基于核磁共振技术的硫酸盐侵蚀下混凝土孔隙率发展规律分析

针对不同浓度硫酸盐侵蚀下混凝土损伤过程中孔结构退化规律问题,对混凝土进行不同质量分数硫酸盐的冻融循环试验。采用核磁共振技术对混凝土损伤过程中的孔结构变化以及试验过程中的质量和相对动弹性模量变化进行分析。结果表明:不同质量分数硫酸盐侵蚀下T₂谱中第一峰变化明显,且同时期随着硫酸盐质量分数的增加,T₂谱第一峰变化幅度增大;盐冻环境下T₂谱第一峰面积与冻融循环次数之间符合指数关系,水冻环境下T₂谱第一峰面积与冻融循环次数之间符合线性关系;微小孔隙率发展与冻融循环次数之间符合线性关系;孔隙率与冻融循环次数、硫酸盐质量分数之间符合显著的线性关系;混凝土的质量和相对动弹性模量损失随着硫酸盐质量分数的增加而增加。

Porosity development analysis of concrete under sulfate attack based on nuclear magnetic resonance

To determine the degradation pattern of pore structures during concrete damage under different sulfate mass fraction, the freeze-thaw cycle test of concrete under different sulfate mass fraction is performed herein. Using nuclear magnetic resonance technology, the change in porosity during concrete damage is analyzed, in addition to the mass loss and relative dynamic elastic modulus change. The results show that the first peak of T₂ spectrum changes significantly under different sulfate mass fraction. In the same period of the freeze-thaw cycle, the change range of the T₂ spectrum first peak increases with increase in the sulfate mass fraction. An exponential relation exists between the first peak area of T₂ spectrum and the number of freeze-thaw cycles in the salt-freezing environment, and a linear relation exists in the water-freezing environment. There is a linear relation between the development of microporosity and the number of freeze-thaw cycles. There is a significant linear relationship between the porosity and the number of freeze-thaw cycles and sulfate mass fraction. The mass loss and the relative dynamic elastic modulus loss in the salt-freezing environment increase with increase in the sulfate mass fraction.