Abrasion of concrete is the progressive loss of concrete mass due to mechanical degradation such as friction, grinding action, impact, overloading, and local crushing. The abrasion resistance of concrete depends upon the paste hardness, aggregate hardness, and the bonding between paste and aggregate. As hard surfaces wear down, the concrete base will become exposed creating an easier target for further damage.
Abrasion of concrete can be natural or artificial. Natural abrasives include sand, gravel, rocks, and soil. Artificial abrasives include silicon carbide, quartz, aluminum oxide, emery paper, and steel wool. Concrete that has been coated with a protective material such as paint will not wear away as quickly as concrete that is not protected.
Concrete that has been worn away by abrasion may appear as rough spheres or flakes where the paste surface has been scraped off. This type of concrete is called scour concrete. Scour concrete is more prone to corrosion than smooth concrete because any open space that is left on the surface allows water to penetrate the concrete and reach the metal inside the container.
Concrete abrasion resistance is influenced by the same factors that determine concrete strength. Low water to cement ratio, low slump value, well-graded aggregate, and air content are examples. Concrete that has high abrasion resistance will also have high strength after it is hardened. Aggregates with large particles (such as granite) will increase concrete strength and hardness while smaller aggregates (such as sand) will reduce strength and hardness.
Concrete that is used for roads must be able to withstand heavy traffic without breaking down. For this reason, concrete used for road surfaces is usually extra-strong. It can be made by adding steel fibers or granules with a coarse surface texture to normal concrete. These additions increase the surface area of the material and so make it more resistant to abrasion. They may also give the concrete a yellow or brown color.
The type of equipment used when laying down asphalt affects how much damage it does to the pavement. Asphalt plants use heavy duty rollers to press the hot bituminous mixture into sheets for use in new road construction or patching old roads. These rolls can get heated up to 350 degrees F (175 degrees C), which is enough to soften most types of asphalt.
Abrasion resistance is the ability of a substance to withstand wear. A material's abrasion resistance allows it to survive mechanical action and prevents materials from being removed from its surface. This permits the material to maintain its integrity and shape. The two main types of abrasion are physical and chemical.
Physical abrasion occurs when particles collide with each other or fall onto the surface of the material causing microscopic scratches. These scars spread out over time and can weaken the material's structural integrity. Chemical abrasion takes place when chemicals are applied to the material's surface to remove toxic substances or clean its surface before applying another layer of material. Examples include cleaning with steel wool or sandpaper and using polyurethane or acrylic paint for their abrasive qualities.
All materials are susceptible to some level of abrasion, but some materials such as glass have very little abrasion resistance while others such as granite have high levels of resistance. Abrasion resistance is determined by factors such as weight per unit area, hardness, elastic modulus, and structure of the material.
The strength does not diminish over time; rather, it appears to level out, whereas the strength of mortar containing 100 percent cement increases. The inclusion of bauxite residue, on the other hand, can enhance the durability of concrete through chloride and carbonation resistance due to pore refinement [10, 11]. Cement manufacturers add 5-15% bauxite residue as a fining agent to improve the flowability of cement paste and reduce dust during mixing.
Bauxite has higher alumina content than limestone or sandstone, which is why it can be used as a substitute for these materials in cement. However, only the residue that remains after pure alumina has been extracted can be used as a cement fining agent. Limestone contains calcium carbonate, which contributes to the alkalinity of concrete and allows it to resist acid attacks from pollutants such as sulfur dioxide from power plants. This is why cement laboratories need to remove some of the calcium carbonate before adding bauxite so that the resulting mixture has enough acidity to function as a fining agent.
Concrete that contains bauxite has higher alumina content than ordinary concrete, which improves its acid/alkali resistance. This means that it can withstand exposure to chemicals such as acids or bases better. Concrete that has high alumina content will not dissolve in acids or alkalis as easily, which is why it's useful for applications where acid resistance or alkali resistance is required.