Optimum Bitumen Content Research Articles

Mechanistic Characteristics of HRS-WC Mixture Using Tabas Stone Waste Coated With Plastic Waste As Aggregate

Utilization of tabas stone waste and polypropylene (PP) plastic waste has not been carried out massively and optimally because it lacks economic value. The Tabas stone waste can be used as an aggregate for pavement. The porous characteristic of tabas stone results in a high rate of absorption and abrasion, so modifications are made by coating the aggregate with an PP plastic. The aim of this experiment was to determine the characteristics of the HRS-WC mixture with the aggregate of tabas stone coated with plastic. The initial step of this research was testing the tabas stone aggregates, bitumen material, and PP plastic according to the SNI procedure, the next step was Marshall test to find the Optimum Bitumen Content (OBC), the OBC value was obtained by 10%. Coating the aggregate with shredded plastic measuring ± 1 cm2 was done on coarse aggregate only using the dry method with the proportions of plastic are 5% and 10% of the total weight of coarse aggregate. The characteristics of the aggregate coated with plastic decrease in the value of absorption and abrasion, but only 10% of the plastic content met the specifications with a value of 2.5% and 19.63%. The Marshall testing on the HRS-WC mixture with plastic-coated aggregates was done at variations in bitumen content of 8.5%; 9%; 9.5%. The mixture at 5% plastic content only 9.5% bitumen content met the specifications, namely: stability 1352.72 kg, flow 3.39 mm, MQ 402.23 kg/mm, VIM 5.75%, VMA 18.62% , and VFB 69.16%. When at 10% plastic content, only 9% and 9.5% bitumen content met the specifications, namely the stability of 1370.06 kg; 1456.21 kg, flow 3.81 mm; 3.98 mm, MQ 365.31 kg/mm; 370.06 kg/mm, VIM 5.77%; 4.89%, VMA 18.07%; 18; 15%, and VFB 68.05%; 73.04%. Asphalt mixture of 9% bitumen content, 10% plastic content has more ITSM value compared to 5% plastic content. This is due to the plastic content in the mixture of 10% plastic content which causes the mixture to be stiffness. Asphalt mixture with a plastic content of 5%, with an bitumen content of 9.5% faster than the mixture with an bitumen content of 8.5% and 9% in the ITFT test. Asphalt mixture with a plastic content of 5%, with a variation of bitumen of 8.5% experienced a decrease in the dynamic creep strain value until the bitumen content was 9.5%. A mixture with a plastic content of 5% aggregate coating is recommended for HRS WC that uses tabas stone.

Enhancing High-Temperature Performance of Flexible Pavement with Plastic-Modified Asphalt.

Previous studies indicate that traditional asphalt mixtures lack the ability to withstand the stresses caused by heavy traffic volumes under high temperatures. To enhance the rutting resistance of flexible pavement under high levels of temperature and loading, extensive laboratory experiments were carried out. A 60/70 grade bitumen was used as a neat sample for comparison. The study introduced three distinct polymers, polypropylene (PP), low-density polyethylene (LDPE), and acrylonitrile butadiene styrene (ABS), at varying concentrations by weight into the neat bitumen. Initially, conventional tests were performed to evaluate the conventional properties of both the neat and modified bitumen, while aggregate tests assessed the mechanical properties of the aggregates. Subsequently, a Marshall mix design was performed to determine the optimum bitumen content (OBC) in the asphalt mixture. Finally, wheel-tracking tests were performed under a specific load and temperature to investigate the rutting behavior of the modified asphalt mixtures. The results of this comprehensive study revealed that the modified asphalt mixtures displayed improved resistance to rutting compared to the neat asphalt mixture. Furthermore, it was also observed that the LDPE exhibited a superior performance against rutting, followed by the PP and ABS. At polymer contents of 3%, 5%, and 7%, the LDPE achieved reductions in rut depth of 13%, 24%, and 33%, respectively, outperforming both PP- and ABS-modified asphalt. These findings not only enhance our understanding of asphalt behavior under diverse conditions but also highlight the potential of plastic-modified asphalt as an effective solution for mitigating rutting problems in road pavements. By incorporating plastic modifiers into asphalt mixtures, this approach aligns with the principles of sustainable construction by reducing plastic waste while improving pavement durability and performance.

Analysis of the Use of Waste Plastics Low-Density Polyethylene (LDPE) along with Bitumen in the Construction of Asphalt Pavement using the Marshall Test

Plastic disposal is a significant problem as it is non-biodegradable and causes air pollution if burned. The utilization of waste plastics in road construction has gained attention due to environmental concerns and the need for sustainable development of infrastructure. This research investigates the performance waste plastics, low-density polyethylene (LDPE) and, in the asphalt road along with the bitumen based on the Marshall Stability Test. The Optimum bitumen content (OBC) is found to be 5.2%. Different concentrations of LDPE (8% and 10% by weight of bitumen) were used. The use of LDPE on the asphalt pavement has Marshall Stability and Marshall flow values in the usable range as specified in the specification criteria of the Standard Specification for Road and Bridge Works (SSRBW). Also, the use of waste plastics in the pavement reduces the cost and helps to promote an environmentally friendly approach to infrastructure development.

Full extraction of asbuton bitumen for binder replacement in warm mix asphalt

Abstract Asbuton can be utilized as an optional binder in asphalt mixture by semi-extraction or full extraction. Full extraction of asbuton by using solvent can maximize the content of bitumen while discarding the mineral. However, different solvent content influenced the asbuton bitumen properties. Thus, this study evaluated the effect of different percentages of toluene solvent on the full extraction. Four different percentages of solvent content 1 to 4 % of toluene were used in this study. The asbuton bitumen was then tested for penetration, softening point, flash point, specific gravity, and thin film oven test. The asbuton bitumen was then used to design warm mix asphalt (WMA). Based on the Marshall mix design, the optimum bitumen content (OBC) is 6.25 %. The WMA with full extraction asbuton bitumen fulfilled the Marshall requirement by stability of 1374 kg, and 96.97% retained stability. It also produced 3.57 mm flow with 3.46 % void in mix, 15.08 % void mineral aggregatte, and 76.41 of void filled bitumen. As a result, it is discovered that full extraction asbuton can serving as the WMA binder replacement.

Utilisation of Waste Sludge from Drinking Water Treatment as a Filler Material in Hot Mix Asphalt.

This research investigated the suitability of using sludge from the treatment of drinking water in hot mix asphalt (HMA) as a filler material. The storage and environmental impact of sludge is an enormous problem, especially for countries with large populations. Two different types of sludges, ferric chloride (FC) and aluminium sulphate (AS), were used as a filler material in HMA. The Hamburg Wheel Tracking (HWT) test, which correlates with rutting, and the Indirect Tensile Strength (ITS) test, which indicates the moisture sensitivity of HMA, were carried out at the optimum bitumen content of the mixes to investigate the usability of sludge in HMA. The test results indicate the usability of FC and AS in HMA compared to the reference mixes. However, the AS type of sludge has better rutting resistance than the FC type. Although the results support the usability of both sludges in HMA, it should be noted that the increased cost of the mix containing sludges due to the combustion process and the increased bitumen content during application should be considered.

A comparative environmental life cycle assessment of road asphalt pavement solutions made up of artificial aggregates

The construction and maintenance of road pavements entail detrimental impacts on the consumption of resources and damage to the natural environment but also make up an opportunity for the large-scale application of circular economy principles and innovative waste valorisation paths. The present study focuses on developing a comprehensive procedure to evaluate the technical and environmental sustainability of replacing high percentage of limestone aggregates with artificial aggregates from municipal solid waste incineration (MSWI) into hot or cold recycled asphalt mixtures for asphalt pavements.The technical feasibility of the designed mixtures was investigated in terms of the main physical and mechanical properties of both the raw materials and the asphalt mixtures with content of artificial aggregates or sand in the range 25–40 % by mass. The environmental feasibility of the asphalt mixtures was evaluated through the SEM-EDS technique, the analysis of the eluate of the leaching test and the ecotoxicity for living organisms.Afterwards, the life cycle assessment (LCA) was applied to detect the critical spots of the life cycle of 1 m2 of a 6 cm-thick binder layer with high percentage of artificial aggregates or sand built and maintained through 30 years analysis period according to 18 impact category indicators.The main results show that, recycling the artificial aggregates into hot asphalt mixtures has on average a negligible effect on the overall environmental performance of the life cycle, and appears to be detrimental only for the consumption of fossil resources due to the higher optimum bitumen content. Looking at the results for cold mixes, the introduction of the artificial aggregates has an effect on the predicted durability of the asphalt layers, which is maximized in the case of coarse artificial aggregates. Consequent environmental benefits regard the global warming potential, fossil resource scarcity and freshwater eutrophication indicators.

Experimental study of improving hot mix asphalt reinforced with carbon fibers

Abstract Using hot asphalt mixtures (HMAs) is very common in flexible pavement construction due to its mechanical properties of durability, water resistance, and riding comfort. It proved to substantially reduce the applied stresses from vehicular traffic to subgrade. However, these types of pavements can undergo different types of distress such as cracks and rutting, which could be the result of weak mixing of the asphalt mixture and/or increasing traffic volumes. Therefore, the need to improve the mechanical properties of hot mix asphalt mixtures using different additives and modifiers was raised. Different materials have been recently used to reinforce asphalt concrete. For the construction of road pavements, using fibers in a HMA has emerged as a significantly more appealing option due to their strengthening properties. The alteration of asphalt binder is expected to benefit from carbon fibers (CFs) more than other types of fiber. In this study, an experimental study is carried out to investigate the effects of adding CFs to the asphalt mixtures with grades of (40–50) which comply with the Iraqi specifications. Twelve Marshall specimens were tested for stability and flow, 24 specimens for moisture failure testing, and two specimens for the rutting resistance of the asphalt mixture. The optimum bitumen content of 5.0% was used to prepare all the specimens. Different percentages of CFs by weight of asphalt (0, 0.2, 0.4, and 0.6%) were implemented to study the performance of paving mixtures. The way to mix the disperse the CFs homogeneously is by dry state (after separating the fibers manually) for 10 min, and then the asphalt was added; the mixture was heated to 165°C and mixed for at least 20 min. The results showed that the optimum properties of the HMA were reached by adding 0.4% CF to the HMA. Marshall stability was increased by 48%, the flow was decreased by 23%, and in addition, rut depth was reduced by 50%. The unit weight and the percentage of air voids in the mix were maintained and, along with other mix properties, are preserved within acceptable limits. Moreover, the indirect tensile strength has increased by 88.6%. Furthermore, moisture susceptibility reached 88%. Therefore, the addition of 0.4% CFs improved the performance of HMA at a high temperature of 60°C, which is close to the paving temperature in Iraq, by reducing the rutting of the asphalt mixture, which is considered the most dangerous tiling problem in Iraq. By improving the performance characteristics of asphalt mixture, the durability of the pavement will increase, and the riding will be more comfortable.

Improvement of Bituminous Pavement by Adding Waste Plastic

The present paper reports the results of a study undertaken to determine the physical properties of aggregates, 80/100 grade bitumen, optimum bitumen content by using Marshall mix design, optimum plastic content and also to compare the results with plain mix. Keywords: Bitumen, Concrete, Aggregates, Cement, Sand Etc.

Pengaruh Penggunaan Limbah Plastik LDPE sebagai Modifikator Campuran AC-WC

In recent years, the increasing amount of plastic waste in many cities in developing countries, including Kupang City, has become a serious environmental problem. The use of plastic waste as a pavement material is one solution to deal with the problem of plastic waste. One type of plastic that can be used as an asphalt mixture modification material is Low Density Polyethylene (LDPE). This research aims to determine the use of LDPE plastic waste modified with AC-WC (Asphalt Concrete-Wearing Course). Five variations of AC-WC mixture were made based on LDPE plastic waste content of 6, 7, 8, 9, 10% based on optimum bitumen content (OBC). Marshall test method was used to determine the OBC and to evaluate the marshall characteristics of LDPE modified AC-WC. The OBC of conventional AC-WC was found to be 5.23% by weight of total aggregate while the ptimum plastic modified bitumen content (OPMBC) of LDPE modified AC-WC was 7.45% by weight of OBC. AC-WC modified with 7.45% LDPE waste had 47.98% higher OPMBC compared to conventional AC-WC

Effects of crumb rubber and styrene-butadiene rubber additives on the properties of asphalt binder and the Marshall performance properties of asphalt mixtures

The primary aim of this study is to evaluate the impact of incorporating crumb rubber (CR) and styrene-butadiene rubber (SBR) additives, ranging from 0% to 5% by weight of bitumen, on the performance of a bituminous concrete mixture using the wet process. Laboratory experiments, including the Marshall test, were conducted to establish the optimum bitumen content (OBC) for the hot mix. The study focuses on determining the optimal proportions of CR and SBR to achieve maximum strength. The results show that increasing the proportions of both CR and SBR leads to significant improvements in strength, with the maximum stability recorded at 16.14 kN and a flow of 1.23 mm for a mix containing 5% CR and 4% SBR. The findings further suggest an inverse relationship between CR content and strength, while an increasing SBR content enhances strength. Consequently, the optimal proportions for incorporating CR and SBR additives are identified as 5% and 4%, respectively.

Pavement design using bituminous surface course with recycled aggregates

The utilization of Recycled Aggregates (RA) in the construction of pavement structure is one of the inventive and eco-friendly construction techniques. This scale down the construction cost without negotiates the strength and the durability of the pavement structures. However, RA is rigid in nature because it is obtained from aged bituminous mixtures to enhance a rejuvenator is usually added in order to lower the stiffness. Rejuvenator surges the utility of the bituminous mixtures and makes them be smoothly paved and compacted. The objective of this study is to design a flexible pavement structure using Stone Matrix Asphalt (SMA) as a surface course in order with RA. In SMA mixture major component is occupied by coarse aggregates, mineral filler, bitumen and a minor component of fine aggregates helps to fill the voids present in coarse aggregate which gives stone-on-stone contact. The bitumen binder and mineral filler form mastic, providing durability to the mixture. In this study, the performance of SMA mixtures with different RA proportions and a rejuvenator will be compared with conventional SMA mixture with zero percentage RA. Marshall Mix design is outlined to find the Marshall and volumetric properties of SMA mixtures and to regulate the Optimum Binder Content (OBC). The mixtures will be compared based on the drain down, stripping, Indirect Tensile strength (ITS) and Semi circular bend (SCB) test results. The analysis and design of flexible pavement structure using the prepared SMA mixtures with different RA contents as surface courses also will be carried out as a component of the study.SMA mixture of 40% replacing RA with 3% of palm sludge oil as rejuvenator exhibits optimum bitumen content where vertical stress, strain and displacement obtain reduction with compared to IRC 37 conventional SMA mixture.

Laboratory Investigation and Machine Learning Modeling of Road Pavement Asphalt Mixtures Prepared with Construction and Demolition Waste and RAP

Due to the decreasing availability of virgin materials coupled with an increased awareness of environmental sustainability issues, many researchers have focused their efforts on investigating innovative technological solutions in the civil engineering domain. This paper aims to evaluate the suitability of construction and demolition waste (C and DW) and reclaimed asphalt pavement (RAP) reused within asphalt mixtures (AMs) prepared for the binder layer of road pavements. Both hot and cold mixing methodologies were investigated. The technical assessment was based on the volumetric and mechanical suitability, according to saturated surface dry voids (SSDV) and indirect tensile strength (ITS) tests carried out at 10 °C, respectively. Laboratory findings showed that all the hot AMs matched the desired target SSDV at the design gyrations number at different optimum bitumen content levels, alternatively showing a non-significant variation or a significant increase in ITS compared to conventional hot mix asphalt. Conversely, the cold AMs with cement and emulsion bitumen showed a greater volume of voids and moisture sensitivity, and lower temperature susceptibility compared to hot AMs, reaching, on average, 11% lower ITS when using coarse C and DW aggregates and 43% lower ITS when using filler from C and DW. These volumetric and mechanical properties were modeled by means of support vector machines and categorical boosting (CatBoost) machine learning algorithms. The results proved to be satisfactory, with CatBoost determination coefficients R2 referring to SSDV and ITS equal to 0.8678 and 0.9916, respectively. This allowed for the mechanical performance of these sustainable mixtures to be predicted with high accuracy and implemented within conventional mix design procedures.

The possibility of reusing recycled aggregates in the production of hot mix asphalt

The use of aggregates resulting from destroying concrete as a substitute for natural aggregates in the production of hot mix asphalt for roads with high traffic loads reduces natural consumption and the amount of scattered waste. The study was conducted by designing the hot mix asphalt using the Marshall method with different proportions of recycled aggregate. The results showed an improvement in the stability, flow and indirect tensile tests of the aggregate compared to the conventional mixture. An increase in the recycle aggregate leads to an increase in the proportion of air voids, but it also leads to a decrease in the proportion of voids in the aggregate and asphalt-filled voids. The optimum bitumen content increases with the amount of recycled concrete. Recycled aggregate can be used as a substitute for natural aggregate in hot mix asphalt design successfully. The study found that increasing the percentage of recycled concrete (RCA) in hot bituminous mixtures led to an increase in air voids (VA) and a decrease in voids in mineral aggregates (VMA) and voids filled with asphalt (VFA). However, these percentages decreased with the increase in RCA due to the behavior of the recycled aggregates under load. The optimum bitumen content (OBC) also increased with the increase in RCA. The asphalt mixture's resistance to tensile stress increased with the increase in RCA up to 50% and at 25˚C and RCA 40˚C by up to 8%. The process of using recycled aggregates as an alternative to natural aggregates in hot bituminous mixtures is applicable up to a certain percentage.

EXPERIMENTS USING ABS PLASTIC SEEDS (ACRYLONITRILE BUTADIENE STYRENE) AS ADDITIONAL MATERIALS IN PORUS ASPHALT MIXTURE

Increasing the strength of the porous asphalt mixture in the field of road contraction, in this context, porous asphalt is often used as road pavement. ABS plastic pellets (Acrylonitrile Butadiene Styrene) have the same properties as asphalt, namely, thermoplastic has a penetration value equivalent to asphalt pen 60/70, plays an important role in road pavement adhesives as an alternative and has high strength and is resistant to deformation itself. The objective of the experiment was to determine the characteristics of Marshall on optimum asphalt content (KAO) and the effect of adding ABS plastic pellets on the performance of porous asphalt was reviewed based on the Marshall test, Cantabro Loss and Asphalt Flow Down. The research used experimental testing methods in the laboratory. The research was conducted with asphalt pen content of 60/70, namely 4%, 4.5%, 5%, 5.5% 6% and additional levels of ABS plastic pellets 0%, 2%, 4%, 6% and 8%. From the planned grade for the addition of ABS plastic pellets mentioned above, the optimum bitumen content is obtained, namely 6% with a VIM value at 6% content of 23.61%, for a VMA value of 27.20%, for a stability value of 924.95 kg and the flow value obtained was 3.23 mm while the MQ value was 311.15 kg/mm. with standard or parameters namely AAPA 2004(Australian Asphalt Pavement Association).

Mechanical performance of cup lump rubber modified asphalt mixtures incorporating polyphosphoric acid

Natural rubber (NR) producing countries face rubber production and price fluctuations. NR production's high cost and low market price have produced an extensive demand for alternative applications of NR. This paper examined the influence of cup lump rubber (CLR) and polyphosphoric acid (PPA) on the mechanical performance of asphalt mixtures. The five modified blends were selected for the hot mix asphalt (HMA) performance analysis. The results revealed that the CLR increasing content in the bitumen ultimately increases the optimum bitumen content (OBC) for the asphalt mixture. There is a significant difference in the base mixture OBC (5.19 %) compared to the cup lump rubber-modified bitumens (CLRMBs). The CLRMB6 + 0.5PPA asphalt mixture OBC was 5.32 %, which is higher among all the mixtures. The rutting findings demonstrated that the control mixture exhibited the highest strain of 1.71 %, followed by CLRMB6 with 1.43 %, CLRMB3 + 0.5PPA with 1.1 %, CLRMB9 with 0.7 %, and CLRMB6 + 0.5PPA with the lowest strain of 0.47 %. The creep stiffness modulus of all mixtures met the minimum requirement of ≥75 MPa. The results implied that the CLR and the PPA displayed incredible potential to improve the asphalt mixture's resilient modulus (MR). The CLRMB9 resilient modulus increased significantly by 22 % compared to the control mixture. The CLRMB6 + 0.5PPA has a higher MR of 5210 MPa than the other modified mixtures and the control mixture with 3521 Ma. Thus, the study's findings suggest that the CLR, in conjunction with the 0.5PPA exhibits a decisive effect on the asphalt mixture performance and could be beneficial as a sustainable material in the pavement industry.

A Review of Rubberised Asphalt for Flexible Pavement Applications: Production, Content, Performance, Motivations and Future Directions

The crumb rubber (CR) recycled from waste tyres could be a viable alternative in achieving green pavements that offer exciting new markets to global investors. Adding CR into flexible pavements enhances their performance and ensures environmental sustainability. This paper will discuss the production variables, CR sizes and contents, blending techniques, optimum bitumen contents, morphology, standard characteristics, rheological characteristics, mechanical performance, greenhouse gas emissions, energy consumption and life cycle cost. This review study found that compared to traditional asphalt mixtures, the CR-modified asphalts had superior performance and longer service life. However, the dearth of information on several factors in CR asphalt production, including greenhouse gas emissions, energy consumption and life cycle cost during recycling, causes many agencies in the global asphalt industry to continue employing costly, energy-consuming additives such as styrene-butadiene-styrene (SBS) instead of CR to enhance asphalt.

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.

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.

Medical Waste Incineration Fly Ash as a Mineral Filler in Dense Bituminous Course in Flexible Pavements.

Medical waste incineration fly ash (MWIFA) contains heavy metals that are toxic by nature and pose numerous health risks. The paper deals with the suitability of MWIFA as a mineral filler in the bituminous layer as an alternative to conventional stone dust (SD) through an appropriate combination of engineering and environmental assessments. Engineering parameters, such as Marshall stability, stability loss, flow, unit weight, air voids (Va), voids filled with asphalt (VFA), and voids in the mineral aggregate (VMA) of the asphalt mixtures, were evaluated with varying filler ratios, from 2% to 10%. All parameters for both fillers at optimum bitumen content satisfied the Marshall Mix Design criteria. The optimum bitumen contents of all filler ratios were within the standard limit recommended by the Bangladesh Roads and Highways Department. It was found that mixes prepared with MWIFA can resist moisture effects, making them durable in the monsoon. The mixes with 5.5% MWIFA as mineral filler performed the best, whereas 9% SD filler was required to achieve similar performance. The environmental test results show no environmental restriction on stabilizing the MWIFA into paving mixtures. The mobility of heavy metals (As, Pb, Cu, Cr, Ni, Cd, Hg, and Zn) from the asphalt-MWIFA mix was insignificant. The cumulative concentrations of heavy metals (Cd, Ni, Zn, Cu, and Pb) from long-term leaching tests were far below the Dutch regulatory limit (U1). MWIFA can be considered an eco-friendly and sustainable mineral filler for the dense bituminous pavement layer.

Use of recycled aggregates in bituminous mixes

Increased construction activities especially in the developing countries like India are consuming huge quantity of construction materials. Construction industries are at the booming level and among the construction activities, pavement construction consumes abundant quantity of natural aggregates as it runs over longer stretches. In addition to this, construction of residential buildings, bridges, public utilities, government offices also consume large quantity of aggregates. Inspite of India having the has second largest road network in the world after United States (US) many of the roads are under upgradation and some of the new roads are being constructed in the upcoming years. This leads to scarcity of natural aggregates and it is high time to seek for sustainable design approaches. Reclaimed asphalt pavement (RAP) is the removed material obtained from the demolition of existing bituminous surfaced pavements. RAP is usually dumped as a stockpile on either side of the roads which causes environment related issues. RAP in its original form constitutes aggregates coated with bitumen. If properly processed, RAP possesses reusable aggregates. To address the scarcity of natural aggregates demand and issues related to waste disposal, present study focusses on investing the effect of recycled aggregates on the performance of bituminous concrete (BC). Initially the stability, flow and volumetric properties of conventional bituminous concrete are determined through Marshall mix design and testing. With the obtained optimum bitumen content, bituminous mixes containing recycled aggregates (RA) with varied proportions (0 to 30%) were tested. From the Marshall test results, it is observed that mix containing 25% RA and 75% conventional aggregates satisfy the requirements of the bituminous concrete.