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

Test methods and influential factors for analysis of bonding between bituminous pavement layers

The durability and maintenance of pavements depend on several factors. One of the most influential is the bond between layers. This bond is responsible for ensuring all layers behave as a single entity, reducing cracks and deformation of the pavement. Several methods, developed by different authors over the past 30 years, to measure bonding between layers are analyzed in this paper. Different research lines are discussed, concluding that the most influential variables are: tack coat type, dosage, mixture type, surface characteristics, temperature, and emulsion breaking time. In order to reach the highest bond strength values, the following factors should be considered: high values of surface macro-texture, low temperatures, the use of heat-adhesive emulsion, a dosage from 300 to 450 g/m2 of residual bitumen and the compaction after emulsion break. Moreover, a non-destructive test method to assess tack coat dosage on site is proposed

Test set-up to determine quality of tack coat

Based on the lessons learned, a device that measures only the quality of tack and is independent of the surface tested was developed. The developed device “UTEP Pull-off Device” measures quality of tack coat in tension mode rather than shear mode; therefore, is independent of tested surface. The developed device is simple, reliable, economical, and could determine the quality of the tack coat in less than 15 minutes. The evaluation of the device in the parking lot as well as in the laboratory identified that the device can consistently identify the quality of tested tack coat. Since the strength of the tack coat is dependent on the set time and test temperature, a test system is proposed that can be used to develop relationship in the laboratory. The developed relationship can then be used in the field to identify adequacy of the tack coat. Preliminary field evaluations indicated that the device has the capability of identifying the quality of the tack coat. The developed device is simple, reliable, economical, and could determine the quality of the tack coat in less than 45 minutes. The major outcome of this project is the UTEP Pull-off Device that can be used for evaluation of tack coat in the field. The new setup not only will improve the quality of bond between the two layers, it will also assist TxDOT in extending the life of the rehabilitated pavement. (Abstract shortened by UMI.

Biocatalytic production of biodiesel from cottonseed oil: Standardization of process parameters and comparison of fuel characteristics

The enzymatic production of biodiesel by transesterification of cottonseed oil was studied using low cost crude pancreatic lipase as catalyst in a batch system. The effects of the critical process parameters including water percentage, methanol:oil ratio, enzyme concentration, buffer pH and reaction temperature were determined. Maximum conversion of 75-80% was achieved after 4 h at 37 °C, pH 7.0 and with 1:15 M ratio of oil to methanol, 0.5% (wt of oil) enzyme and water concentration of 5% (wt of oil). Various organic solvents were tested among which a partially polar solvent (t-butanol) was found to be suitable for the reaction. The major fuel characteristics like specific gravity, kinematic viscosity, flash point and calorific value of the 20:80 blends (B20) of the fatty acid methyl esters with petroleum diesel conformed very closely to those of American Society for Testing Materials (ASTM) standards.Biodiesel Enzymatic transesterification Process parameters B20 Fuel characteristics

Flow Enhancement of Shear-Thinning Liquids in Capillaries Subjected to Longitudinal Vibrations

Application of sinusoidal vibrations in the longitudinal direction causes a significant enhancement in the flow rate of shear-thinning carboxymethylcellulose and polyacrylamide solutions inside capillaries. Depending on the vibration frequency and amplitude, flow enhancements of up to a factor of 9.6 have been realized. Video imaging of a tracer particle inside the tube provides insights into the liquid motion. In particular, it should be noted that the phase shift between the sinusoidal motion of the tube wall and the liquid inside the tube is of high importance in determining the flow enhancement factor