Incorporating Quality Control into Your Repair Project
Create a digital file on each project. The file should contain the preliminary drawing of the site noting the deficiencies. When the project is completed try to take the “after” photos from the same position. If possible, include some action shots of the repair as it happened. This is especially helpful when applying an overlay. Be sure to document the location of any control joints in the original slab. You want to show that you placed the new joints in the overlay atop the original control joints to reduce reflective cracking.
Take Before and After Photos
Use Prepackaged MaterialsMany repair materials require components designed to be mixed in exacting proportions prior to placement. Using prepackaged products takes all the guesswork out of proportioning and ensures that the material will perform at its designed level.
Test Your Repair MaterialsBe sure to check the project specifications to determine if testing of repair materials is required. Materials purchased from vendors should have their manufacturer's test certificate and should be used only as per manufacturer's specifications and approved methods. If you are using ordinary concrete, be sure to take test cylinders to verify the material’s compressive strength. This is the most common test.
Monitor Your Mixing WaterRepair materials are subject to shrinkage, as they often contain higher levels of cementitious materials and finer materials. Using an accurate measuring device for quarts and gallons will help you avoid problems. It is equally important to document the water quantities you add to each batch.
For large jobs, consider purchasing a mixing bucket that is designed with graduated markers that help you pre-measure the water prior to mixing.
Checking the BondThe success of your concrete repair revolves around the strength of one aspect – the bond between the host concrete and the material. The bond is determined by two factors:
- Is the host concrete sound enough to accept the repair?
- Did the material bond effectively during the repair?
Fortunately, there is one test procedure you can use to determine the answer to both questions.
Technicians commonly use ASTM C 1583, Standard Test Method for Tensile Strength of Concrete Surfaces and the Bond Strength or Tensile Strength of Concrete Repair and Overlay Materials by Direct Tension (Pull-off Method).
Often referred to as the pull-off method, a steel disk is affixed to the finished surface and the concrete around the perimeter is scored, so that upward force is only acting on the area directly below the disk.
When testing the host concrete, the steel disk is affixed to the concrete itself. When the bond holds but the concrete fractures at less than 10% of the expected compressive strength of the concrete, it’s a good indicator that the concrete’s upper surface is delaminate or too porous. You will need to remove the weak layer and test again prior to material placement.
The same equipment is used to determine if the bond of an overlay or repair material is strong.
In this test you are measuring the direct tensile strength of a material or bond strength of an interface. This procedure is slightly different.
- First, a shallow core is drilled perpendicular to the surface, leaving the intact core still attached to the material at the area of interest.
- Next, a metal test disc of the same diameter as the core is epoxied/bonded to the surface of the attached core.
- Once the epoxy cures, a bolt is attached to the metal test disc and the jack pulls the bolt/disc until failure occurs.
The failure can occur at the epoxy, overlay (if applicable), interface, or in the substrate. When you pull off the overlay and the substrate, the bond is good. You can learn more about this procedure in the Technical Guideline No. 03739, “Guide to Using In-Situ Tensile Pull-Off Tests to Evaluate Bond of Concrete Surface Materials,” published by the International Concrete Repair Institute (ICRI).
Sealing and ProtectingWhen applicable, try to protect the repaired area by applying a sealer after the repair material is properly cured. If the repairs have occurred near control joints or waterstops, you might want to consider recaulking or applying new sealants to ensure the integrity of the seal.
Check with your White Cap expert to determine the type of sealer that will be compatible to both the host concrete and repair material. They can direct you to a wide selection of materials that will enhance the life of the repair and structure.