For solid waste-based cementitious materials, most scholars focus their research on the hydration reaction of cementitious materials, but there is still a lack of solid waste design that comprehensively considers mechanical properties and durability. Therefore, this article focuses on exploring the mix of design and the microscopic and macroscopic properties of multi solid waste cementitious materials (MSWCMs), namely steel slag (SS), slag powder (SP), desulfurization gypsum (DG), fly ash (FA), and ordinary Portland cement (OPC). According to the orthogonal experimental results, the compressive strength of MSWCMs is optimal when the OPC content is 50% and the SS, SP, DG, and FA contents are 10%, 20%, 5%, and 15%, respectively. The MSWCMs group with an OPC content of 50% and SS, SP, DG, and FA contents of 5%, 15%, 5%, and 25% was selected as the control group. The pure OPC group was used as the blank group, and the optimal MSWCMs ratio group had a 28-day compressive strength of 50.7 megapascals, which was 14% and 7.6% higher than the control group and blank group, respectively. The drying shrinkage rate and resistance to chloride ions were also significantly improved, with maximum increases of 22.9%, 22.6%, and 8.9%, 9.8%, respectively. According to XRD, TG-DTG, and NMR testing, the improvement in macroscopic performance can be attributed to the synergistic effect between various solid wastes. This synergistic effect produces more ettringite (AFt) and C-(A)-S-H gel. This study provides a good theoretical basis for improving the comprehensive performance of MSWCMs and is conducive to reducing the use of cement, with significant economic and environmental benefits.

Ultra-high-performance concrete (UHPC) possesses excellent mechanical properties and durability, but its inherent brittleness significantly limits its structural application under complex loading conditions. This research proposes a composite reinforcement system consisting of steel wire mesh (SWM) and basalt fiber mesh (BFM) based on the composite mesh configuration. Through study of single mesh and composite mesh configurations mixed with 1 vol.% steel fibers on the tensile and flexural properties of UHPC, the multi-scale reinforcement mechanism was revealed. This research designed 11 tensile specimens and 12 flexural specimens, employing a layered casting process to ensure equidistant distribution of the meshes. The results indicate that the SWM significantly increases the peak load and induces strain hardening behavior, while the BFM exhibits no strain hardening response when used alone. Among the layered composite mesh configurations, the steel mesh outer layer (SXS) outperformed the basalt mesh outer layer (XSX), exhibiting the most optimal combined values for the hardening index (I = 1.02) and deformation index (R = 0.91). After incorporating 1% steel fibers, the SXS1+SF1 combination achieved a synergistic improvement in both strength and toughness with energy dissipation during the strain hardening stage reaching 43375.5 N·mm. This composite reinforcement system provides a design-oriented structural approach for achieving a synergistic enhancement of both strength and ductility in UHPC.