The Influence of Aspect Ratio of Steel Fibers on the Conductive and Mechanical Properties of Compound Cement Reactive Powder Concrete

The performance of steel fibers reinforced RPC has a great relationship with the aspect ratio of the fibers. It is necessary to systematically study the relationship between the aspect ratio and the mechanical properties of RPC and the force-electricity response. In this paper, the flexural strength, the compressive strength and the flexural toughness and AC electrical resistance and AC impedance spectroscopy of reactive powder concrete are investigated. The flexural strength, compressive strength, and flexural toughness with the curing age of 1 day and 28 days are tested. The cement is the compound cement in this study, and the mass ratio of ordinary portland cement and sulphoaluminate cement is 1:1, and two kinds of steel fibers with aspect ratios of 30(AR-30) and 75(AR-75) are used. The fiber content is 2% of the concrete volume. Scanning electron microscope (SEM) and scanning electron microscope energy spectrum analysis (EDS) are investigated to analyze the composition of the hydration products. It can be obtained from the research results that the flexural strength and the compressive strength of reactive powder concrete decrease with the increase of steel fibers content with an aspect ratio of 30. The decreasing rates of the flexural strength and the compressive strength with the curing age of 1 d and 28 d are 14.93%similar to 83.26% and 0.40%similar to 46.36% with the incorporation of steel fibers with an aspect ratio of 30. The flexural toughness decreases in the form of a quadratic function with the mass ratio of steel fibers with an aspect ratio of 30. The electrical resistance of reactive powder concrete increases with the increase of steel fibers with an aspect ratio of 30. The maximum decreasing rate of electrical conductivity is 91.16%. The AC impedance spectrum is obtained, and the electric circuit of reactive powder concrete accords with the series conduction model, which parallel electrical resistance and capacitance of pore solution, rapid strength RPC and steel fibers respectively connect with a contact resistance of the electrode and specimens. It is found that the steel fibers network with an aspect ratio of 75 is closer by studying the equivalent circuit diagram.