Particle characteristics of recycled cement-stabilized gravel under abrasion treatment and evaluation of pretreatment effect

To promote the reutilization of recycled cement-stabilized gravel (RCSG) in road base courses, the influence of abrasion parameters on the abrasion effect of virgin aggregate was analyzed. A treatment scheme for RCSG was then proposed. The changes in morphology, gradation, agglomeration rate, and abrasion value of RCSG before and after abrasion treatment were evaluated. A multi-index comprehensive evaluation system based on data envelopment analysis (DEA) was used to recommend the optimal abrasion cycles and size fraction for RCSG. The pavement performance of corresponding cold recycled cement-stabilized mixtures was verified. The results indicated that the agglomeration rate of RCSG of all sizes generally exceeds 20%. Abrasion tests on virgin aggregate verify that steel-ball abrasion increases fine aggregate content. They also determine a preliminary recommended upper limit of 500 abrasion cycles for RCSG pretreatment. The optimal pretreatment condition is determined as 6 steel balls and 400 rotation cycles for RCSG. Under this condition, the overall agglomeration rate of full-size RCSG drops from 30.7% (100 cycles) to 7.9%. Compared with the coarse fraction, the full-size fraction RCSG showed a 54.1% higher abrasion value and an 11.2% lower agglomeration rate. The DEA evaluation shows that the abrasion pretreatment effect on full-size fraction RCSG is superior to that on coarse and single-size fractions. Abrasion pretreatment of full-size fraction RCSG with 6 steel balls and 400 cycles achieves the best balance between particle shaping and energy consumption control. At 30% RCSG replacement, the 7 d and 28 d unconfined compressive strength (UCS) of the cold recycled cement-stabilized gravel mixture increased by 115.6% and 121.2%, respectively, compared with the untreated group.