This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Conference on Asphalt Pavements for Southern Africa (CAPSA15), 11th, 2015, Sun City, South Africa, Aug 1, 2015
Higher traffic volumes and traffic loads have led to an increase in premature pavement failures a... more Higher traffic volumes and traffic loads have led to an increase in premature pavement failures as empirical binder testing has increasingly failed to predict pavement performance. Moreover, empirical tests cannot effectively characterize polymer-modified binders which are being increasingly used in South Africa. This has resulted in a move to establish bituminous binder specifications based on fundamental engineering properties capable of accurately predicting the performance of asphalt mixes. Asphalt pavements are most susceptible to rutting at high in-service temperatures, where the in situ binder plays an important role in resisting deformation from repeated loading, along with the complementary resistance provided by the aggregate structure. The non-recoverable compliance, Jnr, as determined by the dynamic shear rheometer has been found to be an improved indicator of asphalt deformation. Jnr is measured using the multi-stress creep recovery (MSCR) method and considerable work has been done in the last three years in South Africa in preparation for adopting a modification of the Jnr as part of a performance graded specification. The paper reviews the advantages the MSCR method has over other methods confined to measurements within the linear viscoelastic (LVE) region of the binder. Constraints undermining the current MSCR test method are demonstrated. Two temperature zones for South Africa are presented and the Jnr-stress characterisations for typical binders were determined for these zones. A correlation plot of shear strain (permanent deformation indicator) for four asphalt mixes versus Jnr demonstrated the effectiveness of the non-recoverable compliance parameter. The paper concludes by statistically examining the precision and bias of the test method as currently practiced in South Africa and presents a recommendation for the parameters to be implemented for the South African version of the test method.
This paper presents data of a laboratoty investigation on the measurements of air permeability of... more This paper presents data of a laboratoty investigation on the measurements of air permeability of a range of dense bituminous composites using a simple air permeameter developed at the Civil Engineering Materials Unit (CEMU) at The University of Leeds. A wide range of gap graded Hot Rolled Asphalts and Asphaltic Concrete gradations compacted at several levels of compactive effort and using a range of bitumen contents were assessed for air permeability and Marshall Stability. The results show that the permeability of the composites tested at low bitumen contents are high and that these values decrease sharply with an increase in the bitumen content demonstrating that the test can be used with advantage to determine the minimum value of binder content for minimum permeability. The air permeameter is a non destructive test and can detect minor changes in the aggregate gradation, level of compaction or bitumen content. The results show a good correlation between permeability and compacted density and porosity for any one mixture type. The results also show that contrary to what is normally believed, the measured permeability values of selected dense continuously graded Asphaltic Concrete mixtures at their optimum bitumen contents of 5 to 5.5% were considerably lower than conventional gap graded Hot Rolled Asphalt wearing course mixtures at 7 to 7.5% bitumen contents. For the covering abstract see ITRD E107185.
This paper presents a laboratory study to demonstrate the effectiveness of using vegetable oils a... more This paper presents a laboratory study to demonstrate the effectiveness of using vegetable oils as rejuvenating agents for aged asphalt mixtures. The work focused on proposing a laboratory aging protocol whereby loose asphalt base course mixtures oven aged at 150°C for a range of durations, namely 2, 4, 6, 8 and 10hrs prior to compaction. Using this technique, 5 mixes were thus produced at various stages/levels of aging. An additional set of 5 batches were produced and aged in the loose state for 10 hours at 150ºC before rejuvenating the mixtures using vegetable oil. Vegetable oil was added at percentages ranging from 4 to 8% by weight of the bitumen. Rejuvenation of the mixture using the vegetable oils was then assessed by the mechanical and rheological performance of the material and binders. Furthermore, the effect of the addition of vegetable oil rejuvenators was also investigated using SARA analysis. Results indicated that the aging and rejuvenating protocol employed in the lab has been effective, with results of the recovered penetration and softening point tests demonstrating that it is possible to rejuvenate an aged mixture thereby improving the recovered penetration by standard penetration grade designation. However further work must be done to improve the correlation between mechanical performance and rheological characterisation particularly if a rejuvenation chart were to be developed.
From a performance point of view, bitumen is one of the most important constituents of asphalt mi... more From a performance point of view, bitumen is one of the most important constituents of asphalt mixtures. The quality and properties of bitumen depend largely on its chemical composition. Evidence obtained form laboratory oven ageing tests suggests that bitumens having the same grade, but originating form different crudes, can age quite differently. This evidence is further supported by data from laboratory compacted asphalt mixtures. The first part of this study reviews in some detail the effect of the chemical composition of penetration grade bitumens on ageing performance. Simple explanations of the ageing mechanisms are presented in the paper primarily based on chromatographic separation techniques. For the covering abstract see ITRD E145817
h i g h l i g h t s Time-concentration an alternative tool to Time-temperature superposition. Flu... more h i g h l i g h t s Time-concentration an alternative tool to Time-temperature superposition. Fluxed bitumens enable Time-Concentration to replace Time-Temperature shifting. Fluxing bitumens simulative of raising test temperature.
The primary objective of this research was to contribute towards greater sustainability of the co... more The primary objective of this research was to contribute towards greater sustainability of the construction industry in the Qatar by proposing methods to reduce its dependency on primary imported materials. In this investigation, recycled and secondary aggregates (RSA) were combined with non-traditional binders to develop a unique method of manufacturing construction and building blocks. Following an extensive phase of laboratory trials and experimentation, it was realised that many types of graded mineral aggregates, when mixed with vegetable oils (virgin or waste) at optimal proportions, then compacted and thermally cured at elevated temperatures can readily generate hardened composites that have the mechanical characteristics of conventional building blocks. The resultant blocks have been named "Vegeblocks" and are viewed as viable alternatives to conventional concrete blocks. Furthermore, the research has demonstrated the feasibility of producing Vegeblocks composed of 100% recycled aggregate and discarded waste cooking oil. Based on physical and mineralogical properties, each type of aggregate has an optimum oil content for maximum compressive strength, beyond which, any additional oil will result in reduction in mechanical properties. Acceptable compressive strength values were achieved by thermally curing Vegeblocks at of 170 ºC for 24 hours.
Semi-flexible pavements are manufactured by producing a very open porous asphalt skeleton and fil... more Semi-flexible pavements are manufactured by producing a very open porous asphalt skeleton and filling the voids with selected cementitious grouts. The resultant composites, referred to as "grouted macadams", combine the flexibility of the bituminous component with the strength and rigidity of the cementitious component. In this investigation, a range of cementitious grouts was formulated using a variety of binders including ordinary Portland cement, silica fume and fly ash. The grouts were designed to provide improved strength and performance characteristics with reduced water/binder ratios, whilst maintaining high workability. This was achieved with the aid of chemical admixtures that allowed the grouts to penetrate the porous asphalt skeleton under gravity action (i.e. without vibration). The properties of the grouted macadam composites were assessed using a range of engineering, deformation and performance tests. These included compressive strength, stiffness modulus, creep resistance, shrinkage, porosity and permeability up to the curing age of 28 days. The formulated cementitious grouts attained high strength characteristics (90-120 MPa at 28 days), with the pozzolanic materials (silica fume and fly ash) having improved permeability and shrinkage properties. When the grouts were impregnated into the porous asphalt skeleton, the resultant grouted macadam composites showed superior strength to conventional asphalts and much higher resilient properties than that of concrete pavement materials. In addition, the grouted macadams exhibited much lower porosity (<8%) indicating enhanced durability performance. For the covering abstract see ITRD E117840.
Climate change has become a major issue in recent years owing to the emission of greenhouse gases... more Climate change has become a major issue in recent years owing to the emission of greenhouse gases. Mitigation measures are required to overcome the challenges pertained to greenhouse gases emissions. This research paper attributes to the utilization of catalyzed waste vegetable oil as a binder for the production of roofing tiles to replace the conventional construction materials such as clay and cement. A novel methodology of utilizing catalyzed waste oil incorporated with sand and filler was adopted and the innovative product produced entitled as catalyzed Vege-Roofing tiles was produced that discovered to be economical and environmentally friendly in contrast to the traditional binders. It is believed that an extended heat curing of vegetable oil results in a complex oxy-polymerization reaction converting it into a rigid binder. Triplicate prototypes 2 samples were manufactured to optimize the final conditions for the fabrication of catalyzed Vege-Roofing tiles. Optimized conditions were then implemented to produce standard catalyzed Vege-Roofing tiles and these fabricated tiles have shown flexural stress of up to 12 MPa for 18 hours of curing. Moreover, these novel tiles were tested for permeability and water absorption according to the ASTM standards and have shown impermeability and remarkably low water absorption. Progressively, the embodied energy and embodied carbon requirements for these tiles found to be 0.64 MJ/kg and 0.327 kg CO2 per equivalent respectively which is quite less in comparison to the traditional binders. Conclusively, environmentally friendly and economic production of tiles, conservation of existing resources and overcoming the issue of waste management are the remarkable outcomes of this research.
2021 Third International Sustainability and Resilience Conference: Climate Change, Nov 15, 2021
Plastic consumption has increased tremendously over the years due to their versatility which enab... more Plastic consumption has increased tremendously over the years due to their versatility which enables them to be used in various industries. However, the properties of plastics which are non-biodegradable have created serious environmental problems especially polluting the oceans, harming marine organisms, and putting them at risks of extinction. At the same time, conventionally used construction materials such as clay bricks and concrete blocks also lead to other environmental issue such as the over-utilization of natural resources and emission of greenhouse gases. In current study, waste polyethylene terephthalate was used as a sand replacement in the production of interlocking concrete blocks for masonry wall application. Concrete mixtures with various percentages of PET were produced and evaluated for compressive strength and split tensile strength. In addition, microstructural characterization was also performed using Scanning Electron Microscope (SEM). The recycling of waste PET in the production of concrete interlocking blocks will produce sustainability in the construction industry.
Journal of Materials in Civil Engineering, Mar 1, 2010
ABSTRACT A novel construction unit (Bitublock) composed entirely of recycled and waste aggregates... more ABSTRACT A novel construction unit (Bitublock) composed entirely of recycled and waste aggregates and bound with bituminous binders is currently being developed. At present, the manufacturing process requires the new units to be heat cured to convert the bitumen binder from a viscoelastic material into an elastic-brittle material (known as hardening or bitumen aging). The paper investigates the effect of aging and curing processes on the compressive strength of Bitublocks. In this investigation, samples were compacted at pressures of between 8 and 20 MPa and cured at temperatures of between 60 and 160 degrees C for up to 48 h. Compressive strengths approaching 45 MPa were achieved. The range of compressive strengths achieved indicated that the behavior of the bituminous binder during heat curing significantly influences the performance of the Bitublocks and suggested that bitumen hardening is highly influenced by the curing temperature. Oxidation as opposed to polymerization and loss of volatiles was confirmed to be the key role in the bitumen hardening process (only approximately 7% of the total long-term hardening was due to volatilization). The oxidation process can be directly linked to the compressive strength development of Bitublock.
Polyethylene Terephthalate (PET) is one of the most commonly available kinds of plastic present i... more Polyethylene Terephthalate (PET) is one of the most commonly available kinds of plastic present in the municipal solid waste and it is a non-biodegradable semi-crystalline thermoplastic polymer, studied as polyester material. This paper intends to assess impacts of using PET (regular and irradiated) as aggregate that would replace by volume of equal size (10.00-5.00mm) in asphalt blend on the engineering properties of dense graded asphaltic concrete. The volumetric and mechanical properties of the blends incorporating different percent of PET (0, 5, 10, 15 and 20) were determined. In all mixtures, 5.0% optimum bitumen content was utilized. The outcome revealed that aggregate substitution of 10% (equivalent to 2.4% by weight of total mix) with irradiated PET result in optimum Marshall Stability and flow value of 3.6mm. It also showed that mixes with irradiated PET at 100kGy radiation dose have Marshall Stability values higher than mixes with same contents of regular PET. The finding also shows that the addition of PET and utilization of gamma radiation has a critical constructive outcome on the properties of asphalt concrete mixes as the stability increases for mixes with irradiated PET when compared with mixes with regular PET (RPET).
In this paper, test results are presented from laboratory trials of blending discarded tire deriv... more In this paper, test results are presented from laboratory trials of blending discarded tire derived crumb rubber with 60/70pen grade Kuwaiti bitumen. The virgin bitumen, in addition to 15% and 18% crumb rubber blends were tested for PG grading and multiple stress creep recovery at temperatures in the range from 40°C to 70°C. Elastic recovery and nonrecoverable creep compliance showed optimum performance at 18% rubber content. The optimized rubberized-bitumen blend was next converted into a pelletized form which was then used as a partial substitute to the conventional bitumen in the manufacture of continuously graded hot mix asphalts at various binder contents. The rubberized-bitumen pellet contents trialed were 2.5%, 3.0% and 3.5% by mass of mix. The Marshall method of mix design was used to assess the various mixes and the overall volumetric, stability and flow results, though satisfactory, was not entirely sufficient to aid in the selection of the best performing formulation.
The seme-flexible pavement surface is a hybrid type of pavement surface that combines the effect ... more The seme-flexible pavement surface is a hybrid type of pavement surface that combines the effect of both asphalt mix skeleton and cement grout. The current study investigates the influence of cement grouts containing irradiated waste polyethylene terephthalate (PET) on the performance of semi-flexible mixtures. The ordinary Portland cement was partially replaced by regular and irradiated PET as well as with fly ash (FA) in cement grouts. The air voids analysis, degree of grout saturation, Marshal stability, indirect tensile strength (ITS), and tensile strength ratio (TSR) of semi-flexible specimens were evaluated. The semi-flexible mixtures showed superior performance in terms of strength properties. The results indicate that with the irradiation process more waste PET (almost double) can be recycled as compared to regular waste PET in cement grouts for semi-flexible pavement surfaces. This approach will lead to a sustainable solution for recycling waste PET in highway materials for the construction of a hybrid type of pavement surface.
This paper discusses the laboratory design of continuously graded Asphaltic concrete (AC) mixture... more This paper discusses the laboratory design of continuously graded Asphaltic concrete (AC) mixtures containing recycled plastics aggregate replacement (Plastiphalt). Recycled waste plastics, predominantly composed of low density polyethylene (LDPE) in pellet form, were used in dense graded bituminous mixes to replace (by volume) a portion of the mineral aggregates of an equal size, i.e., 5.00.-2.36 mm. The results obtained in this investigation indicate that at the same air-void content, the compacted Plastiphalt mix has lower bulk density than that of the conventional control mix. A 30% aggregate replacement by volume with the LDPE, results in a reduction in bulk compacted mix density of 16%. This reduction in density is advantageous in terms of haulage costs. LDPE partial aggregate replacement also results in a 250% times increase in the Marshall stability (strength) value and an improved Marshall quotient value (resistance to deformation). The value of creep stiffness of the Plastiphalt mix after 1 h loading at 60°C is found to be slightly lower than the control mix; however, the Plastiphalt gives 14% recovery after 1 h unloading time compared to 0.6% for the control mix. The indirect tensile stiffness modulus (ITSM) values of the Plastiphalt compacted mix were found to be lower than that of the control mix, whereas the static indirect tensile strength (ITS) values were found to be much higher. In this study, the future recyclability of the Plastiphalt was also investigated. The mechanical properties of the recycled mix were found to be equal to that of the original Plastiphalt and better than the control mixes.
Proceedings of the Institution of Civil Engineers, May 1, 2009
A conventional grouted macadam is manufactured by producing a highly porous asphalt skeleton (25-... more A conventional grouted macadam is manufactured by producing a highly porous asphalt skeleton (25-35% voids), and filling the voids with a selected highly flowable cementitious grout. Grouted macadam combines some of the best qualities of concrete and asphalt pavements, namely the flexibility and absence of joints which characterise asphalt and the high static bearing capacity and wear resistance of concrete. Moreover grouted macadam layers are impermeable and efficiently distribute the stresses in the underlying base layer. The speed of construction of grouted macadam surfacings and the short duration required prior to opening to traffic is a major advantage over conventional concrete. Current fields of applications include: airport pavements, industrial floors, harbours, bus terminals, distribution centres, and other heavily stressed areas. The aim of this investigation was to assess the fatigue behaviour of a range of grouted macadam mixtures. Indirect tensile fatigue tests and two point bending tests were conducted on laboratory manufactured specimens and on samples extracted from a trafficked pavement test facility. The experimental work provided interesting data on the influence of mixture composition on fatigue life and highlighted differences between strain and stress-controlled fatigue tests on performance of grouted macadam mixtures compared with conventional asphalts. Transport 162 Issue TR2 Investigating the fatigue performance of grouted macadams Oliveira et al. 115
This chapter describes a review of the design and formulation of various cementitious grouts for ... more This chapter describes a review of the design and formulation of various cementitious grouts for semi-flexible pavement surfaces. Additionally, the authors also conducted extensive experimental work on the possibility of using a most effective and innovative way of recycling waste polyethylene terephthalate (PET) by exposing to gamma radiation and using as a replacement of Ordinary portland cement in the formulation of cement grouts for semi-flexible pavement surfaces. In the current study, cement in the grouts was replaced with PET (regular and irradiated), fly ash and silica fume and was evaluated for flowability and strength properties. The study concludes that normal PET causes a significant reduction in compressive strength, however, some of the strength is restored when irradiated PET was used. The recycling of waste PET, as a cement replacement in the cementitious grouts for semi-flexible pavement surfaces, with the irradiation process can be doubled as compared to utilizing normal/regular PET.
Grouted Macadams consist of a single sized porous asphalt layer laid with a traditional asphalt p... more Grouted Macadams consist of a single sized porous asphalt layer laid with a traditional asphalt paver typically to a thickness of up to 60 mm. The porous asphalt skeleton is designed to achieve a high void content (28-32%) whilst maintaining a thick bitumen coating on the aggregate particles. The hot asphalt is rolled using a steel wheeled compactor without vibration. As soon as the bituminous mixture has cooled, the voids in the porous asphalt mixture can be filled with the selected fluid grout (cementitious slurry). The Grouted Macadam sections can normally be opened to vehicular traffic 24 h after the voids have been filled with the cementitious grout. Grouted Macadams thus combine the best qualities of concrete and asphalt pavements, namely the flexibility and freedom from joints that characterize asphalt and the high static bearing capacity and wear resistance of concrete. The aim of this investigation was to establish techniques that would reduce the initial cost of Grouted Macadams whilst maintaining their excellent mechanical and performance properties. Two techniques were established; the first was to redesign the conventional hot mix, hot laid porous asphalt skeleton using bituminous emulsions, thus creating a cold mixed, cold laid porous asphalt skeleton suitable for filling with a cementitious grout. A range of tests including: compressive strength, drying shrinkage, indirect tensile stiffness and dynamic creep tests were carried out on these cold mixes and the results compared with a conventional limestone Grouted Macadam. The second technique progresses even further by investigating the potential for utilizing substandard dolomitic aggregates as an alternative to the conventional limestone aggregates in Grouted Macadams, as a cold mixed, cold laid porous asphalt. For the covering abstract see ITRD E117840.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Conference on Asphalt Pavements for Southern Africa (CAPSA15), 11th, 2015, Sun City, South Africa, Aug 1, 2015
Higher traffic volumes and traffic loads have led to an increase in premature pavement failures a... more Higher traffic volumes and traffic loads have led to an increase in premature pavement failures as empirical binder testing has increasingly failed to predict pavement performance. Moreover, empirical tests cannot effectively characterize polymer-modified binders which are being increasingly used in South Africa. This has resulted in a move to establish bituminous binder specifications based on fundamental engineering properties capable of accurately predicting the performance of asphalt mixes. Asphalt pavements are most susceptible to rutting at high in-service temperatures, where the in situ binder plays an important role in resisting deformation from repeated loading, along with the complementary resistance provided by the aggregate structure. The non-recoverable compliance, Jnr, as determined by the dynamic shear rheometer has been found to be an improved indicator of asphalt deformation. Jnr is measured using the multi-stress creep recovery (MSCR) method and considerable work has been done in the last three years in South Africa in preparation for adopting a modification of the Jnr as part of a performance graded specification. The paper reviews the advantages the MSCR method has over other methods confined to measurements within the linear viscoelastic (LVE) region of the binder. Constraints undermining the current MSCR test method are demonstrated. Two temperature zones for South Africa are presented and the Jnr-stress characterisations for typical binders were determined for these zones. A correlation plot of shear strain (permanent deformation indicator) for four asphalt mixes versus Jnr demonstrated the effectiveness of the non-recoverable compliance parameter. The paper concludes by statistically examining the precision and bias of the test method as currently practiced in South Africa and presents a recommendation for the parameters to be implemented for the South African version of the test method.
This paper presents data of a laboratoty investigation on the measurements of air permeability of... more This paper presents data of a laboratoty investigation on the measurements of air permeability of a range of dense bituminous composites using a simple air permeameter developed at the Civil Engineering Materials Unit (CEMU) at The University of Leeds. A wide range of gap graded Hot Rolled Asphalts and Asphaltic Concrete gradations compacted at several levels of compactive effort and using a range of bitumen contents were assessed for air permeability and Marshall Stability. The results show that the permeability of the composites tested at low bitumen contents are high and that these values decrease sharply with an increase in the bitumen content demonstrating that the test can be used with advantage to determine the minimum value of binder content for minimum permeability. The air permeameter is a non destructive test and can detect minor changes in the aggregate gradation, level of compaction or bitumen content. The results show a good correlation between permeability and compacted density and porosity for any one mixture type. The results also show that contrary to what is normally believed, the measured permeability values of selected dense continuously graded Asphaltic Concrete mixtures at their optimum bitumen contents of 5 to 5.5% were considerably lower than conventional gap graded Hot Rolled Asphalt wearing course mixtures at 7 to 7.5% bitumen contents. For the covering abstract see ITRD E107185.
This paper presents a laboratory study to demonstrate the effectiveness of using vegetable oils a... more This paper presents a laboratory study to demonstrate the effectiveness of using vegetable oils as rejuvenating agents for aged asphalt mixtures. The work focused on proposing a laboratory aging protocol whereby loose asphalt base course mixtures oven aged at 150°C for a range of durations, namely 2, 4, 6, 8 and 10hrs prior to compaction. Using this technique, 5 mixes were thus produced at various stages/levels of aging. An additional set of 5 batches were produced and aged in the loose state for 10 hours at 150ºC before rejuvenating the mixtures using vegetable oil. Vegetable oil was added at percentages ranging from 4 to 8% by weight of the bitumen. Rejuvenation of the mixture using the vegetable oils was then assessed by the mechanical and rheological performance of the material and binders. Furthermore, the effect of the addition of vegetable oil rejuvenators was also investigated using SARA analysis. Results indicated that the aging and rejuvenating protocol employed in the lab has been effective, with results of the recovered penetration and softening point tests demonstrating that it is possible to rejuvenate an aged mixture thereby improving the recovered penetration by standard penetration grade designation. However further work must be done to improve the correlation between mechanical performance and rheological characterisation particularly if a rejuvenation chart were to be developed.
From a performance point of view, bitumen is one of the most important constituents of asphalt mi... more From a performance point of view, bitumen is one of the most important constituents of asphalt mixtures. The quality and properties of bitumen depend largely on its chemical composition. Evidence obtained form laboratory oven ageing tests suggests that bitumens having the same grade, but originating form different crudes, can age quite differently. This evidence is further supported by data from laboratory compacted asphalt mixtures. The first part of this study reviews in some detail the effect of the chemical composition of penetration grade bitumens on ageing performance. Simple explanations of the ageing mechanisms are presented in the paper primarily based on chromatographic separation techniques. For the covering abstract see ITRD E145817
h i g h l i g h t s Time-concentration an alternative tool to Time-temperature superposition. Flu... more h i g h l i g h t s Time-concentration an alternative tool to Time-temperature superposition. Fluxed bitumens enable Time-Concentration to replace Time-Temperature shifting. Fluxing bitumens simulative of raising test temperature.
The primary objective of this research was to contribute towards greater sustainability of the co... more The primary objective of this research was to contribute towards greater sustainability of the construction industry in the Qatar by proposing methods to reduce its dependency on primary imported materials. In this investigation, recycled and secondary aggregates (RSA) were combined with non-traditional binders to develop a unique method of manufacturing construction and building blocks. Following an extensive phase of laboratory trials and experimentation, it was realised that many types of graded mineral aggregates, when mixed with vegetable oils (virgin or waste) at optimal proportions, then compacted and thermally cured at elevated temperatures can readily generate hardened composites that have the mechanical characteristics of conventional building blocks. The resultant blocks have been named "Vegeblocks" and are viewed as viable alternatives to conventional concrete blocks. Furthermore, the research has demonstrated the feasibility of producing Vegeblocks composed of 100% recycled aggregate and discarded waste cooking oil. Based on physical and mineralogical properties, each type of aggregate has an optimum oil content for maximum compressive strength, beyond which, any additional oil will result in reduction in mechanical properties. Acceptable compressive strength values were achieved by thermally curing Vegeblocks at of 170 ºC for 24 hours.
Semi-flexible pavements are manufactured by producing a very open porous asphalt skeleton and fil... more Semi-flexible pavements are manufactured by producing a very open porous asphalt skeleton and filling the voids with selected cementitious grouts. The resultant composites, referred to as "grouted macadams", combine the flexibility of the bituminous component with the strength and rigidity of the cementitious component. In this investigation, a range of cementitious grouts was formulated using a variety of binders including ordinary Portland cement, silica fume and fly ash. The grouts were designed to provide improved strength and performance characteristics with reduced water/binder ratios, whilst maintaining high workability. This was achieved with the aid of chemical admixtures that allowed the grouts to penetrate the porous asphalt skeleton under gravity action (i.e. without vibration). The properties of the grouted macadam composites were assessed using a range of engineering, deformation and performance tests. These included compressive strength, stiffness modulus, creep resistance, shrinkage, porosity and permeability up to the curing age of 28 days. The formulated cementitious grouts attained high strength characteristics (90-120 MPa at 28 days), with the pozzolanic materials (silica fume and fly ash) having improved permeability and shrinkage properties. When the grouts were impregnated into the porous asphalt skeleton, the resultant grouted macadam composites showed superior strength to conventional asphalts and much higher resilient properties than that of concrete pavement materials. In addition, the grouted macadams exhibited much lower porosity (<8%) indicating enhanced durability performance. For the covering abstract see ITRD E117840.
Climate change has become a major issue in recent years owing to the emission of greenhouse gases... more Climate change has become a major issue in recent years owing to the emission of greenhouse gases. Mitigation measures are required to overcome the challenges pertained to greenhouse gases emissions. This research paper attributes to the utilization of catalyzed waste vegetable oil as a binder for the production of roofing tiles to replace the conventional construction materials such as clay and cement. A novel methodology of utilizing catalyzed waste oil incorporated with sand and filler was adopted and the innovative product produced entitled as catalyzed Vege-Roofing tiles was produced that discovered to be economical and environmentally friendly in contrast to the traditional binders. It is believed that an extended heat curing of vegetable oil results in a complex oxy-polymerization reaction converting it into a rigid binder. Triplicate prototypes 2 samples were manufactured to optimize the final conditions for the fabrication of catalyzed Vege-Roofing tiles. Optimized conditions were then implemented to produce standard catalyzed Vege-Roofing tiles and these fabricated tiles have shown flexural stress of up to 12 MPa for 18 hours of curing. Moreover, these novel tiles were tested for permeability and water absorption according to the ASTM standards and have shown impermeability and remarkably low water absorption. Progressively, the embodied energy and embodied carbon requirements for these tiles found to be 0.64 MJ/kg and 0.327 kg CO2 per equivalent respectively which is quite less in comparison to the traditional binders. Conclusively, environmentally friendly and economic production of tiles, conservation of existing resources and overcoming the issue of waste management are the remarkable outcomes of this research.
2021 Third International Sustainability and Resilience Conference: Climate Change, Nov 15, 2021
Plastic consumption has increased tremendously over the years due to their versatility which enab... more Plastic consumption has increased tremendously over the years due to their versatility which enables them to be used in various industries. However, the properties of plastics which are non-biodegradable have created serious environmental problems especially polluting the oceans, harming marine organisms, and putting them at risks of extinction. At the same time, conventionally used construction materials such as clay bricks and concrete blocks also lead to other environmental issue such as the over-utilization of natural resources and emission of greenhouse gases. In current study, waste polyethylene terephthalate was used as a sand replacement in the production of interlocking concrete blocks for masonry wall application. Concrete mixtures with various percentages of PET were produced and evaluated for compressive strength and split tensile strength. In addition, microstructural characterization was also performed using Scanning Electron Microscope (SEM). The recycling of waste PET in the production of concrete interlocking blocks will produce sustainability in the construction industry.
Journal of Materials in Civil Engineering, Mar 1, 2010
ABSTRACT A novel construction unit (Bitublock) composed entirely of recycled and waste aggregates... more ABSTRACT A novel construction unit (Bitublock) composed entirely of recycled and waste aggregates and bound with bituminous binders is currently being developed. At present, the manufacturing process requires the new units to be heat cured to convert the bitumen binder from a viscoelastic material into an elastic-brittle material (known as hardening or bitumen aging). The paper investigates the effect of aging and curing processes on the compressive strength of Bitublocks. In this investigation, samples were compacted at pressures of between 8 and 20 MPa and cured at temperatures of between 60 and 160 degrees C for up to 48 h. Compressive strengths approaching 45 MPa were achieved. The range of compressive strengths achieved indicated that the behavior of the bituminous binder during heat curing significantly influences the performance of the Bitublocks and suggested that bitumen hardening is highly influenced by the curing temperature. Oxidation as opposed to polymerization and loss of volatiles was confirmed to be the key role in the bitumen hardening process (only approximately 7% of the total long-term hardening was due to volatilization). The oxidation process can be directly linked to the compressive strength development of Bitublock.
Polyethylene Terephthalate (PET) is one of the most commonly available kinds of plastic present i... more Polyethylene Terephthalate (PET) is one of the most commonly available kinds of plastic present in the municipal solid waste and it is a non-biodegradable semi-crystalline thermoplastic polymer, studied as polyester material. This paper intends to assess impacts of using PET (regular and irradiated) as aggregate that would replace by volume of equal size (10.00-5.00mm) in asphalt blend on the engineering properties of dense graded asphaltic concrete. The volumetric and mechanical properties of the blends incorporating different percent of PET (0, 5, 10, 15 and 20) were determined. In all mixtures, 5.0% optimum bitumen content was utilized. The outcome revealed that aggregate substitution of 10% (equivalent to 2.4% by weight of total mix) with irradiated PET result in optimum Marshall Stability and flow value of 3.6mm. It also showed that mixes with irradiated PET at 100kGy radiation dose have Marshall Stability values higher than mixes with same contents of regular PET. The finding also shows that the addition of PET and utilization of gamma radiation has a critical constructive outcome on the properties of asphalt concrete mixes as the stability increases for mixes with irradiated PET when compared with mixes with regular PET (RPET).
In this paper, test results are presented from laboratory trials of blending discarded tire deriv... more In this paper, test results are presented from laboratory trials of blending discarded tire derived crumb rubber with 60/70pen grade Kuwaiti bitumen. The virgin bitumen, in addition to 15% and 18% crumb rubber blends were tested for PG grading and multiple stress creep recovery at temperatures in the range from 40°C to 70°C. Elastic recovery and nonrecoverable creep compliance showed optimum performance at 18% rubber content. The optimized rubberized-bitumen blend was next converted into a pelletized form which was then used as a partial substitute to the conventional bitumen in the manufacture of continuously graded hot mix asphalts at various binder contents. The rubberized-bitumen pellet contents trialed were 2.5%, 3.0% and 3.5% by mass of mix. The Marshall method of mix design was used to assess the various mixes and the overall volumetric, stability and flow results, though satisfactory, was not entirely sufficient to aid in the selection of the best performing formulation.
The seme-flexible pavement surface is a hybrid type of pavement surface that combines the effect ... more The seme-flexible pavement surface is a hybrid type of pavement surface that combines the effect of both asphalt mix skeleton and cement grout. The current study investigates the influence of cement grouts containing irradiated waste polyethylene terephthalate (PET) on the performance of semi-flexible mixtures. The ordinary Portland cement was partially replaced by regular and irradiated PET as well as with fly ash (FA) in cement grouts. The air voids analysis, degree of grout saturation, Marshal stability, indirect tensile strength (ITS), and tensile strength ratio (TSR) of semi-flexible specimens were evaluated. The semi-flexible mixtures showed superior performance in terms of strength properties. The results indicate that with the irradiation process more waste PET (almost double) can be recycled as compared to regular waste PET in cement grouts for semi-flexible pavement surfaces. This approach will lead to a sustainable solution for recycling waste PET in highway materials for the construction of a hybrid type of pavement surface.
This paper discusses the laboratory design of continuously graded Asphaltic concrete (AC) mixture... more This paper discusses the laboratory design of continuously graded Asphaltic concrete (AC) mixtures containing recycled plastics aggregate replacement (Plastiphalt). Recycled waste plastics, predominantly composed of low density polyethylene (LDPE) in pellet form, were used in dense graded bituminous mixes to replace (by volume) a portion of the mineral aggregates of an equal size, i.e., 5.00.-2.36 mm. The results obtained in this investigation indicate that at the same air-void content, the compacted Plastiphalt mix has lower bulk density than that of the conventional control mix. A 30% aggregate replacement by volume with the LDPE, results in a reduction in bulk compacted mix density of 16%. This reduction in density is advantageous in terms of haulage costs. LDPE partial aggregate replacement also results in a 250% times increase in the Marshall stability (strength) value and an improved Marshall quotient value (resistance to deformation). The value of creep stiffness of the Plastiphalt mix after 1 h loading at 60°C is found to be slightly lower than the control mix; however, the Plastiphalt gives 14% recovery after 1 h unloading time compared to 0.6% for the control mix. The indirect tensile stiffness modulus (ITSM) values of the Plastiphalt compacted mix were found to be lower than that of the control mix, whereas the static indirect tensile strength (ITS) values were found to be much higher. In this study, the future recyclability of the Plastiphalt was also investigated. The mechanical properties of the recycled mix were found to be equal to that of the original Plastiphalt and better than the control mixes.
Proceedings of the Institution of Civil Engineers, May 1, 2009
A conventional grouted macadam is manufactured by producing a highly porous asphalt skeleton (25-... more A conventional grouted macadam is manufactured by producing a highly porous asphalt skeleton (25-35% voids), and filling the voids with a selected highly flowable cementitious grout. Grouted macadam combines some of the best qualities of concrete and asphalt pavements, namely the flexibility and absence of joints which characterise asphalt and the high static bearing capacity and wear resistance of concrete. Moreover grouted macadam layers are impermeable and efficiently distribute the stresses in the underlying base layer. The speed of construction of grouted macadam surfacings and the short duration required prior to opening to traffic is a major advantage over conventional concrete. Current fields of applications include: airport pavements, industrial floors, harbours, bus terminals, distribution centres, and other heavily stressed areas. The aim of this investigation was to assess the fatigue behaviour of a range of grouted macadam mixtures. Indirect tensile fatigue tests and two point bending tests were conducted on laboratory manufactured specimens and on samples extracted from a trafficked pavement test facility. The experimental work provided interesting data on the influence of mixture composition on fatigue life and highlighted differences between strain and stress-controlled fatigue tests on performance of grouted macadam mixtures compared with conventional asphalts. Transport 162 Issue TR2 Investigating the fatigue performance of grouted macadams Oliveira et al. 115
This chapter describes a review of the design and formulation of various cementitious grouts for ... more This chapter describes a review of the design and formulation of various cementitious grouts for semi-flexible pavement surfaces. Additionally, the authors also conducted extensive experimental work on the possibility of using a most effective and innovative way of recycling waste polyethylene terephthalate (PET) by exposing to gamma radiation and using as a replacement of Ordinary portland cement in the formulation of cement grouts for semi-flexible pavement surfaces. In the current study, cement in the grouts was replaced with PET (regular and irradiated), fly ash and silica fume and was evaluated for flowability and strength properties. The study concludes that normal PET causes a significant reduction in compressive strength, however, some of the strength is restored when irradiated PET was used. The recycling of waste PET, as a cement replacement in the cementitious grouts for semi-flexible pavement surfaces, with the irradiation process can be doubled as compared to utilizing normal/regular PET.
Grouted Macadams consist of a single sized porous asphalt layer laid with a traditional asphalt p... more Grouted Macadams consist of a single sized porous asphalt layer laid with a traditional asphalt paver typically to a thickness of up to 60 mm. The porous asphalt skeleton is designed to achieve a high void content (28-32%) whilst maintaining a thick bitumen coating on the aggregate particles. The hot asphalt is rolled using a steel wheeled compactor without vibration. As soon as the bituminous mixture has cooled, the voids in the porous asphalt mixture can be filled with the selected fluid grout (cementitious slurry). The Grouted Macadam sections can normally be opened to vehicular traffic 24 h after the voids have been filled with the cementitious grout. Grouted Macadams thus combine the best qualities of concrete and asphalt pavements, namely the flexibility and freedom from joints that characterize asphalt and the high static bearing capacity and wear resistance of concrete. The aim of this investigation was to establish techniques that would reduce the initial cost of Grouted Macadams whilst maintaining their excellent mechanical and performance properties. Two techniques were established; the first was to redesign the conventional hot mix, hot laid porous asphalt skeleton using bituminous emulsions, thus creating a cold mixed, cold laid porous asphalt skeleton suitable for filling with a cementitious grout. A range of tests including: compressive strength, drying shrinkage, indirect tensile stiffness and dynamic creep tests were carried out on these cold mixes and the results compared with a conventional limestone Grouted Macadam. The second technique progresses even further by investigating the potential for utilizing substandard dolomitic aggregates as an alternative to the conventional limestone aggregates in Grouted Macadams, as a cold mixed, cold laid porous asphalt. For the covering abstract see ITRD E117840.
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