Research of indoor molding of cold recycled foamed asphalt mixture with secondary hot compaction process considered

Abstract

Cold recycled mixture using foamed asphalt (CRMF) has been widely used as a base due to its environmental advantages. The hot-mix asphalt (HMA) paved on top of the CRMF can produce a secondary hot compaction effect on the CRMF layer. However this secondary compaction effect cannot be considered in the current compaction methods in laboratory. This paper investigates the effect of secondary hot compaction on the CRMF base and optimized indoor molding of cold recycled foamed asphalt mixture with a secondary hot compaction process considered. Two types of indoor molding (secondary large Marshall compaction and secondary vibro-compaction) and two curing temperarues (40 °C and 60 °C) were employed in this study. The indirect tensile strength (ITS) and air voids are used to evaluate mixtures properties before and after the hot-mix asphalt paved for determining which indoor molding method is more consistent with the actual construction. The results indicate that the secondary hot compaction process is beneficial for increasing the ITS and moisture resistance, and decreasing the freezing-thaw resistance. The influence depth of the secondary hot compaction is limited, which is about 5 cm. The traditional one-time large Marshall compaction can only simulate conditions before HMA paving. The secondary large Marshall compaction matches well with the cases in the field. The compaction and curing conditions (compaction-130 blows per side + 48 h curing at 60 °C + compaction-20 blows per side + 24 h curing at room temperature) are recommended to fabricate CRMF in the laboratory.