Evaluating a polymer concrete coating for protecting non-metallic underground facilities from sulfuric acid attack

Abstract

Deteriorating underground facilities built with cement concrete and clay bricks require rapid in situ rehabilitation, and using coating as a corrosion protectant is one method currently being adopted. The performance of a polymer concrete coating was evaluated using a combination of full-scale and laboratory tests. The polyester-based polymer concrete coating had a density of 1.75 g/cm 3 (109 lb/ft 3) and hardness in the range 38–45 (Barcol hardness). A full-scale test on coating applicability and performance on the concrete substrate was performed under an external hydrostatic pressure of over 103 kPa (15 psi) of water, simulating the groundwater condition. Coated concrete cylinders and clay bricks with holidays (pinholes) were used to study the chemical resistance of the coating under acidic environments to represent the worst sewer and accelerated test conditions (ASTM G 20). Bond strength between the coating and the concrete/clay brick substrates were determined using the modified ASTM D 4541 test. The performance of the polymer concrete coating material was studied for over 3 years. The polymer concrete coating was applied with ease on dry and wet concrete surfaces. Test results showed that the polymer concrete coating had good bond strength with clay bricks and wet concrete surface. No failure was observed in 3 years with coated clay bricks. The coating extended the lifetime of dry and wet concrete by a factor of 29 and 71, respectively. The weight change of coated concrete was modeled using a film model.