Abstract: A model of assessing the quality grade of recycled coarse aggregate based on improved set pair analysis was proposed. Firstly, the assessment index system composing seven factors inclusive of apparent density was established by referring to the Standard for Renewable Coarse Aggregate of Concrete (GB/T25177-2010) and the criteria for the rating of indexes were determined. Meanwhile, the connection degree identical discrepancy contrary in traditional set pair analysis was modified using developability of connection degree. The mathematical model based on the improved set pair analysis was constructed to calculate the optimal value of identical discrepancy contrary of single index. Moreover, the index weights were determined by using the entropy weight method and the multiple super-scale weighting method; on such basis, the degree of quality convergence of recycled coarse aggregate was assessed based on the fuzzy comprehensive evaluation theory. The proposed method was applied to comprehensively assess the quality grades of five groups of recycled coarse aggregate samples. Results revealed that the proposed modified set pair analysis method could preliminarily define the range of intervals of each grade, and further reflected the inclination towards which grade. Difference in the degree of connection between different grades was also obvious.

Key words: recycled coarse aggregate, quality rating, improved set pair analysis, entropy weight method, exceeding multiplier method