Concrete Repair Materials
Deteriorated joints can be filled with a repair material. Roadware
For some concrete repairs, the best repair material is simply high quality concrete. But manufacturers have developed some excellent repair materials that include various polymers leading to higher bond strength and durability. Most repair materials today are polymer-modified concrete, meaning that the basic material is a portland cement and aggregate mixture with a polymer (typically latex) added. A couple of important factors in selecting a repair material are:
- Prior to deciding what repair material to use, make sure you know what the intent is: Are you trying to bond a crack together or just cover it up?
- Does the mortar need to stick to overhead or vertical surfaces? Or can it be very flowable to pour into forms or cracks?
- How quickly do you want the repair to achieve full strength?
- Do you want to use a one-part material or are you willing to use a two-component material that may be more difficult to work with but have superior properties?
- One of the most important characteristics of a good repair material is very low shrinkage. The concrete matrix has already gone through its shrinkage, so if the repair material shrinks, it will debond and the repair will fail.
- How important is bond strength? Usually very important--most repairs will be considered failures if the repair material doesn't bond to the concrete matrix. A big part of getting good bond is surface preparation.
- Consider the dimensional characteristics of the repair material: Drying shrinkage can debond a repair. If the repaired area will be under load, the elastic modulus should be similar. Thermal coefficients (the rate at which the material expands or contracts with temperature) should also usually be similar.
- Does the repair material need to be freeze-thaw resistant?
- Does the repair material need to allow water vapor transmission? Water vapor pressure from within the matrix of the concrete can create very high pressures-easily strong enough to debond many repair materials.
- How important is compressive strength or flexural strength? How about abrasion resistance?
Often, selecting the right material will mean compromising between several of these factors and, of course, cost. There are lots of good repair materials available-from W.R. Meadows or Emecole, and many other companies. Figure out what characteristics you need in a repair material then talk with the manufacturer to get the best product for your application.
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