Hot Mix Asphalt Mixtures Research Articles

Mechanical Resistance of Hot-Mix Asphalt Using Phosphorite as Filler

Phosphorites (PF) have small particle sizes and interesting chemical compositions to be used as filler in asphalt mixtures. The present study assessed the performance that a hot-mix asphalt (HMA) displays when the natural filler (NF) is completely replaced by PF. X-ray diffractometry (XRD), X-ray fluorescence (XRF), and scanning electron microscope (SEM) tests were carried out on NF and PF particles. Asphalt mastic was manufactured using a weight ratio of filler (NF and PF) to asphalt binder of 1∶1.2. Penetration, softening point, viscosity, and linear amplitude sweep test were performed on the asphalt mastic. The following tests were carried out on mixes manufactured with NF (control) and PF (HMA-PF): Marshall, indirect tensile strength, Cantabro, resilient modulus, permanent deformation, and fatigue under stress-controlled mode. Additionally, moisture damage resistance was assessed through the tensile strength ratio (TSR) parameter. The HMA-PF mix displayed a better performance in all the evaluated properties, without increasing the optimum asphalt binder content. PF as fillers could be an interesting alternative in the manufacture of HMA mixtures subjected to high temperature climates.

Evaluation of olive pomace and SBS modified bitumen to the performance characteristics

This study investigated the applicability of olive pomace (OP) waste, a biomass waste, in bitumen modification. The OP modification was compared with styrene butadiene styrene (SBS) modified bitumen, which is widely used in asphalt modification, in terms of performance and cost. The OP and SBS binders were tested with conventional and rheological experiments. For this, modified asphalt binders were obtained by adding OP (wt. 4, 8, 15, 19, 25, 30%) and SBS (wt. 4, 4.5%) to pure B 50/70 penetration bitumen. The conventional test results of OP and SBS modified bitumen are close to each other, both modified bitumen decreased the penetration and temperature sensitivity of pure bitumen and increased the softening point. According to rheological test results, it was seen that the critical OP ratio was obtained from the 19% OP addition, and the critical SBS ratio was obtained from the 4% SBS addition and they exhibited the same performance grade. Then, for the hot mix asphalt (HMA) design, the optimum bitumen content was determined according to the Marshall method by using aggregate and B 50/70 pure bitumen, 19% OP, and 4% SBS modified bitumen. The effects of OP and SBS-modified bitumen on the mechanical properties of HMA mixtures were evaluated using Marshall stability tests. It could be said that OP-modified bitumen behaves like a more elastic solid at high temperatures, due to its lower penetration and higher softening point than pure bitumen. It has been observed that 19% OP additive provides an improvement, especially in rutting resistance, fatigue, and thermal crack resistance and 19% OP modified binder can be considered as an alternative to 4% SBS modified binder in general in terms of performance and cost. As a result, it is evaluated that OP can be used as a remedial additive in asphalt modification and contribute to the increase of pavement performance, and also that the damage of this waste material to the environment can be eliminated.

Comparative cracking resistance‐cost study for the hot mix asphalt (HMA) mixtures made of natural and recycled asphaltic materials

AbstractCracking performance of control and RAPed hot mix asphalt (HMA) mixtures was studied under low and medium temperatures. The effects of recycled asphalt pavement (RAP) content (0 and 50%), compaction method, and temperature (−20, 0 and +20°C) on KIf and KIIf were investigated. Cracking resistances of both modes showed similar trends. The fracture toughness of RAPed mixture at +20°C was higher than the control mixture. However, at −20°C, KIf and KIIf obtained from the RAPed mixture were about 22% lower than control mixture. A cost analysis was performed to compare the manufacturing costs of both mixtures. Accordingly, the cost of HMA mixture containing 50% RAP was 26% less than the control mixture. The proposed life‐cost index in the RAPed mixture was 10, 25, and 100% greater than the control mixture at −20, 0, and +20°C, respectively. Temperature and RAP content had the most important impacts on fracture toughness and cost, respectively.

Laboratory Testing of Ferrochrome Slag as an Aggregate in Porous Pavements

Abstract Porous asphalt (PA) is a bituminous mixture that is preferred in surface wearing courses because of its comparably better skid resistance and reduced spraying and hydroplaning risk, leading to improved driving quality compared with dense-graded hot mix asphalt mixtures. Use of recycled materials with satisfactory strength and durability properties as an aggregate in PA mixtures would provide both economic and environmental benefits because natural resources would be preserved, and transportation costs, and consequently CO2 emissions, would be reduced, and the stockpiled recycled material would be employed instead of occupying scarce landscape. However, because of the high air void content and exposure of a larger surface area to atmosphere in PA mixtures, the potential for raveling and rapid aging for any proposed aggregate material needs to be evaluated carefully. This study was conducted to investigate the performance of ferrochrome slag (FS), a by-product of ferrochromium industries, as an aggregate in porous asphalt. Air voids content, permeability, particle loss, tensile strength, and moisture susceptibility were measured on three different gradations of FS and the results were compared with the limits given in construction specifications. The gradation of the slag aggregates along with the bitumen content played a key role on performance of the PA mixtures. The FS specimens prepared at an optimum bitumen content of 6.5 % performed significantly better than limestone (LS) aggregate specimens at the same gradation; the air void content, permeability, and tensile strength of the FS mixtures were 2 %, 50 %, and 16 % higher than the LS mixtures, respectively.

Use of Basic Oxygen Furnace Slag (BOFS) in Superpave Mix Design: BOFS Aggregate Properties

This research aims to evaluate the properties of basic oxygen furnace slag (BOFS) as aggregates used in Superior Performing Asphalt Pavements (Superpave) mix design. A total of five different aggregates, including one limestone and four BOFS aggregates with different ages, were evaluated by the following aggregate properties: specific gravity, water absorption, Los Angles abrasion, aggregate crushing value, angularity, flakiness, soundness (sulfate chemical and freeze-thaw resistance), and expansion characteristics. Then, the volume stability of the hot mix asphalt (HMA) mixture was also discussed based on the aging effect of BOFS aggregate. Test results indicated that aged BOFS aggregate performs better than unaged BOFS aggregate: Aged BOFS aggregate has lower water absorption, lower aggregate crushing value, higher abrasion resistance, and less expansion. The flakiness and angularity of BOFS aggregates were satisfied with Superpave criteria. However, if free-lime (f-CaO) and free magnesium (f-MgO) in BOFS aggregate exist, it may cause the volume stability of asphalt mixtures with BOFS aggregate. In conclusion, if BOFS is appropriately aged and weathered, BOFS can be an alternative to conventional aggregate.

Development of high performing hybrid hot mix asphalt mixtures

ABSTRACT In this study, mixture design volumetrics, moisture-induced damage and fatigue characteristics of hybrid hot mix asphalt (HMA) fabricated with crumb rubber (CRM) and polyvinyl alcohol (PVA) fibre were evaluated. Indirect tensile strength test was conducted to assess several tensile and fracture attributes of control, polymer-modified, CRM-modified, PVA-reinforced and hybrid HMA. Long-term performance of aged hybrid HMA was also assessed using flexural beam fatigue test. Comparison of mixture designs indicated a change in volumetric properties of hybrid mixture with acceptable resistance to stripping. Experimental results revealed that fracture energy and dissipated creep-strain energy of the HMA with 2%CRM and 0.2%PVA doubled relative to polymer-modified HMA. The developed hybrid HMA presented around 29 times higher resistance to repeated load failure with 90% reduction in crack propagation rate and over 12 times higher energy for unit crack propagation compared to conventional HMA. Additionally, effective fibre bridging across the crack and adequate coating of asphalt on CRM through image analysis revealed wider strain distribution, a perverse intricate fracture pattern and better adhesion. The higher fracture resistance, toughness indices, and resilience under repetitive traffic loading of hybrid mixtures could be effective in extending the service-life and enhancing long-term performance of flexible pavements.

Mechanistic evaluation of segregation in HMA mixtures

Segregation in hot mix asphalt (HMA) mixtures is defined as the separation of the coarse aggregate particles in the mixtures from the rest of the mass. Segregation can be a result of aggregate stockpiling and handling, production, storage, truck loading practices, construction practices, and equipment adjustments. Segregation is usually evaluated visually, which is considered as a subjective method with no definite limits and depends on the evaluator’s opinion.This study uses two mechanistic surface texture indicators, i.e., mean texture depth (MTD) that is measured using sand patch method and mean profile depth (MPD) using laser texture profilometer to evaluate if a road section is segregated or not.The sand patch method is standardized in ASTM E965 -15 (2019) “for Measuring Pavement Macrotexture Depth Using Volumetric Technique”. MPD is covered by the international standards ASTM E1845-15 “Standard Practice for Calculating Pavement Macrotexture Mean Profile Depth”.Using both measured MTD values at grid point crossings, and average MPD values at 25 m intervals in the wheel paths, in addition to the use of statistical analysis of the obtained data, assuming that the obtained data are normally distributed and finding the 95% probability limits of the MTD and MPD values, it is possible to prove the closeness of the obtained texture depth indicator data, homogeneity of the road section, and that the segregation is only present at very limited localized locations.

Fracture toughness of Gilsonite modified HMA mixtures under mixed mode I/II loading at different temperature conditions

This study examines the fracture toughness of Gilosonite modified hot mix asphalt (HMA) mixtures. Pure mode I (i.e., Me = 1), two mixed I/II modes (i.e., Me = 0.79 and Me = 0.30), and pure mode II (i.e., Me = 0) by using semi-circular bend (SCB) at the temperatures of −18 °C, 0 °C and 25 °C are selected to perform the tests. Also, three different dosages of Gilsonite (i.e., 6 %, 12 %, and 18 % by weight of bitumen) are used to prepare HMA mixtures. The findings of this investigation demonstrate that the fracture toughness values of HMA mixtures increase with decreases in the temperature from 25 °C to −18 °C. Also, Gilsonite has a different and opposite influence on fracture toughness at different test temperatures. At the temperature of −18 °C, the incorporation of Gilsonite in HMA mixtures has a negative influence on the fracture toughness. Moreover, at this temperature, the fracture toughness decrease with increased Gilsonite dosages in HMA mixtures. Similarly to −18 °C, Gilsonite negatively affects fracture toughness at 0 °C, but less so than at −18 °C. On the opposite side, at the temperature of 25 °C, Gilsonite considerably improves the fracture toughness. which, in all loading modes adding Gilsonite increases the fracture toughness significantly. Maximum improvement at the temperature of 25 °C on the fracture toughness was 93 % and obtained in pure mode II when the Gilsonite dosage in the mixture was 12 %.

RUTTING PERFORMANCE OF TREATED LOW-DENSITY POLYETHYLENE AS ADDITIVE ON THE SUSTAINABLE MIXTURE

Rutting is a major distress issue in conventional flexible pavements causing the service life of road pavement reduced. A lot of efforts had been carried out to modify the hot mix asphalt mixture to overcome the problems. However, asphalt modification mainly increased the initial cost of road construction, which had forced many road agencies and researchers to use waste materials as modifiers. In this study, the potential use of low-density polyethylene powder made by waste plastic bag (treated) as an additive on the performance of rutting resistance was investigated by Marshall, resilient modulus, dynamic creep and double wheel tracker tests. The results showed that 0.75% of treated plastic (TP) by weight of total aggregate attained higher performance in rutting resistance than the conventional mixture. It can be concluded that the waste material additive not only increases the mixture performance but more towards mixture sustainability.

Effect of Recycled Aggregates and Polymer Modified Bitumen on the Marshall Properties of Hot Mix Asphalt- A Case Study

The main objective of this study was to assess the performance and physical properties of hot mix asphalt mixes incorporating recycled aggregates from demolished concrete and compare them with an unmodified hot mix asphalt mixture. Using recycled aggregates offers potential environmental benefits by reducing the load on landfill sites associated with demolished concrete waste. Hot mix asphalt mixes were prepared using the Marshall mix-design technique, with varying proportions (0%, 25%, 50%, and 75%) of recycled aggregates replacing the coarse virgin aggregates. The resulting mixes were compared to a control sample. It was observed that with an increase in the proportion of recycled aggregates, the stability of the mixes decreased. Additionally, the number of air voids and voids filled by mineral aggregates increased. However, laboratory tests indicated that the recycled aggregates modified mixes exhibited comparable performance to conventional hot mix asphalt mixes while providing improved environmental advantages through the recovery and reuse of waste concrete aggregates. These findings highlight the potential of utilizing recycled aggregates in hot mix asphalt as a sustainable approach in asphalt pavement construction.

Performance and cost evaluations of 100% recycled hot asphalt mixtures for pothole patching applications in flexible pavements

Fixing the potholes using bituminous patching mixtures is a critical and costly pavement maintenance activity. The patching mixture's quality significantly affects patch durability and performance; always using the best material available is advisable. This study investigated the feasibility of using 100% hot recycled asphalt pavements (RAP) as a possible patching material by comparing the performance results with cold patching mixtures (CPM) as well as Superpave hot mix asphalt (SHMA) mixtures. Four different RAP mixtures, two fine-graded and two coarse-graded, from two distinct sources, are obtained. RAP mixtures were handled in a laboratory environment to obtain the hot recycled patching materials. Three different rejuvenators were incorporated into hot-recycled pavement material (HRPM) at manufacturer-recommended dosages to determine the best rejuvenator type. Performances of the mixtures are evaluated in terms of linear viscoelastic characterization, permanent deformation, and low-temperature thermal cracking potentials using dynamic modulus, flow number, and indirect tensile strength tests, respectively. The results show that RAP mixtures with any RAP source, gradation, and rejuvenator type outperformed CPM in performance tests and behaved similarly to SHMA mixtures.

Performance of hot-mix asphalt using polymer-modified bitumen and marble dust as a filler

Marble dust waste powder generated by the marble cutting industry has a high alkalinity. In this research, the use of marble dust (MD) as a mineral filler substitute in hot mixed asphalt (HMA) was evaluated. The Marshall mix design was used to determine the optimum bitumen content (OBC) for all of the mixtures. For each of the four MD contents, i.e., 0, 2%, 4%, and 6% by weight of the total aggregates, four different bitumen percentages were used. The results of the Marshall stability test showed that the optimum filler content was 4% MD. Samples were prepared with 0 MD in the control mix and varying percentages of MD as an alternate filler. In addition, MD aided in increasing the Marshall stability, rutting resistance, and permanent deformation and reduced the fatigue life of asphalt mixtures. As the percentage of MD increases, the rutting resistance and stiffness at high temperatures both increase. As the percentage of MD increases, the fatigue life reduces. Rut resistance in high-temperature conditions can be improved by using MD in HMA as a partial substitute for stone dust (SD). In areas where extensive MD waste is present, MD can be incorporated into HMA mixtures instead of conventional fillers.

Low-Temperature Performance Improvement Measures for Emulsified Asphalt Cold Recycled Mixture: A Comparative Study

With the application of cold recycling technology in cold seasons or northern regions, suitable low-temperature performance evaluation methods and low-temperature performance improvement measures of a cold recycled mixture (CRM) became very topical. This study attempts to clarify the manufacturing process of low-temperature beam specimens by simulating the secondary thermal compaction of the overlying hot mix asphalt mixture layer. Next, the applicability of indirect tensile tests, low-temperature bend tests, and SCB tests to low-temperature performance evaluation of CRM is evaluated. The low-temperature improvement measures of emulsified asphalt CRM are analyzed, showing that “primary rolling for 24 times + secondary rolling for 12 times” of the low-temperature beam specimens conforms to the field compaction state of the CRM layer. The low-temperature performance of CRM under different design schemes can be characterized by the fracture work in the indirect tensile tests and fracture energy in the SCB tests. Compared with the ordinary emulsified asphalt CRM, the mixture design scheme of “3% latex +5% regenerant” can significantly improve the low-temperature performance of CRM. The lower the temperature, the more pronounced the improvement effect. Considering that the low-temperature performance of CRM meets the road requirements, the design scheme of “3% latex +5% regenerant” is recommended, while the “3% latex” scheme is the most cost-effective.

Stiffness evaluation of Forta Fibre Reinforced Asphalt Concrete (FRAC) mixture under different pulse repetition load

Pavement structure can be designed either as a flexible or a rigid pavement based on its structural behaviour, with flexible pavements being frequently favored due to its advantages. One of the major problems that normally occurred in road construction was pavement distresses due to the quality of the materials. Numerous studies were carried out to explore sustainable ways to improve the pavement performance especially on modification of the asphaltic concrete in construction phases. This paper investigates the effect of Forta-Fi fiber on stiffness performance of hot mix asphalt mixture (HMA). In this respect, conventional asphalt binder grade 60/70 and Nominal Maximum Aggregate Size (NMAS) 12.5mm were used in the preparation of asphalt mixture specimens as specified in Superpave mix design method. Performance of modified samples incorporating 0.3, 0.5 and 0.7% of total mixture were evaluated for resilient modulus accordance to ASTM D4123 using Universal Testing Machine (UTM). The samples were tested at 25°C and 40°C with pulse repetition period 1000ms, 2000ms and 3000ms to simulate low, medium and high volume of traffic. As a result, the resilient modulus values of modified asphalt mixture improved 38% with 0.3% additive of Forta-Fi at 25°C with 3000ms pulse repetition period, while at 40°C with 3000ms pulse repetition period improved 23% with 0.5% additive of Forta-Fi. Based on these studies, the addition of fibers reinforcement into the asphalt mixture has a significant effect on resilient modulus of fibers reinforced asphalt mixture.

Research on evaluation method of asphalt mixture workability based on minimum mixing energy consumption

The workability evaluation of hot mix asphalt mixtures is of particular importance for the uniformity analysis of asphalt mixtures and influence of later asphalt pavement properties. Currently, workability tests and evaluation systems for hot mix asphalt mixtures are not perfect. In this study, we have developed a testing device, proposed an evaluation index, and established an evaluation system for asphalt mixture workability. The compaction degree, asphalt distribution uniformity evaluation index (ADU), aggregate distribution uniformity evaluation index (HA), and coated uniformity of asphalt film evaluation index (CUAF) were measured to verify the workability evaluation index of asphalt mixture. Test results demonstrated that the newly developed asphalt mixture workability testing device and workability evaluation index accurately quantified the shift law of asphalt mixture workability during mixing process. The variation of the workability law was affected by asphalt type, mixture type, and mixing temperature. Compactness, ADU, HA and CUAF were closely correlated with workability evaluation indexes, and R2 values were 0.73, 0.77, 0.94 and 0.8, respectively. Validation results of the workability evaluation index of compactness, ADU, HA, and CUAF showed that the newly proposed workability evaluation index for asphalt mixture was feasible and effective.

Utilization of reclaimed asphalt pavement (RAP) materials in HMA mixtures for flexible pavement construction

Production of more RAP material waste arises the problem of deposition. To overcome this problem, RAP materials are recycled and re-used in different layers of pavement which will reduce the cost of pavement construction, reduce the environmental pollution. So, partial replacement with natural aggregate (NA) is an alternative for conservation of natural resources. RAP materials contain bitumen on their surface which will reduce the amount of natural bitumen. Replacement of RAP materials with natural aggregate needs suitable blending proportion. This paper represents laboratory evaluation of replacement of Reclaimed Asphalt Pavement (RAP) materials, a varying percentage of 0 to 30% blended with natural aggregate in terms of Marshall Stability, Indirect Tensile strength and Tensile Strength Ratio to be used in hot mix asphalt (HMA) mixtures for construction of surface course of flexible pavement. Marshall Stability, Indirect Tensile strength and tensile strength ratio (wet and dry condition) of natural aggregate blended with RAP 0%, 10%, 20% and 30% were tested and found 20% RAP mix is suitable for the bituminous road construction.

Fracture and fatigue characteristics of high performing novel hot mix asphalt composites

Long-term performance and sustainability of asphalt pavements could be achieved by developing hot mix asphalt (HMA) composite that possesses enhanced resilience, toughness, ductility, and durability under repeated traffic loading and extreme weather conditions. The main goal of this study was to investigate the fracture and fatigue characteristics of a novel HMA composite fabricated with combination of crumb rubber (CRM) and polyvinyl alcohol (PVA) fiber. The fracture properties of the control, CRM modified, PVA reinforced, and novel rubber-fiber HMA composites, was conducted through semicircular bending beam test. Moreover, resistance to reflective and fatigue cracking was assessed to validate the long-term performance of the novel HMA composite. Experimental results revealed that a suitable proportion of CRM and PVA significantly affected the performance of novel rubber-fiber HMA in resistance to fracture, reflective, and fatigue cracking. Fracture energy and flexibility index of the rubber-fiber HMA containing 2% CRM and 0.2% PVA quadrupled relative to PG76-22 HMA after long-term aging. The developed novel HMA composite presented around 8- and 29-times higher resistance to reflective and fatigue cracking, respectively. Additionally, digital image correlation analysis showed that the rubber-fiber HMA composite had a larger strain distribution and a more twisted and intricate fracture pattern. The multi-functional properties of CRM and PVA were visible in scanning electron micrographs, where the rubber act as hyper elastic inclusion and properly coated fibers with asphalt, effectively bridged across cracks thus hindering the crack propagation and increased tolerance to post-peak load deformation. Cost comparison and benefits of conventional and selected modified HMA mixtures indicated that the developed mixture could be a valuable long-term economical alternative pavement material.

Improvement of Moisture Susceptibility for Asphalt Mixture with Ceramic Fiber

Moisture damage is one of the most significant troubles that destroy asphaltic pavement and reduces road serviceability. Recently, academics have noticed a trend to utilize fibers to enhance the efficiency of asphalt pavement. This research explores the effect of low-cost ceramic fiber, which has high tensile strength and a very high thermal insulation coefficient, on the asphalt mixture's characteristics by adding three different proportions (0.75%, 1.5%, and 2.25%). The Marshall test and the Tensile Strength Ratio Test (TSR) were utilized to describe the impact of ceramic fiber on the characteristics of Marshall and the moisture susceptibility of the hot mix asphalt mixture. The Field Emission Scanning Electron Microscopy (FE-SEM) analysis was used to investigate ceramic fibers' microscopic structure and clarify the mechanics of their improved behavior and their distribution within the asphalt concrete mixture. The results showed that the incorporation of ceramic fibers improved the Marshall properties and the asphalt mixture's susceptibility to moisture damage with an optimum fiber content equal to 1.5%, where Marshall stability increased by 39.04%, and the TSR increased by 11.06% at this content compared with the control asphalt mixture.

Moisture Susceptibility of Hot Mix Asphalt Mixtures Modified by Nano Silica and Subjected to Aging Process

Moisture damage is described as a reduction in stiffness and strength durability in asphalt mixtures due to moisture. This study investigated the influence of adding nano silica (NS) to the Asphalt on the moisture susceptibility of hot-mix-asphalt (HMA) mixtures under different aging conditions. NS was mixed with asphalt binder at concentrations of 2%, 4%, and 6% by weight of the binder. To detect the microstructure changes of modified Asphalt and estimate the dispersion of NS within the Asphalt, the field emission scanning electron microscope (FE-SEM) was used. To examine the performance of Asphalt mixed with NS at different aging stages (short-term and long-term aging), asphalt mixture tests such as Marshall stability, flow, and Tensile Strength Ratio Test (TSR) were performed. According to the FESEM images, the NS particles in the mixture were sufficiently dispersed. The findings demonstrate that the NS enhances pavement performance by enhancing stability and volumetric characteristics and reducing susceptibility to moisture damage. Furthermore, TSR values of aged specimens show that increasing the NS content significantly reduces susceptibility to moisture and oxidative aging.

Effect of Locust Bean Pod Ash as Filler on Hot Mix Asphalt Mixtures

At present, the conventional sources for mineral filler in asphaltic concrete mixes are the chemical element of lime, cement, quarry dust and fly ash which has some health hazards. This study presents a laboratory investigation on the effects of locust bean ash as filler in Hot Mix Asphalt (HMA) production for a wearing course in order to find a cost-effective, environmentally friendly and less hazardous alternative to the traditional mineral filler of cement or lime. A total of 90 trials of bituminous mixtures with two types of mineral filler (locust bean ash and ordinary Portland cement) at 4 loading rates of 0, 2.5, 5 and 10% were evaluated for mechanical (strength) and workability performance properties according to standard asphalt mix Marshall Method of design. The Marshall stability, flow, density and void properties were developed for each mineral filler contents and the corresponding optimum binder content were determined for the general specification for roads and bridges in a subtropical region. The 2.5% for the two types of mineral filler was found to produce best performance of the HMA at optimum binder content of 5.5%. Also, the use of locust bean ash was found to be hazardous-free. Similarly, mineral filler from biomass was found to be advantageous for use as mineral filler source in asphalt mix production. Its application in the subtropical region where the biomass wastes are mostly abundant was recommended for HMA.