Ignacio Perez

Compaction is one of the most important factors to be considered while manufacturing laboratory samples of cold in-place recycled (CIR) mixtures. In this study, the effect of three laboratory compaction procedures (static, gyratory, and impact) on the volumetric performance of CIR mixtures was investigated. CIR specimens were manufactured with the same proportion of added water and bitumen emulsion, and using several levels of compaction, varying the number of gyrations and blows. The volumetric properties were evaluated by different procedures, both before and after curing. A comparison between the laboratory results of the different tests, the design target values, and actual in-field values was performed. It was observed that gyratory compaction proved to be the most versatile and one that best represented the real compaction. The bulk density procedure by dimensions was useful for laboratory design; however, it overestimated the sizes of the air void content by more than 10% compared to the field values.

There is a growing trend to promote circular economy practices and reduce petroleum-derived product consumption in the paving sector. In this context, a liquid lignin-rich industrial waste was incorporated at 0% (control), 5%, 10%, 15%, and 20% into a bitumen emulsion to manufacture a lignin-based biobinder for half-warm-mix asphalt (HWMA). The mix of the bitumen emulsion and the industrial waste was made using an Ultra-turrax device, with the final mixing temperature monitored using a thermographic camera. Microstructure analysis was conducted using scanning electron microscopy (SEM). The bitumen was extracted and characterized using needle penetration tests at several temperatures. Additionally, the ring-and-ball softening point, penetration index, and ductility were assessed. Incorporating up to 5% of lignin-rich industrial waste led to a lignin-based biobinder that could be used for a more sustainable and bitumen-efficient HWMA production.

A very appropriate way to encourage and motivate students, and help them to grasp the theoretical concepts better, is the active teaching-learning techniques. During this experience, these techniques have been applied in the optional subject "Road and Airport Infrastructure" of the Master's Degree in Civil Engineering, taught at the University of A Coruña. The experience consisted of the realization of different laboratory practices that allowed the students to attend and participate in tests of bituminous mixtures, following the current standards and writing reports based on the results. After the laboratory practices, the students completed brief surveys that showed their total satisfaction. They motivated the teaching staff to continue carrying out this type of teaching technique in future courses on this subject.

Cold-asphalt mixtures (CAMs) are evolved materials whose mechanical strength increases with their maturation. The relationship between CAM field maturation and laboratory-accelerated cure procedures is not well understood. Furthermore, there is controversy on the recommended methodology for laboratory-accelerated cure. So, in this work, the accelerated curing protocol for a CAM-type gravel emulsion was examined, and its uncontrolled maturation and performance were contrasted. For this, the mixture was subjected to either accelerated curing (from 0 to 7 days in a 50 °C oven) or natural curing (from 0 days to 6 months at 20 3 °C in the laboratory and at an unfixed temperature outside the laboratory). We analysed, as functions of time, the moisture, indirect tensile stiffness modulus (ITSM), and moisture damage resistance. A curing protocol of 2 days at 50 °C yielded ITSM values closer to those obtained under uncontrolled conditions. Nevertheless, total maturation of the mixture was achieved after 3.5 days of curing. The nonlinear weighted least-squares method yielded an expression that better predicted the performance of the gravel emulsion for the first six months of life. The model parameters were easily fitted using ITSM measurements derived from samples cured for 2 days in a 50 °C oven.