What is Scaling?
Scaling Concrete Surfaces - CIP 2
National Ready Mix Concrete Association (NRMCA)
(condensed)
What is Scaling?
Scaling is local flaking or peeling of a finished surface of hardened concrete as a result of exposure to freezing and thawing. Generally, it starts as localized small patches which later may merge and extend to expose large areas. Light scaling does not expose the coarse aggregated. Moderate scaling exposes the aggregate and may involve loss of up to 1/8 to 3/8 inch of the surface mortar. In severe scaling more surface has been lost and the aggregate is clearly exposed and stands out.
Why Do Concrete Surfaces Scale?
Concrete slabs exposed to freezing and thawing in the presence of moisture and/or deicing salts are susceptible to scaling. Most scaling is caused by:
- The use of non-air-entrained concrete or too little entrained air.
- Application of excessive amount of calcium or sodium chloride deicing salts. Chemicals such as ammonium sulfate or ammonium nitrate, can cause scaling as well as induce severe chemical attack on the concrete surface.
- Any finishing operation performed while bleed water is on the surface.
- Insufficient curing. This omission often results in a weak surface skin, which will scale if it is exposed to freezing and thawing in the presence of moisture and deicing salts.
How to Prevent Scaling?
- Concrete exposed to freezing and thawing cycles must be air-entrained.
- In the first year DO NOT use deicing salts such as calcium or sodium chloride, after placing the concrete. Use clean sand for traction. When conditions permit, hose off accumulation of salt deposited by cars on newly placed driveways and garage slabs. Subsequently, use salt sparingly. Never use ammonium sulfate or ammonium nitrate as a deicer.
- Provide proper curing by using curing compound or by covering the surface of newly placed slab with wet burlap. Curing ensure the proper reaction of cement with water, known as hydration, which allows the concrete to achieve its highest potential strength.
- DO NOT perform any finishing operations with water present on the surface. Bull floating must promptly follow initial screeding. Delay finishing operations until all the bleed water has risen to and disappeared from the surface. This is critical with air-entrained concrete in dry and windy conditions where concrete that is continuing to bleed may appear dry on the surface.
- Do not use jitterbug or vibrating screed with high slump concrete.
- Protect concrete from the harsh winter environment. It is important to prevent the newly placed concrete from becoming saturated with water prior to freeze and thaw cycles during winter months. Apply a commercially available silane or siloxane-based breathable concrete sealer or water repellent specifically designed for use on concrete slabs.
V-SEAL provides the perfect 2% moisture vapor transmission rate that is ideal for curing new concrete while saturating the surface with 20 Year Sealer.
V-SEAL contains siliconate, the scientifically engineered hybrid which bridges silane and siloxane maximizing superior chemical saturation and topical protection. And, only V-SEAL contains V-Silane, the “active” silane that chemically grabs the minerals in concrete.
For more information and/or the complete text of this article contact V-SEAL.
