Durability evaluation and life prediction of desert sand grouting material for semi - flexible pavements under sulfate dry - wet cycles based on entropy weight method and grey theory

The application of desert sand in building materials has witnessed certain advancements. However, regarding its utilization in semi - flexible pavement grouting materials within sulfate - eroded environments, the existing comprehensive durability evaluation criteria and life - prediction methods suffer from the limitation of considering only single factors. In this study, semi - flexible pavement desert - sand grouting materials (DSGM) were prepared by substituting river sand with desert sand (DS) at dosages of 0 %, 15 %, and 30 %. The systematic investigation was carried out to explore the impacts of DS content and the number of sulfate dry - wet cycles (DWCs) on the durability of DSGM. Based on the entropy - weight method and the GM(1, 1) model, a comprehensive durability evaluation criterion and a life - prediction model were established, taking into account the variations in mass, compressive strength, and flexural strength. The results of the sulfate DWCs tests indicated that DS enhanced the compactness of the materials by optimizing the interface between aggregates and the paste and filling pores. In the initial stage of sulfate erosion, the expansion products such as ettringite and gypsum increased the density of the matrix in the short term. Nevertheless, with the continuous accumulation of erosion products, the pore network became interconnected, eventually leading to a trend where both the mass loss rate and the compressive - strength loss rate of DSGM first decreased and then increased. After determining the weights of compressive strength, flexural strength, and mass using the entropy - weight method, a comprehensive evaluation criterion centered around the durability value was proposed. This criterion can comprehensively account for the influences of various factors on durability. Furthermore, by introducing the GM(1, 1) model, a life - prediction model was developed, which can accurately predict the attenuation pattern of the durability value of DSGM under different erosion cycles. The findings of this study can provide theoretical support for the engineering applications and durability research of DSGM in sulfate - eroded environments in desert regions.