When it comes to pre-cast concrete structures, durability and strength are essential. However, even the most robust structures can experience damage over time due to weathering, impacts, and other factors. Thus, it is vital to assess the damage and determine the most appropriate repair method to restore the structure to its original strength and stability.
One method to consider is pre-cast concrete crack injection. However, when repairing a structure, it’s vital to consider several key factors to ensure the procedure is done correctly.
1. Type of Damage
When assessing how to repair a pre-cast concrete structure, the first key consideration is the type of damage that the structure has sustained. This will help determine the appropriate repair method and materials needed.
Several types of damage can occur in pre-cast concrete structures, including:
Chipping: Chipping is typically caused by impacts or abrasion and occurs in areas with high foot or vehicle traffic. Depending on its severity, the repair method can range from applying a patching material to replacing the damaged section.
Spalling: This refers to larger pieces of concrete that break off the structure’s surface. It occurs due to freeze-thaw cycles, exposure to harsh chemicals, or age-related deterioration. Repair methods for spalling can include using a bonding agent on the damaged area or replacing the portion.
Cracks: These occur for several reasons, such as shrinkage, settlement, overloading, or exposure to extreme temperatures. The size and location of the damage will determine the appropriate repair method — injecting an epoxy filler, applying a bonding agent, or replacing it entirely.
2. Cause of Damage
It is crucial to know the underlying cause of the damage to ensure that the repair method addresses the root issue. Doing so allows you to prevent it from recurring and ensure the structure’s longevity. In addition, an accurate diagnosis will save you time and money in the long run by avoiding unnecessary costs and procedures.
3. Location of Damage
Damage in visible areas can be an eyesore and negatively impact the perception of your structure. As such, it’s important to consider the visual impact of the chosen repair method. Additionally, the location of the damage may impact the accessibility of the area, which can make the repair more challenging and time-consuming.
4. Age of the Structure
As pre-cast concrete structures age, they may require more extensive repairs than newer structures. The repair method must consider the wear and tear that older systems undergo and the potential for more advanced damage. Failing to consider the age of the structure can result in further damage, structural issues, and even safety hazards.
5. Condition of the Reinforcing Steel
The reinforcing steel in a pre-cast concrete structure provides additional strength but must be replaced if it’s corroded or damaged. Neglecting to consider the condition of the reinforcing steel can compromise the integrity of the repair and worsen the structure’s issue.
6. Local Building Codes
Local building codes may specify certain materials or repair methods that must be used to ensure the structure’s safety and compliance with regulations. Therefore, consulting and checking existing policies before undertaking any repair is crucial to ensure you’re using the right materials and methods. This will also help you avoid fines and sanctions from your community.
7. Structural Integrity
This aspect must be assessed to determine if the damage has compromised the strength or stability of the entire structure. More extensive repairs may be necessary if the damage has affected the foundation’s structural integrity. Ensuring that the building is structurally sound and safe is of utmost importance in these cases.
If the structure is located in a coastal environment, the repair method must consider the potential impact of saltwater corrosion. Failure to do so can lead to further damage or render repair works useless, wasting time and money.
Damage located in hard-to-reach areas can be a challenge to repair. In addition, special equipment or techniques may be needed, which can increase the cost and time required. Therefore, it’s important to consider the accessibility of the damage to plan the repair effectively.
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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:
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.
Here are the two types of semi-structural 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.
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.