Five Factors That Can Lead to Durable Concrete Repair
The techniques, tools, equipment, and materials you use to make concrete repairs are very similar to those you use to place fresh concrete. But there are important differences you should consider as you take on the repair.
By combining these five factors into your repair plans, with the expertise of your White Cap support team, you’ll have the right tools and materials to achieve a durable repair.
When taking on even a “simple” concrete repair, contractors may need to adopt a slightly different set of operational approaches for a successful job. You are facing factors you normally don’t encounter on a new construction project.
Let’s look at some suggestions on how you can take these five challenges that repair projects present.
By combining these five factors into your repair plans, with the expertise of your White Cap support team, you’ll have the right tools and materials to achieve a durable repair.
When taking on even a “simple” concrete repair, contractors may need to adopt a slightly different set of operational approaches for a successful job. You are facing factors you normally don’t encounter on a new construction project.
- You wouldn’t be on the job if there wasn’t a problem that was overlooked in the original construction.
- You are being asked to match up construction materials to create a new cohesive system.
- Most owners want the repair completed as fast as possible, regardless of weather.
- You often must devise a procedure for the repair that is very different from normal construction practices.
- Once the repair procedure is adopted, surface prep of the repair area often becomes the most difficult part of the whole endeavor.
Let’s look at some suggestions on how you can take these five challenges that repair projects present.
1. Look for the Root Cause of the Problem
When you take on a repair project, you want to be sure you’re doing more than just a patch. This begins by taking photos of the area, and perhaps sketching out where the problems are. On exterior areas such as patios, driveways, and sidewalks look for areas of poor drainage, ground movement, and new landscaping features (i.e.: sprinkler heads) that were added after the initial construction. These issues can also cause problems on basement walls. Then assess and define the type of cracks you’re dealing with. The root cause of the problem must be addressed prior to repair for your result to be a durable concrete repair.- Plastic-shrinkage cracks run to mid-depth in a concrete slab or from top to bottom on a poured wall. They are irregular in shape and often don’t extend deep into the concrete. They occur while the concrete is curing, usually because the surface of the concrete dries too rapidly relative to the concrete below and normally don’t present any structural issues.
- Hairline drying shrinkage cracks are very narrow but often extend deep into the slab. They are caused when the concrete changes shape during curing and final hardening.
- Popouts and scaling are defects caused by either poor aggregate in the mix, corrosion of reinforcement, and/or poor finishing techniques. These defects cause the concrete surface to become uneven, allowing further damage by exposing the aggregate underneath.
For a complete list of concrete defects and their causes, the Portland Cement Association (PCA) offers “Types and Causes of Concrete Deterioration”. This document provides a brief description and the potential causes of every type of concrete deterioration that you might see on your projects. It’s a useful addition to your online library of resources.
2. Match the Repair Material to the Concrete
There are three factors you must consider when matching a concrete repair material to hardened concrete:- How it bonds to the existing concrete
- Matching its texture and color to the existing concrete area
- Long-term durability
Manufacturers have recognized these factors and offer you a myriad of choices in repair materials. Many of these materials are designed for specific applications and environmental conditions. To help you select what is best for the repair you're about to undertake, a good starting point is ACI-546.3R-14 Guide to Materials Selection for Concrete Repair published by the American Concrete Institute (ACI). This document provides guidance on the selection of most of the materials used in concrete repair. It clearly identifies 5 key types of repair materials:
- Overlay materials and surface coatings
- Crack repair materials
- Surface sealers
- Carbonation coatings
- Traffic-bearing elastomeric coatings
With this information, the next best action item is to reach out to your White Cap repair specialist. They are familiar with the most current advances in material options within each category. But most importantly, they can provide you with some insights on what materials have recently been successfully used in your area.
The final important action item is to set aside a small area on the project to perform a mock-up of the repair. This will give your team a chance to practice the installation, determine color match, and provide some indication that the repair material will bond to the host concrete.
3. Watch the Weather
There’s often a sense of urgency when performing concrete repairs. Owners want their site back to working order quickly. Mobilization on these projects can be difficult, and space is often at a premium. To ensure that repair materials can cure and bond correctly, you must pay attention to any environmental extremes on the project. These extremes can be hot weather, cold weather, and very dry windy conditions. Your best option is to refer to the repair manufacturer’s instructions for the suggested ambient temperature range recommended for placement.
Generally, concrete repairs involving grouts and mortar should be on surfaces preconditioned and maintained at a temperature between 35°F and 90°F (2°C and 32°C) for 8 – 24 hours prior to the start of work. Presoaking the substrate using hot water (90°F) in cold conditions may aid in raising concrete surface temperatures to eliminate any frost, and cold water in hot conditions can lessen the chance of thermal shock.
When encountering hot weather, develop a plan that will protect the repair material once placed. These materials are often highly cementitious, and experience rapid slump loss or flow. Repaired areas need to be covered and cured quickly to reduce the chance of rapid evaporation. This can cause the repaired area to shrink and affect its ability to bond to the host material.
When encountering hot weather, develop a plan that will protect the repair material once placed. These materials are often highly cementitious, and experience rapid slump loss or flow. Repaired areas need to be covered and cured quickly to reduce the chance of rapid evaporation. This can cause the repaired area to shrink and affect its ability to bond to the host material.
Repairs in cold weather can cause even greater operational challenges. When the host concrete slab or wall has a low temperature, it can affect the setting time for repair materials. Low ambient temperatures will also affect a repair material’s mixing time and flow characteristics. If you are mixing on the jobsite, check the material manufacturer’s instruction to avoid adding water that is too hot. You can create a false set if you’re not careful.
If you must heat the repair area, don’t directly heat the newly placed grout or repair mortar surfaces. A windproof and weatherproof enclosure works best. If you use combustion heaters, be sure to vent them outside the enclosure to avoid contamination and/or dusting that can result from carbonation. Most product manufacturers suggest warming the repair area at least 24-hours following placement to allow the material to achieve 3,000 psi compressive strength.
Several White Cap repair experts participate on the committees that have developed these training modules. They can help provide specific details on these procedures which can be adopted by your project.
If you must heat the repair area, don’t directly heat the newly placed grout or repair mortar surfaces. A windproof and weatherproof enclosure works best. If you use combustion heaters, be sure to vent them outside the enclosure to avoid contamination and/or dusting that can result from carbonation. Most product manufacturers suggest warming the repair area at least 24-hours following placement to allow the material to achieve 3,000 psi compressive strength.
4. Devise a Procedure for the Task at Hand
For simple repairs, White Cap and many product manufacturers have a host of training information that outlines how to best use their products. These instructions often include general recommendations on proper site prep, product prep directions for storage and mixing, and after-placement care. Occasionally you’ll encounter some more difficult repairs that may require your crew to learn some new techniques.
For several years, members of the American Concrete Institute (ACI) and the International Concrete Repair Institute (ICRI) have developed the Repair Application Procedures Certificate Program. This is a series of contractor-focused training programs that provide information on how to tackle these projects. The information includes a list of necessary equipment and safety considerations required by each task.
These on-demand courses include lessons on:
- Structural Crack Repair by Epoxy Injection
- Crack Repair by Gravity Feed with Resin
- Spall Repair by Low-Pressure Spraying
- Surface Repair Using Form-and-Pour Techniques
- Surface Repair Using Form-and-Pump Techniques
- Vertical and Overhead Spall Repair by Hand Application
- Spall Repair of Horizontal Concrete Structures
- Installation of Embedded Galvanic Anodes
- Spall Repair by the Preplaced Aggregate Method
- Leveling and Reprofiling of Vertical and Overhead Surfaces
Several White Cap repair experts participate on the committees that have developed these training modules. They can help provide specific details on these procedures which can be adopted by your project.
5. Build in Time to Prep the Repair Area
The most important aspect of many repair projects happens before the repair material is mixed or placed. Preparing the entire site involves many steps.
Since most repairs occur in public areas, position the proper safety barricades, dust containment screens and warning signs to keep out non-necessary visitors. These precautions can also include the necessary weather-related enclosures when dealing with hot or cold weather.
Another important consideration is to review and monitor adjacent activities that may be ongoing during the repair procedure. Take note of any activity that could cause excessive vibration to the repair area.
When preparing the area for the repair, it must be sound and contaminant-free. This may involve sandblasting, hydro-demolition, or hand grinding. Be sure to have the necessary vacuums and PPE to protect workers from exposure to silica dust.
Another important consideration is to review and monitor adjacent activities that may be ongoing during the repair procedure. Take note of any activity that could cause excessive vibration to the repair area.
When preparing the area for the repair, it must be sound and contaminant-free. This may involve sandblasting, hydro-demolition, or hand grinding. Be sure to have the necessary vacuums and PPE to protect workers from exposure to silica dust.
On many projects, the material installation instructions may reference a roughened surface on the host concrete. The industry standard reference tool for determining concrete surface profiles are the molded rubber comparator chips, available from the International Concrete Repair Institute (ICRI). These samples replicate ten grades of surface roughness and are designed for direct visual and tactile comparison to the concrete surface in question.
Along with prepping the concrete, you might have to clean and replace any reinforcement in the repair area. Be sure that all reinforcement is clean, secure, and positioned to allow adequate cover for protection.
Along with prepping the concrete, you might have to clean and replace any reinforcement in the repair area. Be sure that all reinforcement is clean, secure, and positioned to allow adequate cover for protection.