Design and evaluation of an innovative composite silicate-based surface treatment agent of concrete

Silicate-based surface treatment agent is a sustainable material to provide a sealing coat on the surface of Portland cement concrete to improve its hardness, impermeability, chemical durability, and abrasion resistance. A type of composite surface treatment agent of concrete is introduced in the paper, using potassium silicate and lithium silicate as main agents and different contents of lithium sulfate, urea, triethanolamine, organosilicon polyether surfactant, and fluorocarbon surfactant as additives. An orthogonal test was conducted to evaluate the effects of different proportions of the two main agents and five additives. The gelation time and viscosity of the agent and the rebound value and penetration depth of the tested concrete samples were tested to evaluate the performance of the designed composite material. The results showed that the two main agents had significant influences on the viscosity, while potassium silicate had the greatest influence on the rebound value. For penetration depth, urea, triethanolamine, organosilicon polyether nonionic surfactants, and fluorocarbon surfactants all had significant effects. The proper ingredients were selected based on the test results, and the optimum proportion of the designed surface treatment agent was determined based on variance analysis of the test results. Two representative commercial inorganic surface treatment agents were selected to compare with the optimum proportion of the designed material, and the effects of the material on the microstructures of the concrete specimens were analyzed by scanning electron microscope (SEM). The mechanism is that Calcium Silicate Hydrate (CSH) gel and ettringite generated can effectively improve surface properties of concrete. The results showed that the optimum proportion of the designed material can effectively block micropores in the surface layer, thus significantly decreasing the concrete porosity, which is conducive to the rapid improvement of concrete strength and compactness.