Experimental Investigation for the Analysis of Cold-Recycled Bituminous Mixtures

The Authors present the results obtained in a experimental investigation carried out to provide technical support to the construction of a cold-recycled bituminous sub-base layer of a major Italian motorway. Compliance of the employed materials and of the resulting recycled mixture to requirements set in Technical Specifications and to the adopted job-mix formula were verified by means of laboratory tests. Field observations focused on the evaluation of the void content of the compacted sub-base layer and on its stiffness evolution in the short term curing phase. Finally, mix design was carried out by following a procedure based on the use of the gyratory shear compactor and on the optimization of the composition of the fluid phase. The procedure was validated by performing volumetric and mechanical tests both on the optimized mixture and on a mixture prepared according to the job-mix formula.