concrete additives are substances that are added to concrete before or during the mixing process. They can lower construction costs and alter the properties of hardened concrete. They are usually liquid and are available in a ready-to-use form, which means they can be mixed into concrete at the factory or on-site. They are available in different types and have unique characteristics to serve specific needs. Some of the most common concrete additives are water reducing admixtures, air-entraining agents, concrete deflocculants, set retarding admixtures and coloring admixtures.
Water reducing admixtures are used to reduce the amount of water needed in concrete mixes without affecting its consistency. They make concrete more workable and are especially useful with larger projects. Some of the most popular water reducing admixtures include polycyclic derivatives and phosphates.
Another type of concrete additive is an early strength-enhancing agent, which helps the concrete develop its initial strength faster. This is a great benefit when working in cold weather since it allows finishing operations to start sooner. This type of admixture is typically made from silica dust, which is created as waste during the manufacturing of ferro-silicon and silicon metals. It also has special pozzolanic properties, which give it a high interaction with water-reducing and plasticizing admixtures.
Retarding admixtures slow the chemical reaction known as cement hydration during the early stage of the setting process. This is helpful in reducing the effects of high temperatures, which can speed up the setting process and prevent concrete from curing properly. They are usually calcium chloride, sulfate-based or organic amine and come in different concentrations to achieve the desired result.