The crumb rubber (CR) recycled from waste tyres could be a viable alternative in achieving green ... more 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-sty...
IOP Conference Series: Earth and Environmental Science, 2022
Cold mix asphalt (CMA) is a versatile and energy efficient mixture often prepared at ambient temp... more Cold mix asphalt (CMA) is a versatile and energy efficient mixture often prepared at ambient temperature. Efforts to improve the performance of CMA mixtures recorded appreciable success. Nonetheless, the critical performance measures of moisture and abrasive resistance still baffles researchers. Additionally, CMA’s design, production, testing, and site application is bedevilled by slow rate of strength gain, high void content, and absence of a globally acceptable mix design. This study aimed at assessing CMA’s durability measures using the modified Lottman (moisture damage) and Cantabro tests by adding a 3% palm oil fuel ash (POFA) as filler replacement and 3% cement. Fast-curing mixtures fabricated with a cationic quick-set (CQS-1h) and a rapid-set (RS-1K) emulsion both of medium viscosities with a nominal maximum aggregate size (NMAS) of 4.75 mm were evaluated. In addition to improving the Marshall volumetric properties, POFA’s inclusion is aimed at improving adhesion thereby enha...
Ultra-high performance concrete (UHPC), an advanced class of fiber-reinforced cementitious materi... more Ultra-high performance concrete (UHPC), an advanced class of fiber-reinforced cementitious material with extraordinary mechanical properties, low permeability, shrinkage and creep, and high energy absorption capacity, has seen steady increase in use, with applications covering construction of new members and retrofit of existing ones. Fibers are added in the UHPC mix to bridge cracks, carry tensile stresses, and contribute greatly to member ductility and load capacity. Hybrid fibers comprising micro and macro types are beneficial where the first type resists microcracking and the second targets macrocracking. This study investigates the effects of blending three fiber types, namely, hooked-end steel (referred to as type 1, representing macro fibers class), straight-end steel (type 2, intermediate size fibers), and carbon (type 2, micro size fiber), on the mechanical properties of UHPC. Experimental tests were performed to characterize the following mechanical properties: flowability...
International Journal of Environmental Research and Public Health
The environmental concerns of global warming and energy consumption are among the most severe iss... more The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150–180 °C), the latest research on pavement energy consumption and carbon dioxide (CO2) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also...
The Sultanate of Oman has experienced rapid development over the last thirty years and has constr... more The Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of the Oman 2040 vision. The primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. This review aims to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focuses primarily on employing RAP materials in new pavement projects. Currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. The key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures’ resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Numerous studies have assessed the impact of using RAP in ...
High demand for asphalt binders in road construction verifies the need of finding alternative mat... more High demand for asphalt binders in road construction verifies the need of finding alternative materials through asphalt pavement recycling. This paper investigated the impact of different rejuvenators on the performance of an aged asphalt binder. Virgin Olive oil, virgin cooking oil, waste cooking oil, virgin engine oil, and waste engine oil were added to a 30/40 penetration grade aged asphalt binder at a fixed oil content of 4% for all types. The wet method was used to blend the rejuvenators and aged asphalt binder. The physical, rheological, and chemical properties of the rejuvenated asphalt binder were evaluated using several laboratory tests which include penetration, softening point, bleeding, loss on heating, storage stability, penetration index, ductility, viscosity, dynamic shear rheometer, and Fourier transform infrared spectroscopy. The outcomes of the physical properties showed that the olive, waste, and virgin cooking rejuvenators can restore the aged asphalt binder to a...
This study was conducted to investigate the effect of ageing on bitumen, before and after modific... more This study was conducted to investigate the effect of ageing on bitumen, before and after modification. Nano-clay modified bitumen (NCMB) was produced by adding nano-clay (NC) to 60/70 penetration grade bitumen; then, the binder was tested using conventional tests for properties such as penetration, softening point and viscosity. These tests were carried out on the modified binder before and after ageing. A rolling thin film oven (RTFO) was used to simulate short-term ageing (STA), and a pressure ageing vessel (PAV) was used to simulate long-term ageing (LTA) for the modified binder. After initial results showed an improvement for the modified bitumen regarding the effect of ageing, the investigation continued using Fourier transform infrared spectroscopy (FTIR), where the microstructure distribution of the modified binder before and after ageing was observed. Finally, there was no doubt that the effect of ageing on mixtures should be investigated. For this step, the indirect tensil...
Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in... more Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in hot mix asphalt (HMA) pavements to enhance pavement sustainability. The use of aged asphalt in RAP, which is highly oxidised and has lost its properties due to exposure to traffic loads and climatic conditions throughout its lifespan, can cause asphalt mixtures to stiffen and embrittle, thus negatively affecting the behaviour of asphalt mixtures. This issue may be resolved by including rejuvenating agents that can restore both physical and rheological properties of aged asphalt by increasing maltene fractions and decreasing asphaltene. However, the high restoration capacity of any kind of rejuvenating agent does not assure the durability of restored aged asphalt. This study explored the performance and durability of rejuvenated asphalt mixtures embedded with several types of rejuvenators identified from the extensive literature review. The study serves as a significant reference to pred...
Journal of Rehabilitation in Civil Engineering, 2021
The compacting and mixing processes involving hot mix asphalt during asphalt production can lead ... more The compacting and mixing processes involving hot mix asphalt during asphalt production can lead to air pollution as a result of a high volatile organic compound. An alternative solution that can reduce greenhouse gas emissions is by using warm-mix asphalt (WMA). A proper application of additives to the WMA can improve the asphalt mixture's strength, durability, and workability. In this study, a 60/70 grade asphalt binder was added with 5% of crumb rubber (CR) and three different WMA additives at the recommended dosages, namely Sasobit, Cecabase, and Rediset. The wet method was used to blend the additives with virgin asphalt binders. The mixing and compacting temperatures were set at 135°C and 125°C, respectively, to mix the asphalt mixture. Mechanical performance tests were performed to evaluate the impact of WAM additives with CR on asphalt mixture. Based on the results, all the modified asphalt mixtures showed a better mechanical performance than the virgin asphalt mixture in...
The growing usage of crumb rubber modified in flexible pavements justification and the requiremen... more The growing usage of crumb rubber modified in flexible pavements justification and the requirement for a good comprehension of its physical and rheological properties as well as its elastic behaviors. However, crumb rubber asphalt mixtures demand rising product temperatures than traditional asphalt binder due to the high viscosity of asphalt rubber binder. The main points of this research are to investigate the unaged rheological and physical properties of crumb rubber modifier (CRM) asphalt. In this study, crumb rubber-modified percentages was 0, 5, 10, and 15% from the binder weight, with adding 1.5% warm mix asphalt additive (Sasobit). The wet method was used to mix the CRM with bitumen, the CRM conducted at 177 °C for 30 min whit 700 rpm, and Sasobit conducted at 120 °C for 10 min with 1000 rpm. The results display that various crumb rubber contents have important impacts on modified binder properties. The result shown that increase the complex shear G* and decreased the phase angle δ at high temperature with increased the CRM contents. The rutting resistance parameter was rising with increased CRM percentages at 70 °C. The softening results in rise in the temperature with adding the CRM and the penetration results in reduction with the growing CRM contents. The elastic recovery increased with higher CRM content. The storage stability was within the range for unmodified and 5% of CRM but for 10 and 15% the result was over the range. From the results we conclude that the CRM improves the elasticity and improves the stiffness of the modified binder.
Abstract Tropical countries such as Malaysia experience a high amount of rainfall that can lead t... more Abstract Tropical countries such as Malaysia experience a high amount of rainfall that can lead to a common type of distress on the roads known as moisture damage. Using waste materials as additives in the asphalt mixture is an innovative measure to improve the quality and strength of the mixture. In this study, 5% of crumb rubber (CR) by the total weight of binder was added to the asphalt mixture in three different sizes of 0.075 mm, 0.15 mm, and 0.3 mm. The wet method was applied to blend the CR with virgin asphalt binder grade 60/70. The aggregate gradation applied in this study was 9.5 Nominal maximum aggregate size. The samples were produced with the Superpave gyratory compactor. Moisture sensitivity (ASSTHO T-283) and indirect tensile strength (ITS) tests were performed to evaluate the impact of the CR sizes on the asphalt mixture. The findings showed that the CR addition improved the strength of the asphalt mixture. Furthermore, there was an increment in the ITS with an increasing size of CR. The addition of 5% CR resulted in a minor reduction of the moisture resistance. Thus, a slight improvement in the moisture resistance was detected with a reduction in CR size. Overall, all asphalt mixtures in this study had TSR of more than 80%, thus passing the moisture damage test requirements.
The reclaimed asphalt pavement (RAP) has become a moderately common practice in most countries; H... more The reclaimed asphalt pavement (RAP) has become a moderately common practice in most countries; Hence, rejuvenating materials with RAP have earned publicity in the asphalt manufacturers, mainly due to the increasing raw material costs. In this study, the crumb rubber (CR) and waste frying oil (WFO) utilized as waste materials to restore the properties and enhance the rutting resistance of the RAP. Several physical, rheological, chemical properties of bituminous binders were tested. The result showed that the RAP bituminous binders incorporating WFO and CR decreased softening points and the increased penetration value; these translate to an increase in penetration index. Moreover, the viscosity of the WFO/CR combination reclaimed asphalt pavement binder showed better workability and stiffness, as well as a low storage stability temperature (less than 2.2 °C) with an acceptable loss upon heating. Without chemical reaction was observed between the waste-frying oil with the rubberized b...
Researchers are exploring the utilisation of reclaimed asphalt pavement (RAP) as a recycled mater... more Researchers are exploring the utilisation of reclaimed asphalt pavement (RAP) as a recycled material to determine the performance of non-renewable natural aggregates and other road products such as asphalt binder, in the construction and rehabilitation stage of asphalt pavements. The addition of RAP in asphalt mixtures is a complex process and there is a need to understand the design of the asphalt mixture. Some of the problems associated with adding RAP to asphalt mixtures are moisture damage and cracking damage caused by poor adhesion between the aggregates and asphalt binder. There is a need to add rejuvenators to the recycled mixture containing RAP to enhance its performance, excepting the rutting resistance. This study sought to improve asphalt mixture performance and mechanism by adding waste frying oil (WFO) and crumb rubber (CR) to 25 and 40% of the RAP content. Moreover, the utilisation of CR and WFO improved pavement sustainability and rutting performance. In addition, thi...
The crumb rubber (CR) recycled from waste tyres could be a viable alternative in achieving green ... more 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-sty...
IOP Conference Series: Earth and Environmental Science, 2022
Cold mix asphalt (CMA) is a versatile and energy efficient mixture often prepared at ambient temp... more Cold mix asphalt (CMA) is a versatile and energy efficient mixture often prepared at ambient temperature. Efforts to improve the performance of CMA mixtures recorded appreciable success. Nonetheless, the critical performance measures of moisture and abrasive resistance still baffles researchers. Additionally, CMA’s design, production, testing, and site application is bedevilled by slow rate of strength gain, high void content, and absence of a globally acceptable mix design. This study aimed at assessing CMA’s durability measures using the modified Lottman (moisture damage) and Cantabro tests by adding a 3% palm oil fuel ash (POFA) as filler replacement and 3% cement. Fast-curing mixtures fabricated with a cationic quick-set (CQS-1h) and a rapid-set (RS-1K) emulsion both of medium viscosities with a nominal maximum aggregate size (NMAS) of 4.75 mm were evaluated. In addition to improving the Marshall volumetric properties, POFA’s inclusion is aimed at improving adhesion thereby enha...
Ultra-high performance concrete (UHPC), an advanced class of fiber-reinforced cementitious materi... more Ultra-high performance concrete (UHPC), an advanced class of fiber-reinforced cementitious material with extraordinary mechanical properties, low permeability, shrinkage and creep, and high energy absorption capacity, has seen steady increase in use, with applications covering construction of new members and retrofit of existing ones. Fibers are added in the UHPC mix to bridge cracks, carry tensile stresses, and contribute greatly to member ductility and load capacity. Hybrid fibers comprising micro and macro types are beneficial where the first type resists microcracking and the second targets macrocracking. This study investigates the effects of blending three fiber types, namely, hooked-end steel (referred to as type 1, representing macro fibers class), straight-end steel (type 2, intermediate size fibers), and carbon (type 2, micro size fiber), on the mechanical properties of UHPC. Experimental tests were performed to characterize the following mechanical properties: flowability...
International Journal of Environmental Research and Public Health
The environmental concerns of global warming and energy consumption are among the most severe iss... more The environmental concerns of global warming and energy consumption are among the most severe issues and challenges facing human beings worldwide. Due to the relatively higher predicted temperatures (150–180 °C), the latest research on pavement energy consumption and carbon dioxide (CO2) emission assessment mentioned contributing to higher environmental burdens such as air pollution and global warming. However, warm-mix asphalt (WMA) was introduced by pavement researchers and the road construction industry instead of hot-mix asphalt (HMA) to reduce these environmental problems. This study aims to provide a comparative overview of WMA and HMA from environmental and economic perspectives in order to highlight the challenges, motivations, and research gaps in using WMA technology compared to HMA. It was discovered that the lower production temperature of WMA could significantly reduce the emissions of gases and fumes and thus reduce global warming. The lower production temperature also...
The Sultanate of Oman has experienced rapid development over the last thirty years and has constr... more The Sultanate of Oman has experienced rapid development over the last thirty years and has constructed environmentally friendly and sustainable infrastructure while it continues to find economical alternative resources to achieve the goals of the Oman 2040 vision. The primary concerns are preserving natural resources and reducing the impact of carbon dioxide (CO₂) emissions on the environment. This review aims to encourage the sustainable use of reclaimed asphalt pavement (RAP) materials in pavement construction and focuses primarily on employing RAP materials in new pavement projects. Currently, new construction projects utilise a significant percentage of demolished asphalt pavement to save costs and natural resources. The key issue that arises when mixing RAP into new asphalt mixtures is the effects on the mixtures’ resistance to permanent disfigurements, such as fatigue cracks, that influence asphalt mixture performance. Numerous studies have assessed the impact of using RAP in ...
High demand for asphalt binders in road construction verifies the need of finding alternative mat... more High demand for asphalt binders in road construction verifies the need of finding alternative materials through asphalt pavement recycling. This paper investigated the impact of different rejuvenators on the performance of an aged asphalt binder. Virgin Olive oil, virgin cooking oil, waste cooking oil, virgin engine oil, and waste engine oil were added to a 30/40 penetration grade aged asphalt binder at a fixed oil content of 4% for all types. The wet method was used to blend the rejuvenators and aged asphalt binder. The physical, rheological, and chemical properties of the rejuvenated asphalt binder were evaluated using several laboratory tests which include penetration, softening point, bleeding, loss on heating, storage stability, penetration index, ductility, viscosity, dynamic shear rheometer, and Fourier transform infrared spectroscopy. The outcomes of the physical properties showed that the olive, waste, and virgin cooking rejuvenators can restore the aged asphalt binder to a...
This study was conducted to investigate the effect of ageing on bitumen, before and after modific... more This study was conducted to investigate the effect of ageing on bitumen, before and after modification. Nano-clay modified bitumen (NCMB) was produced by adding nano-clay (NC) to 60/70 penetration grade bitumen; then, the binder was tested using conventional tests for properties such as penetration, softening point and viscosity. These tests were carried out on the modified binder before and after ageing. A rolling thin film oven (RTFO) was used to simulate short-term ageing (STA), and a pressure ageing vessel (PAV) was used to simulate long-term ageing (LTA) for the modified binder. After initial results showed an improvement for the modified bitumen regarding the effect of ageing, the investigation continued using Fourier transform infrared spectroscopy (FTIR), where the microstructure distribution of the modified binder before and after ageing was observed. Finally, there was no doubt that the effect of ageing on mixtures should be investigated. For this step, the indirect tensil...
Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in... more Reclaimed asphalt pavement (RAP) has received much attention recently due to its increased use in hot mix asphalt (HMA) pavements to enhance pavement sustainability. The use of aged asphalt in RAP, which is highly oxidised and has lost its properties due to exposure to traffic loads and climatic conditions throughout its lifespan, can cause asphalt mixtures to stiffen and embrittle, thus negatively affecting the behaviour of asphalt mixtures. This issue may be resolved by including rejuvenating agents that can restore both physical and rheological properties of aged asphalt by increasing maltene fractions and decreasing asphaltene. However, the high restoration capacity of any kind of rejuvenating agent does not assure the durability of restored aged asphalt. This study explored the performance and durability of rejuvenated asphalt mixtures embedded with several types of rejuvenators identified from the extensive literature review. The study serves as a significant reference to pred...
Journal of Rehabilitation in Civil Engineering, 2021
The compacting and mixing processes involving hot mix asphalt during asphalt production can lead ... more The compacting and mixing processes involving hot mix asphalt during asphalt production can lead to air pollution as a result of a high volatile organic compound. An alternative solution that can reduce greenhouse gas emissions is by using warm-mix asphalt (WMA). A proper application of additives to the WMA can improve the asphalt mixture's strength, durability, and workability. In this study, a 60/70 grade asphalt binder was added with 5% of crumb rubber (CR) and three different WMA additives at the recommended dosages, namely Sasobit, Cecabase, and Rediset. The wet method was used to blend the additives with virgin asphalt binders. The mixing and compacting temperatures were set at 135°C and 125°C, respectively, to mix the asphalt mixture. Mechanical performance tests were performed to evaluate the impact of WAM additives with CR on asphalt mixture. Based on the results, all the modified asphalt mixtures showed a better mechanical performance than the virgin asphalt mixture in...
The growing usage of crumb rubber modified in flexible pavements justification and the requiremen... more The growing usage of crumb rubber modified in flexible pavements justification and the requirement for a good comprehension of its physical and rheological properties as well as its elastic behaviors. However, crumb rubber asphalt mixtures demand rising product temperatures than traditional asphalt binder due to the high viscosity of asphalt rubber binder. The main points of this research are to investigate the unaged rheological and physical properties of crumb rubber modifier (CRM) asphalt. In this study, crumb rubber-modified percentages was 0, 5, 10, and 15% from the binder weight, with adding 1.5% warm mix asphalt additive (Sasobit). The wet method was used to mix the CRM with bitumen, the CRM conducted at 177 °C for 30 min whit 700 rpm, and Sasobit conducted at 120 °C for 10 min with 1000 rpm. The results display that various crumb rubber contents have important impacts on modified binder properties. The result shown that increase the complex shear G* and decreased the phase angle δ at high temperature with increased the CRM contents. The rutting resistance parameter was rising with increased CRM percentages at 70 °C. The softening results in rise in the temperature with adding the CRM and the penetration results in reduction with the growing CRM contents. The elastic recovery increased with higher CRM content. The storage stability was within the range for unmodified and 5% of CRM but for 10 and 15% the result was over the range. From the results we conclude that the CRM improves the elasticity and improves the stiffness of the modified binder.
Abstract Tropical countries such as Malaysia experience a high amount of rainfall that can lead t... more Abstract Tropical countries such as Malaysia experience a high amount of rainfall that can lead to a common type of distress on the roads known as moisture damage. Using waste materials as additives in the asphalt mixture is an innovative measure to improve the quality and strength of the mixture. In this study, 5% of crumb rubber (CR) by the total weight of binder was added to the asphalt mixture in three different sizes of 0.075 mm, 0.15 mm, and 0.3 mm. The wet method was applied to blend the CR with virgin asphalt binder grade 60/70. The aggregate gradation applied in this study was 9.5 Nominal maximum aggregate size. The samples were produced with the Superpave gyratory compactor. Moisture sensitivity (ASSTHO T-283) and indirect tensile strength (ITS) tests were performed to evaluate the impact of the CR sizes on the asphalt mixture. The findings showed that the CR addition improved the strength of the asphalt mixture. Furthermore, there was an increment in the ITS with an increasing size of CR. The addition of 5% CR resulted in a minor reduction of the moisture resistance. Thus, a slight improvement in the moisture resistance was detected with a reduction in CR size. Overall, all asphalt mixtures in this study had TSR of more than 80%, thus passing the moisture damage test requirements.
The reclaimed asphalt pavement (RAP) has become a moderately common practice in most countries; H... more The reclaimed asphalt pavement (RAP) has become a moderately common practice in most countries; Hence, rejuvenating materials with RAP have earned publicity in the asphalt manufacturers, mainly due to the increasing raw material costs. In this study, the crumb rubber (CR) and waste frying oil (WFO) utilized as waste materials to restore the properties and enhance the rutting resistance of the RAP. Several physical, rheological, chemical properties of bituminous binders were tested. The result showed that the RAP bituminous binders incorporating WFO and CR decreased softening points and the increased penetration value; these translate to an increase in penetration index. Moreover, the viscosity of the WFO/CR combination reclaimed asphalt pavement binder showed better workability and stiffness, as well as a low storage stability temperature (less than 2.2 °C) with an acceptable loss upon heating. Without chemical reaction was observed between the waste-frying oil with the rubberized b...
Researchers are exploring the utilisation of reclaimed asphalt pavement (RAP) as a recycled mater... more Researchers are exploring the utilisation of reclaimed asphalt pavement (RAP) as a recycled material to determine the performance of non-renewable natural aggregates and other road products such as asphalt binder, in the construction and rehabilitation stage of asphalt pavements. The addition of RAP in asphalt mixtures is a complex process and there is a need to understand the design of the asphalt mixture. Some of the problems associated with adding RAP to asphalt mixtures are moisture damage and cracking damage caused by poor adhesion between the aggregates and asphalt binder. There is a need to add rejuvenators to the recycled mixture containing RAP to enhance its performance, excepting the rutting resistance. This study sought to improve asphalt mixture performance and mechanism by adding waste frying oil (WFO) and crumb rubber (CR) to 25 and 40% of the RAP content. Moreover, the utilisation of CR and WFO improved pavement sustainability and rutting performance. In addition, thi...
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