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Different types of additives are used in asphalt modification to enhance several properties within the asphalt pavement. In various cases, modification is needed by using multiple additives, which is called composite modification. In this study, glass fibre and nano clay were used to modify the asphalt pavement. The amount of these two additives, together with the optimum bitumen content, was determined by the response surface methodology (RSM). Central composite method (CCD) was used for determining the optimum amount of independent variables (nano clay, glass fibre, bitumen content), by evaluating the dependent variables. Marshall mixture design criteria and minimum bitumen content, were the optimal conditions. As a result, the mixture containing 0.2% glass fibre, 3.693% nano clay and 4.096% bitumen content, was predicted to give the most desirable characteristics. Additionally, verification tests were conducted to evaluate the adequacy of the predicted model. The results were within the 95% confidence intervals for all response variables, which demonstrates the validity of the model obtained in the study. Consequently, CCD can be used to obtain design optimisation of asphalt modification with less mixture production for experimental stages. This is a substantial advantage, which supports human safety and environment- friendly practices. [ABSTRACT FROM AUTHOR]

Waste foundry sand (WFS) are industrial by-products from the foundry process which represent challenges for environmental departments with respect to the proper disposal in landfills due to their high production. The road infrastructure such as asphalt paving is a major consumer of mineral aggregates originating from the mining activity of exhaustible natural resources. Thus, the WFS reuse for the construction of roads is an alternative to discarding of waste and a reduction in the use of mineral aggregates. In this article hot mix bituminous (HMB) mixtures were produced containing WFS (by weight) substitution contents in relation to manufactured sand of 25%, 50%, 75% and 100% from two origins: industrial landfill and the steel industry; after mechanical and gyratory compaction, these cylindrical specimens were subjected to mechanical tests of splitting tensile strength and resilient modulus obtaining very similar performances as that of the control mixture (which did not contain WFS). These mechanical results as well as the microstructural characterisation of this HMB containing residue led to the conclusion that the reuse of WFS in the asphalt pavement is technically viable, creating an alternative to by-product disposal and reduction of the financial-environmental costs of highways. [ABSTRACT FROM AUTHOR]

Recently, the reduction of the environmental burdens related to highway infrastructures has been in the spotlight. Within this context, the use of recycled materials in bituminous mixtures for road pavement construction and maintenance has the potential to mitigate the excessive use of non-renewable resources. Nevertheless, the material consumption is only one of the aspects that affects the sustainability of an infrastructure. Other relevant aspects related to environmental issues should be considered. The objective of this work is to evaluate the potential environmental impacts of asphalt mixtures containing crumb rubber (CR) (vulcanised or devulcanised) and reclaimed asphalt pavement (RAP) assuming different Degree of binder Activation (DoA) of the aged binder by means of a life cycle assessment (LCA). The results show that the small amount of CR used for bituminous mixtures application does not justify all the additional consumption of resources and emissions associated with its treatment. These results are explained by the higher environmental impacts stemming from the treatment of the rubber and the higher amount of bitumen employed in the mixture. In turn, for mixtures containing RAP the analysis revealed an improvement in the score of all the environmental indicators considered. [ABSTRACT FROM AUTHOR]

In the rehabilitation of flexible pavements with asphalt layers, it is necessary to apply a bituminous tack coat with a pre-established dosage, which usually does not take into account the degree of texture generated if a milling operation is previously performed since this increases the surface at the interface. On the other hand, when milling, grooves are obtained that could lead to the runoff of bitumen emulsion with excessive deposition in their valleys due to dosages greater than those needed. This work analyses the above mentioned and achieves a compromise solution, with its corresponding method of application, based on the mechanical behaviour obtained with different degrees of texture and validated for typical materials used in Argentina. [ABSTRACT FROM AUTHOR]

A research was conducted to assess the effectiveness of different kinds of Modified Fibres (MF) on the thermal cracking performance of a Stone Mastic Asphalt (SMA) compared to the conventional SMA mixtures modified with SBS Polymer modified Bitumen (PmB). In addition, the capability of rubberised fibres to alleviate the thermal cracking sensitivity was investigated. Besides the main scope, a series of the same SMAs were also produced containing 25% of Reclaimed Asphalt Pavement (RAP) to investigate the effects of RAP on the low-temperature performance of the mixtures, which were modified either with MF or PmB. The experimental plan included both binder and mixture characterisation by means of Bending Beam Rheometer (BBR) test and Thermal Stress Restrained Specimen Test (TSRST). Binder-scale test results showed that the stiffness of all bituminous compounds is increased by the addition of fibres and rubber improves the elasticity of both neat and PmB compounds. In the mixture scale, TSRST results showed no significant difference between the mixtures. However it is noteworthy that, in addition, better low-temperature performance was recorded for virgin mixtures compared to to RAP containing ones. The overall results may confirm the feasibility of modified fibres in the modification of mixtures at low temperatures. [ABSTRACT FROM AUTHOR]

Among the fabrication processes available for obtaining asphalt rubber, terminal blend is the most commonly used in Brazil. On the other hand, the use of field-blended rubber asphalt has been around in the United States for decades, especially in the state of Arizona. The lack of information regarding this technique in Brazil, however, inhibits a more common use in pavement construction/rehabilitation. This case history study was conducted in order to characterise the field performance of the first pavement rehabilitation job in Brazil using a field-blended rubber asphalt mixture and attempt to predict its future performance. A 500-m test section using a field-blended rubber asphalt mixture with a gap-graded aggregate as a surface course was monitored periodically through pavement deflection tests, roughness, rutting and surface conditions. Pavement monitoring revealed good functional and structural conditions after 4 years of service life. Accelerated pavement testing (f-sAPT), conducted in a representative test section using a full scale, mobile traffic simulator, exhibited promising performance. No cracking was observed in the test section and the average maximum rut depth was below limits after simulating 7 years of service life. Results from the f-sAPT simulation were then used to calibrate the performance cracking and rutting models in the Highway Development and Management Model (HDM-4). [ABSTRACT FROM AUTHOR]

Extensive laboratory tests were conducted and the results were compared to the known field performance results of Specific Pavement Studies-1 (SPS-1) sections on US281. The objective was to establish which of the available laboratory test procedures could match the observed field performance. The laboratory tests included the diametral resilient modulus, Asphalt Pavement Analyzer (APA), Hamburg Wheel Tracking Test (HWTT), Repeated Simple Shear Test at Constant Height (RSST-CH), dynamic modulus test, and repeated load permanent deformation test. It was found that both RSST-CH and repeated load permanent deformation test could differentiate the performance of different sections, and the results matched closely with the field performance. The total permanent strain was also found to be a reasonable indicator of field rutting performance. For the wheel tracking tests, the APA performed better than HWTT, but both failed to differentiate some mixes. The moduli at high temperature, including dynamic modulus, axial resilient modulus, shear resilient modulus, and E*/sin δ could screen out the bad mixes. However, those moduli (except for shear resilient modulus) failed to further differentiate the performance of mixes once they were grouped as generally "good" or "bad". [ABSTRACT FROM AUTHOR]

The findings of an extensive literature review on bitumen and asphalt mixture ageing test methods are presented in the paper. The primary factors affecting the durability of bituminous paving mixtures, assuming they are constructed correctly, are age hardening and moisture damage. Ageing of the bituminous binder is manifested as an increase in its stiffness (or viscosity). Water damage is generally manifested as a loss of cohesion in the mixture and/or loss of adhesion between the bitumen and aggregate interface (stripping). Short-term ageing is primarily due to volatilisation of the bitumen within the asphalt mixture during mixing and construction, while long-term ageing is due to oxidation and some steric hardening in the field. Of the tests used to simulate short-term ageing, the extended heating procedures of the thin film oven test (TFOT) and the rolling thin film oven test (RTFOT) are the most frequently used binder methods. In regard to long-term binder ageing, the oxidative pressure ageing vessel (PAV) test and the rotating cylinder ageing test (RCAT) have shown the greatest potential. Asphalt mixture ageing is primarily limited to extended heating methods for loose bituminous material prior to compaction and combinations of extended oven ageing, high and low pressure oxidation and ultraviolet and infrared light treatments. [ABSTRACT FROM AUTHOR]

The need for sustainable and resilient transport infrastructure has led to the development of advanced characterisation techniques, design, and modelling methodologies for asphalt materials. Research efforts can be mainly classified into three categories: new characterisation methods aiming to better understand the molecular structure, chemical composition, rheology, mechanical properties and field performance of asphalt materials; introduction of new materials and characterisation of their behaviour and performance; and development of computational tools to investigate the mechanics and performance of composite pavement. [Extracted from the article]