Structural Effect of Various Superplasticizers on Their Properties and Interaction with Concrete Active Particles

Polycarboxylate ether superplasticizers are branch polymers with a main chain consisting of sodium salt of carboxylic and sulfonic acids ionic groups and polyethylene glycol arms. The efficiency of superplasticizer in concrete depends on the size of main chain, structures of repeating units, ion/branching ratio and density of branches with various side chain lengths. Superplasticizers are interacted and adsorbed on the surface of active particles present in the concrete. In the presence of polycarboxylate superplasticizers, hydration behavior of active sites and formation of crystals were investigated by Fourier transforms infrared spectroscopy, X-ray powder diffractometry and scanning electron microscopy. The results showed that adsorption of superplasticizers on the active species decreased the size of calcium hydroxide (CaOH) crystals and controlled the heat of hydration. Mechanical strengths, fluidity and fluidity retention of the concrete improved in the presence of superplasticizers. Furthermore, superplasticizers decreased the permeability of concrete and made its microstructure more compact.