Influence of cationic polyurethane on mechanical properties of cement based materials and its hydration mechanism

The cation polyurethane (PUC) was used to improve the mechanical property of cement-based materials. Meanwhile, hydration kinetics, mineral phase compositions and microstructure characterization of hydration products were also investigated by isothermal calorimetry, quantitative X-ray diffraction and scanning electron microscope. The results show that the addition of PUC accelerated the cement hydration, altered the mineralogical compositions and morphology of hydration products, and correspondingly the microstructure of cement based materials. It is found that the addition of PUC decrease the brittleness of cement-based materials, especially for the early age. When the dosage of PUC is 0.5%, as the optimal mixing amounts, the tensile strengths of hardened cement pastes at 1 day, 3 day and 7 day separately increase by 49.92%, 93.63% and 88.44%, simultaneously the flexural strengths also exert corresponding increases by 8.38%, 26.61% and 36.40%, comparing with the plain cement-based materials. While, the addition of sand, will migitigate or even eliminate this toughness improving benefit due to the introduction of interfacial zone.