Admixtures in concrete
Admixtures are the material either in form of a powder or liquid. These are added to concrete to enhance the performance of concrete. These material help the concrete attain a shape that it cannot attain with normal concrete mixtures.
Concrete admixtures are chemical or mineral ingredients of the concrete that are added to it either before or during the batch mixing. These admixtures give a certain functionality or peculiarity to the concrete. These products enhance the performance of the concrete by imparting strength to it so that it can combat the challenging weather conditions in an effective manner. The inclusion of these admixtures can lead to increase or decrease of the setting time, enhanced quality, resistance to sulphate, superb finish, and much more. Basically, there are two types of admixtures that is chemical and mineral. The chemical admixtures are available in a powdered or liquid form, whereas, the mineral ones are available in the form of a fine grain.
Types of admixtures
Chemical admixtures are as follows:
Accelerator: As the name suggests, these are known for accelerating the hardening process of concrete. It is advisable to use accelerators under the cold weather conditions. The three major chemicals used as accelerators are calcium chloride, calcium nitrate, and sodium nitrate.
Retarders: These are employed for slowing down the hardening process of the concrete. These are broadly used in areas prone to a high-temperature. Under hot weather conditions, it is probable that the concrete may partially set even before the completion of pouring hence the use of a retarder helps in maintaining the liquidity in concrete .
Air entraining agents: These chemical admixtures induce small bubbles of air into the concrete. These agents enhance the durability of the concrete but reduces its strength to a large extent.
Water reducers: These chemical admixtures reduce the proportion of water in the concrete to enhance its workability. These are also known as plasticizers. The most popular water reducer is lignosulfonate.
Pigments: These are the colouring agents that are used for altering the colour of a concrete mix.
Corrosion inhibiting agents: These chemical admixtures are used to protect the steel in concrete from corrosion.
On the other hand various types of mineral admixtures are fly ash, limestone, silica fume, high reactivity metakaolin, ground granulated blast furnace slag, and much more. These inorganic materials have the pozzolanic or the latent hydraulic properties in them. They are very finely grated or broken and are added to the concrete mix for improving the properties of the concrete. It can also be used as a replacement for the ordinary portland cement.
It is always advisable to test a small portion of the concrete admixture first before employing the whole batch to the structure in the process. This helps in ascertaining the absolute behaviour of the concrete well in advance.
In addition, the concrete admixture suppliers should adopt righteous business policies so as to stay for a long period of time in the industry.
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