Concrete Additive for Residential Patio

Concrete Additives for Residential Patio: What You Need To Know

Cement is the primary ingredient used in concrete, but many of us don’t spend much time at all thinking about it. We see concrete so often in the world around us that it can seem to blend in. That said, concrete additives, more correctly known as concrete admixtures, are an important component of the construction industry, and it is important to understand the quality of the additives that you may see in concrete used in various applications.

Compressive and Flexural strength

Concrete must have sufficient compressive and flexural strength to meet design specifications. Compressive strength refers to how the concrete stands up when pressure is applied uniformly across the concrete. Flexural strength is a measure of the concrete’s ability to resist bending forces.

Certain concrete admixtures, when used correctly, can help increase the overall strength of concrete, or help the concrete reach a relatively high strength in a shorter period of time.

Permeability, Cracking, Freeze / Thaw

How does the concrete hold up to the elements? The concrete might become damaged in the cold, and cracks may appear within the concrete when water that penetrates into the concrete freezes. This causes deterioration of the slab, necessitating repair or replacement in a short amount of time. Testing the concrete’s permeability and resistance to cracking from freezing is important.

Concrete admixtures can be used to reduce the permeability of the concrete, allowing it to better stand up to water penetration. Additionally, using an air-entraining agent to control the air content of the concrete allows for somewhere for freezing water to expand into in a freeze event.

Delaminating, Scaling, Spalling, Abrasion Resistance

Quality concrete should have a high level of abrasion resistance, and should be resistant to damage in the form of scaling and/or spalling. Once these types of damage begin, the damage just accelerates.

Using admixtures to reduce permeability, boost the paste bond, and strengthen the cement matrix can help reduce concrete’s tendency to delaminate, scale, and spall.

Efflorescence

When salt and mineral deposits migrate out of concrete, the resulting white streaking is referred to as efflorescence. The porous concrete near the surface is where you are most likely to see efflorescence occur. This is a natural part of what concrete does, but it can be unsightly, especially on a residential patio.

Certain admixtures can help reduce efflorescence by reducing the concrete’s permeability. When water has a more difficult time migrating through the concrete, it is less likely to be able to carry the minerals in solution and deposit them on the concrete surface.

Site conditions

Depending on how far away from the concrete plant a pour is, certain admixtures like hydration stabilizers may be required to ensure the concrete arrives on site in a workable state. Weather conditions will factor in as well, and accelerators or hydration stabilizers can be used to aid in placing the concrete in hot or cold weather. In hard-to-access locations where pumping the concrete may be required, pumping aids and water reducers can help the pumping process go more smoothly.

Reinforcing

Many patio and larger slabs will have steel reinforcing bars or cages embedded in the concrete slab. In these slabs, it’s important to use epoxy-coated rebar or a corrosion inhibitor to help protect the rebar from corrosion, and in turn protect the concrete from the expansion due to the corrosion. This is especially true in environments where the slab will be exposed to marine conditions with saltwater or cold-weather conditions, where de-icing salts might be applied.

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