The mechanism of action of these additives is to create a steric repulsion (space barrier) and they have high performance. The percentage of solids in these additives has a direct effect on the consumption of the additive.

These compounds, also called PCs or comb polymers, are the newest type of superplasticizer additives. The backbone of these compounds is based on the polymerization of acrylic acid or allylic acid and has side chains attached to the structure of methoxy poly ethylene glycol. One of the common structures of these compounds is shown in Figure 1.

In this type of water-reducing additive, the polyethylene oxide’s (PEO) side chain is responsible for dispersing the cement particles, and this is done by creating a space barrier (Steric Hindrance). In fact, unlike other lubricants such as melamine and naphthalene sulfonate based additives as well as lignosulfonate (which disperses particles through electrostatic repulsion forces), the dominant mechanism in the performance of poly carboxylate additives is through spatial inhibition. The carboxylate group is neutralized by the addition of sodium hydroxide and the formation of sodium salts, and when decomposed in solution, it takes on a negative charge, which becomes the connection point for adsorption of the additive on the surface of cement particles.

New properties can be achieved by making changes in the structure of this material, such as changes in side chain length, chain density, type and length of the main chain, and so on. The molecular weight of poly carboxylates is from 20,000 to 80,000 grams per mole and they have different properties depending on the chemical structure.