Assessment of Early Hydration and Microstructures of Portland Cement Incorporating Calcined Attapulgite

Calcined attapulgite (CAG) is a fibrous calcined clay with strong pozzolanic activity, which is a good candidate for the development of cementitious materials to meet the requirements of CO 2 emission reduction. In this paper, the effects of CAG on the early hydration, microstructure and mechanical properties of cementitious materials were evaluated, and the influence mechanism was further explained by XRD, TG-DTG, SEM–EDS, and hydration kinetics analysis. The results show that CAG accelerates the hydration rate and promotes the early hydration process of cement by introducing additional active sites. The secondary reaction of CAG in cement consumes Portlandite (CH) in cement hydration products and dissolves Mg 2+ to promote the formation of hydrotalcite. The microfiber morphology and good compatibility of CAG in cementitious materials promote the establishment of the network structure of hydration products, inhibiting microcracks and making the structure more compact. CAG promotes the strength development, and the compressive strength reaches the optimal value of 82 MPa with 6% CAG.