Shrinkage properties of self-curing aeolian sand semi-rigid base

ObjectiveRoad construction in desert regions was constrained by shortages of conventional materials, and the dry climate with a large diurnal temperature range increased the susceptibility of semi-rigid bases to drying-shrinkage cracking. In this study, aeolian sand was used to replace fine aggregate in a cement-fly ash stabilized crushed-stone mixture. A composite self-curing technique suitable for desert conditions was proposed based on synergistic moisture regulation using superabsorbent polymer (SAP) and evaporation retardant. The shrinkage properties of aeolian sand semi-rigid base were investigated.MethodFirst, the orthogonal test was employed to quantify the influences of key factors, i.e., binder proportion, SAP content and additional mixing water, on the drying shrinkage of aeolian sand semi-rigid base. Second, the laboratory simulations reflecting desert climatic conditions were conducted with different curing regimes to evaluate how SAP and evaporation retardant regulate shrinkage development and water-loss evolution. Finally, the empirical shrinkage prediction model was established for the studied mix proportions.ResultThe binder proportion was the dominant factor governing drying shrinkage. Both SAP content and additional mixing water had statistically significant influences on 28-day average drying-shrinkage coefficient. Incorporating SAP reduced the 28-day coefficient by more than 35% on average, and delayed the time at which cumulative water loss approached a steady stage. The composite self-curing system consistently lowered drying-shrinkage strain with different curing regimes at the same age. Mechanistically, SAP provided internal water supply via an absorption-release process, thereby slowing the drop in internal relative humidity. The evaporation retardant formed a crystalline surface layer film that suppressed moisture evaporation. When used together, they further reduced cumulative drying-shrinkage strain and the shrinkage coefficient.ConclusionThe developed shrinkage prediction model based on the experimental database captures the age-dependent evolution of shrinkage. It can be used to predict shrinkage properties at different ages. The findings provide theoretical support and practical guidance for material design and curing control in desert road engineering.