Effects of core-shell polycarboxylate superplasticizer on the fluidity and hydration behavior of cement paste

Abstract Polycarboxylate superplasticizer nanomicelles (nano-PCEs) with a core-shell structure were prepared via aqueous emulsion copolymerization in one pot. The shells are constructed with hydrophilic segments of poly(acrylic acid)-co-poly(isobutenyl polyethenoxy ether) (PAA-co-PHPEG), offering the water-reducing performance and stability for nano-PCEs. The cores are self-assembled with hydrophobic segments of polystyrene-co-poly(hydroxyethyl acrylate) (PS-co-PHEA), endowing nano-PCEs with good loss resistant of fluidity for cement pastes. The chemical structure of nano-PCEs was verified by the nuclear magnetic resonance spectrum (1H NMR) and fourier transform infrared spectroscopy (FTIR), and the 16-48 nm diameter of nano-PCE nanomicelles was determined by dynamic laser scattering (DLS) and transmission electron microscopy (TEM). Compared with comb PCEs, the cement paste containing nano-PCEs exhibited better fluidity retention of three hours by mini-slump measurements, lower hydration heat and more delayed hydration heat evolution by isothermal calorimetry tests. Furthermore, the hydrolysis and adsorption behavior of nano-PCEs in alkaline cement pastes were deduced, and a working mechanism of nano-PCEs was theoretically explained. This new type of superplasticizer nanomicelles can be used as a long time rheology modifying agent in fresh cementitious systems.