Preparation of early strength concrete using all solid waste-based cement: Strength formation mechanism and carbon footprint evaluation

Addressing the dual challenges of high carbon emissions in the cement industry and solid waste disposal, this study innovatively utilized coal gangue, carbide slag, and desulfurized gypsum to prepare an all solid waste-based cement (ASWBC) and developed an early-strength concrete. The formation mechanism of the mechanical properties and the carbon reduction effects of its early-strength concrete were systematically analyzed through microstructural characterization and carbon footprint assessment. The results indicate that ASWBC concrete exhibited excellent early-age strength, achieving a compressive strength of 35.01 MPa at 6 h, which is 48.6 % higher than that of sulfoaluminate cement (SAC) concrete. It also demonstrates good continuous strength development, reaching a 28 d strength of 54.84 MPa. Its performance advantages originate from the rapid hydration of C 4 A 3 S̄ forming ettringite and aluminum gel, which construct a dense microstructure, coupled with the subsequent hydration of C 2 S producing C-S-H gel that refines the pore structure. Furthermore, the carbon emissions from the ASWBC concrete preparation process were reduced by 29.04 % compared to Ordinary Portland Cement (OPC). The core emission reduction mechanisms include: the substitution of natural resources with solid waste eliminating CO 2 from limestone decomposition, a 38.9 % reduction in coal consumption due to low-temperature calcination, and the replacement of 28 d standard curing with 3 d natural curing reducing energy consumption. Consequently, the carbon emission per unit strength of per ton of concrete (C 0 = 3.66 kg/MPa·t) was optimized by 45.1 % compared to OPC. This research provides a waste recycling technological pathway for the construction materials industry, offering both high performance and low-carbon attributes. • A novel cement was entirely prepared from industrial solid wastes, eliminating the use of natural raw materials. • Achieves 35.01 MPa in 6 h, 48.6 % higher than SAC, with excellent early strength. • Reduces carbon emissions by 29.04 % and optimizes the carbon efficiency ratio by 45.1 % through multi-path emission reduction.