Concrete spalling is the deterioration of concrete due to environmental factors, poor installation, and other reasons. It has the potential to wreak havoc on a concrete structure. So, protecting the concrete early can avoid the dangers and also avoid having to replace it later. HomeQuicks outlines some of the main causes of spalling and the ways to prevent it.
LIN-SEAL is a compound used to prevent the spalling and scaling of concrete. It is recommended by many state Departments of Transportation for prolonging the life of concrete exposed to water, de-icing salts, and other destructive materials.
Spalling concrete is a concrete that has chipped off, been damaged, broken or flaked due to factors such as excess temperature, moisture, corrosion, weathering, mechanical pressures that stress the concrete, or poor installation causing the concrete to wear out. Concrete spalling is also known as concrete cancer. It has the capacity to cause serious hazards, public injury, and loss of public property, as it can damage the whole structure, like damage to reinforcing bars within the concrete. Hence, spalling concrete is an issue that needs attention. It should never be left exposed or without being treated. It is very important to address the spalling issues when they begin to occur.
The signs of spalling are a chipped and flaky surface, chunks of concrete coming out from the installation, and concrete starting to crack. Their signs may also include marked lines, discoloration, and roughness of the concrete. The best time to address spalling is when concrete is first poured, by taking steps to prevent it from occurring.
Causes of Concrete Spalling
✦ One of the main reasons of spalling concrete is a natural process called carbonation. Water seeps into the concrete and causes the reinforcement bars and other elements embedded in the concrete to corrode, thereby creating cracks and bulges in the concrete surface. Steel reinforcement bars are used in concrete to provide durability to it. A poor quality steel can also cause spalling.
✦ Another reason for spalling is water. Rainwater or water from any other external source first makes its way into the capillaries of concrete. During cold days, water freezes inside the concrete and forms snow or ice, which expands and cause the concrete to break, thus developing cracks on the surface. As this cycle continues, the outer surface continues to undergo spalling, resulting in weathering. This is also called freeze thaw weathering.
✦ De-icing salts and rock salts can also cause spalling in the same way as mentioned above. Water containing dissolved salts penetrates the concrete and crystallizes inside it when the water evaporates. The crystals of salt expand in volume which creates stress on the concrete and hence wears away the surface.
✦ High temperatures can also lead to spalling. When exposed to extreme temperatures either over time or all of a sudden, the surface gets much hotter than the concrete underneath. This leads to differential thermal expansion which in turn causes stress between the surfaces. Large masses of concrete begin to separate and develop cracks. Alternatively, the heat may cause the release of water within the concrete.
✦ During firefighting operations, water poured on the heated concrete surface can also cause spalling. The cold water that is poured breaks materials like gravels and sand and causes the concrete to crumble.
✦ Sandblasting is another cause of spalling.
✦ Poor installation is another reason for spalling. This refers to an improper mixture of ingredients while pouring the concrete at the time of construction or when the structure is subjected to high pressure by overloading.
✦ One way to prevent stalling is by protecting the steel reinforcement bar from corroding. This can be done by providing an appropriate amount of concrete cover. One inch of cover is required to protect the steel reinforcement bar (rebar), i.e., no rebar should be placed at a distance lesser than one inch from the concrete surface. Also, it is essential that the concrete is properly amalgamated during installation.
✦ Spalling can be prevented by mixing the concrete with air-entrained concrete. Air entrainment is the introduction of tiny air bubbles in the concrete by adding an air entraining agent, a surfactant (a type of chemical that includes detergents) or an air-entraining portland cement to the concrete in a proper quantity. These tiny bubbles are air pockets that provide tiny chambers where freezing water can expand, thereby relieving internal pressure on the concrete. This prevents the concrete from damage.
✦ Spalling can be prevented by curing the concrete well. Curing is the process where the concrete is protected from the loss of moisture and kept within a proper temperature range. The concrete should be kept as dry as possible by mixing it with an appropriate quantity of water. This is because high water content can weaken the material. This is done to maximize its strength, increase structural integrity, and reduce permeability.
✦ The carbonation process, which causes spalling of concrete, can be slowed down or prevented by painting the ceiling regularly.
✦ Use a water-repellant sealer after the concrete is cured. It is the most vital ingredient used in concrete to protect it and prevent spalling. There are a many sealants available. Concrete Treat can be used as a sealer on outdoor and indoor concrete to prevent penetration of moisture into it. It is perfect for both outdoor and indoor concrete. It can be applied to both dry and wet concrete with a brush, sprayer, roller, or any other applicator. It takes only two to four hours for drying and creates an invisible, glass-like barrier deep in the pores of concrete. It prevents water, ultraviolet rays, and salts from entering the concrete. Polyurethane or epoxy sealers are durable but expensive. They provide good protection from abrasion and chemical spills, but not from UV rays and moisture. It also eliminates the need for the application of concrete blankets.
✦ A moisture-laden environment speeds up the carbonation process. So proper ventilation is required to keep the humidity level to a minimum.
✦ If the concrete installation shows symptoms of spalling, the best way for protection is informing the site’s owner or a concrete professional to address them. Longer the concrete is left untreated, the greater the cracks, pits, and flakes are going to form and thus pose a higher risk of serious damage.