Optimization study on the material composition of cold-mix ultra-thin overlay

To improve the road performance of cold-mix ultra-thin overlay (CMUTO), the abrasion test and noise test methods were adopted to optimize the material composition of CMUTO from the particle size of gravel in the support structure layer, the gradation of cold mix, and the combination of structural layers, to analyze the influence on the abrasion and noise characteristics, and to validate the performance through the application of the entity project. The results show that the smaller the gravel particle size of the support structure layer and the lower the aggregate content of 4.75 and 2.36 mm in the cold mix, the more conducive the improvement of the abrasion resistance of CMUTO. The effect of the support structure layer on abrasion resistance is more significant than that of the cold mix. The combination of upper and lower layers has a coupling effect on the abrasion resistance of CMUTO. With the increase in abrasion duration, the abrasion value increases first and then tends to level off. Among the nine structural combinations, reduced noise levels are associated with smaller gravel particle sizes in the support layer and lower coarse aggregate content in the cold mix gradation. The use of appropriate material composition for CMUTO can effectively reduce the driving noise. With increasing abrasion time, the equivalent continuous sound level shows a decreasing trend. The field test results of an entity project show that CMUTO has good performance in terms of noise characteristics, anti-skidding performance, and water sealing performance.