In situ characterization of self-cementing properties of recycled materials

In the last years, the emerging environmental & financial issues has led the international scientific community to spend more and more research efforts on the use of recycled materials in road construction, encouraging the standardization committees to modify their references. In some Countries the re-use of construction materials is becoming mandatory, reaching high percentages of recycling materials overall the aggregates used in road constructions. In this context the release of specifications, based on in situ performance criteria, assumes greater importance enabling the widespread use of secondary raw materials. The saving up due to the use of recycled materials covers both the economic aspects (reduced supply of virgin materials) and the environmental ones (lower quarrying of inert material and less dumping of waste materials) related to the infrastructure works. The correct understanding of the on time behaviour of recycled materials, particularly those containing significant quantities of crushed concrete, is of fundamental importance in order to ensure their proper design and built on. The aim of this paper is to highlight the selfcementing properties of recycled materials, according to the evolution of the stiffness characteristics assessed at different curing times, using non destructive devices (LWDFWD). Tests carried out with these instruments allow high levels of reliability guaranteeing more detailed investigation, thus increasing the data available for Qc/Qa. The tests were performed on a trial field consisting of 4 different types of recycled materials. Results show a significant increase in stiffness, expressed in terms of Surface Modulus, as a function of the curing time. The analysis of data acquired by some pressure cells located at the base of the recycled layer allows confirming the increase of stiffness of the materials shown by the deflection test results.