Asphalt Cement Research Articles

From Street to Road: An Innovative Approach to Explore Discarded Chewing Gum as a Performance-Enhancing Modifier for Road Pavement Applications.

To uncover the potential benefits of discarded chewing gum (DCG) as a performance-enhancing modifier for road pavement applications, its influence on the asphalt binder’s attributes was profoundly examined. The base AP-5 asphalt along with its specimens dosed with various fractions of DCG (e.g., 3, 6, and 9 wt%) were analyzed by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thin-layer chromatography-flame ionization detection (TLC-FID), scanning electron microscopy (SEM), atomic force microscopy (AFM), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). Brookfield viscometer, ring and ball softening point, needle penetration, and dynamic shear rheometer (DSR) tests were adopted to inspect the physical and rheological changes of asphalt cement after DCG incorporation. FT-IR disclosed that the asphalt-gum interaction was not chemical but physical in nature, whilst XRD demonstrated the existence of talc filler in DCG, which may confer the bituminous mixes with exceptional engineering properties. Iatroscan analysis evinced that the gum treatment particularly altered the aromatic and resin fractions; meanwhile, the content of saturates and asphaltenes remained relatively unchanged. SEM divulged that the DCG has a complete dissolution within the bitumen matrix, which becomes rougher due to higher dose administration. AFM revealed that the steady gum introduction amplified the size of bee-like structures, shrunk their peri-phase domains, and wiped out the para-phase domains entirely. TGA/DTGA/DSC data highlighted that the high-temperature-stable additive slightly affected the thermal properties of blends. DSR and empirical rheological tests showed that the waste gum made the bitumen less vulnerable to heat and tender, thereby boosting its resistance against fatigue cracking at intermediate service temperatures. On top of that, DCG widened the thermal window of bitumen performance grade (PG), and preserved its viscosity at standard temperatures, leading to maintaining an appropriate workability for asphalt mix. In brief, the use of discarded chewing gum as an asphalt modifier is feasible and could mitigate plastic pollution and provide durable roadways by delivering superior performance.

Effect of Cement Grouts Containing Irradiated Polyethylene Terephthalate on Properties of Semi-Flexible Mixtures

The seme-flexible pavement surface is a hybrid type of pavement surface that combines the effect of both asphalt mix skeleton and cement grout. The current study investigates the influence of cement grouts containing irradiated waste polyethylene terephthalate (PET) on the performance of semi-flexible mixtures. The ordinary Portland cement was partially replaced by regular and irradiated PET as well as with fly ash (FA) in cement grouts. The air voids analysis, degree of grout saturation, Marshal stability, indirect tensile strength (ITS), and tensile strength ratio (TSR) of semi-flexible specimens were evaluated. The semi-flexible mixtures showed superior performance in terms of strength properties. The results indicate that with the irradiation process more waste PET (almost double) can be recycled as compared to regular waste PET in cement grouts for semi-flexible pavement surfaces. This approach will lead to a sustainable solution for recycling waste PET in highway materials for the construction of a hybrid type of pavement surface.

Effect of Polypropylene Fibers on moisture Susceptibility of Warm Mix Asphalt

Warm Mix Asphalt (WMA) is a modern energy-saving process that uses environmentally friendly materials, has lower mixing and compaction temperatures, and uses less energy and releases less contaminants than conventional hot mix asphalt. Moisture damage poses one of the main challenges of the material design in asphalt pavements. During its design life, the asphalt pavement is exposed to the effect of moisture from the surrounding environment. This research intends to investigate the role of the polypropylene fibres for modifying the moisture susceptibility for the WMA by using different percentages of polypropylene (namely 2, 4, and 6%) by weight of the binder of the control mixture (WMA). In this paper, the physical characteristics of the asphalt cement, Marshall properties, Tensile Strength Ratio (TSR) and Index of Retained Strength (IRS) were determined to establish the effect of the polypropylene on the moisture susceptibility of the WMA. The results displayed that the modification of the AC with polypropylene caused an increase in the optimum asphalt content by 1.03, 3.09, and 11.3%, with the addition of 2, 4 and 6% of the P.P., respectively. The moisture resistance of the asphalt mixture was enhanced by adding the P.P., according to the rise in the Tensile Strength Ratio (TSR) and Index of Retained Strength (IRS) values. The TSR value showed 9.4, 18.2 and 19.5% increase when the P.P. increased from 0.00 to 0.02, 0.04, and 0.06, respectively; besides, the IRS showed improvement with the addition of the P.P. to the WMA. Doi: 10.28991/cej-2021-03091704 Full Text: PDF

Influence of aging on the physicochemical behavior of photocatalytic asphalt cements subjected to the natural environment

This investigation evaluates aging characteristics and photocatalytic performance of asphalt cements modified with titanium dioxide (TiO2) at different percentages (3, 5, and 7% by weight of the asphalt binder). Conventional and photocatalytic asphalt cements were used to manufacture specimens of hot mix asphalt (HMA) compacted in the laboratory with a Gyratory Compactor and subjected to environmental conditioning for 6, 12, or 18 months in which they were exposed to temperature changes, rain, and sunlight. FTIR (Fourier-Transform Infrared Spectroscopy), MSCR (Multiple Stress Creep and Recovery), and degradation of methylene blue (MB) tests were carried out to evaluate the influence of aging on the chemical and mechanical properties. Besides, the photocatalytic efficiency of asphalt cements extracted from aged asphalt concrete specimens by the reflux method was also studied. FTIR results indicated that photocatalytic asphalt cements exhibit greater aging resistance over time than conventional asphalt binders. MSCR results showed that mechanical properties represented by deformation recovery and non-recoverable creep compliance parameters improved with TiO2 content and environmental conditioning time. On the other hand, the MB degradation tests indicated that the photocatalytic efficiency of modified asphalt cements increases with the TiO2 content and remains between 20 and 25% for all environmental conditions assessed in this study.

Effect of Waste Oil Shale Ash on Properties of Asphalt Cement and Asphalt Concrete Mixtures: State of the Art

Effect of Waste Oil Shale Ash on Properties of Asphalt Cement and Asphalt Concrete Mixtures: State of the Art

Stress concentration in the vicinity of road сoating cracks

The article presents the results of a computer analysis of the stress-strain state of a multilayer asphalt pavement under the influence of traffic loads. Based on the finite-element model of coating deformation, a study was made of the mechanical behavior of the system considered for various structural schemes for the existence of vertical cracks in various layers of the structure under the action of vertical transport loads. The effects of stress concentration in the system due to high-gradient deformation fields and structural imperfections of the multilayer coating were found.
 Multi-layer asphalt roads are one of the most common construction projects. Based on a review of the tasks of science about their strength and durability, these structures can be attributed to significantly complex types of building systems. This is primarily due to the multi-parameter nature of the factors that determine their design, material properties, types of loads and the impact on them, as well as their operating conditions. Therefore, designers of road structures and specialists who are involved in the theoretical modeling of the mechanical behavior of layered massifs during operation have to take into account many additional factors that complicate their work. These include the most important design and operational features of these systems, which significantly affect the nature of the distribution of stress and strain fields, as well as their intensity. First of all, they include special structural schemes of the road and pavement. It is a multilayer three-dimensional package having disproportionately different sizes along each direction.
 Hidden (as well as obvious) vertical cracks and horizontal delamination of the structure, sometimes permissible under operating conditions, can be added to the design model of a structure. Such violations of the continuity of the system also lead to discontinuity of the displacement functions, which further worsens the system’s performance and complicates the task of its modeling.
 The materials of the coating layers, which include asphalt concrete, cement, crushed stone, sand, soil, and others, also bring particular specificity to the work of the road structure. All of them differently resist tensile, compression and shear, and asphalt concrete is also elastic-viscous - plastic material, whose properties are largely dependent on temperature.

Recycling of Dolomite and Basalt Asphalt Mixes of Existing Highway at Damietta Governerate.(Dept.C)

Recycling of asphalt mixes can be defined as the restoration of aged mixes. The purpose of this research is to evaluate some old asphaltic surface courses in Damietta governerate for their potential of being recycled. Two types of old asphalt surface in Damietta were sampled and transported to the highway laboratory at Mansoura University. One of the two mixes was a dolomite crushed stone mixed at 6.64 asphalt content and the other was a basalt aggregate mixed at 5.2% asphalt content. Control mixes were also prepared using two virgin aggregates similar to those aggregates under study and designed according to Marshall method. It was found that the two Damietta asphalt mixes had high potential to be hot recycled after the addition of a 12% softener and 30% virgin aggregate. No extra addition of asphalt cement was needed in most cases.

Interface damage and arching mechanism of CRTS II slab track under temperature load

To study the interface damage and the arching deformation of China railway track system (CRTS) II slab track under high-temperature conditions, a three-dimensional (3D) finite element model of the CRTS II slab track was developed. A cohesive zone model (CZM) with a non-linear constitutive law was utilized to simulate the interface damage between the precast slab and the cement asphalt (CA) mortar layer. The model was verified by comparing the simulation results with the experimental results. The effects of the overall temperature rise and positive temperature gradient on the interface damage and deformation of the track structure under the different damage levels of the joint concrete were studied. The analysis indicates that when the joint concrete is intact, the interface between the precast and the CA mortar layer does not appear damage under the effect of the overall temperature rise or the positive temperature gradient. The damage of the joint concrete is an inducement for the interface damage and the arching of the slab track under the action of high temperature. The interface damage area and the height of the interface gap increase with the increase of the damage degree of the joint concrete. Especially under the action of the overall temperature rise, the interface gap can reach more than 30 mm. More attention needs to be paid to the construction quality and maintenance of joint concrete.

Surface microscopic properties of various aggregates using laser scanning confocal microscope

The surface morphology of aggregates has a significant effect on the aggregates, which in turn affects the technical performance of asphalt mixtures and cement concrete. In this study, the surface micro-morphology (SMM) of a) four typical natural aggregates, b) recycled concrete aggregate (RCA), and c) recycled brick aggregate (RCB) were investigated using laser scanning confocal microscope, and combined with image analysis technology, roughness theory and fractal theory for quantitative evaluation. Limewater immersion and physical abrasion were performed on each aggregate to investigate the effect of these processes on SMM. Results show that the surface micro-roughness and fractal dimensions of different aggregates varied predictably with the formation conditions of aggregates. After being immersed in limewater, the surface micro-roughness of basalt, limestone and diabase increased, but their fractal dimensions did not change, while the surface micro-roughness of granite, RCA and RCB decreased by 20–30%, and their fractal dimensions increased by 0.65.%, 1.69% and 0.43%, respectively. The effect of physical abrasion on the SMM of aggregates was related to the hardness of the aggregates. After physical abrasion, the surface micro-roughness and fractal dimensions of the six aggregates were reduced.

MICRONIZED CRUMB RUBBER INFLUENCE ON INDEX PROPERTIES OF WARM ASPHALT BINDERS

Primarily, the main aim of recycling waste tires in the form of micronized crumb rubber into asphalt cement as modifiers are to enhance their engineering properties in addition to the associated solid waste management benefits. Often, these modifiers are used to achieve reasonably stiffer binders i.e.; low penetration; high softening point; and high penetration index, to realize higher resistance to deformation under the influence of traffic and temperature. The study assessed the effects of Micronized Crumb Rubber (MCR) on the penetration, softening point, and penetration index of 80-100 PEN bitumen impregnated with 2.5 % Sasobit (fixed by weight). The MCR modified warm asphalt binders were prepared by further blending with different percentages of minus 40 mesh size MCR powder (from0 – 15 % by weight of the bitumen stepped at 2.5%). Subsequently, penetration and softening point tests were conducted on each blend, and the corresponding penetration indices were evaluated. The results show that MCR addition gradually decreases the penetration values while conversely increases both the softening point values and the penetration indices as well. Thus, MCR might be used to improve the flow and thermal susceptibility resistance of warm asphalt binders

An examination of natural rubber modified asphalt: Effects of rubber latex contents based on macro- and micro-observation analyses

At present, relatively no reliable conclusion regarding an optimum natural rubber content based on the theoretical and fundamental approach to understanding up to the micro-scale of chemical and mechanical interactions in the natural rubber-asphalt cement matrix as the natural rubber modified asphalt (NRMA) exists. This study aimed to examine the effects of natural rubber latex (NRL) contents in natural rubber modified asphalt (NRMA) binder. A series of micro-observation techniques, including scanning electron microscopy (SEM), X-ray diffraction (XRD), nuclear magnetic resonance (NMR), differential scanning calorimetry (DSC), and Fourier transform infrared spectroscopy (FT-IR), were performed. For the general performance tests, macro observations through a series of penetration tests, softening point, viscosity, ductility, and dynamic shear modulus (G*) for evaluating the asphalt binder properties were also conducted. Study results showed that the performance of NRMAs (3%–12% NRL contents) depended on their NRL contents due to varying internal interactions between NRL and the asphalt binder. The NRMA with an optimal content of 7% NRL revealed crosslinking and bridging interactions between NRL and an original asphalt cement was observed, and the chemical bonds were also identified.

Interfacial failure and arching of the CRTS II slab track reinforced by post-installed reinforcement bars due to thermal effects

To prevent damage of the China Railway Track System (CRTS) II slab track induced by thermal effects, post-installed reinforcement (PIR) bars between the prefabricated slabs and the concrete base have been utilized in the track. This work presents a study on the interfacial failure and arching of the CRTS II slab track reinforced by PIR bars due to the effects of temperature change. To this end, a novel finite element model of the track was established, in which the non-linear interfacial interaction between the track slabs and the cement asphalt (CA) mortar layer was simulated by a cohesive zone model, the non-linear constitutive material properties of track concrete were represented by a concrete damaged plasticity (CDP) model, and the non-linear bond-slip relationship between PIR bars and track concrete was characterized by non-linear spring elements. Comparison between simulation results and experimental data indicates that the proposed modelling technique is capable of evaluating the performance of the track reinforced by PIR bars. The combined action of insufficient bond strength between PIR bars and concrete, and insufficient bond strength between track slabs and CA mortar layer, was analyzed. Numerical analysis results show: (1) The temperature rise of interface failure between the concrete slabs and the CA mortar layer can be improved by 6 °C after PIR bars installation. (2) The PIR bars are effective in reducing arching displacement of slabs caused by temperature rise in both lateral direction and longitudinal direction of track slabs. (3) Both PIR bond strength and interface bond strength influence the maximum arching displacement of track slabs significantly.

Behavior of the Dynamic Modulus and Fatigue in Asphalt Mixtures with Blast Oxygen Furnace Slag and Blast Furnace Dust

Slag from a Blast Oxygen Furnace (BOF) is produced during the transformation of cast iron, coming from the blast furnace, into steel during the integrated steelmaking process, just as blast furnace dust (BFD) is produced during the transformation of the iron mineral into cast iron. These residues have generated environmental problems due to the accumulation and inadequate disposal thereof. Consequently, this study aims to analyze the use and behavior of the dynamic modulus and the fatigue in asphalt mixtures with partial (50 %) and total (100 %) substitution of the coarse aggregate for BOF slag and the fine aggregate for BFD. The results are compared with the behavior of a mixture elaborated with conventional aggregates. To achieve this objective, the chemical and physical properties of BOF and BFD were determined along with the optimum asphalt cement content, determined using the Ramcodes methodology. Tests were carried out to evaluate the physical characteristics, the dynamic modulus, and the fatigue of each type of mixture. The results of this study demonstrate adequate fatigue behavior and a slight reduction in dynamic modulus in mixtures with BOF and BFD. This allows us to deduce that the use of these residues is feasible and thereby to contribute to sustainable development and the protection of the environment.

Interface Mechanical Properties and Damage Behavior of CRTS II Slab Track considering Differential Subgrade Settlement

To analyze the effects of differential subgrade settlement on the interface mechanical properties and damage behavior of the China Railway Track System (CRTS) II slab track, a three-dimensional finite element (FE) model considering the uneven support of the subgrade was developed. A cohesive zone model was used to simulate the interface damage between the precast slab and the cement asphalt (CA) mortar layer. The effects of settlement amplitude, wavelength, and temperature gradient were analyzed. The results indicated that the interface stress is significantly affected by the settlement amplitude. There exists a particular settlement wavelength that results in the maximum interface stresses. Considerable attention should be paid to the effect of the temperature gradient load, which may cause interface damage in the differential settlement region.

Assessment of Durability Properties of Reclaimed Asphalt Pavement Using Two Rejuvenators: Waste Engine Oil and Asphalt Cement (60-70) Penetration Grade

The production of asphalt pavements using Reclaim Asphalt Pavement (RAP) has achieved economic and environmental benefits. However, one of the main challenges when using untreated RAP in pavement construction is the hardness of the binder due to aging. The purpose of this study is to recycle and restore damaged asphalt using two types of regenerative agents: Waste Engine Oil (WEO) and Asphalt Cement (AC (60-70)) Penetration Grade. Five ratios (1, 1.5, 2, 2.5 and 3) % of both types of regenerators were added to the RAP, separately, for the purpose of regeneration. Marshall Test was performed on the regenerated samples in order to obtain the optimum ratios for the regenerative additives, which will be adopted in subsequent tests, which include; indirect tensile strength (ITS), tensile strength Ratio (TSR) and Duple Punch Shear Strength Test (DPSST) to evaluate the performance of regenerated RAP mixes and compare them with the original RAP. The results indicated that (1.5 and 3) % are the optimal ratios for (WEO and AC (60-70)), respectively. In addition, the results of the performance tests indicated that the regenerated RAP mixes are better than the original RAP in terms of cracking resistance, stripping resistance and resistance to moisture damage, as well as achieving the specification requirements for the surface course. It can be concluded that rap recycling using (WEO and AC (60-70)) is an effective process that reduces paving costs, reduces environmental pollution and leads to gain sustainable paving.The first section in your paper

Study of the Properties of Open Graded Asphalt Mixtures With the addition of SBS

Porous asphalt (PA) is widely used in a growing number of countries where porous asphalt is applied for a variety of purposes, e.g. for the effective drainage of rainwater, traffic safety (high slip resistance), the control of noise pollution and lower temperatures surrounding the city. However, it has many other disadvantages, such as poor resistance to rutting, poor resistance to fatigue, and PA is susceptible to raveling (wastage of aggregates from the pavement surface), due to effects of climatic and traffic loading. In general, this type of mixtures is not as good as traditional mixtures. This research aims to study and improve the properties of porous mixtures using SBS. In this paper, laboratory tests were carried out to the materials involved in the composition of this mixture: binder, aggregate, and additive. SBS is used in the proportion of (2.0, 3.0, and 4.0) % of the weight of the binder. It was found that this additive leads to reduce the permeability and air void, but not as large as that without polymer modifier by (1.7 %, 3%, and 3.5%), while in the case of abrasion loss (aged and unaged) decrease by (4.1, 6.67 and 10.92) (4.7, 6.3and 2.6)% respectively. The drain down value is decreased by (16.5%, 38.25%, and 43.51%) respectively, from original asphalt cement.

Investigating the Effect of Olive Husk Ash on the Properties of Asphalt Concrete Mixture

Technology in transportation used available resources to make it safe, fast, suitable, easy, economic, and environmental to transport people and goods. Olive Husk became an environmental problem as waste materials especially in the Middle East where huge quantities are found. The objective of this research is to investigate the effect of addition of Olive Husk Ash (OHA) on the properties of asphalt concrete mixtures. Marshall Test was used to perform the asphalt concrete mixture by the addition of OHA to the binder of asphalt; different percentages of OHA (0, 5, 10, 15, and 20%) by volume were added to the binder. Five percent of asphalt cements (5, 5.5, 6, 6.5 and 7%) by weight and limestone aggregate were used for preparing asphalt mixture specimens to find the optimum content of asphalt that could be used in the binder. Tests on flow, stability, air void percentage and void in mineral aggregate, retained stability, stiffness, and retained stiffness were made. The principle results on OHA as filler in Asphalt binder improves the Marshall Stability, and void in mineral aggregate and decrease in flow, retained stability, stiffness, and retained stiffness with a 10%-15% of olive husk ash replacement of asphalt binder. The contribution that OHA could be used as a pavement construction material in field.

Environmental and Cost Impact Assessment of Pavement Materials Using IBEES Method

For road pavements, hot-mix asphalt (HMA) and Portland cement concrete (PCC) are the materials most commonly used. In the selection of one of these materials, their economic performance and environmental performance are evaluated to determine which material exhibits excellent overall performance. However, no overall performance assessment exists in the construction community attributed to the lack of method providing easy-to-use and informative criteria for the decision-making process. Thus, in this paper, a new method that enables a comprehensive overall performance assessment is proposed, which is called Improved Building for Environmental and Economic Sustainability. After an eco-economic life-cycle assessment is performed, along with environmental performance and economic performance evaluation, the best-fit pavement material can be selected. This method has proven that the use of HMA for road pavements reduces the environmental impact by 27.1%P (i.e., percentage point), whereas the use of PCC reduces cost by 19.7%P. The existing Building for Environmental and Economic Sustainability (BEES) method shows that the performances of both HMA and PCC were over-assessed by 4.6%P and 7.4%P, respectively, since the environmental performance and economic performance cannot be computed quantitatively by incorporating the environmental and cost impact index into existing BEES model, the Improved BEES method accurately projects environmental performance and economic performance attained through the application of the environmental and cost impact index, hence, encouraging more informed decision. This method facilitates in articulating a quality decision making through the consideration of both the environmental performance and economic performance, hence reducing unnecessary costs generated from the trial and error due to the use of the existing method. Moreover, it promotes the development of a sustainable construction technology.

Factors influencing the performance of cement emulsified asphalt mortar – A review

Cement emulsified asphalt mortar (CEAM) is an essential component in the ballastless slab track system. It is a semi-rigid composite material consisting mainly of hardened cement paste and demulsification asphalt, possessing the advantages of both ordinary Portland cement and asphalt. Its primary functions include: supporting structures, adjusting the slab track's geometry during construction, and dissipating/reducing orbital vibration. In this review, the preparation technology of CEAM was introduced at first. Subsequently, the hardening mechanism between asphalt emulsion and cement in CEAM was summarized. Meanwhile, the influence of asphalt emulsion type and dosage, sand to cement ratio (S/C), water to cement ratio (W/C), common auxiliary additives, and temperature on the properties of CEAM were compared and analyzed. This current review concludes that the most significant influence on CEAM performance is the mass ratio of asphalt to cement. With the increase of asphalt content, hardened cement asphalt paste (CA paste) would show two different overall mechanical properties. Besides, the effects of the S/C ratio and W/C ratio on high strength CEAM are not the same as that of low strength CEAM. Future research is recommended: to develop sustainable CEAM without prejudice to the performance; and to further analyze the interaction mechanism between emulsified asphalt and cement materials from the microscopic perspective.

Evaluating the mechanical properties of thin asphalt overlay incorporating reed ash

Thin Asphalt Overlay (TAO) is a preservation maintenance technique that has been shown to overcome shortcomings in the functional properties of surface pavement layers. Although TAO is not a structural layer, its application sustains the pavement’s structural strength and increases its lifespan, which is a valuable effect for the paving industry. Due to recent realisation of the limits of natural resources and the high cost of raw materials, the paving industry has also developed a secondary target of incorporating waste materials as an alternative to conventional raw materials, both to reduce environmental pollution and minimise costs, in such applications. This study focuses on evaluating the effect of using reed ash (RA) in this manner on the mechanical properties of TAO. The control TAO mixture was densely graded, with a 9.5 mm nominal maximum aggregate size (NMAS) utilising a 40/50 asphalt binder grade. Three percentages of RA were incorporated, 6%, 12% and 18%, to produce modified asphalt binder. To verify the effect of this material on cracking behaviours, resistance to permanent deformation of TAO, indirect tensile strength, creep compliance, and wheel track tests were carried out on both control and modified asphalt mixtures. The results showed a significant enhancement in the performance of TAO modified with 6% RA as compared to the control mixture, although the very high dosage of 18% reduced the performance of the relevant TAO mixtures. This study thus indicates that using this waste material can offer an alternative solution for asphalt cement modification, increasing sustainability, if dosages are carefully controlled.