Influence factors of strength and performance of foamed asphalt cold recycled mixture

This paper investigates the factors that influence the strength and moisture damage resistance of foamed asphalt cold recycled mixtures. The relevant factors include gradation, asphalt penetration, mixing temperature, particle size of virgin aggregates, and the curing time and moisture content. Indirect tensile strength (ITS) tests under dry and wet conditions were conducted to evaluate the mixture properties. The test results indicated that minute variation in foaming parameters (i.e. expansion ratio and half-life) for asphalt binders with different penetration grades, had no significant effect on the strength and performance of foamed asphalt cold recycled mixtures. The results also revealed that the mixture with medium-grained gradation exhibited higher ITS than mixtures with coarse- and fine-grained gradation. As the temperature of the added virgin aggregates increased, the ITS and moisture damage resistance of the mixture increased as well, but the difference was quite small. It was also observed that the mixture demonstrated better ITS and moisture damage resistance when using filler in material design. The relationships between curing time, moisture content, and strength of the mixture during curing were also investigated, and the variations of strength formation was summarised. The significance of the studied factors was finally analysed using a one-way analysis of variance based on the test results.