In the early 1990s, Raven Lining Systems coated three brick manholes in Tulsa, Okla., that were experiencing large amounts of infiltration due to a significant loss of mortar. The manholes were 4 in. in diameter and ranged in height from 5 to 7 ft. They were resurfaced with a cementitious product and top coated with Raven 405. Raven Lining sought to verify the integrity of the 405 product after 26 years of service.
Manhole No. 247 is 5.5 ft deep with repairs to the inlet and outlet. During the inspection, no active leaks were found. Three 20-mm dollies were glued to the coating and cored to test adhesion. The results for the adhesion pulls included 280 psi (100% substrate failure); 198 psi (95% substrate failure, 5% adhesive failure) and 195 psi (25% substrate failure, 75% adhesive failure).
Manhole No. 248 is 7 ft deep with repairs to the inlet and outlet. One active leak was found on the south side of the structure, approximately 1 ft above the bench. Three 20-mm dollies were glued to the coating and cored. The result of the adhesion pulls included 500 psi (5% substrate failure, 95% adhesive failure); 420 psi (95% substrate failure, 5% adhesive failure) and 460 psi (90% substrate failure, 10% adhesive failure).
Manhole No. 249 is 7 ft deep. No leaks were detected in the coating; however, cracking of the coating occurred around the transition from the concrete manhole to the cast ring. Four dollies were glued to the coating and cored for adhesion testing. The results for the adhesion testing included 605 psi (100% substrate failure); 400 psi (100% substrate failure); 380 psi (100% substrate failure) and 485 psi (97% substrate failure, 3% adhesive failure).
After 26 years of service, the adhesion of the coating maintains structural support against the forces from hydrostatic pressures.
