Use of calcium oxide as active filler for bituminous stabilised materials

With the increasing usage of cold recycling techniques on maintenance of flexible pavements, increases also the need to better characterise the properties of cold recycled mixtures, usually composed of aggregates, reclaimed asphalt–RAP, active filler and bitumen. Understanding the mechanical behaviour of cold recycling mixtures is necessary to set the design process on a performance based approach. This study was designed to evaluate evolution of mechanical behaviour related with the use of quicklime (calcium oxide) as active filler in a BSM mixture; the quicklime was added on different contents up to 5%, considering that its chemical reaction with water can be very convenient to deal with environmental limitations on the construction of a BSM layer. Alongside, this study also compares in a qualitative way the changes in mechanical properties when lime or cement are used as active filler. Indirect tension tests and monotonic triaxial tests were run on BSM mixtures produced with either quicklime or cement added in different amounts. The results show that the use of quicklime may bring various advantages to cold recycling operations, with negligible performance variation even when added in 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 in field operations.