盐侵冻融循环下聚乙烯醇纤维混凝土孔结构分形特征OA北大核心CSTPCD

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≤1 000 nm)and large pores(r＞1 000 nm)increase,which weaken the frost resistance of PVA fiber concrete.The PVA fiber concrete has a certain fractal characteristic,and the fractal dimension Dmax increases before five times freeze-thaw cycles and decreases with the increase of freeze-thaw cycles times.