Synergistically modified boron sludge-based magnesium oxysulfate cement for rapid road repair

To address the demand for rapid road repair and promote the resource utilization of boron mud (BM), a multi-modified magnesium oxysulfate cement (BMMOC) was developed. The novelty of this study centers on systematically elucidating the synergistic modification mechanism of BM, mineral admixtures, and polymers in the MOS system. Results reveal a critical “dual-regulation” effect of BM: at a 10% optimal substitution, the paste achieves an ideal working window (initial set 76 min, final set 185 min) while delivering peak mechanical performance (28 d compressive strength 72 MPa, 7 d bond strength 1.5 MPa). However, BM dosages ≥ 15% cause performance degradation due to inert interference. Further, mineral admixtures enhance long-term compressive strength by up to 18% via pozzolanic reactions, while polymers improve bond strength by 20% through film-forming and dispersion actions. Microstructurally, both modifiers synergistically promote the formation of the strength-governing 5.1.7 phase (5Mg(OH) 2 ·MgSO 4 ·7H 2 O). This work provides a novel, scientifically validated strategy for high-value solid waste recycling and the design of sustainable, high-performance rapid road repair materials.