Concrete dates back to 3000 BC when the Egyptians used an early form of it to build the pyramids. Because of advancements in technology and a diverse market, concrete has come a long way since that first formula. However, it is still a relatively fragile substance. Typically composed of water, Portland cement and an aggregate (rock or sand), the finished product is able to hold up well under pressure, but it is still susceptible to wear and tear. Knowing how to prevent concrete deterioration is useful, but if the concrete is already crumbling you’ll need to know what is causing the breakdown in order to treat it.
The water to cement ratio in concrete can contribute greatly to its durability or ability to resist degradation. Although it does not corrode like some metals will, it is still susceptible to corrosion from chemicals and physical effects due to its porosity.
Concrete can be chemically weakened because it is porous. When elements are allowed to penetrate into the concrete, corrosion is the result. The corrosion can spread to the reinforcements used – in most cases re-bar – which will lead to rust, decomposition and a decrease in strength. Acids can also contribute to degradation since they can actually dissolve the cement mixture in concrete. This will obviously result in diminished structural reliability. Efflorescence is another common problem caused by water soluble salts. These salts are brought to the surface by water that has penetrated the concrete. As the water evaporates, the salt residue is left on the surface in the form of a white powder.
Using fibers in the mix to reinforce the concrete can supplement wire mesh, eliminating rust and corrosion. The fibers also minimize cracking, whereas mesh only holds existing cracks together. A concrete hardener or densifier can help remedy the penetration of acids into the concrete. A concrete hardener will also protect from salt and water intrusion, which lead to efflorescence, or white dusting.
Because concrete is porous, is it susceptible to freeze-thaw damage. As water penetrates into concrete and the temperatures drop, it will freeze and expand, putting pressure on the substance. This pressure can exceed the concrete’s strength, resulting in cracking and spalling.
To prevent this from happening, air entraining admixtures can be used in the initial concrete mix. The air entraining agents create microscopic air bubbles in the concrete. When the water freezes and expands, it will expand into the air bubbles instead of into the concrete, preventing damage. A concrete hardener can protect from further water infiltration and freeze-thaw damage.
Although concrete performs well under pressure, heavy loads and constant pressure can wear it down, resulting in loss of strength, abrasions, cracks and more. Preventing this type of physical breakdown may be impossible, but minimizing the appearance of constant wear and tear is an option. Sand blasting or diamond grinding will even out abrasions and divots in concrete; concrete maintenance sealers can provide a protective coating from surface scuffs. Determining the cause of degradation will help you find solutions to prevent further breakdown and keep your concrete looking new and fresh.