Assessing the Field Curing Behavior of Cold Recycled Asphalt Mixtures

Cold recycling techniques in road construction have been of rising interest because of huge environmental benefits in terms of energy saving, emission reduction, and preservation of natural resources. The improvement on selection and quality of the raw materials and binders as well as the enhancement of the knowledge on mixture performance are leading to the intensive use of cold recycling techniques in place of traditional ones. One of the main differences between cold and hot techniques is the evolutive development of performance, generally identified as curing process, due to the presence of water and hydraulic binders in the cold mixtures. Environmental-related factors such as temperature, humidity, wind, and rainfall significantly influence the curing process and, as consequence, the mixture properties over time. Several laboratory curing protocols have been developed by universities, research centers, and agencies, but a clear relationship between simulative procedures in laboratory and the field is still an open challenge. This paper aims at characterizing the short-term and midterm curing behavior of a cold recycled material (CRM) mixture. A CRM mixture was selected and characterized in laboratory, and the in-plant production procedure was validated. The CRM mixture was used to build the binder course of an instrumented pavement in the Republic of San Marino. Volumetric and mechanical testing on laboratory-produced specimens and cores were analyzed considering the temperature and moisture sensor measurements in field. Results address to a new insight for laboratory procedures and prediction models matching laboratory conditions and the real curing condition in field.