振技术水泥砂浆反复高温热损伤的研究

摘要/Abstract

摘要： 为了研究水泥砂浆反复经历高温及局部水冷作用后的损伤演化特征,将水泥砂浆试件中部进行钻孔,将试件加热到400 ℃并且向孔洞注水冷却至室温,重复操作。采用低场核磁共振技术、数字声波仪器、数码显微镜分别研究了水泥砂浆试件在高温及局部水冷作用下的损伤行为。结果表明,随着高温及局部冷却次数增多,试件小孔孔径及数量不断增大,而大孔孔径则减小,试件在经过第一次处理后其性能劣化最明显,且局部注水冷却使得孔洞周围的损伤大于其他部位。同时,随着高温及局部冷却次数增多,概率密度峰值所对应的灰度值增大并向右移动。另外,高温弱化了胶凝材料与砂粒的胶结能力,反复高温处理使得水泥浆与砂粒之间的胶结能力进一步削弱,试件的波速减小,但孔洞中注水冷却产生的温度应力使得胶凝材料与砂粒的胶结能力急剧下降,温度骤降产生的温度应力对胶凝材料与砂粒间的胶结能力的影响远大于反复高温处理。

关键词: 水泥砂浆, 低场核磁共振, 核磁共振成像, 反复高温, 局部水冷, 损伤, 灰度值, 波速

Abstract: In order to study the damage evolution characteristics of cement mortar subjected to repeated high temperature and local water cooling, the central part of the cement mortar specimen was drilled. After heating the specimens to 400 ℃, water was poured into the hole for cooling, and then the operation was repeated continuously. Low field nuclear magnetic resonance technology, digital acoustic instrument and digital microscope were used to study the damage behavior of cement mortar specimens under repeated 400 ℃ and local water cooling. The results show that with the increase of high temperature treatment and local cooling times, the pore size and content of the small hole of the specimen increase continuously, while the pore size of the large hole decreases. After the first treatment, the performance degradation of the specimen is the most obvious, and the damage around the hole is greater than other parts due to local water injection cooling. Meanwhile, with the increase of high temperature treatment and local cooling times, the gray value corresponding to the peak probability density increases and moves to the right. In addition, the heat treatment weakens the cementing ability of cement mortar and sand particles. Repeated high temperature treatment further weakens the cementing ability of cement mortar and sand particles, and the wave velocity of specimen is reduced. However, the temperature stress generated by water injection cooling in the hole causes a sharp decline in the cementing ability. The effect of temperature stress caused by sudden drop of temperature on cementing ability of cement mortar and sand is much greater than that of repeated high treatment.

Key words: cement mortar, low field nuclear magnetic resonance, nuclear magnetic resonance imaging, repeated high temperature, local water cooling, damage, gray value, wave velocity

中图分类号:

TQ172

唐进才, 宁麟, 张增, 王皋, 唐俊林. 基于低场核磁共振技术水泥砂浆反复高温热损伤的研究[J]. 硅酸盐通报, 2022, 41(10): 3403-3412.

TANG Jincai, NING Lin, ZHANG Zeng, WANG Gao, TANG Junlin. Repeated High Temperature Thermal Damage of Cement Mortar Based on Low Field Nuclear Magnetic Resonance Technology[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2022, 41(10): 3403-3412.

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