The alkali-silica reaction, more commonly known as concrete cancer, is a detrimental swelling reaction that occurs over time in concrete between the highly alkaline cement paste and the reactive amorphous silica found in many common aggregates, with sufficient moisture. This process is what gives a structure to the specific cancer. Concrete cancer occurs when steel reinforcement within a concrete slab begins to rust. As the steel oxidizes, it expands and displaces the surrounding concrete, causing it to become brittle and crack, compounding the problem.
Concrete is porous, absorbing the acid created during the chipping process, accelerating corrosion and exposing the internal steel structure to air and water. Again, this speeds up the corrosion process and ultimately leads to significant and costly property damage. The concrete used in buildings is reinforced with steel and iron bars or meshes. When exposed to air and water (for example, through higher level leaks), a weak carbonic acid begins to form and the rods begin to corrode.
Flat concrete roofs are an example of a building structure that is particularly vulnerable to leaks and water-driven concrete cancer if they are not properly waterproofed. Concrete is a porous material and can easily absorb the elements that surround it, including this corrosive acid. Once corrosion begins, the steel expands, causing the surrounding concrete to crack, which is known as concrete chipping. Chipping can trigger a vicious cycle by further exposing steel to the elements and accelerating the level of corrosion.
To reinforce concrete buildings, the material is usually poured around an iron support or steel bars and mesh. While this generally keeps the structure of a building high, this combination of materials can also lead to the development of cancer in concrete, especially in buildings with inadequate waterproofing or construction defects. Building Impact Leads to Tragic Compromise of Structural Integrity. Concrete cancer occurs when concrete absorbs water and salt air, which oxidizes the steel it contains.
When it expands, it cracks the concrete. To prevent this from happening, concrete must be properly waterproofed. When carbonation of concrete and concrete does not cover steel properly, polymer-modified repair is often used. Regardless of whether the damage is severe or moderate, waterproofing and integral sealing after repair are important to minimize the risk of cancer recurrence in concrete.
Stress fractures can also be caused by wear or bearing weight, which means that water can penetrate the concrete and therefore react with the steel. If chloride pollution is the problem in buildings near the ocean, you may need specialized repair work to treat concrete cancer. When a waterproofing membrane fails or there are gaps around the membrane, it can start the concrete degradation process. Concrete cracking also provides an easy path for water to enter the concrete and attack the steel reinforcement underneath.
If the damage caused by concrete cancer is moderate, you may be able to remove damaged concrete, clean and replace oxidized and exposed steel, and fill in cracks. However, concrete cancer can hide under paint or other building material, such as tiles or bricks. Watch for signs such as concrete chips (cracks, etc.), rust spots that seem to leak from inside the concrete, bubbles from concrete plaster, or leaks that appear in raised concrete. So how can you detect if your building has concrete cancer? One of the first telltale signs is the presence of ferrous stains on the concrete surface.
Cracking accelerates the concrete cancer process by exposing more steel, significantly weakening the building. If you have detected signs of concrete cancer in your building, consult a professional and get advice on the type of repair work to be done. This is especially important for concrete in exposed areas, as water entering the concrete through the cracks will cause the problem to worsen quickly. Concrete cancer can be a serious and costly problem if left untreated, misdiagnosed, or given an irreparable remedy.
So why does concrete chipping occur in the first place? There are many reasons behind this, so being alert at the concrete stage is certainly a necessity.
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