Rehabilitation of Digester Including Crack Repairs

The Problem
This digester located in Texas was showing severe deterioration, including deep cracks along the floor that were leaking water in areas throughout the unit. The number of cracks and leaks suggested that the water membrane underneath the slab may have aged and fatigued. Epoxytec recommended a combination of CPP Sprayliner and CPP Trowelable. CPP has been used to rehabilitate water/wastewater infrastructures throughout the country for the last three decades. It is an effective method for preventing corrosion and addressing deterioration in a single system.

Products that Out-perform
CPP is a moisture-insensitive, highly adhesive, chemical-resistant, 100%-solid, high-strength, reinforced epoxy applied by trowel. CPP Sprayliner is equal to “standard” CPP once cured; however, this version is packaged more conveniently for those seeking to utilize plural-component, heated-spray applications. The material can be sprayed at an ultra-high build between 1/16” and 1/4” (62.5–250 mils) per pass. Blended with reinforcing agents and various fibers, Epoxytec CPP Sprayliner creates a reinforced lining as a fiber-reinforced polymer (FRP) when cured, offering high strength and flexural properties for partially or fully deteriorated structures.

The severity of the cracks and nature of the deterioration in this digester led to the need for a creative, effective solution combining traditional CPP and CPP Sprayliner, the same proven product applied using two different methods.

The Application
Surface preparation included abrasive blasting to achieve clean, sound, profiled concrete (in accordance with SSPC-SP 13/NACE No. 6. “Surface Preparation of Concrete”).
The concrete was then sprayed with an initial coat of CPP Sprayliner to achieve an even finish throughout the substrate and to attempt to seal any hairline cracks and low-pressure leaks.

After allowing the initial coat to cure, drilling on some major leaking areas was conducted to alleviate pressure away from the cracks. Next, standard CPP was applied to these open cracks to finalize the repairs (now with no pressure).
Once the majority of the cracks were sealed and repaired and the material was cured, the contractor grouted the relief drill holes and patched them with CPP trowelable. The final step included spraying a coat of CPP Sprayliner to make all the surfaces uniform.

A Final Look
A knowledgeable contractor combined with a proven product allowed this successful application. All cracks were addressed, and CPP Sprayliner provided sealed protection that will prevent corrosion and future deterioration. This solution resulted in enormous cost savings for the end user and allowed a quick return to service without replacement or major reconstruction.