Surface damage

Surface Damage

Damage to the surface of concrete has a variety of terms attached to it, scaling, spaling, popping, flaking, peeling or pitting. Simplified, surface damage is when the top layer of concrete fails and deteriorates, leaving pit marks and/or the aggregate below the surface exposed.

Surface damage is caused by any of, or combination of the following:

1) freeze/thaw cycles 2) inferior concrete

3) abused concrete 4) time of placement/curing

1) Freeze/thaw cycles are the main cause, they occur in the winter months when inconsistent temperatures cause water or melting ice to freeze in the pores of the surface. Water saturates the surface of the concrete, it then freezes and expands causing the top layer to fail.

Salts and de-icers increase this freeze/thaw cycle. Salt crystals also accumulate (over time) in the concretes pores and effectively lower the vapor pressure of any water reaching it (salt attracts water to itself), literally making water wetter, this causes the water to penetrate at a deeper and faster saturation rate than normal. Concrete is most vulnerable when this critical (90%) saturation takes place, making freeze damage more likely.

2) The concrete industry has specifications concerning exterior concrete. Exterior concrete must have adequate psi, as well as have sufficient air entrainment. A low p.s.i. weakens the entire slab, including the surface, and a weak surface is more vulnerable to freeze/thaw cycles.

	psi - (pounds per square inch) is a number used to measure the strength of the concrete. For example, exterior concrete should be approximately 4000 psi.
	air-entrainment - A liquid additive designed to create tiny air bubbles throughout the concrete to help the surface withstand freezing and thawing. Absence of, or, not enough air, leaves the surface vulnerable.

3) Adding too much water to the mix, adding water too many times, wetting the surface of the concrete during finishing, or overworking the surface lowers the psi and raises the water-cement ratio of the surface, overworking the surface, and over-mixing the material also reduces the percentage of air-entrainment.

*Some of these actions must be taken based on the material delivered and it's condition at that time.

water-cement ratio- measures the percentage of water and cement in the concrete, the higher the ratio the weaker the concrete, a direct correlation to the psi.

4) Concrete needs ample time and temperatures to properly cure. Concrete poured in extreme weather may not meet these criteria. Techniques are available to help in the cold weather, such as blankets, straw and plastic coverings. Extreme heat is also detrimental to concrete. The use of curing compounds and water-curing techniques are recommended to keep the temperature of the concrete at an acceptable level and slow hydration. Concrete placed under extreme weather conditions which were not cured properly are prone to surface damage.

It is not our intent to place blame. These are facts of the business. A conscientious contractor can do all things properly and still experience some problems. The opposite is also true. A certain percentage of damage seems to be the "norm" for today's concrete, despite conditions or contractor. The common denominator could be the material.

If your concrete has surface damage, aside from replacing it, your best option is a quality sealer properly applied. We cannot guarantee that the damage will cease completely, but we can significantly reduce the effects.

more info: • Why seal?

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