Excessive emissions of carbon dioxide can lead to greenhouse effect thus destroying the ecological balance. Therefore, effective measures need to be taken to reduce the emission of carbon dioxide. In this study, the influence of carbon dioxide curing on the mechanical strength and NaCl freeze-thaw deterioration of reactive powder concrete (RPC) with the assembly unit of sulphoaluminate cement and ordinary Portland cement was investigated. The ratio of sulphoaluminate cement ranged from 0% to 100% by the total mass of cement with the curing age ranging from 1 d to 28 d. The mechanical strength of RPC with 50% ordinary Portland cement and 50% sulphoaluminate cement containing the polypropylene fibers ranging from 1% to 4% by volume of RPC were investigated. Moreover, the following mass and mechanical strength loss rates, the carbonation depth, the chloride ion migration coefficient and the relative dynamic elastic modulus (RDEM) during NaCl freeze-thaw cycles were determined. Finally, the scanning electron microscope (SEM) and X-ray diffraction were applied in investigating the carbonation process of RPC. Results showed that the addition of sulphoaluminate cement could improve the mechanical strength of RPC at low curing age (lower than 7 d). However, when the cuing age reached 7 d, the sulphoaluminate cement demonstrated negative effect on the mechanical strength. Moreover, the carbon dioxide curing led to increases in the mechanical strength and when ordinary Portland cement was added the enhancing effect was more obvious. Furthermore, the carbon dioxide curing could effectively improve the resistance of NaCl freeze-thaw cycles and increase the carbonation depth. Finally, the increasing dosages of polypropylene fibers were advantageous to the mechanical strength and the resistance of NaCl freeze-thaw cycles. From the researching results of the microscopic performance, the carbon dioxide curing could improve the compactness of hydration products and reduce the content of calcium hydroxide especially at the curing age of 3 days.
Epoxy coating has been proven to protect steel bars from corrosion. However, the damage of epoxy coating is inevitable, and this may lead to more serious corrosion of steel bar. In order to study the corrosion resistance of steel bars with damaged epoxy coating, two groups of coating-damaged bar and one group of coating-intact rebar were designed, and six specimens were made. The influence of electrolyte concentration on the corrosion rate of steel bars was studied by setting different concentrations. After 30 days of accelerated corrosion, electrochemical data were recorded by the electrochemical workstation. The experimental result shows that the steel bars with coating damage have obvious polarization curve characteristics of corrosion, and corrosion resistance decreases obviously. According to the corrosion current and potential, the larger the damaged area of the coating, the faster will be the corrosion rate. According to the polarization curve data, the polarization resistance is modified, and the result is closer to the real polarization resistance value. The calculated corrosion rate shows that the corrosion rate of reinforcement is affected by both electrolyte concentration and coating damage area, and electrolyte concentration has a greater influence on the corrosion rate.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.