Early-Stage Hydration Retardation Mechanism in High-Ferrite Cement Clinker Doped with a Massive Amount of CuO

High-ferrite cement (HFC) has attracted widespread attention due to its advantages, such as low sintering temperature and excellent corrosion resistance. The application of Cu-containing waste in HFC will promote the cement industry toward low-carbon and sustainable development. However, massive amounts of CuO can cause a delay in HFC hydration. The main aim of this paper was to investigate the retardation mechanism of CuO on the hydration of HFC using X-ray diffraction, mercury intrusion porosimetry, isothermal heat-conduction calorimetry, scanning electron microscopy, inductively coupled plasma-optical emission spectroscopy, thermogravimetric analysis and derivative thermogravimetry, among others. The results showed that compared with the undoped clinker, the maximum heat release peak of the clinker doped with 1.5% by weight of CuO was delayed for about 60 h, the hydration induction period was extended from 37 to 89 h, and the compressive strength was zero at 3 days. Through the study of cement suspension at 3 days, it was found that the retardation mechanism is mainly due to the obstruction of Ca leaching. On one hand, the C3S content in the HFC clinker decreases and the grain size of the calcium silicate minerals increases, on the other hand, the Ca2(OH)4·4Cu(OH)2·H2O coats clinker particles at the early stage, leading to a lower hydration degree of the HFC clinker.