Rutting prediction of a granular material for base layers of low-traffic roads

[Abstract:] This paper analyses the permanent deformation performance of an unbound granular material for base layers of low-traffic roads. The material has been subjected to repeated triaxial loads. The shakedown theory was used to classify the structural response of the unbound granular material to the applications of load cycles. Three models were fitted to express the cumulative permanent strain as a function of the number of load cycles. In general, the predictions of two models previously studied by other researchers proved to be good but in the long-term, they tended to underestimate the measured values. In contrast, a third new model – the sum of two well known models – offered excellent predictions, which in the long-term did not tend to either underestimate or overestimate the measured values

Mezclas asfálticas dosificadas con RCD para carreteras de bajo tráfico

[Resumen:] En este artículo se estudia la viabilidad técnica de utilizar áridos procedentes de residuos de construcción y demolición en mezclas asfálticas en caliente. Se eligió una mezcla gruesa con diferentes porcentajes de áridos reciclados. Los parámetros Marshall cumplen lo estipulado en el PG-3 para tráficos T3. Las mezclas asfálticas en caliente fabricadas con diferentes porcentajes de áridos reciclados tienen una mala adhesividad. Con áridos calizos se obtiene una mejor adhesividad. La adhesividad mejora notablemente al eliminar el mortero de cemento adherido a los áridos reciclados

Construction and demolition debris in hot mix asphalt

This work evaluates the resistance to fatigue cracking of hot asphalt mixtures made with aggregates from construction and demolition debris. The mixtures were fabricated with 50% recycled aggregates to be used as road bases and binder courses in roads with low traffic volumes. For each mixture studied the fatigue law constants in deformation were obtained as well as the dynamic modulus. These results were compared to those obtained in hot asphalt mixtures elaborated with only virgin aggregates from quarries

Ensayos de resistencia de las mezclas asfálticas al ataque de carburantes. Recomendaciones sobre el tiempo de inmersión en baño

Este congreso tivo lugar na Coruña do 2 ao 4 de xullo de 2008.[Resumen:] Una de las limitaciones que tienen las mezclas asfálticas como material para pavimentación es su falta de resistencia al ataque de los carburantes derivados del petróleo. Existen diversos procedimientos para determinar la resistencia de los materiales asfálticos a la acción de los carburantes. En el caso de selladores y tratamientos superficiales pueden encontrarse diversas normas de ensayo, tanto en la series europeas como americanas. Sin embargo, en lo referido a la evaluación de mezclas asfálticas propiamente dichas, existe una notable falta de normalización. Esta ponencia estudia en laboratorio algunos aspectos fundamentales de los procedimientos para evaluar la resistencia de las mezclas asfálticas respecto a la acción de los carburantes. Como resultado de la investigación se hacen algunas recomendaciones de buena práctica para los procedimientos de pérdida de peso tras inmersión en carburante, con o sin cepillado posterior, y respecto a la estabilidad Marshall conservada tras inmersión. En particular, respecto al período de inmersión, uno de los factores con más influencia, a la vista de los resultados de laboratorio y su tratamiento estadístico, se recomienda que sea de 24 horas, excepto en el ensayo de pérdida de peso tras inmersión sin cepillado posterior, en el que los datos obtenidos resultan más significativos si el período de inmersión es de 7 días

Quality control of manufacturing and hot storage of crumb rubber modified binders

The ultimate performance of crumb rubber modified (CRM) binders is linked to the accurate control of the properties during manufacturing and hot storage. However, due to their complexity, asphalt technologists find the characterisation of these materials still challenging. In this study, the adoption of a Dual Helical Ribbon (DHR), a novel mixing/measuring device for rotational viscometers, is proposed for the real-time monitoring of CRM binders during manufacturing and hot storage. According to the laboratory results, manufacturing periods of 45-60 min at 195 degrees, as well as storage temperatures not exceeding 150 degrees C, are recommended for this type of modified binders. (C) 2019 Elsevier Ltd. All rights reserved

Impact of construction and demolition waste aggregates on stripping in hot mix asphalt

[Abstract:] This paper analyzes the effect of water on the durability of hot asphalt mixtures made with recycled aggregates from construction and demolition debris. Indirect Tensile Stress tests were carried out to evaluate stripping behavior. The mixtures tested were fabricated with 0%, 20%, 40% and 60% recycled aggregates. Two types of natural aggregates were used: schist and calcite dolomite. An increase in the percentage of recycled aggregates was found to produce a decrease in the Tensile Stress Ratio of the hot asphalt mixtures. To study this phenomenon, two and three factor Analysis of Variance (ANOVA) were performed with Indirect Tensile Stress being used as the dependent variable. The factors studied were the percentage of recycled aggregates (0%, 20%, 40% and 60%), the moisture state (dry, wet) and the type of natural aggregate (schist, calcite). On the basis of the ANOVA results, it was found that the most important factor affecting resistance was the moisture state (dry, wet) of the specimens. The percentage of recycled aggregate also affected Indirect Tensile Stress, especially in the dry state. The type of natural aggregate did not have a significant effect on Indirect Tensile Stress. The hot asphalt mixture specimens made with different percentages of recycled aggregates from construction and demolition debris and of natural quarry aggregates showed poor stripping behaviour. This stripping behaviour can be related to both the poor adhesion of the recycled aggregates and the high absorption of the mortar of cement adhered to them.Ministerio de Educación y Ciencia; BIA 2006-14742-C02-01Xunta de Galicia; 07TMT012118P

Study of the effect of four warm mix asphalt additives on bitumen modified with 15% crumb rubber

Due to a growing concern over global warming, the bituminous mixture industry is making a constant effort to diminish its emissions by reducing manufacturing and installation temperatures without compromising the mechanical properties of the bituminous mixtures. The use of mixtures with tyre rubber has demonstrated that these mixtures can be economical and ecological and that they improve the behaviour of the pavements. However, bituminous mixtures with a high rubber content present one major drawback: they require higher mixing and installation temperatures due to the elevated viscosity caused by the high rubber content and thus they produce larger amounts of greenhouse gas emissions than conventional bituminous mixtures. This article presents a study of the effect of four viscosity-reducing additives (Sasobit®, Asphaltan A®, Asphaltan B® and Licomont BS 100®) on a bitumen modified with 15% rubber. The results of this study indicate that these additives successfully reduce viscosity, increase the softening temperature and reduce penetration. However, they do not have a clear effect on the test for elastic recovery and ductility at 25 °C

Mechanical properties of hot mix asphalt made with recycled aggregates from reclaimed construction and demolition debris

[Resumen:] En este trabajo se dosificaron mezclas bituminosas fabricadas con áridos reciclados de residuos de construcción y demolición. Se realizaron una serie de ensayos que permitieron caracterizar el comportamiento mecánico de estas mezclas. Los parámetros mecánicos de las mezclas con áridos reciclados son similares a los de las mezclas fabricadas únicamente con áridos naturales de cantera. Sin embargo, las mezclas bituminosas con áridos reciclados tuvieron un mal comportamiento frente a la disminución de la resistencia por pérdida de cohesión por la acción del agua. No obstante, mediante la selección de materiales de mejor calidad y corrección de este mal comportamiento, existen posibilidades de utilizar áridos reciclados en mezclas bituminosas. Para ello será necesario ampliar la primera aproximación realizada en este artículo.[Abstract:] The mix design for asphalt mixtures containing recycled aggregates from construction and demolition debris was evaluated. The tests conducted to characterize the mechanical behaviour of these mixtures showed that the mechanical properties of mixtures with recycled and virgin aggregate are similar. The asphalt mixtures containing recycled aggregate proved to have lower resistance to water action. Nonetheless, recycled aggregate was found to be potentially usable in asphalt mixtures if higher quality materials are selected and such low resistance is corrected. This will call for expanding upon the preliminary work described in the present article

Empleo de residuos de construcción y demolición en mezclas bituminosas

Este congreso, organizado pola Universidade da Coruña, tivo lugar na Coruña do 2 ao 4 de xullo de 2008[Resumen:] En este trabajo se dosificaron mezclas bituminosas fabricadas con áridos reciclados de residuos de construcción y demolición. Se realizaron una serie de ensayos que permitieron caracterizar el comportamiento mecánicos de estas mezclas. Los parámetros mecánicos de las mezcla con áridos reciclados son similares a los de las mezclas fabricadas únicamente con áridos naturales de cantera. Sin embargo, las mezclas bituminosas con áridos reciclados tuvieron un mal comportamiento frente a la disminución de la resistencia por pérdida de cohesión por la acción del agua