Effect of lime on short-term bearing capacity of bitumen emulsion recycled mixtures

Cold recycling is one of the most employed rehabilitation techniques for asphalt pavements and it is becoming more and more important as the reduction of emissions becomes a priority in the reduction of the greenhouse effect. The main advantages of asphalt cold recycling techniques are the use of reclaimed materials and the lack of need to heat the aggregates to make the mixtures: These possibilities allow for reduced consumption of natural aggregates and emissions providing, at the same time, many technical and economical benefits. The reduction of emissions in the use of reclaimed materials is due to a reduction of transport, in particular that reduction is bigger when the reclaimed materials are used in place. Nevertheless, the so-called cold in place recycling has challenges to control the water content in the mixtures and of quickly achieving a sufficient bearing capacity to allow the completion of the re-paving work. Generally the solution is provided by the use of active fillers, mainly Portland cement, able to absorb water and stiffen the mixtures. Sometimes the in place working conditions make necessary (presence of clay soils) or suggest (high moisture content) the addition of lime, but its effect on cold mixtures performances is, at the moment, not completely understood. In an effort to improve on-site performance of recycled mixtures, the authors developed an extensive research programme aimed to investigate the effects provided by the introduction of lime in cold recycled mixtures as active filler. The basic idea was to analyse the bearing performance of pavement layers made with bituminous emulsion cold recycled mixes with different blends of active fillers (cement, lime). This paper evaluates the short term bearing capacity of recycled mixtures: Assessment provided are based on results of deflectometric tests carried out on a trial section specifically built in Italy, close to Florence. Tests have been undertaken using LWD (Lightweight Deflectometer) and FWD (Falling Weight Deflectometer) immediately after compaction and after 24 hours of curing. The obtained results, even though they need to be confirmed by the analyses of long- Term behaviour, positively support the use of lime as an active filler. © 2014 Taylor & Francis Group, London.