The modern construction industry utilises a variety of chemical admixtures to get desirable qualities along with an outlook to promote sustainability. An admixture is a material other than aggregate, cement, water, and fibre reinforcement used as an ingredient in concrete mortar and added to the batch either before or during mixing.
Chemical admixtures are the smallest part of a concrete mix, even then they impart significant beneficial concrete properties in regards to environment optimisation, performance, and durability leading to sustainability. The incorporation of waterproofing chemicals in the concrete mix has been recognised as an integral means to improve the performance of concrete. Waterproofing chemicals should not be regarded as a substitute for good mix design, for use of suitable materials, or of good quality. There are several waterproofing chemicals like water reducers, air-entraining admixtures, accelerators, anti-freezing admixtures, alkali-aggregate inhibitors, corrosion inhibitors, shrinkage compensating admixture etc.
Following are the reasons why waterproofing chemicals should be used in concrete:
- To maintain adequate freezing and thawing resistance in concrete
- To inhibit alkali-aggregate reactions
- To effect the above combination
- To adjust the setting time
- To increase workability without transforming water content
- To alleviate segregation and bleeding
- To accelerate early strength gain rate
- To improve the pumpability of concrete
- To increase the strength
- To reduce permeability and improve potential durability
- To minimise water content without transforming workability
- To minimise the total cost of the materials
- To compensate for poor aggregate properties
- To depress the freezing point of water at very low temperatures in concrete
The interaction between Portland cement and most of the waterproofing chemicals can be found in detail in various literatures. The chemical admixtures like air-entraining agents, water reducers, accelerators, and retarders are used worldwide from past fifty to sixty years.
The most commonly used waterproofing chemicals in normal strength concrete in India are water reducers or superplasticisers, retarders, and accelerators. The use of waterproofing admixtures requires a complete understanding of their actions. The professionals in the concrete construction industry must be educated and engaged about proper selection and use of chemical admixtures like water reducers and superplasticisers, accelerators, and retarders that are used in cement concrete.
Thus, waterproofing chemicals have an essential role to play in successful waterproofing of structures. The admixtures are very important in construction, and the proper knowledge of admixtures among industry professionals is the need of the day.