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An eco-friendly and high-efficient preparation approach to synthesizing polycarboxylate superplasticizers (PCE) co-polymers based on microwave induction was described. Meanwhile, a series of detailed comparative studies about the effects of microwave induction and conventional thermal inductions on the conversion rate and reactivity ratio in the polymerization reaction, molecular structure, adsorption behavior and fluidizing effect of PCE co-polymers were reported. The results revealed that the green advances of PCE co-polymer preparation by microwave induction in the preparation time and conversion rate compared to conventional thermal induction. At lower dosage, the PCE co-polymer synthesized by microwave induction also has excellent dispersibility in the fresh cement paste (fcp). Furthermore, under microwave induction, relative reactivity of macromonomer (α-methallyl-ω-hydroxy poly (ethylene glycol) ether (HPEG)) is increased in polymerization system, and the monomers ratio of the co-polymers closer to feeding ratio is achieved.

As the most effective superplasticizer, the comb-like PCE polymers also severely retard early cement hydration and hence decelerate early strength growth of concrete, which is undesired in some applications. In this study, a series of PCEs with different molecular architectures, including varied side chain length and density were synthetized by co-polymerizing acrylic acid and α-methallyl-ω-hydroxy poly(ethylene glycol) ether. Impacts of the obtained PCEs on cement hydration and early strength of mortar were investigated. Results show that adsorption of PCEs on cement grains is highly dependent on polymer architectures. Higher side chain length and density lead to lower adsorption amount and consequently higher early strength of mortar. It is interestingly found that the retardation effect of the PCEs on cement hydration is simply proportion to their absolute adsorption amounts on cement surface, while the complexation of R−COO− group with Ca2+, which is independent on polymer architectures, plays a minor role.