scholarly journals Laboratory Evaluation of Gradation Improvement of Marginal Materials for Foamed Bitumen Stabilisation

2020 ◽  
Vol 10 (12) ◽  
pp. 4224
Author(s):  
Greg White ◽  
Roberto Espinosa
Keyword(s):  
Granular Material ◽  
Effective Treatment ◽  
Granular Materials ◽  
Laboratory Evaluation ◽  
Variable Effect ◽  
Construction Specifications ◽  
Average Modulus ◽  
Indirect Tensile ◽  
Foamed Bitumen ◽  
Pavement Construction

Foamed bitumen stabilisation is an attractive technology for increasing the use of marginal materials in pavement construction and rehabilitation. However, by their very nature, marginal materials do not meet the prescriptive requirements of many standard specifications. Consequently, performance-related evaluation is required. For foamed bitumen stabilised marginal materials, the cured and saturated moduli are common performance-related parameters that are also used for characterisation during structural pavement design. In this research, the indirect tensile moduli of three foamed bitumen stabilised marginal granular materials were compared to the modulus of a standard or premium material, in both cured and saturated conditions, after 3, 7 and 14 days of accelerated laboratory curing. The results indicated that the magnitude of granular material marginality was not related to the stabilised material modulus. Furthermore, the gradations of the two most marginal materials were improved by blending with another granular material and the improved marginal materials were also stabilised and tested. The gradation improvement had a variable effect on the stabilised material modulus, with the average modulus increasing by more than 20%. The modulus increase associated with the gradation improvement was related to the basis and magnitude of granular material marginality, with the saturated modulus of the most plastic marginal material increasing by the greater amount after improvement. It was concluded that foamed bitumen stabilisation is a particularly effective treatment for marginal granular materials. Furthermore, when used in combination with gradation improvement, the resulting foamed bitumen stabilised material can perform similarly to standard materials, based on cured and soaked modulus values. However, to allow the use of foamed bitumen stabilised marginal materials in pavement construction, specifications must be more performance-related and the current limits on plasticity and gradation must be relaxed.

scholarly journals Rejuvenation Mechanism of Asphalt Mixtures Modified with Crumb Rubber

CivilEng ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 370-384
Author(s):  
Hossein Noorvand ◽  
Kamil Kaloush ◽  
Jose Medina ◽  
Shane Underwood
Keyword(s):  
Tensile Strength ◽  
Dynamic Loading ◽  
Creep Compliance ◽  
Asphalt Mixture ◽  
Crumb Rubber ◽  
Indirect Tensile Strength ◽  
Laboratory Evaluation ◽  
Strength Testing ◽  
Noise Mitigation ◽  
Indirect Tensile

Asphalt aging is one of the main factors causing asphalt pavements deterioration. Previous studies reported on some aging benefits of asphalt rubber mixtures through laboratory evaluation. A field observation of various pavement sections of crumb rubber modified asphalt friction courses (ARFC) in the Phoenix, Arizona area indicated an interesting pattern of transverse/reflective cracking. These ARFC courses were placed several years ago on existing jointed plain concrete pavements for highway noise mitigation. Over the years, the shoulders had very noticeable and extensive cracking over the joints; however, the driving lanes of the pavement showed less cracking formation in severity and extent. The issue with this phenomenon is that widely adopted theories that stem from continuum mechanics of materials and layered mechanics of pavement systems cannot directly explain this phenomenon. One hypothesis could be that traffic loads continually manipulate the pavement over time, which causes some maltenes (oils and resins) compounds absorbed in the crumb rubber particles to migrate out leading to rejuvenation of the mastic in the asphalt mixture. To investigate the validity of such a hypothesis, an experimental laboratory testing was undertaken to condition samples with and without dynamic loads at high temperatures. This was followed by creep compliance and indirect tensile strength testing. The results showed the higher creep for samples aged with dynamic loading compared to those aged without loading. Higher creep compliance was attributed to higher flexibility of samples due to the rejuvenation of the maltenes. This was also supported by the higher fracture energy results obtained for samples conditioned with dynamic loading from indirect tensile strength testing.

scholarly journals A frictional Cosserat model for the slow shearing of granular materials

2002 ◽  
Vol 457 ◽  
pp. 377-409 ◽  
Author(s):  
L. SRINIVASA MOHAN ◽  
K. KESAVA RAO ◽  
PRABHU R. NOTT
Keyword(s):  
Angular Velocity ◽  
Granular Material ◽  
Shear Layer ◽  
Granular Materials ◽  
Layer Thickness ◽  
Couette Flow ◽  
Velocity Fields ◽  
Cosserat Continuum ◽  
Cosserat Model ◽  
Cylindrical Couette Flow

A rigid-plastic Cosserat model for slow frictional flow of granular materials, proposed by us in an earlier paper, has been used to analyse plane and cylindrical Couette flow. In this model, the hydrodynamic fields of a classical continuum are supplemented by the couple stress and the intrinsic angular velocity fields. The balance of angular momentum, which is satisfied implicitly in a classical continuum, must be enforced in a Cosserat continuum. As a result, the stress tensor could be asymmetric, and the angular velocity of a material point may differ from half the local vorticity. An important consequence of treating the granular medium as a Cosserat continuum is that it incorporates a material length scale in the model, which is absent in frictional models based on a classical continuum. Further, the Cosserat model allows determination of the velocity fields uniquely in viscometric flows, in contrast to classical frictional models. Experiments on viscometric flows of dense, slowly deforming granular materials indicate that shear is confined to a narrow region, usually a few grain diameters thick, while the remaining material is largely undeformed. This feature is captured by the present model, and the velocity profile predicted for cylindrical Couette flow is in good agreement with reported data. When the walls of the Couette cell are smoother than the granular material, the model predicts that the shear layer thickness is independent of the Couette gap H when the latter is large compared to the grain diameter dp. When the walls are of the same roughness as the granular material, the model predicts that the shear layer thickness varies as (H/dp)1/3 (in the limit H/dp [Gt ] 1) for plane shear under gravity and cylindrical Couette flow.

scholarly journals Laboratory Evaluation of the Use of Florida Washed Shell in Open-Graded Asphalt Mixtures

Materials ◽  
2021 ◽  
Vol 14 (22) ◽  
pp. 7060
Author(s):  
Mohammad Alharthai ◽  
Qing Lu ◽  
Ahmed Elnihum ◽  
Asad Elmagarhe
Keyword(s):  
Tensile Strength ◽  
Asphalt Mixture ◽  
Asphalt Mixtures ◽  
Indirect Tensile Strength ◽  
Laboratory Evaluation ◽  
Void Content ◽  
Coarse Aggregates ◽  
Significant Difference ◽  
Indirect Tensile ◽  
Marshall Stability

This study investigates the substitution of conventional aggregate with a Florida washed shell in open-graded asphalt mixtures and evaluates the optimal substitution percentage in aggregate gradations of various nominal maximum aggregate sizes (NMASs) (i.e., 4.75, 9.5, and 12.5 mm). Laboratory experiments were performed on open-graded asphalt mixture specimens with the coarse aggregate of sizes between 2.36 and 12.5 mm being replaced by the Florida washed shell at various percentages (0, 15, 30, 45, and 100%). Specimen properties relevant to the performance of open-graded asphalt mixtures in the field were tested, evaluated, and compared. Specifically, a Marshall stability test, Cantabro test, indirect tensile strength test, air void content test, and permeability test were conducted to evaluate the strength, resistance to raveling, cracking resistance, void content, and permeability of open-graded asphalt mixtures. The results show that there is no significant difference in the Marshall stability and indirect tensile strength when the coarse aggregates are replaced with Florida washed shell. This study also found that the optimum percentages of Florida washed shell in open-graded asphalt mixture were 15, 30, and 45% for 12.5, 9.5, and 4.75 mm NMAS gradations, respectively.

scholarly journals Application of the foamed bitumen and bitumen emulsion to the road base mixes in the deep cold recycling technology

2016 ◽  
Vol 11 (4) ◽  
pp. 291-301 ◽  
Author(s):  
Marek Iwański ◽  
Anna Chomicz-Kowalska
Keyword(s):  
Mechanical Properties ◽  
Portland Cement ◽  
Base Layer ◽  
The Road ◽  
Road Base ◽  
Bitumen Emulsion ◽  
Recycling Technology ◽  
Indirect Tensile ◽  
Foamed Bitumen ◽  
Cold Recycling

This paper presents findings of a study concerning the influence of binder type on the mechanical properties of road base in the cold recycling technology. The principal aim of this investigation was to evaluate the mixes in scope of susceptibility to moisture and low-temperatures. In the comparative research foamed bitumen and bitumen emulsion were used in four different concentrations (2.0%, 2.5%, 3.0%, 3.5%). The materials used in the study were reclaimed from an existing road construction layers: reclaimed aggregate from the road base and reclaimed asphalt pavement obtained by milling the surface and binder course. Portland cement in 2.0% concentration was used as a hydraulic binder. The evaluated parameters were: indirect tensile strengths, tensile strength retained and indirect tensile stiffness modulus at 25 °C. These tests were complemented by an evaluation of susceptibility to moisture and frost according to modified procedures implemented by American researchers: Tunnicliff, Root and Lottman. Moreover, tests for low-temperature cracking were conducted according to Finnish standard. The investigations showed that the use of foamed bitumen for road base layer produced in the cold recycling technology results in better mechanical properties and resistance to moisture and frost compared to using bitumen emulsion. The use of 2.5% of foamed bitumen and 2.0% of Portland cement in the recycled road base allowed to meet the established criteria.

scholarly journals Frictional properties between geocells filled with granular material

2021 ◽  
Vol 20 (2) ◽  
pp. 332-345
Author(s):  
Gökhan Altay ◽  
◽  
Cafer Kayadelen ◽  
Taha Taskiran ◽  
Baki Bagriacik ◽  
...  
Keyword(s):  
Granular Material ◽  
Normal Stress ◽  
Granular Materials ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Frictional Properties ◽  
Geotechnical Structures ◽  
Series Of Experiments ◽  
Restricted Volume

The parameters concerning the interaction between geocell and granular materials is required for the design of many geotechnical structures. With this in mind, a series of experiments using simple direct shear tests are conducted in order to understand the frictional properties between geocells filled with granular materials. The 54 test samples are prepared by filling the geocell with granular materials having three different gradations. These samples are tested at three different relative densities under three different normal stress levels. As a result, it was observed that interface resistance between the geocells filled with granular material is found to be generally greater than in the samples without geocells. Additionally, these samples with geocells are found to be stiffer; this is due to the fact that the samples with geocell gained more cohesion because geocells confined the grains within a restricted volume.

The Influence of Hydrated Lime, Portland Cement and Cement Dust on Rheological Properties of Recycled Cold Mixes with Foamed Bitumen

2017 ◽  
Author(s):  
Przemysław Buczynski ◽  
Marek Iwanski
Keyword(s):  
Portland Cement ◽  
Rheological Properties ◽  
Complex Modulus ◽  
Hydrated Lime ◽  
Laboratory Evaluation ◽  
Cement Kiln ◽  
Direct Tension ◽  
Stiffness Modulus ◽  
Hydraulic Binder ◽  
Foamed Bitumen

This article presents a laboratory evaluation of the viscoelastic properties of recycled base courses produced with different fillers. The aim of this study was to investigate the influence of loading time and temperature on the complex modulus (E*) and the phase angle (6) of recycled base courses with respect to selected additives used. The mixtures contained reclaimed asphalt pavement RAP, crushed stone from existing base courses and virgin aggregate. Foamed bitumen 50/70 at 2.5% was used as a binder. The hydraulic binder constituted 3.0% of the recycled base course mixture. Portland cement, hydrated lime and cement kiln dust CKD were added as fillers. Evaluation of rheological properties of recycled base courses according to selected additives was carried out to the procedure set out in EN 12697-26 annex D. The evaluation of stiffness modulus was conducted in the direct tension- compression test on cylindrical samples (DTC-CY). The samples were subjected to the cycles of sinusoidal strain with an amplitude Bo < 25μB. All tests were performed over a range of temperatures (5 ºC, 13 ºC, 25 ºC, 40 ºC) and loading times (0.1 Hz, 0.3 Hz, 1 Hz, 3 Hz, 10 Hz, 20 Hz). The results were used to model stiffness modulus master curves of the recycled base courses containing selected additives in the hydraulic binder.

Twenty-Five Years of Pavement Smoothness Specifications in Georgia

1996 ◽  
Vol 1545 (1) ◽  
pp. 11-15 ◽  
Author(s):  
Ronald Collins ◽  
Wouter Gulden ◽  
Dan R. Brown
Keyword(s):  
South Dakota ◽  
Mix Design ◽  
Response Type ◽  
Department Of Transportation ◽  
The Public ◽  
Measurement Systems ◽  
Construction Specifications ◽  
Pavement Construction

The traveling public generally recognizes the smoothness of a pavement as a major indicator of quality. A newly constructed pavement can have excellent materials, mix design, compaction, and so forth, but if the public considers the ride rough, the quality is considered poor. While continually striving to improve the quality of paving materials in mix designs, the Georgia Department of Transportation (GDOT) began an effort in 1968 to attain the ability to accurately measure the smoothness of a pavement so that this indicator of quality could be measured and specified during construction. GDOT has been using response-type smoothness-measurement systems in its construction specifications for acceptance of projects since 1972 and since 1979 for both rejection and acceptance. The evolution of the pavement smoothness-measuring program in Georgia, the program operating procedures, and the current smoothness specifications are described. The long-term benefits of smoothness specification for pavement construction are also discussed, as is GDOT's effort to replace the Mays Meter trailer systems currently used with South Dakota–type, laser-based road profilers.

Application of simulation technologies in the analysis of granular material behaviour during transport and storage

2005 ◽  
Vol 219 (1) ◽  
pp. 43-52 ◽  
Author(s):  
P Chapelle ◽  
N Christakis ◽  
J Wang ◽  
N Strusevich ◽  
M. K. Patel ◽  
...  
Keyword(s):  
Granular Material ◽  
Granular Materials ◽  
Large Scale ◽  
Computational Models ◽  
Research Programme ◽  
Size Segregation ◽  
Materials Handling ◽  
Simulation Tools ◽  
And Storage

Problems in the preservation of the quality of granular material products are complex and arise from a series of sources during transport and storage. In either designing a new plant or, more likely, analysing problems that give rise to product quality degradation in existing operations, practical measurement and simulation tools and technologies are required to support the process engineer. These technologies are required to help in both identifying the source of such problems and then designing them out. As part of a major research programme on quality in particulate manufacturing computational models have been developed for segregation in silos, degradation in pneumatic conveyors, and the development of caking during storage, which use where possible, micro-mechanical relationships to characterize the behaviour of granular materials. The objective of the work presented here is to demonstrate the use of these computational models of unit processes involved in the analysis of large-scale processes involving the handling of granular materials. This paper presents a set of simulations of a complete large-scale granular materials handling operation, involving the discharge of the materials from a silo, its transport through a dilute-phase pneumatic conveyor, and the material storage in a big bag under varying environmental temperature and humidity conditions. Conclusions are drawn on the capability of the computational models to represent key granular processes, including particle size segregation, degradation, and moisture migration caking.

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