Stability Of Bitumen Research Articles

Evaluation of the properties of bitumen modified by SBS copolymers with different styrene–butadiene structure

ABSTRACTFour styrene–butadiene–styrene(SBS) modified bitumens had been prepared by a base bitumen, a crosslinking agent and four SBS copolymers which differ in styrene blocks content and molecular configuration (radial or linear) under the same experimental conditions. Conventional properties, morphology, thermal behavior and microstructure were investigated by means of conventional tests, fluorescence microscopy, differential scanning calorimetry (DSC), and Fourier transform infrared (FT‐IR) spectroscopy. In terms of linear SBS polymers, the SBS molecule with the styrene content of 30% has a perfect dispersion and complete stretching in bitumen matrix, and in this case, the conventional properties and thermal stability of bitumen are enhanced substantially. However, the star SBS polymer due to long branched chains forming the preferable steric hindrance to enhance the intensity of base bitumen, plays a more important role in improving the conventional properties of base bitumen than linear SBS polymers. Furthermore, the FT‐IR spectra indicate that, the main bands assignations of four modified bitumens are identical and the significant variation is the peak intensity. And a noncomplete crosslinking reaction happens between the bitumen and each SBS polymer, which can efficiently prevent excessive cross‐linking from affecting the intrinsic bitumen characteristics. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40398.

Preparation process to affect stability in waste polyethylene-modified bitumen

An analysis of waste polyethylene (WPE) modified bitumens prepared using a variety of approaches is described in this study. The WPE was obtained from commercially-available packaging bags. It has recently been shown that addition of WPE to bitumen enhances the high temperature stability of the modified bitumen. In this paper, WPE-modified bitumens were prepared using a high-speed shear mixer employing different processing parameters. High temperature storage stability tests and morphological analysis showed that a shear rate of 3750rpm, at 150°C and shear time of 1.5h to be the optimal processing parameters of storage stability. In addition, differential scanning calorimetry (DSC) and thermal gravimetric analysis (TGA) were used to analyze the thermal stability of the WPE-modified bitumen. We found that the thermal stability of the modified bitumen surpassed that of the base bitumen, but was generally independent of the preparation parameters.

Performance of cold recycling materials with foamed bitumen and increasing percentage of reclaimed asphalt pavement

The increasing use of bitumen-stabilised materials (BSMs) in the world and especially in Southern Africa necessitates further research into the fundamental properties and behaviour of BSMs. In particular, bitumen stabilisation is increasingly being used to rehabilitate base layers of pavements incorporating thick asphalt layers, resulting in higher percentages of reclaimed asphalt pavement (RAP) in the mixes. There is a significant need for improved understanding of these materials, which is the main objective of the study being undertaken. The extended knowledge gained from this research is intended to improve current mix design and structural design practices. The project's aim is to investigate the feasibility and suitability of producing BSMs that include RAP with relatively high blending ratios of recycled graded crushed stone. In this study, the RAP used in each mix design contains materials with relatively fresh binder. The proportions range from 100:0 to 0:100 of graded crushed stone: RAP. Tri-axial tests at different temperatures are carried out to determine shear properties, resilient modulus and permanent deformation behaviour of the mix. The findings show that the RAP type and percentage influence the rutting resistance, indirect tensile strength (ITS) and moisture susceptibility of the BSMs. A portion of this study is dedicated to the characterisation of the permanent deformation behaviour and to the moisture damage simulation.

Marshall properties of waste polymer and nanoclay modified bitumen

Polymer modified bitumen is emerging as one of the important construction materials for flexible pavements. The addition of polymers in bitumen improves the deformational stability and durability of bitumen. Also Montmorillonite nanoclay has been successfully used as additive in polymer to significantly improve the thermal stability and mechanical properties. The present study, the effect of waste low density polyethylene (LDPE), polypropylene (PP) obtained from waste carry bag, crumb rubber obtained from Waste tyre (CR)and nanoclay (MMT) on Marshall stability have been evaluated. Waste plastics, whose disposal is a matter of concern can be used successfully to modify the bitumen, these waste polymers are added in 2%, 4% and 6% whereas nanoclay is added in 1,2 and 3 % in 60/70 penetration grade bitumen and its effect on stability and flow of bitumen are evaluated. The result of experimental study shows that there is significant improvement in the Marshall Stability of bitumen due addition of waste polymer and nanoclay.

RHEOLOGICAL PROPERTIES OF RECYCLED LOW DENSITY POLYETHYLENE AND POLYPROPYLENE MODIFIED BITUMEN

Polymer-modified bitumen has been used in civil engineering practice from a long time. The addition of polymers in bitumen improves the deformational stability and durability of bitumen. In the present study, the effect of waste Low Density Polyethylene (LDPE) and Polypropylene (PP) obtained from waste carry bag, on various properties of bitumen such as penetration, ductility softening point have been evaluated. Waste plastics, whose disposal is a matter of concern can be used successfully to modify the bitumen, these waste polymers are added in 2%, 4%, 6%, 8%and 10% percentages in 60/70 penetration grade bitumen and its effect on different properties of bitumen are evaluated. The result of experimental study shows that there is significant improvement in the properties of bitumen due to LDPE and PP modification.

Interpretation of laboratory and full-scale testing of New Zealand foamed bitumen pavements using finite-element modelling

A large research project on foamed bitumen (FB) stabilisation was conducted in New Zealand. The project consisted of an extensive laboratory and full-scale testing of FB pavements. The objective of this paper is to interpret the performance of FB pavements by using finite-element (FE) modelling. The mechanical properties of the materials were calculated using testing data and used as material inputs in the FE modelling. The Mohr–Coulomb and Drucker–Prager material models were adopted to calculate plastic deformation, which is related to pavement rutting. Results of the modelling indicate that increasing the FB content increases the tensile strength and modulus of the pavements, reducing the plastic deformations in the subgrade and the stabilised layer. In addition, adding FB reduces sensitivity to rutting when pavement is overloaded or the asphalt surface layer is cracked.

Manufacturing Terminal and Field Bitumen-Tyre Rubber Blends: The Importance of Processing Conditions

No-agitation Tyre Rubber Modified Bitumens (TR-MBs), also known as “terminal blends” or “field-blends”, are quite new technologies leading to bituminous binders similar to polymer modified bitumens in terms of both rheology and needed efforts during paving operations. Their manufacturing, as well as other TR-MBs, is strongly dependent on the selected processing variables as well as on the chosen materials. This study presents a literature review to provide an overview of the TR-MB technologies which focuses on the influence of processing conditions on the modification process, storage stability and overall properties of the final bitumen - tyre rubber blends.

A study into the processing of bitumen modified with tire crumb rubber and polymeric additives

This work focuses on the influence that processing variables (such as gap between rotor and stator of the mixer, time and temperature) exert on both mechanical properties and hot storage stability of bitumen modified with crumb tire rubber and polymeric additives, with the aim of optimizing the formulation of bitumen modified with low solubility materials.The experimental results obtained reveal that all the polymeric additives used yield an improvement in both the rheological and technological properties of the binder. Processing time leads to an increase in both the primary aging and rubber digestion, with the latter effect predominant for times of up to 2–3h. Processing temperature increases the amount of rubber digestion and improves the elasticity of the resulting binder.

The Effect of Nanoclay on Rheological Properties and Storage Stability of SBS-Modified Bitumen

Linear and branched grades of styrene-butadiene-styrene (SBS) triblock copolymer are commonly used for modifying physical, mechanical, and rheological properties of bitumen. Because bitumen and SBS are incompatible, SBS-modified bitumen is not storage stable at elevated temperatures. Incompatibility of branched SBS is greater than linear SBS. To obtain greater compatibility between SBS and bitumen, organophilic montmorillonite/SBS-modified bitumen mixtures, prepared by melt intercalated blending, were used. Results showed that the presence of nanoclay could improve the storage stability, aging, and high-temperature performance of polymer-modified bitumen (PMB) significantly. Of course, this effect can be seen by proper dispersion of organophilic montmorillonite (OMMT) in SBS and obtaining a homogenous blend, which is calleed an exfoliated structure. The structure of OMMT/SBS/bitumen blend was characterized by X-ray diffraction (XRD).

Decreasing Moisture Susceptibility of Gravel Road Surface Aggregate by Hydrophobic Treatment Agent

The use of a special hydrophobic treatment agent to reduce the moisture susceptibility of gravel road surface aggregate was studied. A treatment agent and dosage were chosen on the basis of positive results from earlier studies concerning different base course aggregates of paved roads. Laboratory pretesting samples from a chosen test site confirmed that, for example, in tube suction tests the dielectric value of the aggregate treated with the chosen agent and dosage was lowered remarkably as compared with untreated aggregate. This result indicated improved water resistance. The treated aggregate also showed increased abrasion resistance and was less density-susceptible as compared with the untreated aggregate. As a result of the encouraging results from the preliminary tests, a 500-m unpaved test section was constructed in 2009. Ordinary bitumen stabilization machinery was used for simultaneous spreading and mixing of 1% resin-based treatment agent emulsion to the gravel surface aggregate. Although the water content was lower than expected, the construction of the test section succeeded; it will be monitored regularly by falling weight deflectometer measurements and visual inspections.

A preliminary study on foamed bitumen stabilisation for Western Australian pavements

Currently, the popularity of conventional cementitious stabilisation had been challenged by an innovative soil improvement technique, known as foamed bitumen stabilisation. Many Australian highway and road agencies have dedicated significant investigation and funds to investigate this technique in order to achieve a more flexible and fatigue resistant stabilised material suitable for a wide range of pavement conditions. This study aimed to report the preliminary study of the foamed bitumen properties and the mix procedures conducted at Curtin University which simulated the construction of the trial foamed bitumen stabilised project in Western Australia. Our findings show that 2.5% of cold water spraying into 180°C virgin Class 170 bitumen can produce foamed bitumen with a 15 to 20 times expansion rate and 20 s half-time suitable for foaming aggregates. Both resilient modulus and permanent deformation tests failed to predict an optimum foamed bitumen content when the aggregate was mixed with 1% hydrated lime, compacted at 100% optimum moisture content and plastic sealed curing for 7 days at room temperature. However, the ratio of crushed granite roadbase to limestone was found to be significant and a mixture consisting of 75% crushed rock base and 25% crushed limestone was determined as the optimum aggregate proportion, as it showed the best performance in unconfined compressive strength tests and obtained relatively higher values in indirect tensile strength tests. Based on our preliminary results, due to adding more foamed bitumen to in-situ recycled aggregate seems to reduce the performance of materials, a more comprehensive laboratory investigation of the foamed bitumen stabilisation process in Western Australia would be essential.

Bitumen Colloidal and Structural Stability Characterization

ABSTRACT Turbidimetric titration and analysis using SARA (Saturates, Aromatics, Resins and Asphaltenes) were done for bitumen, aged bitumen and recycled bitumen, and their index of colloidal stability (P) and Gaestel Index (iC) were calculated. The results show that with deep aging of the bitumen, its colloidal stability decreases. Changes in the SARA fractions influence the colloidal stability of the bitumen. The asphaltenes is the most influential factor. The recycling effect of rejuvenator C was good and that of rejuvenator A was bad. Higher aromatics, moderate saturates and lower asphaltenes content of the rejuvenator can produce a good regeneration effect. Hence, the colloidal stability of aged bitumen can be restored when the proper rejuvenator is chosen. The structural stability of bitumen was characterized using a three-dimensional titration. The experimental results indicate that for the bitumen after PAV aging, polar interactions and hydrogen bonding are stronger than that of unaged bitumen, but the dispersive force is lower.

Full-Scale Experiment on Foam Bitumen Pavements in an Accelerated Testing Facility

Foam bitumen stabilization is a viable alternative for reducing aggregate consumption in New Zealand. An accelerated full-scale experiment on foam bitumen pavements was conducted in the Canterbury Accelerated Pavement Testing Indoor Facility as part of a Transit New Zealand research project to study the effects of foam bitumen on unbound granular materials. Six pavement sections were tested. Three were constructed with foam bitumen contents of 1.2%, 1.4%, and 2.8% and with a common active filler content of 1.0% cement. Two more pavements were constructed with adding cement only (1.0%) and foam bitumen only (2.2%). In addition, one control section with the untreated unbound material was tested. Strains were collected with a three-dimension Emu soil strain system installed in each pavement section. Results showed that surface deflections decreased at sections with higher bitumen contents. After the application of 5,710,000 equivalent standard axles, the control section and all sections that had been stabilized with cement only and bitumen only showed large amounts of rutting. Conversely, little rutting was observed in the three sections stabilized with 2.2% foam bitumen and 1.0% cement. Water was introduced into these three pavements with additional accelerated loading; this caused the section with the lowest foam bitumen content to fail. These results showed that foam bitumen and cement had a significant effect on improving the performance of the materials studied. Material samples taken for indirect tensile strength (ITS) and repeat load triaxial (RLT) for laboratory tests showed that the ITS test was a good predictor of the pavement performance and produced a clear trend, although RLT results were not conclusive.

Cost evaluation of foam bitumen and other stabilisation alternatives

As the demand for a cost efficient and environmental friendly pavement stabilisation method increases, so has foamed bitumen stabilisation for unbound granular pavement layers started to gain broad acceptance worldwide. The work forms part of a larger project aimed at investigating the feasibility and potential applications of the foamed bitumen stabilisation technique in order to speed up its adoption in New Zealand. In this paper, a cost-analysis exercise comparing the capital cost of eight base course stabilisation alternatives in addition to hot mix asphalt (HMA) alternative was made. Cement, lime and foam bitumen stabilisation versus HMA design alternatives were compared. The foam stabilised mix represents a high quality base course material stabilised with 2.0% cement and 3.5% foam bitumen. The results of this analysis showed that foam bitumen stabilisation using high quality aggregates and about 2% cement is competitive compared to unbound materials because a reduced layer thickness is required.

Effect of Aggregate Gradation, Mineral Fillers, Bitumen Grade, and Source on Mechanical Properties of Foamed Bitumen–Stabilized Mixes

With the rapid growth of traffic volumes and axle loads, the use of efficient and cost-effective stabilization methods is imperative. The use of foam bitumen stabilization is rapidly growing because of its environmentally friendly benefits and its high field performance properties. In this study, a detailed investigation of the mechanical properties of foam-stabilized mixes was carried out. The experimental work presented compares the mechanical properties of foam-stabilized mixes created with two different gradations and eight bitumen types from six different sources. Different types of mineral fillers, including hydrated lime, fly ash type C, portland cement, and pond ash, were used in the mix design. The volumetric properties, resilient moduli, indirect tensile strengths, fracture energies, and California bearing ratio (CBR) values were investigated. Temperature and moisture susceptibilities were studied and compared for different types and grades of bitumen. Foam-stabilized mixes provided lower temperature susceptibility than did hot-mix asphalt. The effect of bitumen source and grade on moisture susceptibility was inspected. The foam-stabilized mixes provided reasonable moisture resistance as the index of retained strength exceeded 80% to 90% after 5 days of soaking. The effect of aggregate gradation and mineral fillers on the indirect tensile strength and the fracture energy was evident. Hot-mix asphalts provided higher tensile strength and fracture energy than did foam-stabilized mixes. Foamed bitumen stabilization significantly enhanced the CBR values as the soaked CBR of foam-treated specimens provided higher CBR values than the conventional untreated aggregates.

Effect of Aggregate Gradation, Mineral Fillers, Bitumen Grade, and Source on Mechanical Properties of Foamed Bitumen-Stabilized Mixes

With the rapid growth of traffic volumes and axle loads, the use of efficient and cost-effective stabilization methods is imperative. The use of foam bitumen stabilization is rapidly growing because of its environmentally friendly benefits and its high field performance properties. In this study, a detailed investigation of the mechanical properties of foam-stabilized mixes was carried out. The experimental work presented compares the mechanical properties of foam-stabilized mixes created with two different gradations and eight bitumen types from six different sources. Different types of mineral fillers, including hydrated lime, fly ash type C, portland cement, and pond ash, were used in the mix design. The volumetric properties, resilient moduli, indirect tensile strengths, fracture energies, and California bearing ratio (CBR) values were investigated. Temperature and moisture susceptibilities were studied and compared for different types and grades of bitumen. Foam-stabilized mixes provided lower temperature susceptibility than did hot-mix asphalt. The effect of bitumen source and grade on moisture susceptibility was inspected. The foam-stabilized mixes provided reasonable moisture resistance as the index of retained strength exceeded 80% to 90% after 5 days of soaking. The effect of aggregate gradation and mineral fillers on the indirect tensile strength and the fracture energy was evident. Hot-mix asphalts provided higher tensile strength and fracture energy than did foam-stabilized mixes. Foamed bitumen stabilization significantly enhanced the CBR values as the soaked CBR of foam-treated specimens provided higher CBR values than the conventional untreated aggregates.

Influence of Crumb Rubber Concentration on the Rheological Behavior of a Crumb Rubber Modified Bitumen

Bitumen is widely used in construction. Its applications go from binder for road asphalts to built-up roofing membranes and other waterproofing uses. The use of crumb tire rubber as a binder modifier may contribute to solving a waste disposal problem and to improving the quality of road pavements. This paper deals with the effect that rubber concentration exerts on the thermorheological properties of rubber-modified bitumens. The results obtained confirm that the rheology and storage stability of these modified binders are largely dependent on rubber concentration. The linear viscoelastic measurements carried out revealed an improvement of both low and high in-service properties of the binder. The viscous flow measurements showed an important increase in viscosity and a noticeable reduction in temperature susceptibility. A swelling process of the crumb rubber by light components of the maltenic fraction was confirmed by modulated differential scanning calorimetry (MDSC). The stability tests, performed on samples stored at 180°C, demonstrated that the storage stability of rubber-modified bitumen was improved as rubber concentration increased.

04/02689 Effect of origin and technology on the chemical composition and colloidal stability of bitumens: Baginska, K. and Gawel, I. Fuel Processing Technology, 2004, 85, (13), 1453–1462

04/02689 Effect of origin and technology on the chemical composition and colloidal stability of bitumens: Baginska, K. and Gawel, I. Fuel Processing Technology, 2004, 85, (13), 1453–1462

Effect of origin and technology on the chemical composition and colloidal stability of bitumens

The investigated materials were the bitumens produced from naphthenic (Venezuelan) and paraffin-naphthenic (Uralian) crude oils by different technological methods. The bitumens of 70 and 50 pen were analyzed for generic composition, macrostructure and colloidal stability. The size of asphaltene micelles and the extent of their aggregation were influenced by the chemical type of the feedstock and the method of bitumen production. SEM examinations of asphaltenes made it possible to discern micelles ranging in size from 110 to 260 nm. Examinations of Uralian bitumens revealed particles of a smaller size as compared to those of the asphaltenes from Venezuelan bitumens, but the extent of aggregation was greater for Uralian asphaltenes. Air-blowing increased the extent of aggregation of asphaltene micelles. Fractionation of asphaltenes and analysis of bitumens by the GPC method showed a higher content of the heaviest components in bitumens, which were subjected to a more intensive oxidation. The bitumens under study exhibited a satisfactory colloidal stability. The slightly higher colloidal stability parameter of bitumens from naphthenic crude oil is likely to be due to a smaller aggregation of asphaltene micelles and a greater resins to asphaltenes ratio in these bitumens.

New Zealand Experience with Foam Bitumen Stabilization

Foamed bitumen stabilization is burgeoning steadfastly and internationally. Although it involves higher initial material costs than cement or lime stabilization, it offers the advantages of being free from transverse shrinkage cracking and of being a fast technique that minimizes traffic delays. This work forms part of a larger project aimed at investigating the feasibility and potential applications of the foamed bitumen stabilization technique to speed its adoption in New Zealand. In this research, the foaming characteristics of two sources each of two grades of bitumen currently in use in New Zealand are presented. The effect of bitumen source and grade and the type of fines were studied. Fly ash Type C was used to modify the aggregate gradation to adjust the percentage of the fine fraction (passing the 75μm sieve). Portland cement was used at 2% by the dry weight of aggregates as a partial replacement for the fly ash. The foamability results for each source were quite different. For each source, the softer grade provided better quality foam than the harder grade. Two groups of mixes were prepared. The two groups were identical except that the first group contained 2% portland cement as a partial replacement of the fly ash. Optimum foam and water contents were determined for the two groups. The effect of curing time on the resilient modulus of foam-stabilized mixes was investigated. Both groups showed high resilient modulus values and rapid rates of increase of the moduli with curing time.