Aging effects on recycled WMA porous asphalt mixtures

Nowadays, the use of reclaimed asphalt pavements (RAP) is often combined with Warm Mix Asphalt (WMA) technologies with several benefits in terms of environment, cost and mechanical performance. Concerns still exist related to in-service and aging characteristics of warm recycled mixtures since WMA technologies have been developed over the last decade and hence long term performance data are not available yet. The objective of this experimental study is to evaluate the aging effect on recycled porous asphalt (PA) mixtures produced at reduced temperatures using different WMA additives (organic, chemical and zeolite) and including 15% of RAP. In this sense, long term aging was simulated in the laboratory on compacted specimens by means of the Viennese Aging Procedure (VAPro). Rheological properties of the extracted bitumen samples were measured in order to evaluate possible links between bitumen and mixtures performance. As far as mixtures are concerned, stiffness tests were carried out before and after aging, whereas fatigue resistance was evaluated on long term aged mixtures to compare long term performance of HMA and WMA porous asphalt. Mixtures as well as bitumens results showed that the lower aging process that WMA mixtures undergo during production affects mixtures stiffness at the beginning of service life. Only the presence of the organic additive increases the stiffness of WMA bitumens and mixtures due to the crystalline network structure that forms in the bitumen. On the other hand, extensive long term aging effects were measured in case of WMA mixtures. Nonetheless, overall fatigue results showed that long term fatigue performance of WMA mixtures are not significantly affected compared to HMA regardless of WMA additive types

A Laboratory Approach for Characterizing the Evolutive Behavior of Cold Recycled Mixtures

Cold recycled mixtures (CRM) offer a cost-effective and sustainable alternative to conventional hot technologies for the rehabilitation of asphalt pavements. Reclaimed asphalt pavement (RAP) is the main aggregate source for CRM, while binders normally include asphalt emulsion (or foamed asphalt) and portland cement. Because of the presence of water, emulsion and portland cement, CRM are evolutive materials and thus require a certain curing time to develop their long-term properties. The present study describes a laboratory approach for characterizing the properties of CRM, focusing on their evolutive behavior. The experimental activities were carried out in parallel at École de Technologie Supérieure in Montreal, Canada and at Università Politecnica delle Marche in Ancona, Italy. A common reference CRM composition was chosen in terms of grading curve, asphalt emulsion and portland cement contents. Locally available materials were selected to produce the CRM. Water loss by evaporation and indirect tensile strength (ITS) were measured for a 28-days period, in fixed curing conditions. The evolution of these properties was analyzed using the Michalis-Menten model, in order to achieve a quantitative characterization of the curing process. The results showed that different dosages of water resulted in different rates of water loss by evaporation, but did not penalize the development of ITS. Moreover, for both CRM, a good correlation was found between water loss and ITS. Finally, the data showed that after 28 days of curing in the selected laboratory conditions, the evaporation process was virtually completed

A procedure for characterizing the curing process of cold recycled bitumen emulsion mixtures

Due to the presence of water, emulsion and cement, cold recycled mixtures (CRM) are evolutive materials and thus require a certain curing time to develop their long-term properties. The present study describes a laboratory approach for characterizing the properties of CRM, focusing on their evolutive behaviour. The experimental activities were carried out in parallel at the École de technologie supérieure (ÉTS) in Montréal, Canada and at the Università Politecnica delle Marche in Ancona (UNIVPM), Italy. The evolution of water loss by evaporation and indirect tensile strength (ITS) was measured and analyzed using the Michalis-Menten model, in order to achieve a quantitative characterization of the curing process. The results showed that different dosages of water resulted in different rates of water loss by evaporation, but did not penalize the development of ITS. Moreover, for both CRM, a good correlation was found between water loss and ITS. Finally, the data showed that after 28 days of curing in the selected laboratory conditions, the evaporation process was virtually completed

A comprehensive analysis of the genetic diversity and environmental adaptability in worldwide Merino and Merino-derived sheep breeds

Background: To enhance and extend the knowledge about the global historical and phylogenetic relationships between Merino and Merino-derived breeds, 19 populations were genotyped with the OvineSNP50 BeadChip specifically for this study, while an additional 23 populations from the publicly available genotypes were retrieved. Three complementary statistical tests, Rsb (extended haplotype homozygosity between-populations), XP-EHH (cross-population extended haplotype homozygosity), and runs of homozygosity (ROH) islands were applied to identify genomic variants with potential impact on the adaptability of Merino genetic type in two contrasting climate zones. Results: The results indicate that a large part of the Merino's genetic relatedness and admixture patterns are explained by their genetic background and/or geographic origin, followed by local admixture. Multi-dimensional scaling, Neighbor-Net, Admixture, and TREEMIX analyses consistently provided evidence of the role of Australian, Rambouillet and German strains in the extensive gene introgression into the other Merino and Merino-derived breeds. The close relationship between Iberian Merinos and other South-western European breeds is consistent with the Iberian origin of the Merino genetic type, with traces from previous contributions of other Mediterranean stocks. Using Rsb and XP-EHH approaches, signatures of selection were detected spanning four genomic regions located on Ovis aries chromosomes (OAR) 1, 6 and 16, whereas two genomic regions on OAR6, that partially overlapped with the previous ones, were highlighted by ROH islands. Overall, the three approaches identified 106 candidate genes putatively under selection. Among them, genes related to immune response were identified via the gene interaction network. In addition, several candidate genes were found, such as LEKR1, LCORL, GHR, RBPJ, BMPR1B, PPARGC1A, and PRKAA1, related to morphological, growth and reproductive traits, adaptive thermogenesis, and hypoxia responses. Conclusions: To the best of our knowledge, this is the first comprehensive dataset that includes most of the Merino and Merino-derived sheep breeds raised in different regions of the world. The results provide an in-depth picture of the genetic makeup of the current Merino and Merino-derived breeds, highlighting the possible selection pressures associated with the combined effect of anthropic and environmental factors. The study underlines the importance of Merino genetic types as invaluable resources of possible adaptive diversity in the context of the occurring climate changes