Influence of CaO-based expansive agent, superabsorbent polymers and curing temperature on pore structure evolution of early-age cement paste

Cracks easily generate in concrete at early age owing to the shrinkage deformation. CaO-based expansion agent (CEA) and superabsorbent polymers (SAP) have been extensively used for the mitigation of concrete shrinkage. The macroscopic properties of concrete are highly determined by the microstructure. In this study, the influence of CEA and SAP addition on the pore structure evolution of cement paste under different curing temperatures was evaluated via low-field nuclear magnetic resonance spectroscopy. Test results indicated that, in cement paste, a higher CEA content led to a higher porosity and a larger most probable pore diameter (MPPD). Meanwhile, SAP addition increased the porosity and MPPD of CEA cement paste at early age but decreased them after 7 d, and a higher SAP content always brought a higher porosity and MPPD. Furthermore, the addition of SAP led to a lower porosity and MPPD of CEA cement paste than that of plain cement paste after 14 d. Moreover, the porosity and MPPD of CEA cement paste decreased first and subsequently increased as the curing temperature raised.