Cracking in asphalt materials

This chapter provides a comprehensive review of both laboratory characterization and modelling of bulk material fracture in asphalt mixtures. For the purpose of organization, this chapter is divided into a section on laboratory tests and a section on models. The laboratory characterization section is further subdivided on the basis of predominant loading conditions (monotonic vs. cyclic). The section on constitutive models is subdivided into two sections, the first one containing fracture mechanics based models for crack initiation and propagation that do not include material degradation due to cyclic loading conditions. The second section discusses phenomenological models that have been developed for crack growth through the use of dissipated energy and damage accumulation concepts. These latter models have the capability to simulate degradation of material capacity upon exceeding a threshold number of loading cycles.Peer ReviewedPostprint (author's final draft

Characterization of Asphalt Treated Base Course Material

INE/AUTC 11.0

A New Materials and Design Approach for Roads, Bridges, Pavement, and Concrete

Increased understanding of demand for transport energy and how to improve road pavement materials would enable decision makers to make environmental, financial, and other positive changes in future planning and design of roads, bridges, and other important transportation structures. This research comprises three studies focused on pavement materials and a fourth study that examines energy demand within the road transportation sector. These studies are as follows: 1. A techno-economic study of ground tire rubber as an asphalt modifier; 2. A computational fluid dynamics analysis comparing the urban heat island effect of two different pavement materials – asphalt and Portland Cement Concrete; 3. A new approach that modifies the surface of ground tire rubber using low-cost chemicals and treatment methods to be used in asphalt applications; and 4. Analysis of road transport energy demand in California and the United States. The findings of these studies include that 1. GTR is an effective and economically suitable additive for modified asphalt, 2. the suitability of PCC pavements in urban settings should be reexamined, 3. Surface modification of GTR materials can improve compatibilization of particles for the manufacture of asphalt materials, and 4. gasoline sales are generally price inelastic in both the U.S. and California. Ultimately, these four studies improve understanding of road pavement materials and transport energy demand. They lay out important information about the future of the relationship between materials and design in the transportation industry. These findings may be used by engineers, policymakers, and others in the industry to better consider implications of decisions involved in design, creation, and modification of structures using pavement and concrete, including roads, bridges, etc

New Mixture Additives for Sustainable Bituminous Pavements

In an effort to improve mechanical properties of asphalt concrete, an exploratory research using mixture additives was attempted. Two different types of additives on two material scales were used: asphalt concrete (AC) level and binder level. At the start of this study, the effect of natural cornhusk fibers on the resistance of two types of AC mixtures on cracking were tested for hot-mix asphalt (HMA) and cold-mix asphalt (CMA). The results showed slight improvements in cracking resistance in cornhusk reinforced HMA, and in the case of the CMA, marshal flow. Overall, based on the test results, cornhusk-reinforced HMA and CMA may not significantly improve critical mechanical properties given the added cost of fibers. In addition, cornhusk fibers proved difficult to properly disperse in HMA and CMA when mixed in laboratory. However, when fibers were mixed in an asphalt production plant, the fibers appeared to become more distributed. The second part of this study, two different types of carbon nano-fillers (F1 and F2) with different surface properties and sizes were added to two different asphalt binders: the base binder and the polymer modified binder. Also, mastic samples were prepared by replacing parts of the limestone filler by the carbon nano-fillers. It was observed that the nanoscale additives interacted with the binder quite differently. Additive F1 did not show a drastic improvement in the mechanical properties, fatigue resistance, and rutting resistance of the base and polymer modified binder at the mastic and the binder scale; however, additive F2 improved all the above- mentioned properties. From the experimental investigation, it can be inferred that part of the polymer modification can be replaced by additive F2. Although additive F1 showed a minimal change, it could be useful in improving the secondary application of the pavement, such as the electrical conductivity, thermal conductivity, and absorption of radiation for energy storage, which was not the scope of this study but appears worthy to investigate

The Investigation of Cold-mix Asphalt Creep Stiffness Testing Using Multiple Test Apparatuses and Gradations

Many current methods of designing and testing Cold In-Place Recycled (CIR) asphalt are undesirable because they require large amounts of material and significant preparation. In an effort to lessen the cost and time of materials testing, this research utilizes several different methods of small scale testing of creep stiffness. These methods include using a Discovery Hybrid Rheometer (DHR) and a three point bending test to find the creep stiffness of emulsion based CIR. The new testing methods utilized samples on the scale of up to a hundredth the size of what the traditional methods of testing require. The two smaller scale tests were compared to the traditional Indirect Tension Test (IDT) testing. In order to fully evaluate the two reduced sample size test methods, this research observed the effect of gradation, temperature, emulsifier type, and Recycled Asphalt Pavement (RAP) content on creep stiffness. If successful, the use of these new test methods could significantly decrease the damage done to roads, and reduce the cost of material management incurred through the quality control testing methods for pavement. Results showed very good correlation between DHR and IDT testing with a proportional difference between the samples. The standard deviations between the DHR and IDT testing were 18.6% and 19.2% of the mean values respectively, indicating similar accuracies of tests. The tests were also able to distinguish between types of material. The proportional difference between the IDT and DHR is expected and is due to the difference of sample and loading configuration. This research begins the validation of using smaller scale DHR tests for CIR stiffness testing

Mechanical and structural assessment of laboratory- and field-compacted asphalt mixtures

Compaction forms an integral part in the formation of the aggregate orientation and structure of an asphalt mixture and therefore has a profound influence on its final volumetric and mechanical performance. This article describes the influence of various forms of laboratory (gyratory, vibratory and slab-roller) and field compaction on the internal structure of asphalt specimens and subsequently on their mechanical properties, particularly stiffness and permanent deformation. A 2D image capturing and image analysis system has been used together with alternative specimen sizes and orientations to quantify the internal aggregate structure (orientation and segregation) for a range of typically used continuously graded asphalt mixtures. The results show that in terms of aggregate orientation, slab-compacted specimens tend to mimic field compaction better than gyratory and vibratory compaction. The mechanical properties of slab-compacted specimens also tend to be closer to that of field cores. However, the results also show that through careful selection of specimen size, specimen orientation and compaction variables, even mould-based compaction methods can be utilised with particular asphalt mixtures to represent field-compacted asphalt mixtures

Effect of Metallic Waste Addition on the Physical and Mechanical Properties of Cement-Based Mortars

© 2018 by the authors. Licensee MDPI, Basel, Switzerland. This is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).This paper investigates the influence of the type and amount of recycled metallic waste on the physical and mechanical properties of cement-based mortars. The physical and mechanical properties of cement mortars, containing four different amounts of metallic waste (ranged 4 to 16% by cement weight), were evaluated by measuring the bulk density, total porosity, flexural and compressive resistance, and dynamic elastic modulus by ultrasonic tests. All the properties were measured on test specimens under two curing ages: 7 and 28 days. Additionally, the morphological properties and elemental composition of the cement and metallic waste were evaluated by using Scanning Electron Microscopy (SEM), energy dispersive X-ray spectroscopy (EDXS), and X-ray fluorescence (XRF). Main results showed that the addition of metallic waste reduced the bulk density and increased the porosity of the cement-based mortars. Furthermore, it was observed that flexural and compressive strength proportionally increased with the metallic waste addition. Likewise, it was proven that elastic modulus, obtained by compressive and ultrasonic tests, increases with the metallic waste amount. Finally, based on a probability analysis, it was confirmed that the addition of metallic waste did not present a significant effect on the mechanical performance of the cement-based mortars.Peer reviewedFinal Published versio

Laboratory evaluation of Rediset modified bitumen based on rheology and adhesion properties

Warm mix asphalt (WMA) could significantly reduce the production temperature of asphalt mixtures. Lower production temperature meaning reduced fossil fuel consumption and greenhouse gas emission which in turn avoid environmental pollution in the road construction process. This study aims to characterise the properties of bitumen with the addition of a type of WMA additive – Rediset. The influence of Rediset on bitumen surface energy was evaluated by using the Dynamic Contact Angle (DCA) test. Complex modulus and phase angle of bitumen were evaluated through frequency sweep test using Dynamic Shear Rheometer (DSR). The high-temperature viscosity of bitumen was measured using a corn and plate system which installed in the DSR equipment. Finally, the Pneumatic Adhesion Tensile Testing Instrument (PATTI) test was performed to measure the tensile strength and moisture susceptibility of aggregate-bitumen combinations. The results show that the Rediset reduces the surface energy of bitumen. Moreover, as seen in the DSR test, the complex modulus increased while the phase angle decreased at the low frequency range due to the addition of Rediset. The decreased bitumen viscosity because of the addition of Rediset demonstrating reduced mixing and compaction temperature of asphalt mixture. In addition, the addition of Rediset could improve the bonding strength of aggregate-bitumen combinations at medium and high service temperatures but has no influence at low temperature. Furthermore, the Rediset is able to increase the retained tensile strength which in turn reduces the moisture susceptibility of asphalt mixture

A new machine for acquire pavement texture

This paper presents a prototype machine for the acquisition and characterization of the macrotexture and megatexture of road surfaces. The development stages of the prototype machine involved: 3D data acquisition system configuration and calibration - based on laser triangulation technique, 3D surface reconstruction of the road surface and texture characterization using appropriated indicators, such as the Mean Profile Depth (MPD) and the Texture Profile Level (L), by applying different and complementary mathematical techniques. The prototype machine created is able to work in laboratory and in field, allowing an acquisition accuracy of 0.5 mm. The contribution of this research is in developing a prototype machine capable of acquiring an extensive area road surface with high precision 3D data.(undefined