The use of quicklime as an active filler on cold recycled mixtures stabilized with bitumen

With the increasing usage of cold recycling techniques on maintenance of flexible pavements, also increases the need to better characterize the properties of cold recycled mixtures, usually composed of aggregates, reclaimed asphalt, active filler and bitumen, understanding the properties of cold recycling mixtures to set the design process on a performance-based approach. This research was designed to evaluate evolution on mechanical behaviour related with the use of quicklime (calcium oxide) as active filler on a BSM mixture with 100% RAP; the quicklime was added on different contents up to 5%, stabilised either with emulsion or foam bitumen, considering that the heat derived from its chemical reaction with water can be very convenient to deal with environmental limitations on the construction of a BSM layer. Alongside, this research also compares, in a qualitative and quantitative way, the changes in mechanical properties when cement is used as active filler. Indirect tension tests and simplified monotonic triaxial tests were run on emulsion and foam-based BSM mixtures produced with either quicklime or cement, added on different amounts. The mixtures were also subjected to temperature measurements on post-mixing phase. The results show that the use of quicklime may bring various advantages to cold recycling operations, with considerable increase and maintenance of temperature, up to around 20° C, with manageable performance variation, even when added on higher amounts. Results also indicate that mixtures designed with cement are more susceptible to mechanical behaviour changes when compared to the ones designed with lime, which suggests that mixtures designed with cement need a more precise mix design and specially a more accurate mixing control on field operations.