盐侵冻融循环下聚乙烯醇纤维混凝土孔结构分形特征

Pore Structure Fractal Characteristics of PVA Fiber Concrete under Salt Erosion and Freeze-Thaw Cycle

为研究聚乙烯醇(PVA)纤维对混凝土孔结构的影响及其与抗冻性能的联系,本文通过核磁共振技术对冻融循环作用下PVA纤维混凝土的微观孔结构进行了测试,分析了核磁共振T2谱和孔隙分布变化规律,并基于分形理论探究了其孔隙分形特征,揭示了冻融循环作用下PVA纤维混凝土孔结构与分形维数之间的关系。结果表明,PVA纤维混凝土在冻融循环前期表现出较好的抗冻性能;中孔(100 nm<r≤1000 nm)和大孔(r>1000 nm)的数量及占比增加,削弱了PVA纤维混凝土的抗冻性能;PVA纤维混凝土具有一定的分形特征,分形维数D_(max)在5次冻融循环前增大,而后随着冻融循环次数增加不断减小。

To study the effect of polyvinyl alcohol(PVA)fibers on pore structure of concrete and its connection with frost resistance performance,the microscopic pore structure of PVA fiber concrete under the action of freeze-thaw cycle was tested by nuclear magnetic resonance(NMR)technology,the NMR T2 spectrum and the change rule of pore distribution were analysized,and the pore fractal characteristics were explored based on fractal theory to reveal the relationship between the pore structure of PVA fiber concrete under the action of freeze-thaw cycle and fractal dimension.The relationship between pore structure and fractal dimension of PVA fiber concrete under the freeze-thaw cycle was revealed.The results show that PVA fiber concrete shows better frost resistance in the pre-freeze-thaw cycle period.The number and percentage of medium pores(100<r≤1000 nm)and large pores(r>1000 nm)increase,which weaken the frost resistance of PVA fiber concrete.The PVA fiber concrete has a certain fractal characteristic,and the fractal dimension D_(max) increases before five times freeze-thaw cycles and decreases with the increase of freeze-thaw cycles times.