Effect of Compounding Retarder and PCE on the Early Properties and Hydration of High-Belite Sulphoaluminate Cement

Abstract

To cope with the problem that the setting time and hardening time of high-belite sulphoaluminate cement (HBCSA) is too fast and not easily controlled, three common retarders, citric acid (CA), β-cyclodextrin (β-CD), and borax (B), were selected and compounded with polycarboxylate superplasticizer (PCE). Based on the cement slurry fluidity, fluidity loss, setting time, and mechanical properties of cement mortar, combined with X-ray diffraction (XRD), scanning electron microscopy (SEM), and Zeta potential tests, the interaction and mechanism of different retarders and high-belite sulphoaluminate cement were studied. The results show that β-CD and CA can significantly delay the hydration process of HBCSA cement, effectively improve the fluidity loss, and make the dispersion more stable, but the strength of cement mortar decreases, which is not conducive to the development of strength. However, the addition of B has no obvious retarding effect on the HBCSA cement, and the dispersibility of the cement paste decreases. In microscopic tests, XRD and SEM tests verified that the combination of retarder and PCE had a certain inhibitory effect on the early hydration of HBCSA, and the zeta potential indicated that the addition of retarder would interact with PCE to improve the fluidity loss of HBCSA. In addition, when the retarders CA and B were, respectively, compounded with β-CD, the two would have a synergistic effect. The retardation effect is more obvious, and the time interval between the initial and final setting is shorter, which is more controllable. The initial fluidity is also improved under the auxiliary plasticization of cement paste by β-CD.