1,721,003 research outputs found
Color durability of pigmented slurry surfacing after artificial aging tests simulating weathering and traffic
No full textIn the new vision of complete street, the use of colored pavements has been promoted in recent years to improve road user safety and to enhance the reorganization and aesthetic of the urban environment. But, besides several benefits these pavements undergo environmentally and traffic induced changes in appearance, faster than the traditional ones, a few months after installation. Thus, the laboratory-scale investigation analyzed the color durability of pigmented slurry seals, which were prepared using a clear synthetic emulsion and mineral pigments, subject to different artificial accelerated aging procedures. They simulated the exposition to sunlight at high temperature (QUV weathering tester), the aggression of chemical products (salt brine bath) used for winter maintenance operations and the dynamic actions of vehicle tires (loaded wheel tester). The analyses of color change measured with a spectrophotometer highlighted the extreme sensitivity of pigmented thin surfacing to physical and mechanical stresses. Specifically, the thermal and photo-oxidation of the binder film induced by the UV exposure at high temperature and its wear caused by the dynamic passage of rubber tire produced a large supra-threshold color difference on the samples' surface. These results suggest how a correct mix-design, both in the materials choice and ingredients dosage, should be properly calibrated on the basis of the pavement end-use and of the prevailing climatic conditions to ensure color consistency throughout the pavement lifetime
Expanded polystyrene (EPS) in road construction: Twenty years of Italian experiences
Full text linkExpanded polystyrene (EPS) is a thermoplastic material, derived from pre-expanded polystyrene beads, that combines an extreme lightweight with versatile strength and thermal insulation. These characteristics made EPS an excellent alternative to natural materials for the feasibility of building and construction projects that would otherwise destined, for time and implementation costs, to be postponed or alienated. Specifically, this technology has been successfully used in road infrastructure sector in the last twenty years in the construction of roads, bridge abutments, lightweight embankments and backfills, above all for the rapid restoration of compromised roads following landslide or calamitous events, representing an interesting and resilient solution in areas exposed to seismic risk or persistent vibratory actions. Thus, the authors want to offer a critical analysis of different EPS road applications in Italy, considering benefits and drawbacks, proposing technical and economic considerations for ideal conditions of use and suggesting failure analysis methods and tools. © 2020 The Author(s)
Influence of chemical additives and wax modifiers on odor emissions of road asphalt
No full textThe use of a broad range of asphalt additives is a well-established practice in road pavement engineering for the production of high-performance hot-mix and warm-mix asphalt mixtures. The study aimed to verify and to assess, though an analytical-sensory approach based on artificial olfactory system (AOS), the effects of five different asphalt additives (chemical additives, odor suppressant agent and wax modifiers) on the odorous patterns of asphalt emissions at typical mixing and laying temperatures. The AOS has made possible to identify a specific odor fingerprint of each additive. However, once added to asphalt, these agents did not establish with binder effects of synergy, additivity or antagonism, but appear to be as neutral elements by an odorous point of view. The odorous patterns of emissions generated by heating neat asphalt at various temperatures in laboratory scale tend to coincide with those of asphalt/additive mixtures, underlining how the bituminous binder odor resulted to be hiding or masking compared to that of only-additives. © 2018 Elsevier Lt
Daytime and nighttime color appearance of pigmented asphalt surface treatments
No full textThe use of distinctive and decorative road colored pavements intended for motorized traffic, cyclists and pedestrians have dramatically increased worldwide. They could take the form of overlay, when the colored material is placed on top of the pavement, or embedded, when the colored material is mixed directly into the pavement, exploiting the natural chromatic properties of stone aggregates or powder pigments. Colored pavements are not generally considered as signs or road markings and therefore, no having a legal status, are not subjected to chromaticity requirements. Thus, the paper proposed a rational methodology for the chromatic characterization of colored asphalt pavements, considering different thin cold pigmented high friction road surface treatments, i.e. pigmented slurry seals (red, green and blue), prepared with a clear synthetic emulsion. The experimental procedure had the ambition to predict the chromatic aspect of these pavements, based on direct instrumental measurements of chromaticity coordinates on laboratory scale samples, for several pigment contents in daytime and nighttime. Experimental results testified how the correct transfer and application of a particular color to a road pavement, which often perform traffic functions, cannot be separated from an integrated design between pavement materials selection and road lighting project. © 2019 Elsevier Lt
Optimization of electric arc furnace aggregates replacement in dense-graded asphalt wearing courses
Full text linkElectric arc furnace (EAF) aggregates, by-products of the homonymous steelmaking process, represent an ideal solution for asphalt mixtures, above all for wearing courses where skid resistance and durability are essential functional requirements. Their use, which is subordinate to the compliance of chemical specifications, finds some practical interest limits mainly related to transportation (extremely high bulk specific gravity) and placement (unsatisfactory compaction) operations. Thus, the aim of this experimental study was to determine an ideal artificial to natural aggregates replacement rate, also identifying the most suitable particle size range, for dense-graded asphalt wearing courses. The results highlighted how the best balance between compaction and mechanical performances was registered by a mix which was formulated considering a partial replacement of 54% (v/v%), distributed only in the coarsest fraction. The introduction of limestone as “excipient” in the coarse -fine and finer size ranges reduces the weight of the mixture, guaranteeing at the same time an optimum compaction degree, high levels of stiffness in the viscous-elastic region and Marshall stability and extended fatigue life
The influence of laying patterns on the behaviour of historic stone pavements subjected to horizontal loads
No full textStone pavements are of great importance both for their historical and cultural value and for the most modern ecological and aesthetic requirements appreciated thanks to the use of natural materials of different colours, shapes and sizes which are laid in different patterns. Since stone block pavements are made up of individual elements with irregular side surfaces that interact with each other, an important parameter that must be considered in the design is their structural strength to horizontal stresses mainly due to braking, turning and accelerating vehicles. In this study horizontal load tests were performed on stone pavements built in a wide laboratory test chamber to analyse the load-shifting behaviour for different geometric arrangements. The displacements distribution of the elements was determined by a photogrammetric analysis. The tests have shown that the behaviour of the stone pavements in the horizontal plane is significantly influenced by the laying pattern, both in terms of translations and interaction between the elements. © 2020 Elsevier Lt
Criteria for the selection and design of joints for street pavements in natural stone
No full textNatural stone pavement can produce a high quality attractive streetscape with a long service life. Although the formal analogy with the interlocking concrete pavements, the peculiarities and singularities of the stone elements pose enormous challenges to the designers which have at their disposal only limited standards and guidelines. The joints represent one of the most important part of the stone paving system, performing multiple tasks: stabilize the elements, transmit and dissipate loads, control the water disposal and contribute to the aesthetic. But, the analytical study of the joints is inexplicably an understudied topic in the technical and scientific literature: many problems resulted in stone pavements from lack of understanding of joints’ purposes and functions. Thus, the paper highlighted the conceptual steps necessary to the selection of the optimal jointing solution. Several aspects related to the stone elements’ characteristics and laying that contribute to the joints’ optimized performance have been evaluated. After a brief description of the main defects that can affect stone pavements, a state of practice regarding the jointing materials with the related application techniques have been reported. © 2020 Elsevier Lt
Electronic nose for smart identification of roofing and paving grade asphalt
No full textAsphalt is a complex mixture of hydrocarbons, whose properties strongly depend on the source and type of crude oil and refining processes. From a technical standpoint, intensive investigations carried out by the construction sector, above all by road researchers, have attempted to understand relationships between asphalt binder chemical structure, morphology and physical characteristics. Nevertheless, one challenge that the advance research on asphalt products actually face is to transfer this extremely high level of knowledge to applied industrial technologies for finding easy-to-use, quick and cost-effective test methods for quality control and identification of asphalt binders at refinery, terminal and plant. Thus, this paper focused on the development of a protocol for fingerprinting, including identification and discrimination, of asphalt cements using two different electronic noses (e-noses), also known as artificial olfactory systems (AOS). E-nose is a biomimetic non-destructive intelligent sensing instrument, which is designed to mimic the human sense of smell to detect, compare and classify odor sample, producing a qualitative output (fingerprint). Results suggested that a complementary combination of electronic nose technique and well-established analytical methodologies could be successfully used for the identification and discrimination of roofing and paving grade asphalt cements. Specifically, both sensing instruments were able to perform a good discrimination between products characterized by a different chemical nature and to verify the refinery process stability during production and a batch-to-batch crude oil consistency. © 2019 The Authors. Published by Elsevier B.V
Use of bending beam rheometer test for rheological analysis of asphalt emulsion-cement mastics in cold in-place recycling
Full text linkThis paper focused on exploiting the potential of the bending beam rheometer (BBR) test for analyzing asphalt emulsion-cement (AEC) mastics tailored for cold in-place recycling applications in the first weeks of curing, i.e. phase which implies the coexistence of viscoelastic and brittle materials. A consistent modified BBR testing protocol, which includes the experimental solutions devised for the practical execution of these unconventional rheometric measurements (sample preparation and test procedure), was proposed. The authors suggested to introduce glass microspheres, acting as "inert solid skeleton", in the production of AEC mastics for BBR prismatic beams, to study the interaction between asphalt emulsion and cement in thin film and to limit the specimens' shrinkage and warpage during the curing period. Finally, a feasibility study for validating the new modified experimental setup was presented, highlighting, with an explanatory overview of the types of results that can be expected, the macroscopic behaviors of some AEC mastics as a function of different parameters (asphalt binder to cement ratio, curing time and temperature). (C) 2019 Elsevier Ltd. All rights reserved
Half-warm mix asphalt with emulsion. An experimental study on workability and mechanical performances
No full textOne of the major sustainability-related challenge facing materials for asphalt pavements is the energy consumption and the release of harmful and odorous fumes. Reductions in these emission levels have been progressively achieved by a number of cleaner and low-temperature technologies. Recently, a further step towards an improved road pavement sustainability is represented by the half-warm mix asphalt (HWMA) mixtures, which are produced between 70 °C and 100 °C without negatively affecting their final performances. Among these methodological approaches, a very interesting solution for urban or low volume traffic roads is represented by HWMA mixtures prepared with a conventional warm emulsion and heated aggregates. Although this technique is capable of combining the advantages of hot and cold mixes, limiting some drawbacks, it is still little known and remains confined only to some regional areas (in Spain with the term mezclas templadas). There are no standards or specifications, but only some construction practices resulting from the experience gained in the field. Thus, a laboratory-scale experimental study was set up to analyze in detail the behavior of dense-graded HWMA mixes prepared with emulsion intended for a surface course layer of a low or medium traffic road. The objective was to evaluate the influence of three mix-design variables, such as compaction temperature, binder content and aggregate gradation on the volumetric and mechanical, i.e. indirect tensile strength and moisture susceptibility, properties of these mixtures. The rank comparison between the selected mixtures represented the starting point for improving on the one hand the mix-design process and on the other the operational procedures of production, transportation and placement
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