Effect of multi-walled carbon nanotube on reactive powder concrete (RPC) performance in sulfate dry-wet cycling environment

Abstract

Sulfate erosion is one of the most harmful chemical corrosions, which can cause the durability problem of a cement-based material. Multi-walled Carbon nanotubes (MWCNTs) are nanomaterials that can be utilized as an additive for cement-based material. However, the research on the durability of MWCNTs modified cement-based material under sulfate dry-wet cycles is rare. The purpose of this research is to understand the effect of MWCNTs on the mechanical and microstructure properties of reactive powder concrete (RPC) during dry-wet cycles with a high concentration of sulfate. The sulfate accelerated erosion phenomenon of RPC with or without carbon nanotubes were discovered. In this research, the degradation rule of RPC subjected to sulfate erosion was investigated from several directions including compressive strength changes, mass loss, and variation of relative dynamic elastic modulus (RDEM). Moreover, the microstructure and phase composition of RPC were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Inner pores and porosity were tested by X-ray computed tomography (CT) images. The results show that with the addition of MWCNTs, RPC showed better sulfate resistance and the type of sulfate is related to the property of corroded RPC. MWCNTs not only fill the pores and cracks within the samples, but also form bridges between cracks, which strengthens the resistance to sulfate attacks. In addition, the MgSO4 solution caused more expansion damage to RPC compared with the Na2SO4 solution in this research.