cement plasticiser is a type of additive that improves the consistency of concrete and mortar mixes. It helps the ingredients to coagulate together better, which in turn makes it easier to spread, pour and shape. It also increases the strength of the finished product. Unlike cement dye, it does not contain any chlorides or other corrosive components and is compatible with all types of cement.
Why is cement plasticiser important?
Cements such as clinker, pozzolan and fly ash need to be mixed with water to form the right consistency for construction. However, adding too much water can result in the formation of a concrete with poor mechanical properties such as reduced compressive and flexural strength, high permeability and frost damage. cement plasticisers increase the workability of the mix so that a higher water/cement ratio can be used without significantly reducing its strength.
A common misconception is that household washing up liquid can be used as a substitute for concrete plasticiser. Although it works in the short term, using washing up liquid in your mortar will have a negative effect on its long-term performance and can lead to a weaker, more crumbly mix once it has dried.
Traditional lignosulfonates, naphthalene condensate and melamine sulfonate plasticisers work by electrostatic repulsion to disperse the cement particles in the water/cement system. However, newer products such as polycarboxylate ethers (PCE) are based on a different chemical structure which gives them the ability to work in a slightly different way. They work by steric stabilisation which causes the cement particles to be surrounded by sheaths of aligned water molecules that prevent close approach of the particles, providing the best possible lubrication and fluidity.