Use of Super absorbent polymer in concrete

Abstract

As the role of the concrete increases in the construction Industry due to urbanization of cities and development of industrial area concrete will play essential role in the construction of modern structures. As such efficiency of concrete regarding its various characteristics such as strength, durability, impermeability, shrinkage and creep must be improved. Mitigation of autogenous, drying and plastic shrinkage is the most critical and complex phenomenon of HSC (high strength concrete). In HSC water-binder ratio is low with highly active mineral admixtures such as silica fume widely used in bridges and skyscrapers but it is subjected to early cracking because of intense heat of hydration. This problem could not be solved with traditional external curing because of very low permeability of HSC so after a long research some researchers shifted their attention to internal curing by using polymers, polymers which are capable of absorption and controlled desorption of water within concrete without any other disadvantages like reduction in strength and durability of concrete. SAP (super absorbent polymer) has been gaining popularity with its use in concrete. SAP is a hydrophilic compound in nature. Acrylic acid and acrylamide of potassium and sodium salts are the most commonly used SAP for the purpose of use in concrete. The hydrophilic group of COOH and NH2 contributes to the high-water absorbing capacity of SAP products some of which have a tendency of absorbing 500 to 1000 times its own weight. The desorption of SAP promotes the hydration of surrounding cement paste and advances the primary hydration heat peak. Hydration of cement is increased by 5% around the cement almost Equal to An Increase of W/C By 0.04. Addition of SAP promoted Ca (OH) 2 which improves alkalinity. SAP Increases the internal curing, reduces autogenous shrinkage and increase the relative humidity. The use of super absorbent polymer in concrete is proven to have many positive effects on the properties of concrete in both of its stages, fresh concrete and harden concrete. SAP increases workability of fresh concrete and also releases water when the internal relative humidity of the hardened concrete decreases which Increases internal curing and produce hydrated cement products which increases the strength of hardened concrete.in this study a critical review has been done to overcome the autogenous shrinkage by addition of sap.