Manholes are an essential component of an area’s sewage system, serving as maintenance access points and providing structural support for the pipes. They are also crucial to the system’s proper operation, allowing for wastewater collection, transport, and treatment.
However, manholes can deteriorate and become damaged over time. The most common causes of manhole damage are corrosion, ground movement, and heavy traffic. These can result in leaks, blockages, and collapses, requiring costly repairs and posing safety risks to the public.
Manhole rehabilitation may appear daunting, but it can be accomplished efficiently and effectively with the right knowledge and resources. Using trenchless techniques enables efficient and cost-effective maintenance. This method involves repairing the utility hole from the inside.
Listed below are the steps to effective rehabilitation:
Step 1: Preparing the Substrate
Prepare the concrete and steel substrates so the restorative materials can adhere sufficiently. This will also ensure the repair’s success and extended durability. Next, remove loose and contaminated substrate material through pressure washing, grinding, or abrasive blasting.
Verify that the Concrete Surface Profile (CSP) is suitable for the application of repair mortars — per SSPC-SP12/NACE No. 6 — requiring a CSP equivalent to medium-grit sandpaper. Lastly, inspect the concrete’s pH level to confirm whether the surface is contaminant-free. If the pH is less than 10, contaminants are still present on the substrate, and additional actions may be required.
Step 2: Injecting the Grout Material
Injecting grout into a manhole is a rehabilitation step that aids in the repair and stabilization of the structure. In concrete structures, grout fills voids, cracks, and joints. It is also typically composed of cement, water, and different aggregates.
The trenchless procedure involves drilling holes through the concrete whenever cracks or leaks exist. Then, you should inject a low-viscosity, water-activated polyurethane grout that follows the path of the infiltrating water around the structure. The grout hardens in place and creates a tight seal between the underside and the soil.
The optimal grout material for a particular rehabilitation depends on the project’s conditions and requirements. Some examples include the following:
- Epoxy grout
- Polyurethane grout
- Cement-based grout
- Hybrid grout or multi-component grout
Step 3: Rehabilitating the Structure
Next, it’s time to address and repair the structural issues of a manhole, which may include cracks, holes, deformations, and corrosion of the steel reinforcement. The appropriate cementitious repair mortar will vary depending on the substrate, the service environment, and the coating.
One of the most popular repair materials that can be used is cementitious microsilica repair mortars. This mixture possesses superior strength, durability, flowability, adhesion, and impermeability. You can also use cementitious calcium aluminate repair mortars. They are distinguished for their rapid hardening, heat resistance, low shrinkage, and eco-friendly properties.
Step 4: Applying the Coatings and Linings
Applying corrosion-resistant coatings or linings to a manhole is an essential step in the rehabilitation process that prevents further deterioration and damage to the structure. Typically, these substances are applied to the walls and floor to create a barrier against water, chemicals, and other potentially damaging factors.
Freestanding Liners
A freestanding semi-structural liner is typically composed of a fiberglass-reinforced polymer (FRP) material that is durable, corrosion-resistant, and lightweight. Furthermore, it is designed to be self-supporting and can be used to repair structural defects like cracks and holes.
Bonded Liners
Unlike a freestanding semi-structural liner, a bonded liner is firmly attached or adhered to the existing structure. Therefore, it requires surface preparation of the current system and a proper installation and curing process to ensure effective adhesion.
Contact SealGuard for High-Quality Sealing Products and Solutions
Manhole rehabilitation can increase the sewer system’s overall flow capacity, prevent infiltration and exfiltration, and reduce the risk of collapse. It can also optimize the manhole’s condition to avoid further deterioration and extend its lifespan.
Don’t let leaky manholes bring your sewer system to a standstill! Try SealGuard’s top-of-the-line sealing products and solutions today and experience the difference for yourself.
Contact us now to learn more about how we can help keep your manholes leak-free and your sewer system running smoothly!