Experimental study aimed at highlighting warnings for proper design, construction and control of geocomposite-reinforced asphalt pavements

The proper use of interlayers in asphalt pavements can be an effective and economic option to enhance their service life. However, the presence of a foreign element at the interface should be properly taken into account during design, construction and control of reinforced pavements. Given this background, the present laboratory study investigated stiffness and interface bonding properties of reinforced asphalt systems in order to achieve fundamental information for a correct design as well as proper construction and control of reinforced pavements. To accomplish this objective, different composite reinforcements (grids/fabrics embedded in bituminous membranes) were studied as interlayers of double-layered systems prepared with both traditional and polymer-modified asphalt concretes. Dynamic flexural tests and static interface shear tests were carried out. Unreinforced reference systems was also studied for comparison purposes. Results confirmed the abovementioned warnings that will allow delineating some preliminary guidelines related to the use of reinforcements in pavements

Aesthetic and Mechanical Suitability of a Clear Synthetic Resin as a Unconventional Binder for Road Pavements

Current environmental awareness interests several aspects of civil engineering, including road construction. Indeed, new challenges related to environmental pollution and landscape preservation must be faced. In this sense, clear road pavement surfaces represent an effective technology aimed at guaranteeing environmental-friendly aesthetic pavements. The use of clear synthetic resin as a binder involves several benefits for the mitigation of in-service reached temperatures and the heat distribution within pavements (with appreciable effects on pavement mechanical performance too). The present paper illustrates an experimental study aimed at analysing the chromatic and mechanical properties of a clear synthetic resin and thus its suitability as a binder for road pavement mixes. Chromatic characteristics were assessed through digital image analysis at different aging conditions. A dynamic shear rheometer was used to evaluate the linear viscoelastic properties as well as fatigue and rutting potential of the binder in a wide range of temperatures and frequencies. A conventional 35/50 penetration grade bitumen was also investigated for comparison purposes. The clear resin exhibited limited changes in colour (darkening effects), mainly in the case of short-term aging. On the other hand, a low temperature-dependency of such a binder was observed up to 58\ub0C. Slightly increased aptitude to rutting at the higher temperatures was detected, even if it is worth noting that clear in-service mixtures would achieve lower temperatures than traditional "black" materials at a given environmental condition (air temperature, solar radiation, etc.). The resin also exhibited a softer behaviour, along with an enhanced fatigue resistance. Overall, the studied innovative binder showed promising results in view of its effective use in road paving

Steel slag as valuable aggregate in eco\u2013friendly mixtures for asphalt pavements

Research and application concerning the use of environmentally friendly materials and technologies in road pavements have reached high relevance mainly due to the increasing public consciousness addressed to environmental protection and preservation. In this sense, the possible use of steel slags for construction applications (including road pavements) has a strategic importance to convert a waste into a valuable resource, taking also into account that ferrous slag may have a lower potential to negatively impact the environment. The environmental sustainability of asphalt mixtures prepared with steel slags can be further enhanced adopting the so-called Warm Mix Asphalt (WMA) technology. In fact, WMA is an asphalt concrete modified with additives that can be produced and applied at lower temperatures than the traditional Hot Mix Asphalt (HMA), thus reducing energy consumption, gas and fume emissions. Given this background, the paper illustrates a part of a wide research study aimed at verifying the utilization feasibility of steel slags in warm asphalt concretes. In particular, midrange and high-service temperature properties as well as water susceptibility of warm mixtures containing steel slags were assessed in the laboratory. The warm modification was performed using a chemical tensoactive additive, whereas slags were taken from a metallurgical plant equipped with an electric arc furnace (EAF). A WMA prepared with only natural aggregates was also studied for comparison purpose. The performance characterization was carried out through both static and cyclic laboratory tests. The results mainly showed that asphalt mixtures prepared combining chemical warm technology and EAF steel slag aggregates demonstrate promising field applicability

Rheological Behaviors of Waste Polyethylene Modified Asphalt Binder: Statistical Analysis of Interlaboratory Testing Results

This article investigated the effect of waste polyethylene (PE) on the modified asphalt binders' rheological behavior from a statistical point of view. The interlaboratory testing results from the RILEM Technical Committee 279 Valorization of Waste and Secondary Materials for Roads Task Group 1 were used for this purpose. First, an unaged 70/100 penetration graded neat binder was selected as the reference material. Next, a single 5 % content of waste PE additives (PE-pellets and PE-shreds) was mixed with a 95 % neat binder to prepare two PE modified binders. Then, dynamic shear rheometer-based temperature-frequency sweep tests were performed over a wide range of temperatures and frequencies to evaluate the rheological properties of these three binders. Different rheological behaviors were observed in the isochronal plots at high temperatures. Based on a reproducibility precision requirement proposed for phase angle, 28 degrees C was set as the transition temperature across the rheological behaviors. Next, according to the three rheological behaviors defined in a previous study by the authors, statistical analysis was introduced to identify sensitive rheological parameters and determine the thresholds. Results indicate that the phase angle measured above 28 degrees C and 1.59 Hz can be used as a sensitive parameter to discriminate the three rheological behaviors of PE modified binders. The thresholds among different behaviors were also calculated as an example for phase angle measured at the highest common testing temperature of 70 degrees C. Additional experimental evaluations on more types of PE modified binders, especially at intermediate and high temperatures, are recommended to better understand their influence on the rheological behavior of PE modified binders

Innovative composite materials as reinforcing interlayer systems for asphalt pavements: an experimental study

4noInterlayers for asphalt reinforcement are considered an effective option to enhance pavement service life. In this regard, innovative factory-made composite materials can be designed as interlayer systems able to combine reinforcing and stress-relieving properties. This can be accomplished by embedding grids or fabrics in bituminous membranes. Given this background, this study considered dynamic flexural properties and interface shear strength of asphalt systems reinforced with different composite membranes obtained by changing the embedded reinforcement and/or the bituminous compound. Results clearly rank the studied materials showing enhanced fatigue response of reinforced asphalt layers. However, interface shear properties strongly suggest proper design and adequate selection of the installation depth.reservedmixedPasetto M.; Pasquini E.; Giacomello G.; Baliello A.Pasetto, M.; Pasquini, E.; Giacomello, G.; Baliello, A

Performance Evaluation of Foamed Bitumen Bound Mixtures made with Recycled and Artificial Aggregates and Fibres

The paper describes a research aimed at analysing the performance of mixtures for road base and sub-base layers, made with foamed bitumen, cement, recycled and artificial aggregate as well as different types of fibres, used in order to enhance adhesion and structural properties of the mixes. Reclaimed Asphalt Pavement (RAP), Electric Arc Furnace (EAF) steel slag, foundry sand and fly ash were used in the experiment as alternative secondary aggregates. A control mixture prepared with quarried natural aggregate (limestone) was also studied for comparison purposes. Such Cement-Bitumen Treated Mixtures (CBTM) were manufactured using 70/100 pen foamed bitumen and CEM I 32.5 R Portland cement. Three types of fibres were also alternatively added to the mixtures: structural, polypropylene and cellulose/glass fibres. The comparative mechanical characterization was based on fatigue resistance (EN 12697-24), indirect tensile strength (EN 12697-23) stiffness (EN 12697-26) and water susceptibility (EN 12697-12). The research permitted to recognize the overall positive, but different, contribution of fibres to the performance of mixtures, and define most appropriate fibre content and field of application. Moreover, the contribution of the different waste materials to the structural properties and durability of the studied mixes has been ascertained and new construction solutions have been proposed