The experimental investigation described in this paper refers to the performance-related characterization of cold-recycled bituminous mixtures employed for the construction and maintenance of road pavements. One of the most critical issues that have to be examined for these mixtures is their short term behaviour under loading, since in the early phases after laying they are more similar to unbound granular materials than to traditional hot bituminous mixtures. In such a context, the authors carried out triaxial tests on a reference cold-recycled mixtures by employing the equipment generally recommended for subgrade soils and foundation materials. Slender laboratory compacted specimens, prepared by means of a gyratory shear compactor, were subjected to triaxial tests for the determination of resilient modulus and of shear strength parameters at three different temperatures (20, 40 and 60°C) and in three different curing conditions (short term, intermediate and full curing). The obtained results were analyzed according to models already available in literature and were discussed by taking into account the internal structure and composition of the mixture.

High volumes of construction and demolition waste (CDW) are continuously produced worldwide. The European Commission aims to increase the recycling of nonhazardous CDW to a minimum of 70% in weight terms by 2020. Hence, there is increasing pressure on researchers to focus on the valorization of these alternative materials for use in the world of construction alongside traditional materials. CDW contains materials from excavation and/or demolition and are typically heterogeneous in terms of composition, grain size, and toughness; furthermore, some particles are more sensitive to degradation processes than others. One solution for an increase in durability while maintaining sufficient strength levels is chemical stabilization with cementitious binders. The paper illustrates the results of a laboratory investigation into the properties of CDW when subject to stabilization with cement kiln dust (CKD). Mixtures of CDW stabilized with ordinary portland cement (OPC) were prepared for comparison purposes. The results obtained with CKD are encouraging because it increases the strength and stiffness of CDW, thus leading to a material completely made up of recycled wastes and by-products usable in the formation of pavement subbases and subgrades. As regards the curing time, all mixtures saw a significant increase in their mechanical parameters when passing from 7–28 days to 365 days of curing.

The paper presents the results of a laboratory investigation seeking to quantify the effects of fine quantity and type on the workability and resilient response of aggregate-fine soil mixtures for subbase formation. Laboratory devices were used to simulate in-field conditions and compact samples and evaluate their resilient response under pulsing loads. Four different types of fines passing through a 63 mm sieve (one non-plastic silt and three silty-clays exhibiting plastic behaviour) in three different quantities (5.4, 10.8 and 16.2%) were combined with coarser aggregates while maintaining the same grading distribution. A variant of the generalized model proposed in the Mechanistic Empirical Pavement Design Guide was calibrated to distinguish the contribution of fine type to resilient modulus from that of moisture content and suction. The results evidenced an improvement in mixture workability during the compaction process when using plastic fines instead of non-plastic ones. However, the quantity of plastic fines should be limited (lower than 10.8% within the aggregate skeleton) in order to achieve a high compaction level and to attain a hardening resilient behaviour rather than the softening one observed in the case of granular materials containing non-plastic fines.

In the experimental study described in this paper, rutting properties of different bituminous binders and those of corresponding mixtures characterized by common composition and volumetrics were investigated and compared. Single shear creep-recovery (SSCR) tests were carried out on binders for the determination of their creep compliance rate (CCR), whereas bituminous mixtures were evaluated by referring to their Flow Number (FN), derived from repeated compressive loading tests. Analysis of experimental data revealed the existence of a strong correlation between rutting parameter of binders and permanent deformation response of mixtures. This confirmed the potential of the proposed testing procedure of being adopted for the evaluation of rutting properties of bituminous binders and for their consequent perfomance-related ranking