Bitumen Film Research Articles

Effect of bitumen concentration and film thickness on rupture of water-in-oil toluene-diluted bitumen emulsion films using DC polarization

The stability of emulsion films of the water-oil-water (W/O) type against stepwise application of DC voltage ramps is explored. Films are formed from toluene-diluted bitumen solutions and DC polarization is applied on equilibrium films having a constant diameter. Film thickness, h, is measured microinterferometrically and at a given critical voltage, Vcr, film rupture is detected. The goal is to investigate the applicability of Vcr parameter for characterization of film stability as a function of concentration of real bitumen solutions, Cs. The equilibrium film thickness, h, corresponding to each bitumen concentration, is also monitored. A description statistics, analysis of variances (ANOVA), t-tests and multiple comparison tests are employed to analyse the experimental results. The standard deviations (relative to the mean) of Vcr and h obtained are rather large, whereas the standard errors are small indicating that obtained Vcr and h data are representative to the entire film population at a specific concentration. The results for the 95% confidence intervals of means are indicative for the sensitivity of the critical voltages towards changes in bitumen concentration and suggest overall picture of increased critical voltages with the concentration. However, in terms of thickness values, confidence intervals suggest sensitivity of this parameter in relation with concentration changes but no clear trend is revealed. ANOVA shows that for both variables, Vcr and h, the overall differences in the mean values among the concentration groups are greater than would be expected by chance, i.e. there are statistically significant differences. This statistic also allows estimation of the overall impact of these effects and large ones were found. Implementation of independent t-tests and multiple comparison tests reveal in greater intimacy which concentration pairs express statistically significant differences in terms of Vcr and h as well as the strength of these effects. Multiple linear regression model was built in order to distinguish the importance of predictor variables (Cs and h) in determination of the outcome variable (Vcr). Measured critical voltages are found to be with relatively large standard deviations. It is found that the inclusion in the model of the variable thickness explains larger amount of the variation in Vcr values in comparison with the model, containing only the concentration. Thus, film thickness appears to be an important parameter that leads to improvement of the predictive power of the model. The B-values for both predictors are positive indicating positive relationships with Vcr. Therefore, as bitumen concentration increases, critical voltage increases; as film thickness increases so does critical voltage. It is inferred that the concentration has a bit larger comparable impact on critical voltage than the thickness.

Cohesion Properties of Bitumen of Different Structures

The method and equipment for determining the mechanical properties of different road bitumen were developed in KhNAHU. The method has three schemes of deformation and fracture of binders, which are located in thin layers. As a result, the following quality parameters of bitumen can be defined: the limiting tensile strength, specific energy fracture, the limiting shear strength (cohesive strength) and the glass transition temperature. The paper shows the dependence of these parameters on the change in thickness of bitumen films, the strain rate (load) and temperature. Information about the cohesive strength of asphalt with different viscosities and different structural types (“Sol” “Gel” and “Sol-Gel”) is shown here. Bitumen composition has different influence on its strength, so comparisons of cohesive binder properties with the same consistency were made.

A framework for characterizing RAP clustering in asphalt concrete mixtures

Recycled Asphalt Pavement (RAP) is commonly used in asphalt for road rehabilitation or new constructions. Nevertheless, some physical and chemical phenomena that occur during production, laying and compaction of mixtures containing RAP are not yet completely explored. One of the main aspects is represented by the interaction between the aged bitumen from RAP and the virgin bitumen added to the mixture as well as the creation of clusters among small-size RAP particles. In this paper several combinations of mixtures are studied, varying the amount of RAP, the type of new binder and the testing temperature in order to obtain a suitable data set for the development of a framework for characterizing clustering of RAP during mixing hot recycled asphalt concrete based on the parameters mentioned above. For analyzing the experiments, the Response Surface Methodology (RSM) was applied. The set of points (combinations tested) for calibration of the models was selected using the Dohelert network, which is a design optimization strategy that allows the effective estimation of the models coefficients. The agglomeration of RAP particles is investigated for all virgin binders used and for all the percentages of RAP. It was shown that the quantity and the quality of virgin aggregates play a significant role in the clusters formation. Moreover, this experimental work suggested that revised formula for the calculation of the bitumen film thickness is needed, in order to include the combined effect of bitumen penetration and fabrication temperature.

Effect of film thickness on resistance to permanent deformation in asphalt mixtures

The resistance of asphalt mixtures against permanent deformation is one of important requirements that have to be verified in the design process of asphalt mixtures. In the case of asphalt concrete the European Standard EN 13108-1:2006 Bituminous Mixtures. Material Specifications. Part 1: Asphalt Concrete allows empirical (compositional recipes and requirements) or fundamental approach for testing of permanent deformation resistance. A fundamental approach specifies asphalt concrete in terms of performance-based requirements linked to limited prescription of composition and constituent materials. In this design approach a triaxial cyclic compression test is used to verify resistance to permanent deformation. The presented study investigates characteristics of resistance to rutting of asphalt concrete mixtures (eight mixtures of AC 11 from different producers) determined by triaxial cyclic compression test. The basic conclusions and statements of main factors influenced resistance to rutting (type of binder, binder content, and aggregate gradation) have been worked out from prevenient experience and experimental measuring. But measured test results presented in the following paper point out differences in resistance however the bitumen contents are relatively the same. During detailed investigation the tested asphalt mixtures had small differences in aggregate gradation. Changes in gradation make change of aggregate specific surface and the mixture needs different bitumen content to coat aggregate particles, to bound them to each other and to make stiff material resistant to rutting. The results from measuring of resistance to permanent deformation show the relation between aggregate specific surface and bitumen film thickness and permanent deformation.

Experimental evaluation of cohesive and adhesive bond strength and fracture energy of bitumen-aggregate systems

Degradation of asphalt pavements is an inevitable phenomenon due to the combined effects of high traffic loads and harsh environmental conditions. Deterioration can be in the form of cohesive failure of the bitumen and/or bitumen-filler mastic or by adhesive failure between bitumen and aggregate. This paper presents an experimental investigation to characterise the cohesive and adhesive strength and fracture energy of bitumen-aggregate samples. The pneumatic adhesion tensile testing instrument test and the peel test were used to quantify the tensile fracture strength and fracture energy of different bitumen-aggregate combinations, with a view to analyse the influence of several parameters on the strength of the bitumen film or bitumen-aggregate interface. From the experimental results, harder (40/60 pen) bitumen tends to show much higher tensile strength and fracture energy than softer (70/100 pen) bitumen. Tensile strength is shown to be sensitive to testing temperature with the failure regime changing from cohesive to mixed cohesive/adhesive failure with decreasing temperature. In addition, the results show that aggregate properties do not influence the bonding strength if cohesive failure occurs, but with adhesive failure, granite aggregate tends to produce a higher bonding strength than limestone aggregate in the dry condition. In terms of the peel test, the fracture energy experienced an increasing trend with increasing film thickness. However, the normalised toughness decreased when film thickness increased from 0.2 to 0.9 mm.

Evaporative Weathering of Diluted Bitumen Films

Summary One of the issues for the pipeline transportation of diluted bitumen (dilbit) is the fate and behaviour of the dilbit if it is spilled in freshwater systems; in particular, the evaporation rate and the change in physical properties of the film after evaporation and exposure to water (weathering). In this study, the evaporative weathering of dilbit Cold Lake Winter Blend (CLWB) and light crude oil Alberta Sweet Blend (ASB) films were compared. Evaporation rates were measured for films on glass over time (up to 30 days) at different air-flow rates and at temperatures of 5, 15, and 25C. The solvent content, density, and viscosity of the films were measured after different weathering times. A second set of tests at 15C was performed on both dilbit and light-crudeoil films on water. As expected, the mass-transfer rate increased with increasing temperature and decreasing film thickness in all cases. The evaporation of the dilbit was found to be limited by the diffusion rate of the lighter components through the film while that of the light crude oil was limited by convective mass transfer to the air above. The density and viscosity of both the CLWB and ASB films correlated to the amount of evaporated material at all conditions examined, including different film thicknesses, temperatures, and air-flow rates. It appears that the volatile components evaporate in the same order at any conditions; therefore, film composition, density, and viscosity are only functions of the amount evaporated. The evaporation rates, density, and viscosity of CLWB and ASB films weathered over water were identical to those corresponding films weathered on glass, within the error of the measurements; that is, contact with still water had no effect on weathering.

Optical and UV-Aging Properties of LDH-Modified Bitumen.

Layered double hydroxides (LDHs) are an ultraviolet-light (UV) resistant material. In this study, LDHs were used to modify bitumen. The optical and UV aging properties of LDHs modified bitumen were investigated. Firstly, the thin films of bitumen, with and without LDHs, were prepared. By using the UV-Vis spectrophotometer, absorbance, reflectance, and transmittance of bituminous thin film were evaluated. The morphology of LDHs-modified bitumen was observed by using fluorescence microscopy (FM). Finally, the aging resistance of LDH-modified bitumen was investigated by using the UV-aging oven. Results indicated that the LDHs, especially with 5 wt % in the bitumen, can effectively absorb and reflect the UV light and improve the UV-aging resistance of bitumen. This implied that the addition of LDHs into bitumen had the potential to prolong the service life of asphalt pavement.

Investigation into engineering properties and strength mechanism of grouted macadam composite materials

To further understand engineering properties of grouted macadam composite materials (GMCM) used as a surfacing layer in pavement, the mechanical properties and durability characteristics of GMCM were evaluated, and the relevant strength mechanisms were investigated at the micro level. Results indicate that GMCM has better high-temperature stability, fatigue performance and moisture stability than that of conventional asphalt mix, while it shows an acceptable decrease in low-temperature crack resistance due to the relative brittleness of hardened cement paste. The hardened cement paste also generates a spatial network crystalline lattice in asphalt mix skeleton to form a three-dimensional integral coagulation-crystalloid structure. This facilitates the asphalt mix skeleton and hardened cement paste to bear loads in unison and increase durability of the GMCM. Further, the fibre-like hydrated products of fresh cement slurry on the bitumen film surface increase the interfacial strength between bitumen and hardened cement paste due to toughening and bridging effects, which plays an important role to enhance mechanical properties and durability of GMCM. Finally, GMCM strength is from the internal friction of asphalt mix skeleton, the network structure of hardened cement paste and the adhesion between porous asphalt mix and hardened cement paste. It is concluded that GMCM can better meet the requirements of mechanical properties and durability characteristics than the conventional asphalt mix.

A Comparative Study on Properties of Malaysian Porous Asphalt Mixes with Different Bitumen Contents

Inadequate bitumen content in porous pavement construction may result in incomplete coating of aggregates which a thin bitumen film can oxidize rapidly resulting in premature failure of the pavement. This and presents the effects of porous asphalt prepared with 4.0% and up to 6.0% binder content with 0.5% increments binder. Bitumen penetration grade 60/70 and crushed granite were used in preparing the porous asphalt specimen. The porous asphalt mixes were compacted by applying 50 blows on each face using a Marshall Impact compactor. The specimens were tested for air voids, indirect tensile strength and water permeability and abrasion loss. The moisture sensitivity was assessed according to the AASHTO T283 procedures. The result shows that the increasing of bitumen content has decreased the, bulk density air voids, coefficient of permeability and abrasion loss values However, the Indirect Tensile Strength (ITS) has significantly increased and this is a good indication to resistance against moisture sensitivity. It can be concluded that the increasing of bitumen content in porous asphalt has increased the thickness of binder coating around the aggregates. This results reduction in air voids and water permeability, on the other hands it increases resistance to disintegration and ITS value which give better resistance to moisture sensitivity of porous specimens.

Reinforcement of asphalt concrete pavement by segments of exhausted fiber used for sorption of oil spill

The paper is aimed at construction of the experimental road pavement made of dispersed reinforced asphalt concrete. Electronic paramagnetic resonance, infrared spectroscopy and fluorescent bitumen studies were used to prove that disperse reinforcement of asphalt concrete mixtures with fibers of exhausted sorbents reduce the selective filtration of low polymeric fractions of petroleum bitumen and improve its properties in the adsorption layer. Sesquioxides are neutralized as catalysts aging asphalt binder. This leads to improvement in the elasticity of bitumen films at low temperatures and provide better crack resistance of coatings to reduce the intensity of the aging of asphalt binder, and, therefore, to increase the durability of road pavements. The experimental road pavement made of dispersed reinforced asphalt concrete operated during 4 years and demonstrated better transport- performance properties in comparison with the analogue pavements.

Influence of the gritting material applied during the winter services on the asphalt surface performance

Gritting materials such as de-icing agents are widely applied during the winter to help thawing ice and snow on road surfaces. They remain on the road for a certain period of time, which may affect the surface properties of the pavement, such as micro- and macro-texture and thus the skid resistance. In this paper, asphalt specimens are taken from a test track and subjected to a successively increasing polishing duration with various gritting materials as polishing agents with the Aachen Polishing Device. The skid resistance of these specimens is determined according to the Wehner/Schulze method. Results show that the skid resistance behavior was influenced by de-icing agent in terms of bitumen removal and polishing of the aggregates. In comparison with sand, de-icing salt has a positive effect on the skid resistance since it removes the bitumen film on the surface of the aggregates very fast while polishing the aggregates only to a minimal extent. It is therefore an optimal option for de-icing in winter services with regard to skid resistance and traffic safety.

STUDI PERILAKU CAMPURAN LATASTON (HRS-WC) DENGAN “LIMBAH KARET BAN LUAR” SEBAGAI BAHAN PENGGANTI SEBAGIAN ASPAL

STUDI PERILAKU CAMPURAN LATASTON (HRS-WC) DENGAN“LIMBAH KARET BAN LUAR” SEBAGAI BAHAN PENGGANTISEBAGIAN ASPALCandra Putra Kiswara 1& Andi Saiful A21&2Jurusan Teknik Sipil Fakultas Teknik Universitas Muhammadiyah MalangAlamat korespondensi : Jalan Raya Tlogomas 246 Malang 65144e-mail: candra_sum@yahoo.co.id, andiamal99@yahoo.co.idABSTRACTWaste to be one of the problems facing the nation at this time. Community is very disturbed bythe presence of various types of waste that is around their neighborhood. Ranging from industrialwaste to the waste home.The basic requirements of a road construction is to prepare the surface layer of a flat andstrong to ensure high security for a long time and the preservation of every detail in a variety ofweather. It required an asphalt mixture that is capable of supporting loads as well as capture thedamaging effects of traffic and the weather (climate) and can provide good service.With the addition of waste tire rubber is significantly affect mixture properties such Lataston(HRS-WC) Stability, Marshall Quontient, Flow and Air Voids. This is evidenced by the results oftesting using a Marshall. The average value of stability the average of 1220 kg. For Lataston (HRSWC)mix with additives outer tire rubber to rubber optimum levels (KKO) 11,50%, to produce amixture of qualities: Marshall Stability value = 1220 kg, Marshall Quotient value = 7,2 kN / mm,Value Air Marshall voids = 10,00%, Value Bitumen film thickness = 5,6 mm.Key Word: Waste Tire Rubber, Marshall Caracteristic

Newly observed effects of water on the microstructures of bitumen surface

Bitumen films with a thickness of 350–400μm were prepared on glass microscope slides and studied using atomic force microscopy (AFM) in tapping mode. Upon heating and cooling, elliptical microstructures appeared on the bitumen film surface as expected for bitumen containing wax. These microstructures had different sizes and orientations, and depending on the bitumen type either covered the whole surface of the bitumen film or not. In cases where the surface was not completely covered, both the periphase (elliptical microstructure), considered here to be a wax crystallite, and the perpetua phase (matrix around the periphase) were observed. Typically, at the center of the crystallite, the so-called “bee” microstructure was found, consisting of observed hills and valleys. The bitumen films were submerged in water at ∼23°C, under different experimental conditions, and experienced deformations as a response to forces exerted due to the presence of water. As a result, new topographic features were observed on the bitumen film surfaces, e.g. the microstructures were strongly affected. The valleys of the “bee” microstructure as well as the interfaces between the periphase and the perpetua phase contained material with different mechanical properties from the surrounding surface. The increase in the exposure time to water or larger deformation resulted in the spreading of the material which filled the valleys on the original surface. It is proposed that tension, bending and pressure as a result of water exposure, resulted in cracking of the weakest points of the surface structure. After cracking the material situated underneath the cracked surface seeped up through the cracks, for instance due to upward and downward pressures exerted on the film. From these results, it was concluded that the valleys of the “bee” microstructure and the interfaces between the periphase and the perpetua phase were the weakest points on the bitumen surface microstructure and, therefore, were the first to crack. Furthermore, the appearance of nano-bumps on the surface of the wax crystallites was detected, but neither on the perpetua phase nor on the “new” material which seeped through the possible cracks. This observation suggests that the chemical and mechanical nature of the wax crystallites is different from that of the perpetua phase and of the “new” material which filled the valleys.

On the oxidative ageing mechanism and its effect on asphalt mixtures morphology

This paper investigates the influence of mixture morphologies and microstructures on oxidative ageing of asphalt mixtures. For this, an oxidative ageing mechanism based on a diffusion–reaction process was developed. Previously, most asphalt oxidative ageing modeling research focused on unidirectional diffusion of continuous oxygen flow through bitumen films, which is far from the actual boundary conditions in asphalt mixtures. For this reason in the current study, a finite element (FE) analysis has been conducted in which 3D mixture morphology was considered. Mixture morphology is the combination of mineral aggregate packing, porosity, air-void distribution and their interconnectivity. One dense and one open graded field asphalt mixture core were scanned with a computerized tomography X-ray scanner. In the analyses, the developed oxidative ageing model was implemented. The FE analysis showed that the effect of the air-void distribution, their interconnectivity and the mineral aggregate packing has a significant effect on the resulting age hardening of the overall mixture. Furthermore, from the microstructural investigation done in this research, strong indications were found that, depending on the bitumen and its conditioning, water soluble thin films are formed due to ageing. This means that ageing and moisture damage are strongly interlinked and this should thus be considered in the design of the asphaltic materials and the prediction of their long term performance.

NUMERICAL ANALYSIS OF ASPHALT MIXTURE AND COMPARISON WITH PHYSICAL MARSHALL TEST

This paper addresses simulation of asphalt on the macroscopic scale, using the Discrete Element Model (DEM). Asphalt mixture is considered as a particulate solid composed of relatively stiff deformable layered spherical particles embedded into a homogenised matrix. The discrete model presents a 3D network of one-dimensional elements connecting particle's centres and comprising mutual interaction of particles. The contribution of the film layer and the interface thickness for normal stiffness is described analytically and illustrated by simulation results. Development of the normal interaction model of layered particles contacting via interface on the meso scale is the key point of the current development. The model applied aiming to simulate deformation of asphalt mixture is able to capture properties of the weaker matrix interface while layered particle comprises of bitumen film in meso scale. The developed technique is applied for simulation of Marshall test, i.e. diametric compression of cylindrical specimen, widely used for characterisation of asphalt mixtures. Finally, suitability of the model is illustrated by comparison with the available experimental results.

Assessing the stripping properties of granite aggregates in bituminous mixtures

The properties of aggregates in asphalt pavements are an important influence on the service lives of pavements. Aggregates should be covered by bitumen film and the film should remain stable under the effects of water and traffic loads. We studied the stripping behavior of eight different types of granitic rock in bituminous mixtures. First, we conducted petrographic examinations and mineralogical and chemical analyses of the samples. Surface roughness and surface tension tests were then performed. Finally, stripping and pull-out tests were conducted on the granite aggregates. We found that the stripping caused by water is dictated by mineralogical and chemical composition and surface tension, whereas the stripping caused by traffic loads is controlled by mineralogical and chemical composition and the surface roughness of granite aggregates.

Microstructural changes in bitumen at the onset of crack formation

For the first time the initiation and early stages of damage and microcrack growth in bitumen under mechanical loading conditions have been observed on the micrometer length scale by atomic force microscopy (AFM). Bitumen films have been applied on flexible substrates. Tensile loading of the substrate leads to straining of the substrate itself as well as the bitumen film that has been attached to it. The surface microstructure of the bitumen film has been studied with AFM for three loading levels: no loading, moderate (5% strain) and high loading (10% strain) conditions. The initiation and onset of propagation of microcracks have been observed for the moderately loaded specimen. It is found that damage in the shape of crazes and cracks does only occur in one of the two microstructural phases of bitumen, i.e. in the ellipse-shaped domains. Subsequent application of higher loading levels leads to complete embrittlement and fragmentation of the elliptical domains into lamellar structures which tend to align and orient in a direction perpendicular to the direction of loading.

Implementation of modified pull-off test by UTM to investigate bonding characteristics of bitumen and basic oxygen furnace slag (BOF)

Modified pull-off tests were implemented to investigate the bonding characteristics of bitumen and basic oxygen furnace slag by Universal Test Machine. Sandwich-like samples were prepared, which consist of two aggregate cubes and one layer of bitumen film. Therefore a stone–bitumen–stone structure was realized under pull-off strength in Universal Test Machine with a special designed clamp. The experimental variables included three aggregate sources (basic oxygen furnace slag, basalt, and granite), two bitumen film thicknesses, three test temperatures and moisture treatment. During test the pull-off strengths were measured when samples were subjected to various experimental conditions. By means of reliability analysis, the modified pull-off test was validated as a test procedure of good reproducibility for routine use. Stronger pull-off strength can be observed between basic oxygen furnace slag and bitumen at various bitumen film thicknesses, temperatures and even in moisture condition. Temperature dominates the fracture type of aggregate and bitumen, which is also related remarkably to bitumen retained area on aggregate. Generally there is a decrease trend in pull-off strength as increase in temperature and bitumen film thickness. The results are in accord with fracture energies.

Micromorphology and microrheology of modified bitumen by atomic force microscopy

The rheological study of bitumen is essential to improve the performance of pavements. Bitumen properties are traditionally determined by means of dynamic shear rheometer measurements. In this work, we aim to demonstrate that atomic force microscopy (AFM) can be a powerful complementary tool to the characterisation of bitumen. In particular, we compare the mechanical properties of pure and modified bitumen. Two different anti-oxidant additives were used: PPA (poly-phosphoric acid) and LCC (cashew nut oil) at concentrations of 1% and 2%, respectively. We will show that the AFM technique is able to distinguish the effects of both additives in the morphological and micromechanical properties of bitumen films.

DEPENDENCES OF SMA MIXTURE AND ITS BITUMINOUS BINDER PROPERTIES ON BITUMEN BATCHING SYSTEM, MIXING TIME AND TEMPERATURE ON ASPHALT MIXING PLANT

Bitumen holds the aggregate in hot mix asphalt (HMA). Without asphalt binder, HMA would simply be crushed stone or gravel. A bitumen batching system (BBS) is comprised of bitumen storage, transportation, weighing and discharge equipment in an asphalt mixing plant (AMP). The function of the equipment is to batch the binder heated up to working temperature and to discharge it into a mixer in batches. In the entire system, the binder is exposed to high temperature and oxygen. Bitumen is slowly oxidized when it is in contact with oxygen. The degree of oxidation is highly dependent on temperature, time and thickness of a bitumen film. This article models the key factors influencing on the dynamics of bitumen oxidation in BBS equipment. Stone mastic asphalt (SMA) mixture was produced from the same materials according to the same job-mix formula (JMF) in neighbouring batch type AMP by changing the mixing time of materials from 20 to 60 s. Bitumen binder was separated from the taken SMA samples and its gradation was identified. Thus, Marshall specimens were produced and tested. Penetration Pen25 of bitumen binder recovered in rotary evaporator, softening point Tsp was determined and penetration index Ip was calculated. The presented findings of experimental investigation show that the properties of bitumen binder in BBS working at two different technologies changed inconsistently. Due to gravitation, the bitumen intensively flowing into a mixer (BBS1) is impacted by oxidation more than the bitumen batched by a high-pressure pump (BBS2).