Development of an estimative model for the optimal tack coat dosage based on aggregate gradation of hot mix asphalt pavements

In this work the performance of tack coats on asphalt pavement layers is analysed. Adjustment models based on experimental measurements were implemented, relating surface layer macro-texture and aggregate content larger than 8 mm. The best fits were obtained with a Gompertz model, which follows the expected physical macro-texture changes outside the test range. Shear strength was analysed, through prediction curves of each evaluated tack coat dosage, with an optimum tack coat performance for aggregate contents larger than 8 mm between 45% and 50%, and no relevant influence of the tack coat dosage used.The authors would like to acknowledge the support provided by the Technologic Research Construction Group (GITECO) and the Group of Roads of Santander at Cantabria University for the development of tests and samples. We would also like to thank the company Emilio Bolado S.L. and the Society for the Development of Cantabria Region (SODERCAN) for the material provided, and the DID Research Department from the Austral University of Chile for the support

Influencia del coeficiente estructural de una base reciclada con cemento sobre la deformación permanente en la subrasante – una aproximación con el método Sudrafricano

Trabajo de investigaciónEn la investigación se diseñaron pavimentos con una base reciclada con cemento, variando el módulo resiliente de la subrasante y el espesor de la sub-base granular, en cada caso. Para cada uno de los diseños se determinó la respuesta estructural (esfuerzo y deformación en la subrasante) a través de un software y con los resultados obtenidos se determinó la relación entre la deformación permanente en la subrasante y el número de ejes equivalentes correspondientes.1. INTRODUCCIÓN 2. PLANTEAMIENTO DEL PROBLEMA 3. OBJETIVOS 4. MARCO TEÓRICO 5. ESTADO DEL ARTE 6. PREGUNTA DE INVESTIGACIÓN 7. ALCANCES Y LIMITACIONES 8. METODOLOGÍA 9. CÁLCULOS Y RESULTADOS 10. ANÁLISIS DE RESULTADOS 11. CONCLUSIONES Y RECOMENDACIONES 12. BIBLIOGRAFÍAPregradoIngeniero Civi

Physio-chemical evaluation of asphalt-aggregate interactions

The durability of selected asphalt concrete components and mixtures from six projects were evaluated with the newly recommended net adsorption test and the more common ASTM D4867 (a modified Lottman), respectively. The net adsorption test was used to assess the durability of the adhesion of the asphalt to the aggregate surface in the presence of water. The ASTM D4867 method evaluated the retained strengths of compacted mixture resistance after freeze/thaw conditioning. The net adsorption results indicated at least two of the six projects could be susceptible to moisture related adhesion problems. The test method was adjusted to use the full aggregate gradation rather than only the fine fraction. A comparison of these results to those originally reported by Strategic Highway Research Program (SHRP) researchers showed good agreement in both trends of results and withinlaboratory test method variability (about 0.14 mg/g). The mixture testing indicated that three of the six projects had tensile strength ratios of less than 70 percent and could be expected to show some evidence of moisture related damage. An evaluation of these results suggested that any moisture sensitivity could be due to mix design parameters such as lower film thicknesses, and lower initial strengths rather than a chemical loss of adhesion at the asphalt-aggregate interface. The influence of conventional mix design parameters on the moisture sensitivity of asphalt concrete mixtures should be more thoroughly investigated prior to any consideration of the use of additives.Minnesota Department of Transportatio

EFFECT OF MATERIAL TRANSFER DEVICES ON FLEXIBLE PAVEMENT SMOOTHNESS

The initial smoothness of a pavement is linked to both future pavement smoothness and pavement life. Research was conducted to study the effects of adding a material transfer device to the paving train. The focus was to determine if the use of a material transfer device improved flexible pavement smoothness. An automated data collection van was used to collect pavement profile data, and smoothness was quantified with the international roughness index in inches per mile. An infrared camera and a rolling wheel were used to detect and locate portions of the mat with temperature differences of more than 10 deg C (19 deg F). It was found that a material transfer device significantly improved flexible pavement smoothness. Fewer areas with temperature differences of more than 10 deg C were noted when a material transfer device was used, and areas with these temperature differences were found to be significantly rougher than locations that had more uniform temperatures. In an additional finding, unrelated to the use of a material transfer device, the extension of the screed to one side of the paver caused a significant increase in roughness in the wheelpath on that side