The effect of alkyl acrylate ester side chain length of polycarboxylate superplasticizer on the flow behaviour of concrete

Polycarboxylate superplasticizers (PCEs) are vital to develop concrete-based materials with low CO2 footprint, good fluidity, and workability. Designing PCEs with high dispersion property is specially critical for high strength concrete due to their elevated viscosity. Systematically exploring the effect of side chain length on their conformation, adsorption capacity, and charge distribution on the suspended cement particles, as well as on the flow behavior, and workability of concrete is necessary. Here, PCEs holding a side chain of TPEG-2400 (nEO = 52) were modified with 3 different length of acrylic esters at molar ratios of acrylic acid (AA): macromonomer (MM): ester of 4: 1: 2.5. It was observed that PCE with the shortest ester side chain length (MA-PCE) showed the highest adsorption and electrostatic repulsion due to its lowest surface tension, largest hydrodynamic radius, and highest zeta potential, reducing the solid-liquid interface energy, and exposing the highest amount of negatively charged carboxyl groups to anchor upon the surface of cement particles thereby promoting its dispersion performance and rheological properties. The outstanding dispersing effect of MA-PCE was demonstrated by the T500 and efflux time of concrete. The findings that the side chain length of ester group of PCEs can not only influence their adsorption but also their conformation pave the way to design other high dispersion PCE with high workability of concrete.