Admixtures are materials added to concrete mix to modify its properties and improve characteristics such as strength, water resistance, heat resistance, flexibility, and durability. These admixtures can be in the form of powders, liquids, pastes, or fibers and are added to the concrete mix during production, transportation, or installation stages.
There are many types of admixtures for concrete, but below are some of the most common types and their applications:
Plasticizers: Including polymers, polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), and others. These additives can increase water and impact resistance and alter the behavioral properties of concrete, improving the properties of the concrete paste.
Silica-based Additives: Including silica fume, silica flour, and others. These additives can reduce the weight of concrete and increase its compressive strength and thermal insulation.
Pozzolanic Additives: Including mineral materials like coal ash, industrial by-products such as fly ash, and rice husk ash. These additives can enhance the compressive strength, chemical resistance, and resistance to corrosion.
Fiber Additives: Including metal fibers, polypropylene fibers, and glass fibers. These additives can increase the tensile strength of concrete and control cracks that may occur in the concrete.
Coloring Additives: Used to create different colors in concrete. These additives can change the visual appearance of concrete and make it more aesthetically appealing.
Repair Additives: Including epoxy resins and repair mortars. These additives are used for repairing and restoring concrete surfaces with damages or cracks.
Each of these additives, as well as other concrete admixtures, is used for specific reasons and contributes to improving and modifying the properties of concrete. However, the use of any admixture should be done in accordance with the specific needs and relevant standards.