D. Lo Presti

Binder design of high RAP content hot and warm asphalt mixture wearing courses

Reclaimed Asphalt Pavement (RAP) has shown great potential for being used in the construction or maintenance of roads. However, RAP is usually downgraded to lower pavement layers and the percentage of RAP used in wearing courses is still moderate (≤30%). The research and results contained in this paper focus on the definition of binder recipes aimed at increasing the percentage of RAP in hot and warm mix asphalt wearing courses. A review of current internationally used blend design methodologies is presented followed by case studies aimed at defining binder recipes for high RAP content asphalt mixture wearing courses to be further used for mix design and production in asphalt plants. Binder design has been carried out by means of rotational viscosity, Dynamic Shear Rheometer, Bending Beam Rheometer and conventional experimental tests with results showing that the amount of RAP used in a mix can be increased through the development of an accurate binder design and the selection of an appropriate rejuvenator. As a result, laboratory design showed that using up to 90% of RAP is a feasible option. However, the percentage of RAP to be used is highly dependent on the properties of the initial RAP binder, so every case has to be independently and carefully studied. The research presented is carried out as part of the CEDR Transnational Road research Programme Call 2012 (http://allback2pave.fehrl.org) and the Marie Curie Initial Training Network action, FP7-PEOPLE-2013-ITN (http://www.superitn.eu).

Effects of laboratory aging on properties of biorejuvenated asphalt binders

AbstractThis paper presents the results from a laboratory investigation on the effects of aging on the properties of two binders recovered from two different sources of Reclaimed Asphalt (RA) and a...

Reclaimed asphalt test specimen preparation assisted by image analysis

This paper presents a laboratory investigation aimed at establishing a protocol for the production of homogeneous asphalt mixtures test specimens, incorporating reclaimed asphalt by using a gyratory compactor with coring and trimming works. Stone mastic asphalt specimens were compacted at the previously identified target densities with the final aim of obtaining specimens with a fixed and homogeneous air void distribution. A microstructural study was conducted to characterize the homogeneity in the air void distribution using X-ray computed tomography (CT) combined with image analysis techniques. The study concluded that the gyratory compactor is suitable for producing homogeneous test specimens for the specified mixtures and a set of detailed procedures has been proposed for the production of the compacted specimens and to perform the microstructural study.

Fundamental characterisation of reclaimed asphalts: the importance of testing homogeneous specimens

This study highlights the importance of defining appropriate specimen manufacturing procedures when assessing the fundamental properties of reclaimed asphalt (RA) mixes for further modelling purposes. Two gyratory compactor procedures were used: the first leading to specimens with a non-uniform air voids distribution and the second tailored to obtain homogeneous specimens. The study was performed by using three stone mastic asphalts incorporating up to 30% of RA but designed to have identical properties. A detailed characterisation of the loose mixes and binders, an X-ray computer tomography micro-structural study of the manufactured specimens and a further mechanical characterisation showed that testing non-homogeneous gyratory specimens leads to a significant overestimation of the mechanical properties of asphalt mixes. This study has been developed within the FP7 project ReRoad.

Mechanistic procedure for parameter determination of multiplicative decomposition based constitutive models

Abstract By exploiting the Clausius–Planck local energy dissipation inequality, a large strain, three-dimensional constitutive model has been developed for the monotonic and cyclic response prediction of various asphaltic materials. The model consists of a Zener non-linear, visco-elastic component acting in series with a stress dependent viscous component. A novel computational scheme has been developed for solution of the coupled system of equations expressing the interdependent response of these two in series components. An explicit, mechanistic, parameter determination procedure is presented for the laboratory determination of all necessary model parameters. Examples of model parameter determination and utilisation for prediction of the response of a recycled asphalt mix and a stone mastic asphalt mix are presented.

Tests Campaign Analysis to Evaluate the Capability of Fragmentation Test to Characterize Recycled Asphalt Pavement (RAP) Material

Cold and hot recycling of reclaimed asphalt pavement (RAP) is increasingly gaining in popularity worldwide due to the need to increase the sustainability of asphalt pavement, both from environmental and economic perspectives. Despite the increasing of use of these techniques, we are still faced with the problem of correctly characterizing RAP. In the framework of the RILEM TC 237-SIB TG6, a Round Robin Test (RRT) was performed in order to evaluate the capacity of the fragmentation test to characterize RAP materials. A total of 5 laboratories located in 4 different countries were involved in the testing program. This paper focuses on the presentation of the fragmentation test method and the results of the RRT performed on different sources of RAP. To differentiate RAP materials in terms of size alteration vulnerability, fragmentation tests were performed at three different temperatures (5, 20 and 40 °C) on different sources of RAP. Fragmentation testing consists in evaluating the amount of materials passing through a control sieve of a coarse uniform RAP material after a fixed series of strokes carried out with a normalized falling mass. Results show that fragmentation is reduced when the testing temperature increases. Fragmentation tests performed on natural aggregates indicate that they do not vary with the testing temperature, and such test results are a function of the amount of foreign matter in the RAP. The results also show that the test is suitable for differentiating RAP materials from different sources.