Mechanism analysis and effect of styrene–acrylate copolymer powder on cement hydrates

In this paper a styrene–acrylate copolymer (SAE) powder was used to modify Portland cement paste. The concentration of the products of hydration was investigated using X-ray diffraction (XRD). Also the physical and chemical interactions occurring in the modification process were studied using Fourier-transform infrared spectrometer (FTIR). The results show that the addition of SAE powder facilitates the formation of ettringite (AFt). The hydration product tetracalcium aluminate hydrate (C4AH13) begins to appear in the cement paste after 7 days, its formation slightly decreases with an increase in the SAE powder–cement ratio (mp/mc). Single-sulfur hydrated calcium sulphoaluminate (AFm) is also found in the cement paste beginning after 7 days; however its content is very small. Also as the mp/mc is increased the amount of calcium hydroxide (Ca(OH)2) in the hydrating cement paste decreases, this effect is more pronounced at earlier ages. FTIR analysis indicates that Ca2+–carboxyl complexes form during the hydration of cement paste containing SAE powder.

► SAE powder promotes the formation of AFt in cement pastes.
► C4AH13 appears in cement pastes after 7 days and SAE powder decreases its content.
► SAE powder promotes C3A hydration and that is more pronounced for later ages.
► SAE powder decreases the amount of Ca(OH)2 and this decline is more significant at earlier ages.
► Ca2+–carboxyl complexes form in cement pastes modified with SAE powder.