Superabsorbent polymers are swell-able substances, which may soak up many times their very own weight of liquids by forming a gel. These substances are extensively utilized in industrial merchandise such as baby diapers. This video below demonstrate the working of SAP.
Superabsorbent polymers (SAP) have the potential to be used as an admixture to enhance the self sealing of cracks in cement-based supplies similar to concrete.
Use Of SAP In Concrete
Modern self-compacting cementitious systems are widely used these days, containing both chemical and mineral admixtures which modify the hydration kinetics and enhance properties within the fresh and hardened state.
In modern concrete systems, water cement (W/C) ratio is often less than 0.40, Super plasticizer (SP) is used to attain desired flow value at low water cement ratios. In early age (24 hours) shrinkage, autogenous shrinkage contribution may be significant
Throughout mixing of the concrete, the SAP will soak up water and form macroinclusions. when concrete hardens absorbed water is released by SAP to mitigate early shrinkage.
Self Sealing Properties Of SAP
In a recent research a unique characteristic of SAP is discovered, that its swelling capability changes considerably with the ionic content material of the solution.
When added to a concrete mix, SAP absorbs about 3-20 grams of water per gram of SAP and swells only slightly. When the concrete sets and hardens, the SAP progressively releases its absorbed water and collapses.
Throughout this entire process SAP lies dormant within the concrete till cracking occurs that exposes the SAP. Now if concrete crack is subjected to some aqueous solution again expansion of SAP occurs much more than the initial rate. This expansion helps in concrete sealing.