- Why Concrete Cracks
- 5 REASONS WHY CONCRETE CRACKS
- How to Repair Wide Cracks in Concrete
- Preventing Random Cracks In Concrete
Cracks are the end result of these forces.
Why Concrete Cracks
The bottom line is a low water to cement ratio is the number one issue effecting concrete quality - and excess water reduces this ratio. Know the allowable water for the mix the contractor is pouring- or be very sure you have chosen a reputable contractor who will make sure the proper mix is poured. It is more expensive to do it right- it simply takes more manpower to pour stiffer mixes.
Also, rapid drying of the slab will significantly increase the possibility of cracking. The chemical reaction, which causes concrete to go from the liquid or plastic state to a solid state, requires water. This chemical reaction, or hydration, continues to occur for days and weeks after you pour the concrete.
5 REASONS WHY CONCRETE CRACKS
You can make sure that the necessary water is available for this reaction by adequately curing the slab. Read here about the methods to cure concrete and understand how your contractor will cure the concrete. Reason 3 - Improper strength concrete poured on the job.
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Concrete is available in many different strengths. Verify what strength the concrete you are pouring should be poured at. Control joints help concrete crack where you want it to. The joints should be of the depth of the slab and no more than times in feet of the thickness of the concrete in inches.
How to Repair Wide Cracks in Concrete
So 4"concrete should have joints ' apart. The ground upon which the concrete will be placed must be compacted. The sub grade must be prepared according to your soil conditions.
Some flatwork can be poured right on native grade. In other areas 6"of base fill is required along with steel rebar installed in the slab. Understand what you contractor is doing about each of the above listed items and you will get a good concrete job.
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Preventing cracks home Why concrete cracks: Top 4 reasons Acceptable Crack Widths Start with a Sound Subgrade Make sure the subgrade is compacted Subgrades and subbases for concrete slabs: Why having good support is critical to success Modify the Concrete Mix Use a low water-to-cement ratio Concrete admixtures that control cracking Install Joints Be active in deciding where control joints will be placed Joints in concrete slabs: Types and where to locate Properly Cure the Concrete Properly curing concrete slabs: Why and how to cure Allow time to water cure Related Information: How to build high-quality slabs on grade Section Sponsor Carbon Fiber Crack Repair Free Product Information from Rhino.
Hairline cracks are commonly observed in freshly placed concrete and their occurrence is owed to the phenomenon of plastic shrinkage.
As the name implies, these cracks are very small- about 0. The main cause behind the generation of hairline cracks in concrete is plastic shrinkage which is the rapid depletion of moisture from the fresh concrete within its plastic state.
Preventing Random Cracks In Concrete
The causes for these cracks to show up can be due to the variations in air temperature, concrete temperature, relative humidity and wind velocity at the surface of the concrete. These factors can cause high rates of evaporation in either hot or cold weather. There are many methods and techniques to prevent this type of crack in case of rapid loss of moisture due to hot weatherand dry winds. This is the first and foremost step in the repair of hairline cracks in the concrete. Inspection of the crack is done and if any oil or stains have penetrated the crack and have discoloured the concrete, the stains will have to be addressed before repairing the crack.
The sealant is a filler material that is penetrated into the crack. The ideal sealant must have low surface tension and low viscosity. These two characteristics allow the liquid sealer to penetrate deeply into the crack. Crack repair materials for concrete are often polymer-modified cement grouts, silicone or latex caulking, or epoxies. Polymer-modified cement grout is the typical material used to fill pinholes and voids in concrete during manufacture.
If cracks occur before the concrete is sealed, this is often the material used to repair them.