Analysis on the Anti-cracking and Anti-permeability Performance of Polypropylene Fiber-Reinforced Concrete in Subway Retaining Structure

Abstract

In this paper, regarding the problems of subway and tunnel retaining structures such as cracking and seepage, we study the stress, strain and temperature changes of the new polypropylene fiber-reinforced concrete (PFRC) through laboratory test and engineering measurement. The results show that mixing polypropylene crude and fine fiber into concrete can greatly improve the tensile strain and deformation performance of basic concrete. The amount of polypropylene fiber added has something to do with the aggregate composition of the concrete, and polypropylene fiber has little effect on the tensile modulus of the concrete. Compared with the purely crude fiber and fine fiber concrete, the blended fiber-reinforced concrete has the greatest increase in the tensile strength over the basic concrete. The results show that, after crude and fine fiber is added into the ordinary concrete, cracks on the concrete surface are greatly reduced and the width of the cracks is also within the standard, which is in accordance with the intended anti-cracking and anti- permeability target. Concrete is mostly likely to have cracks 1 week after being placed, so the internal temperature of concrete must be strictly controlled.