A Method for Preparing Low-Temperature and High-Strength Recycled Cement Clinker

Abstract To convert concrete waste into low-carbon cementitious materials, this study employed CaSO 4 as a mineralizer and Al 2 O 3 as a supplementary component. Systematic investigations were conducted on the mineral composition, functional groups, and micromorphology of recycled calcium sulfoaluminate cement (RCSC) clinker, as well as key properties of RCSC hydration products. The results indicate that when only 2% by weight CaSO 4 and 8% by weight Al 2 O 3 were added to hardened cement powder (HCP), the compressive strengths of the hydration products were 50, 65, and 70 MPa at calcination temperatures of 1,300°C, 1,400°C, and 1,450°C, respectively. This approach not only achieves the recycling of concrete waste but also reduces both energy consumption and carbon emissions during recycled cement production. The significant strength enhancement of RCSC is attributed to the formation of substantial Ca 4 Al 6 O 12 SO 4 (ye’elimite) from CaO, CaSO 4 , and Al 2 O 3 under high-temperature conditions. Upon hydration, Ca 4 Al 6 O 12 SO 4 reacts to form ettringite (AFt), which interpenetrates and interweaves with calcium silicate hydrate (C─S─H) to construct a three-dimensional network structure. This network fills the internal pores of the hydration products and reinforces the cohesion of C─S─H. Additionally, a performance control method for RCSC based on three parameters ( C m , P , and n ) is proposed, providing an important theoretical basis for its performance regulation.