Abstract: The optimal mass fraction of fly ash was determined based on the principles of maximum strength and appropriate stiffness, with cement and recycled brick aggregate mass fractions and curing age set as control parameters. Mechanical properties of 15 recycled brick mix water stabilizing materials(recycled brick mix water stabilizing material, RBSM)under different mix designs were investigated. The comprehensive performance of RBSM was evaluated using the entropy-weighted TOPSIS(technique for order preference by similarity to ideal solution)model, yielding optimal values for each parameter. Results indicate,(1)Early-age splitting tensile strength and unconfined compressive strength first increase then decrease with rising fly ash content, peaking at 10% mass fraction. Compressive rebound modulus increases with fly ash content, confirming 10% as the optimal fly ash content in cement.(2)The optimum moisture content of RBSM gradually increases with the mass fraction of recycled brick aggregate, while the maximum dry density decreases accordingly.(3)During the early curing stage, the splitting strength of RBSM gradually decreases with increasing recycled brick aggregate mass fraction, while the unconfined compressive strength first increases and then decreases, peaking at a mass fraction of 50%. As the curing age increases, the mechanical strength of RBSM improves.(4)Through entropy-weighted TOPSIS theory, optimal mass fractions for cement and recycled brick aggregate were determined. The final recommended optimal mix design for recycled brick-based water-stabilized materials was 10% fly ash mass fraction in cement, 7% cement mass fraction in recycled brick-based water-stabilized material, and 50% recycled brick aggregate mass fraction in recycled brick aggregate.

Key words: recycled brick-concrete water-stabilizing material, mechanical properties, entropy weight TOPSIS, comprehensive performance evaluation, optimal quality score