Adjusting concrete resistance to corrosive ions by varying carboxyl contents in chemical additives

Abstract

In this study, polycarboxylate ether-based superplasticizers (PCEs) with various carboxyl densities were synthesized as chemical additives to evaluate the effect of PCE carboxyl density on the resistance of concrete to chloride permeability and sulfate attack. The microstructures of concrete, the properties of PCEs, and the cement hydration processes were investigated to explore the improvement mechanism of PCE-doped concrete resistance to chloride permeability and sulfate attack. Results show that increase in carboxyl density of doped PCEs was advantageous for concrete resistance against chloride permeability and sulfate attack. As the carboxyl content increased, PCE molecules were adsorbed on the cement more efficiently, leading to delayed cement hydration and formation of less foams. Therefore, the number of microcracks and the total porosity of the concrete decreased with increase in carboxyl content of the doped PCE, producing concrete with better resistance against chloride permeability and sulfate attack. By improving concrete resistance to chloride and sulfate ions via doping higher-carboxyl content PCEs, this work can contribute to the development of essential infrastructure constructed with considerable longevity and reliability in tropical marine environments.