The Influence of NaCl Internal and External Erosion on the Properties of Steel Scoria Reactive Powder Concrete

This paper the flexural and compressive strengths of the reactive powder concrete (RPC) with steel scoria and quartz sand containing NaCl are investigated. Moreover, the RPC’s mass, the chloride ion permeability and the carbonation depth (Dc) are determined. The mass ratios of steel scoria and the NaCl are 0%~20% and 0%~0.25% by mass of binder materials and the quartz sand respectively. The RPC specimens are exposed to the NaCl erosion environment. The scanning electron microscope-energy dispersive spectrometer (SEM-EDS) and X-ray diffraction (XRD) spectrum are acquired for analyzing the mechanism of RPC’s performance. Results show that the flexural strength, the compressive strengths, the mass and the dynamic modulus of elasticity (RDME) of RPC decrease in the form of cubic function with the mass ratio of NaCl. When the mass ratio of steel scoria is 10%, the mechanical strengths and the RDME are the highest. The RPC’s flexural strength, the compressive strength and the RDME decrease by rates of 4.94%~42.28%, 5.11%~48.65% and 8.72%~226.1% after NaCl erosion. Meanwhile, the corresponding mass loss rate, the chloride ion permeability, the Dc are increased by rates of 1.32%~27.63%. RPC with 10% steel scoria shows the lowest performance degradation. The SEM-EDS results show that the pores and cracks inner RPC and the Cl and Ca elements are increased by the NaCl. The Fe and Ca elements are increased by the added steel scoria. The addition of steel scoria exhibit decreasing effect and the added NaCl shows increasing effect on the Ca (OH)2 crystals respectively.