Effect of Modified Tetraethyl Orthosilicate Surface Treatment Agents on the Permeability of Airport Pavement Concrete

In this paper, three modified tetraethyl orthosilicate surface treatment agents were prepared by using tetraethyl orthosilicate (TEOS) as the preparation monomer, isobutyltriethoxysilane (IBTS) as the hybridizer, and acrylic acid, phosphoric acid, and hydrochloric acid as the catalysts. The effects of the three modified tetraethyl orthosilicate surface treatment agents on the permeability of airport pavement surface concrete were investigated by water absorption tests, water contact angle tests, water penetration resistance tests, chloride ion penetration resistance tests, and carbonation tests, and the mechanisms of action of the modified tetraethyl orthosilicate surface treatment agents were analyzed by microscopic tests. The results showed that all three tetraethyl orthosilicate surface treatment agents could significantly improve the impermeability of concrete, among which the modified tetraethyl orthosilicate surface treatment agent with hydrochloric acid as the catalyst had the most obvious effect on the improvement of the impermeability of concrete. Acrylic acid was weaker than hydrochloric acid as the catalyst of a modified tetraethyl orthosilicate surface treatment agent for the improvement of concrete impermeability; it was only slightly stronger than hydrochloric acid as the catalyst of modified tetraethyl orthosilicate surface treatment agent in terms of the improvement of concrete's resistance to water penetration, and the difference between the two was not significant. Phosphoric acid as a catalyst of the modified tetraethyl orthosilicate surface treatment agent was the least effective for concrete impermeability; it was only stronger than the other two modified tetraethyl orthosilicate surface treatment agents in the improvement of concrete resistance to carbonation, and the carbonation depth of the concrete was only 1 mm in 28 days. SEM and MIP tests showed that the modified tetraethyl orthosilicate surface treatment agents improved the impermeability of concrete mainly by producing additional hydrated calcium silicate gel to plug microcracks and pores, reduce the total porosity of the concrete and the number of multi-harmful and harmful pores, and improve the compactness of the concrete. The test results can provide a reference for the development of modified tetraethyl orthosilicate surface treatment agents and their application in airport pavement surface engineering.