Presentation delivered at the CalAPA Spring Asphalt Pavement Conference April 9-10, 2014 in Ontario. Topic: The critical role compaction plays in the HMA construction process, plus methods and standards of measurement and problems to be avoided.
Effect of air void on dense graded bituminous mixAvinash Bhosale
SEMINAR FOR effect of air voids on dense graded bituminous mix.
MATERIALS USE FOR NATIONAL HIGHWAY.
such as Dense bituminous macadam.
air voids in road pavement and how to analyse it.
Design and construction of highway (flexible pavementsuraj vishwakarma
This document discusses the design and construction of roads. It describes the different materials used in road construction like aggregate and asphalt. It explains the functions of different pavement layers and the importance of thickness design based on traffic volume and soil properties. The construction process involves preparing each layer from the subgrade to the wearing surface. Tests are conducted on aggregate and bitumen to ensure quality of materials used in road construction.
Pavement is a layered structure constructed over soil to support vehicle loads. It has multiple layers - subgrade, sub-base, base, and surface course. Pavements are classified as flexible, rigid, or composite based on material properties. Flexible pavements are made of asphalt and deform under loads, while rigid pavements are made of concrete and resist deformation. Pavement design considers factors like traffic loads, material properties, environment, and failure criteria to determine layer thickness to support loads over the design life.
Sight distance is the length of road visible ahead of the driver at any instance.
Sight distance available at any location of the carriageway is the actual distance a driver with his eye level at a specified height above the pavements surface has visibility of any stationary or moving object of specified height which is on the carriageway ahead.
The sight distance between the driver and the object is measured along the road surface.
The document discusses the use of recycled asphalt pavement (RAP) in stone matrix asphalt mixes, with RAP replacements of 10%, 30%, and 50% tested. Laboratory tests such as the Marshall test and indirect tensile strength test were conducted on specimens to evaluate the performance of mixes with different RAP contents. The results of the tests were analyzed to determine the optimum RAP percentage for stone matrix asphalt based on strength and economic considerations.
This document summarizes a presentation on subgrade stabilization methods for concrete pavements. It discusses the role of the subgrade in pavement performance and outlines various treatment options including removal and replacement, compaction, geotextiles, chemical stabilization using lime and cement. The presentation provides details on laboratory testing and construction steps for lime and cement stabilization, including mixing, compaction, curing and quality control. Subgrade stabilization improves the strength and uniformity of the subgrade for use as a construction platform and structural layer.
Effect of air void on dense graded bituminous mixAvinash Bhosale
SEMINAR FOR effect of air voids on dense graded bituminous mix.
MATERIALS USE FOR NATIONAL HIGHWAY.
such as Dense bituminous macadam.
air voids in road pavement and how to analyse it.
Design and construction of highway (flexible pavementsuraj vishwakarma
This document discusses the design and construction of roads. It describes the different materials used in road construction like aggregate and asphalt. It explains the functions of different pavement layers and the importance of thickness design based on traffic volume and soil properties. The construction process involves preparing each layer from the subgrade to the wearing surface. Tests are conducted on aggregate and bitumen to ensure quality of materials used in road construction.
Pavement is a layered structure constructed over soil to support vehicle loads. It has multiple layers - subgrade, sub-base, base, and surface course. Pavements are classified as flexible, rigid, or composite based on material properties. Flexible pavements are made of asphalt and deform under loads, while rigid pavements are made of concrete and resist deformation. Pavement design considers factors like traffic loads, material properties, environment, and failure criteria to determine layer thickness to support loads over the design life.
Sight distance is the length of road visible ahead of the driver at any instance.
Sight distance available at any location of the carriageway is the actual distance a driver with his eye level at a specified height above the pavements surface has visibility of any stationary or moving object of specified height which is on the carriageway ahead.
The sight distance between the driver and the object is measured along the road surface.
The document discusses the use of recycled asphalt pavement (RAP) in stone matrix asphalt mixes, with RAP replacements of 10%, 30%, and 50% tested. Laboratory tests such as the Marshall test and indirect tensile strength test were conducted on specimens to evaluate the performance of mixes with different RAP contents. The results of the tests were analyzed to determine the optimum RAP percentage for stone matrix asphalt based on strength and economic considerations.
This document summarizes a presentation on subgrade stabilization methods for concrete pavements. It discusses the role of the subgrade in pavement performance and outlines various treatment options including removal and replacement, compaction, geotextiles, chemical stabilization using lime and cement. The presentation provides details on laboratory testing and construction steps for lime and cement stabilization, including mixing, compaction, curing and quality control. Subgrade stabilization improves the strength and uniformity of the subgrade for use as a construction platform and structural layer.
Traffic studies are carried out to analyze traffic characteristics and help decide geometric design and traffic control measures. The main traffic studies include traffic volume, speed, origin-destination, traffic flow characteristics, capacity, and accident studies. Traffic volume studies measure the number of vehicles on a road section over time and are used for planning, operations, and analysis. Speed studies measure the speeds of vehicles using methods like short-distance timing or radar guns.
The document discusses pavement maintenance practices on the Dhaka-Chittagong Highway in Bangladesh. It provides background on the highway, which is a vital transportation route connecting Dhaka and Chittagong, the largest port city. The study evaluates the surface condition of 20 segments of the highway using the Roads and Highways Department's visual assessment method. Common maintenance techniques used on the highway include double bituminous surface treatment and asphalt overlays. The findings indicate that segments experience deterioration due to heavy commercial vehicle traffic, requiring reconstruction or resurfacing every 3-5 years. The 4-laning expansion project aims to improve the highway to support increasing traffic volumes.
This document summarizes different techniques for assigning routes in transportation network modeling. It describes the all-or-nothing assignment method, direction curve method, capacity restraint assignment techniques, and multi-route assignment technique. For each method, it provides details on the approach, limitations, and examples of models that use the technique. The document is presented by five students as part of their course on urban transportation systems.
Taxiway design and geometrical design of taxiwayBALAJI ND
A taxiway is a path for aircraft at an airport to connect runways to aprons, hangars and terminals. The document discusses factors that influence taxiway layout, including length, width, sight distance, turning radius and separation clearance. Exit taxiways, fillets, holding aprons and bypass taxiways are also addressed. Taxiways allow aircraft to move at lower speeds between airport facilities compared to takeoff and landing on runways.
The document discusses different methods for recycling pavements, including flexible and rigid pavements. For flexible pavements, it describes in-place hot and cold recycling processes as well as hot and cold central plant recycling. For rigid pavements, it discusses breaking, crushing and processing concrete to produce recycled concrete aggregate (RCA), which can be used in new concrete. It notes that recycling provides benefits like reduced costs, preservation of resources and the environment.
The document outlines the steps involved in highway route location, which includes reconnaissance, preliminary, and final location surveys. The reconnaissance survey evaluates feasibility of corridor routes based on topography, traffic, land use, environment, and economics. The preliminary survey determines horizontal and vertical alignments and evaluates routes for cost, environment, safety, and cost-benefit. The final survey fixes the center line and collects additional data like cross-sections and elevations for working drawings. The overall process aims to find a location that minimizes costs while considering traffic needs and impacts.
This document discusses the design of flexible granular pavements. It outlines the different types of pavement, including flexible pavements made of unbound granular materials and sometimes bituminous or cement stabilized materials. It also discusses rigid pavements made of Portland cement concrete. The document then focuses on analyzing the structural capacity of pavements and the factors considered in design, such as subgrade strength, pavement materials, and design traffic loading over the life of the pavement. Case studies are also presented.
The content of presentation slides describe the concept of road safety auditing and its application starting from the planning of the road project until opening the road.
Geophysical methods of soil/Foundation testing Pirpasha Ujede
Geophysical methods such as seismic refraction and resistivity testing provide non-invasive subsurface investigation over large areas more quickly and cheaply than traditional boring and testing. However, geophysical results require interpretation and are less definitive. Both methods are important, with geophysical testing used for initial screening and borings to accurately determine soil properties. Seismic refraction uses shock waves to determine layer velocities and depths, while resistivity measures subsurface resistivity variations related to moisture, compaction, and material to infer stratigraphy.
Fly ash is a byproduct of coal combustion in thermal power plants. Huge quantities of fly ash are generated and can be used beneficially in road construction. Fly ash has physical and chemical properties making it suitable for use in embankments and as a stabilizer in subgrades and bases. When used in embankments, fly ash must be compacted properly and protected with an earthen cover to prevent erosion. Engineering tests are required to evaluate the properties of fly ash before using it in road construction. National highway authorities are increasingly using fly ash to reduce costs and promote sustainable construction practices.
topics which are discussed in this slide are,
1) pavement and requirement for pavement design.
2) Rigid and flexible pavement .
3) pavement design method.
The document discusses highway geometric design and its key elements. It aims to maximize safety, comfort and efficiency while minimizing costs and environmental impacts. Geometric design considers the road's alignment, cross-section, sight distances and intersections. Elements include the carriageway, shoulders, formation width, right of way, side slopes, berms and side drains. Camber and super elevation help drain water and counteract centrifugal forces on curves. Sight distance requirements like stopping sight distance ensure drivers can see far enough to stop safely.
Highway failure & their maintenance seminar reportBeing Deepak
This document provides an introduction to flexible pavement design and construction. It discusses the types of pavements including flexible, rigid, and composite. It also covers materials used like cement, aggregate, sand, and bitumen. Construction methods for bituminous roads are presented including mix types like premix and various laying techniques. Highway maintenance objectives and activities are defined.
This document provides guidelines for traffic signal design and operation. It discusses:
1. Signal types including fixed time, vehicle actuated, and semi-vehicle actuated signals. Signal displays include green, amber, and red indications.
2. Warrants for signal installation based on minimum vehicular or pedestrian volumes, interruption of traffic flow, or accident experience.
3. Design considerations like signal height, location, size of lenses, and maintenance procedures. Traffic data collection and site conditions should also be analyzed.
4. Coordinated signal timing using time-distance diagrams to allow continuous traffic flow at a predetermined speed along a route with multiple signals.
This document discusses traffic engineering and road user characteristics. It defines traffic engineering as dealing with planning and design of roads and highways, as well as traffic operation related to safe and efficient transportation. The key points covered include:
- The scope of traffic engineering includes traffic studies and analysis, traffic control and regulation, planning, geometric design, and administration.
- Traffic characteristics and road user characteristics are important to study, including physical, mental, and emotional traits of drivers.
- The functions of a traffic engineer include data collection and analysis, transportation planning, traffic design, and measures to operate and regulate traffic.
- Road user behavior is influenced by physical, psychological, and environmental factors. Reaction time and visual abilities
This document discusses different types of pavements, including flexible, rigid, and semi-rigid pavements. It describes key design factors for both flexible and rigid pavements such as traffic load, pavement materials, subgrade strength assessed by CBR value, and design life. The document emphasizes the importance of pavement design, noting it accounts for nearly half the road construction cost. Good pavements are important as they can easily bear and transmit loads.
The Benkelman beam is the simplest and the oldest deflection
test device, developed in the United States in the mid-1950s. Its used to measure the structural capacity of a flexible pavement.
The document discusses different types of pavements. It describes flexible pavements as having multiple layers that distribute loads through aggregate interlock. Rigid pavements distribute loads through the beam strength of concrete slabs. Flexible pavements are composed of surface, base, and sub-base layers over a subgrade, while rigid pavements typically only require a concrete surface layer. Both pavement types are designed to reduce loads from vehicles to prevent damage to the subgrade. The document compares advantages and disadvantages of flexible and rigid pavements.
Progress Assessment of Pavement Management SystemsAgileAssets Inc.
The Session will start with a brief history of ICMPA conferences. After that, speakers will present
in detail the history and development of Pavement Management Systems (PMS), the lessons
learned and based on this experience, how to produce betters PMS.
The document provides an overview of the Superpave mix design method, which was developed under the Strategic Highway Research Program to replace the Hveem and Marshall mix design methods. Key aspects of the Superpave method include tying asphalt binder and aggregate selection to the mix design process, accounting for traffic and climate, using a gyratory compactor to determine density, and evaluating moisture susceptibility.
This document discusses compaction of hot mix asphalt (HMA) pavement. It states that compaction is the most important factor in HMA pavement performance, as inadequate compaction can reduce the life of the pavement. It describes how compaction works to reduce the air voids in HMA by reorienting aggregate particles. It also discusses factors that affect compaction, including mix properties, temperature, and equipment used. Vibratory steel wheel rollers are highlighted as they can provide greater compaction force through both static weight and dynamic vibration of the drums.
Traffic studies are carried out to analyze traffic characteristics and help decide geometric design and traffic control measures. The main traffic studies include traffic volume, speed, origin-destination, traffic flow characteristics, capacity, and accident studies. Traffic volume studies measure the number of vehicles on a road section over time and are used for planning, operations, and analysis. Speed studies measure the speeds of vehicles using methods like short-distance timing or radar guns.
The document discusses pavement maintenance practices on the Dhaka-Chittagong Highway in Bangladesh. It provides background on the highway, which is a vital transportation route connecting Dhaka and Chittagong, the largest port city. The study evaluates the surface condition of 20 segments of the highway using the Roads and Highways Department's visual assessment method. Common maintenance techniques used on the highway include double bituminous surface treatment and asphalt overlays. The findings indicate that segments experience deterioration due to heavy commercial vehicle traffic, requiring reconstruction or resurfacing every 3-5 years. The 4-laning expansion project aims to improve the highway to support increasing traffic volumes.
This document summarizes different techniques for assigning routes in transportation network modeling. It describes the all-or-nothing assignment method, direction curve method, capacity restraint assignment techniques, and multi-route assignment technique. For each method, it provides details on the approach, limitations, and examples of models that use the technique. The document is presented by five students as part of their course on urban transportation systems.
Taxiway design and geometrical design of taxiwayBALAJI ND
A taxiway is a path for aircraft at an airport to connect runways to aprons, hangars and terminals. The document discusses factors that influence taxiway layout, including length, width, sight distance, turning radius and separation clearance. Exit taxiways, fillets, holding aprons and bypass taxiways are also addressed. Taxiways allow aircraft to move at lower speeds between airport facilities compared to takeoff and landing on runways.
The document discusses different methods for recycling pavements, including flexible and rigid pavements. For flexible pavements, it describes in-place hot and cold recycling processes as well as hot and cold central plant recycling. For rigid pavements, it discusses breaking, crushing and processing concrete to produce recycled concrete aggregate (RCA), which can be used in new concrete. It notes that recycling provides benefits like reduced costs, preservation of resources and the environment.
The document outlines the steps involved in highway route location, which includes reconnaissance, preliminary, and final location surveys. The reconnaissance survey evaluates feasibility of corridor routes based on topography, traffic, land use, environment, and economics. The preliminary survey determines horizontal and vertical alignments and evaluates routes for cost, environment, safety, and cost-benefit. The final survey fixes the center line and collects additional data like cross-sections and elevations for working drawings. The overall process aims to find a location that minimizes costs while considering traffic needs and impacts.
This document discusses the design of flexible granular pavements. It outlines the different types of pavement, including flexible pavements made of unbound granular materials and sometimes bituminous or cement stabilized materials. It also discusses rigid pavements made of Portland cement concrete. The document then focuses on analyzing the structural capacity of pavements and the factors considered in design, such as subgrade strength, pavement materials, and design traffic loading over the life of the pavement. Case studies are also presented.
The content of presentation slides describe the concept of road safety auditing and its application starting from the planning of the road project until opening the road.
Geophysical methods of soil/Foundation testing Pirpasha Ujede
Geophysical methods such as seismic refraction and resistivity testing provide non-invasive subsurface investigation over large areas more quickly and cheaply than traditional boring and testing. However, geophysical results require interpretation and are less definitive. Both methods are important, with geophysical testing used for initial screening and borings to accurately determine soil properties. Seismic refraction uses shock waves to determine layer velocities and depths, while resistivity measures subsurface resistivity variations related to moisture, compaction, and material to infer stratigraphy.
Fly ash is a byproduct of coal combustion in thermal power plants. Huge quantities of fly ash are generated and can be used beneficially in road construction. Fly ash has physical and chemical properties making it suitable for use in embankments and as a stabilizer in subgrades and bases. When used in embankments, fly ash must be compacted properly and protected with an earthen cover to prevent erosion. Engineering tests are required to evaluate the properties of fly ash before using it in road construction. National highway authorities are increasingly using fly ash to reduce costs and promote sustainable construction practices.
topics which are discussed in this slide are,
1) pavement and requirement for pavement design.
2) Rigid and flexible pavement .
3) pavement design method.
The document discusses highway geometric design and its key elements. It aims to maximize safety, comfort and efficiency while minimizing costs and environmental impacts. Geometric design considers the road's alignment, cross-section, sight distances and intersections. Elements include the carriageway, shoulders, formation width, right of way, side slopes, berms and side drains. Camber and super elevation help drain water and counteract centrifugal forces on curves. Sight distance requirements like stopping sight distance ensure drivers can see far enough to stop safely.
Highway failure & their maintenance seminar reportBeing Deepak
This document provides an introduction to flexible pavement design and construction. It discusses the types of pavements including flexible, rigid, and composite. It also covers materials used like cement, aggregate, sand, and bitumen. Construction methods for bituminous roads are presented including mix types like premix and various laying techniques. Highway maintenance objectives and activities are defined.
This document provides guidelines for traffic signal design and operation. It discusses:
1. Signal types including fixed time, vehicle actuated, and semi-vehicle actuated signals. Signal displays include green, amber, and red indications.
2. Warrants for signal installation based on minimum vehicular or pedestrian volumes, interruption of traffic flow, or accident experience.
3. Design considerations like signal height, location, size of lenses, and maintenance procedures. Traffic data collection and site conditions should also be analyzed.
4. Coordinated signal timing using time-distance diagrams to allow continuous traffic flow at a predetermined speed along a route with multiple signals.
This document discusses traffic engineering and road user characteristics. It defines traffic engineering as dealing with planning and design of roads and highways, as well as traffic operation related to safe and efficient transportation. The key points covered include:
- The scope of traffic engineering includes traffic studies and analysis, traffic control and regulation, planning, geometric design, and administration.
- Traffic characteristics and road user characteristics are important to study, including physical, mental, and emotional traits of drivers.
- The functions of a traffic engineer include data collection and analysis, transportation planning, traffic design, and measures to operate and regulate traffic.
- Road user behavior is influenced by physical, psychological, and environmental factors. Reaction time and visual abilities
This document discusses different types of pavements, including flexible, rigid, and semi-rigid pavements. It describes key design factors for both flexible and rigid pavements such as traffic load, pavement materials, subgrade strength assessed by CBR value, and design life. The document emphasizes the importance of pavement design, noting it accounts for nearly half the road construction cost. Good pavements are important as they can easily bear and transmit loads.
The Benkelman beam is the simplest and the oldest deflection
test device, developed in the United States in the mid-1950s. Its used to measure the structural capacity of a flexible pavement.
The document discusses different types of pavements. It describes flexible pavements as having multiple layers that distribute loads through aggregate interlock. Rigid pavements distribute loads through the beam strength of concrete slabs. Flexible pavements are composed of surface, base, and sub-base layers over a subgrade, while rigid pavements typically only require a concrete surface layer. Both pavement types are designed to reduce loads from vehicles to prevent damage to the subgrade. The document compares advantages and disadvantages of flexible and rigid pavements.
Progress Assessment of Pavement Management SystemsAgileAssets Inc.
The Session will start with a brief history of ICMPA conferences. After that, speakers will present
in detail the history and development of Pavement Management Systems (PMS), the lessons
learned and based on this experience, how to produce betters PMS.
The document provides an overview of the Superpave mix design method, which was developed under the Strategic Highway Research Program to replace the Hveem and Marshall mix design methods. Key aspects of the Superpave method include tying asphalt binder and aggregate selection to the mix design process, accounting for traffic and climate, using a gyratory compactor to determine density, and evaluating moisture susceptibility.
This document discusses compaction of hot mix asphalt (HMA) pavement. It states that compaction is the most important factor in HMA pavement performance, as inadequate compaction can reduce the life of the pavement. It describes how compaction works to reduce the air voids in HMA by reorienting aggregate particles. It also discusses factors that affect compaction, including mix properties, temperature, and equipment used. Vibratory steel wheel rollers are highlighted as they can provide greater compaction force through both static weight and dynamic vibration of the drums.
The document discusses bituminous mix design and the Marshall mix design method. It describes the objectives of mix design as developing an economical blend of aggregates and asphalt that meets design requirements such as sufficient asphalt, stability, air voids, and workability. The Marshall mix design procedure involves selecting and testing aggregates and asphalt, developing trial blends, compacting specimens, and evaluating properties according to criteria like stability, flow, air voids, and tensile strength ratio. Calculations are also required to determine properties like theoretical maximum density and voids in the mix.
This document discusses mix proportioning of concrete. It provides information on various types and properties of concrete, factors affecting strength and workability, methods of mix design, and the general steps involved in mix proportioning. The key points are:
1) Concrete mix proportioning determines the relative amounts of ingredients to achieve the desired properties in an economical way.
2) Factors like water-cement ratio, aggregate size and grading, cement content affect the strength, workability and durability of concrete.
3) Common mix design methods include ACI, IS, and trial batch methods. The general steps are selecting slump, aggregate size, water content, water-cement ratio, and calculating cement and aggregate
Mix design practice (bituminous mix) ce 463abhay mishra
The document discusses various methods for designing bituminous mixes, including the Marshall, Hveem, and Modified Hubbard-Field methods. The objective of bituminous mix design is to determine an optimal blend of aggregates and bitumen that provides sufficient bitumen for durability while maintaining stability, voids, and other properties to meet traffic and weather demands. Key steps involve preparing trial mixtures, testing stability and voids, and analyzing results to select the design bitumen content.
rutting performance evaluation of polymer modified binder in HMA mix design Nur Zulkifli
The document provides background information on a study evaluating the rutting performance of hot mix asphalt (HMA) using polymer modified binders. It discusses factors that contribute to rutting in flexible pavements like excessive traffic loads and inadequate mixture stability. The objectives of the study are to determine and compare the rutting performance of HMA mixtures using unmodified and polymer modified binders. The scope will focus on evaluating rutting performance through the Asphalt Pavement Analyzer using three binder types (unmodified and two polymer modified) based on the Superpave mix design method.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
EVALUATION OF PERFORMANCE OF HIGH CALCIUM FLY ASH AS A MINERAL FILLER IN MIX ...civej
In the present research work, traditional mineral filler, high calcium Fly Ash, is used in the mix design of micro surfacing is evaluated with possibility of replacing it with other environmental friendly and cost effective selected fillers. The chemical analysis and material testing performed on high calcium Fly Ash filler indicate its suitability for incorporation in the mix design. The optimum mix design for microsurfacing Type II and Type III is determined through trial and error method. Also, the performance of a laboratory design mix is evaluated with field application. The field experimentation indicate that the mineral filler showed good performance for the test conducted on field after 24 hours and 6 months of application. The results evaluated in the field for skid resistance and surface texture indicate high calcium Fly Ash can be utilized for microsurfacing of road pavement.
Evaluation of Performance of High Calcium Fly Ash as a Mineral Filler in Mix ...civejjour
In the present research work, traditional mineral filler, high calcium Fly Ash, is used in the mix design of
micro surfacing is evaluated with possibility of replacing it with other environmental friendly and cost
effective selected fillers. The chemical analysis and material testing performed on high calcium Fly Ash
filler indicate its suitability for incorporation in the mix design. The optimum mix design for microsurfacing
Type II and Type III is determined through trial and error method. Also, the performance of a laboratory
design mix is evaluated with field application. The field experimentation indicate that the mineral filler
showed good performance for the test conducted on field after 24 hours and 6 months of application. The
results evaluated in the field for skid resistance and surface texture indicate high calcium Fly Ash can be
utilized for microsurfacing of road pavement.
Use of Waste Tyre as Subgrade in Flexible PavementIRJET Journal
This document summarizes a study on using waste tire pieces as a subgrade material in flexible pavements. The researchers conducted various tests on soil mixed with crumb rubber from shredded waste tires at different proportions. Specifically, they performed proctor tests to determine optimum moisture content of the soil. California bearing ratio (CBR) tests were then conducted on soil with 0% tire content to establish a baseline. The CBR value was found to be 9.49% based on results at a penetration of 5mm. The study aims to evaluate using tire shreds mixed with soil as subgrade material for flexible pavements. The researchers found initial indications that tire pieces may improve soil strength properties. Further testing of soil-tire mixtures will
The document summarizes a study that characterized the mechanical properties of the concrete-asphalt interface in bonded concrete overlays. Laboratory tests were conducted on composite cylindrical specimens under different temperatures, moisture conditions, and loading types. Results showed the interface stiffness was strongly related to and weaker than the asphalt stiffness. The interface softened significantly under wet conditions. Shear fatigue testing found damage occurred primarily in the asphalt, not the interface. Specimens fatigued dry recovered stiffness better than wet specimens, suggesting water exposure weakens the interface. The study provides insight into the mechanical behavior of the concrete-asphalt interface.
COMPARATIVE STUDY OF THE EFFECT OF TREATED COIR FIBER AND NATURAL RUBBER MODI...IAEME Publication
This study compares four different open graded friction course (OGFC) mixes prepared with different binders and fibers: PG 60/70 bitumen, PG 60/70 with coir fiber, natural rubber modified bitumen (NRMB), and NRMB with coir fiber. Coir fiber was surface treated to improve durability and temperature stability before being added to reduce drain down loss. Mix designs were conducted according to the NCAT procedure and laboratory tests evaluated properties like drain down, abrasion loss, and permeability. The NRMB mix with coir fiber was found to provide adequate strength and permeability while draining water quickly and was selected as the optimum mix.
This study investigates the performance of asphalt concrete mixtures modified with traditional additives like rubber, polyethylene and lime, as well as nano modifiers like nano silica and silica fume. Marshall tests, indirect tensile strength tests, direct compression tests and wheel tracking tests are conducted on samples with different modifiers to evaluate performance. An economic analysis of material costs to produce 1 ton of unmodified and modified mixtures is also conducted. Test results indicate that nano silica provides the best improvement in stability, strength and rutting resistance, while silica fume is the next best performer. However, nano silica significantly increases costs, while silica fume only increases costs by 14% compared to the unmodified mixture.
This document discusses concrete mix design and proportioning. The objective of mix design is to determine the most economical combination of materials to produce durable concrete of required strength under given conditions, using minimum cement and water. Factors considered include workability, strength, durability and economy. The principles are to use minimum cement and water while maintaining workability and quality. Concrete strength is directly related to the water-cement ratio, with lower ratios producing stronger, more durable concrete. Common mix design methods include the absolute volume method and ACI standards for different concrete types.
International Journal of Engineering Research and Applications (IJERA) is an open access online peer reviewed international journal that publishes research and review articles in the fields of Computer Science, Neural Networks, Electrical Engineering, Software Engineering, Information Technology, Mechanical Engineering, Chemical Engineering, Plastic Engineering, Food Technology, Textile Engineering, Nano Technology & science, Power Electronics, Electronics & Communication Engineering, Computational mathematics, Image processing, Civil Engineering, Structural Engineering, Environmental Engineering, VLSI Testing & Low Power VLSI Design etc.
IRJET- Modified Mix Design for Low Noise Asphalt Pavement with Recron FiberIRJET Journal
This document discusses a study on modified mix design for low noise asphalt pavement using Recron fiber. The study aimed to determine the properties of permeable asphalt pavement incorporating Recron fibers. Marshall stability tests were conducted on samples with varying fiber contents (0%, 1%, 1.5%, 2%) to determine the optimum fiber content. The results showed that stability increased with higher fiber content. Specifically, the 2% fiber content sample achieved the highest stability of 12.81 kN, indicating fibers improve the strength and durability of permeable asphalt pavement. The study concluded Recron fiber is a viable additive for enhancing the properties of low noise, permeable asphalt pavements.
Erik Updyke, project manager for the City & County Pavement Improvement Center, focuses on pavement quality for local agencies in a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Comparison of Marshall and Superpave Asphalt Design Methods for Sudan Pavemen...IJSTA
This document compares the Marshall and Superpave asphalt mix design methods. It discusses that the Marshall method currently used in Sudan may be contributing to early pavement failures. The Superpave method is performance-based and better simulates field conditions. The document reviews the key differences between the two methods, such as compaction and specimen dimensions. It then outlines a study conducted in Sudan to directly compare mix designs and properties developed using the Marshall and Superpave methods. The Superpave mixes showed better performance characteristics. Therefore, adopting Superpave in Sudan may improve pavement performance.
Dan Staebell with Cargill examines the use of WMA, RAP and other technologies to lower asphalt's carbon footprint in a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Marco Estrada with PRS provides an industry perspective of cold in-place recycling in a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Dr. Dave Jones of the University of California Pavement Research Center provides an academic perspective of in-place recycling in a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Larry Hernandez with Caltrans provides the department's perspective on in-place recycling in a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Dr. John Harvey, director, University of California Pavement Research Center, reviews the most recent research with regard to Reclaimed Asphalt Pavement during a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Buzz Powell, technical director, Asphalt Pavement Alliance, examines various trends in the industry from a national perspective in a presentation delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Chris Sparks with MacRebur delves into the utilization of reclaimed plastics into asphalt pavement mixes delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Scott Dmytrow with PavementACES, a noted pavement preservation expert, provides an update on various tools and techniques in the pavement preservation space delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Presentation by Joseph Dongo of Caltrans on the department's eTicketing initiative for construction materials transport delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Alex Richardson with Haul Hub delivers a presentation on eTicketing technology delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Presentation on Environmental Product Declarations and benchmarking delivered by Amlan Mukherjee of WAP Sustainability during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario.
Presentation by Cathrina Barros of Caltrans, co-chair of the Women of Asphalt California Branch, on Women of Asphalt Activities in 2023 and 2024 delivered during the CalAPA Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario
Presentation on the City & County Pavement Improvement Center delivered at the California Asphalt Pavement Association Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Presentation by Sean Devine of X-B-E on the "Hey NAPA" research tool utilizing AI technology, and other implications of AI for our industry, delivered at the California Asphalt Pavement Association Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
An overview of the Caltrans District 8 program and priorities delivered at the California Asphalt Pavement Association Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Update on the Joint Training & Certification Program for materials technicians in California delivered at the California Asphalt Pavement Association Spring Asphalt Pavement Conference March 7-8, 2024 in Ontario, Calif.
Presentation on "Pointers & TIps" related to Environmental Product Declarations (EPDs) from the perspective of an asphalt plant expert delivered by T.J. Young at the CalAPA EPD workshop on Oct. 25, 2023 in Sacramento.
Presentation titled "The Emerald Eco-Label Tool & Lessons Learned" delivered by Amlan Mukherjee, Ph.D., P.E. of WAP Sustainability Consulting at the CalAPA EPD workshop on Oct. 25, 2023 in Sacramento.
Presentation on the national perspective on Environmental Product Declarations (EPDs) delivered by Joseph Shacat of the National Asphalt Pavement Association (NAPA) at the CalAPA EPD workshop on Oct. 25, 2023 in Sacramento.
Presentation on "Challenges for Environmental Product Declarations (EPDs) Implementation" delivered by Dr. John Harvey of the University of California Pavement Research Center (UCPRC) at the CalAPA EPD workshop on Oct. 25, 2023 in Sacramento.
More from California Asphalt Pavement Association (20)
Introduction- e - waste – definition - sources of e-waste– hazardous substances in e-waste - effects of e-waste on environment and human health- need for e-waste management– e-waste handling rules - waste minimization techniques for managing e-waste – recycling of e-waste - disposal treatment methods of e- waste – mechanism of extraction of precious metal from leaching solution-global Scenario of E-waste – E-waste in India- case studies.
Batteries -Introduction – Types of Batteries – discharging and charging of battery - characteristics of battery –battery rating- various tests on battery- – Primary battery: silver button cell- Secondary battery :Ni-Cd battery-modern battery: lithium ion battery-maintenance of batteries-choices of batteries for electric vehicle applications.
Fuel Cells: Introduction- importance and classification of fuel cells - description, principle, components, applications of fuel cells: H2-O2 fuel cell, alkaline fuel cell, molten carbonate fuel cell and direct methanol fuel cells.
Literature Review Basics and Understanding Reference Management.pptxDr Ramhari Poudyal
Three-day training on academic research focuses on analytical tools at United Technical College, supported by the University Grant Commission, Nepal. 24-26 May 2024
Redefining brain tumor segmentation: a cutting-edge convolutional neural netw...IJECEIAES
Medical image analysis has witnessed significant advancements with deep learning techniques. In the domain of brain tumor segmentation, the ability to
precisely delineate tumor boundaries from magnetic resonance imaging (MRI)
scans holds profound implications for diagnosis. This study presents an ensemble convolutional neural network (CNN) with transfer learning, integrating
the state-of-the-art Deeplabv3+ architecture with the ResNet18 backbone. The
model is rigorously trained and evaluated, exhibiting remarkable performance
metrics, including an impressive global accuracy of 99.286%, a high-class accuracy of 82.191%, a mean intersection over union (IoU) of 79.900%, a weighted
IoU of 98.620%, and a Boundary F1 (BF) score of 83.303%. Notably, a detailed comparative analysis with existing methods showcases the superiority of
our proposed model. These findings underscore the model’s competence in precise brain tumor localization, underscoring its potential to revolutionize medical
image analysis and enhance healthcare outcomes. This research paves the way
for future exploration and optimization of advanced CNN models in medical
imaging, emphasizing addressing false positives and resource efficiency.
DEEP LEARNING FOR SMART GRID INTRUSION DETECTION: A HYBRID CNN-LSTM-BASED MODELgerogepatton
As digital technology becomes more deeply embedded in power systems, protecting the communication
networks of Smart Grids (SG) has emerged as a critical concern. Distributed Network Protocol 3 (DNP3)
represents a multi-tiered application layer protocol extensively utilized in Supervisory Control and Data
Acquisition (SCADA)-based smart grids to facilitate real-time data gathering and control functionalities.
Robust Intrusion Detection Systems (IDS) are necessary for early threat detection and mitigation because
of the interconnection of these networks, which makes them vulnerable to a variety of cyberattacks. To
solve this issue, this paper develops a hybrid Deep Learning (DL) model specifically designed for intrusion
detection in smart grids. The proposed approach is a combination of the Convolutional Neural Network
(CNN) and the Long-Short-Term Memory algorithms (LSTM). We employed a recent intrusion detection
dataset (DNP3), which focuses on unauthorized commands and Denial of Service (DoS) cyberattacks, to
train and test our model. The results of our experiments show that our CNN-LSTM method is much better
at finding smart grid intrusions than other deep learning algorithms used for classification. In addition,
our proposed approach improves accuracy, precision, recall, and F1 score, achieving a high detection
accuracy rate of 99.50%.
TIME DIVISION MULTIPLEXING TECHNIQUE FOR COMMUNICATION SYSTEMHODECEDSIET
Time Division Multiplexing (TDM) is a method of transmitting multiple signals over a single communication channel by dividing the signal into many segments, each having a very short duration of time. These time slots are then allocated to different data streams, allowing multiple signals to share the same transmission medium efficiently. TDM is widely used in telecommunications and data communication systems.
### How TDM Works
1. **Time Slots Allocation**: The core principle of TDM is to assign distinct time slots to each signal. During each time slot, the respective signal is transmitted, and then the process repeats cyclically. For example, if there are four signals to be transmitted, the TDM cycle will divide time into four slots, each assigned to one signal.
2. **Synchronization**: Synchronization is crucial in TDM systems to ensure that the signals are correctly aligned with their respective time slots. Both the transmitter and receiver must be synchronized to avoid any overlap or loss of data. This synchronization is typically maintained by a clock signal that ensures time slots are accurately aligned.
3. **Frame Structure**: TDM data is organized into frames, where each frame consists of a set of time slots. Each frame is repeated at regular intervals, ensuring continuous transmission of data streams. The frame structure helps in managing the data streams and maintaining the synchronization between the transmitter and receiver.
4. **Multiplexer and Demultiplexer**: At the transmitting end, a multiplexer combines multiple input signals into a single composite signal by assigning each signal to a specific time slot. At the receiving end, a demultiplexer separates the composite signal back into individual signals based on their respective time slots.
### Types of TDM
1. **Synchronous TDM**: In synchronous TDM, time slots are pre-assigned to each signal, regardless of whether the signal has data to transmit or not. This can lead to inefficiencies if some time slots remain empty due to the absence of data.
2. **Asynchronous TDM (or Statistical TDM)**: Asynchronous TDM addresses the inefficiencies of synchronous TDM by allocating time slots dynamically based on the presence of data. Time slots are assigned only when there is data to transmit, which optimizes the use of the communication channel.
### Applications of TDM
- **Telecommunications**: TDM is extensively used in telecommunication systems, such as in T1 and E1 lines, where multiple telephone calls are transmitted over a single line by assigning each call to a specific time slot.
- **Digital Audio and Video Broadcasting**: TDM is used in broadcasting systems to transmit multiple audio or video streams over a single channel, ensuring efficient use of bandwidth.
- **Computer Networks**: TDM is used in network protocols and systems to manage the transmission of data from multiple sources over a single network medium.
### Advantages of TDM
- **Efficient Use of Bandwidth**: TDM all
Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapte...University of Maribor
Slides from talk presenting:
Aleš Zamuda: Presentation of IEEE Slovenia CIS (Computational Intelligence Society) Chapter and Networking.
Presentation at IcETRAN 2024 session:
"Inter-Society Networking Panel GRSS/MTT-S/CIS
Panel Session: Promoting Connection and Cooperation"
IEEE Slovenia GRSS
IEEE Serbia and Montenegro MTT-S
IEEE Slovenia CIS
11TH INTERNATIONAL CONFERENCE ON ELECTRICAL, ELECTRONIC AND COMPUTING ENGINEERING
3-6 June 2024, Niš, Serbia
1. Compaction of Hot Mix Asphalt
Pavements (HMA)
Ed Lyon, PE, GE April 9, 2014
2. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
• “Compaction is the process by which the
volume of air in an HMA mixture is reduced by
using external forces to reorient the
constituent aggregate particles into a more
closely spaced arrangement. This reduction of
air volume in a mixture produces a
corresponding increase in HMA unit weight, or
density (Roberts et al., 1996). “
Compaction – Defined
3. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Quality Characteristics Affected by Compaction
– Stability / Strength
– Fatigue Life
– Durability
– Moisture Sensitivity
– Raveling
Importance of Compaction
4. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
• “Compaction is the process by which the
volume of air in an HMA mixture is reduced
by using external forces to reorient the
constituent aggregate particles into a more
closely spaced arrangement. This reduction of
air volume in a mixture produces a
corresponding increase in HMA unit weight, or
density (Roberts et al., 1996). “
Compaction – Defined
5. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
• “Compaction is the process by which the
volume of air in an HMA mixture is reduced
by using external forces to reorient the
constituent aggregate particles into a more
closely spaced arrangement. This reduction of
air volume in a mixture produces a
corresponding increase in HMA unit weight, or
density (Roberts et al., 1996). “
Compaction – Defined
The volume of air in an HMA pavement is important because it
has a profound effect on long-term pavement performance.
6. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
– Fatigue Resistance “A reduction in air voids from 8% to 3% could
more than double pavement fatigue life” (Scherocman, 1984a).
– Durability “compacting a well-designed paving mixture to low air
voids retards the rate of hardening of the asphalt binder, and results
in longer pavement life, lower pavement maintenance, and better
all-around pavement performance.” McLeod (1967)
– Raveling. Kandhal and Koehler (1984) found that raveling becomes a
significant problem above 8% air voids and becomes a severe
problem above 15% air voids.
Positive Effect of Compaction
– Moisture Damage. “Air voids in insufficiently compacted HMA are high and tend to be interconnected
with each other. Numerous and interconnected air voids allow for easy water entry which increases the
likelihood of significant moisture damage.” (Kandhal and Koehler, 1984; Cooley et al., 2002)
7. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Negative Effects of Excess
Compaction
Balance -
For dense-graded HMA, for use on high traffic pavements in place air voids
between 3 and 8 percent generally produce the best compromise of pavement
strength, fatigue life, durability, raveling, rutting and moisture damage
susceptibility.
– Decreased Stability and Strength. Kennedy et al.
(1984) concluded that tensile strength, static and
resilient moduli, and stability are reduced at low air
void content.
– Rutting. The amount of rutting which occurs in an
asphalt pavement is inversely proportional to the air
void content (Scherocman, 1984a)
8. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Aggregate Gradation
Aggregate Gradation
– Gradation has a direct affect
on the effort required to
properly compact a pavement
Fuller’s maximum density line:Passing (%) = (d/D)n ; n = 0,45 (FHWA)
9. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Aggregate Gradtaion – VMA
VMA – Voids in Mineral Aggregate
– The volume of the intergranular void space between the aggregate
particles of a compacted paving mixture that includes the air voids
and the effective binder content AASHTO R-35
HIGH VMA = High Voids, harsh or stiff mix
• High stability
• Difficult to compact
LOW VMA = Low Voids, densely graded mix
• Lower stability
• Easier to compact
10. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Relative Compaction
How are common practices set up to ensure that the finished
pavements have in place air voids between 3 and 8 percent ?
Relative compaction is the ratio expressed as a
percentage between the field in place density
and a laboratory test standard.
Relative to What Standard ?
11. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Common Practice – Specifying
Relative Compaction
LAB TEST MAXIMUM DENSITY (LTMD)
• Specified Air Voids in the lab between 3% and 5%
• Compacted Briquette ÷ Theoretical Max SpG
• Specified Relative Compaction 95% to 96% of LTMD
• Field Density ÷ Compacted Briquette
In Place Air is equal to the sum of the air voids in the lab and air voids from the field
relative compaction tests
Example: 3.5% Air Voids in the lab, 96.4% Compaction
In Place Air = 3.5% + 100% – 96.4% = 7.1 %
12. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
LTMD - Marshall Method
• Mechanically Compacts Briquettes in steel molds using the
Impact from the Marshall Hammer.
• Mix Design based on optimum asphalt content that yields air
voids in the compacted briquettes of 4% when comparing
briquette density to Rice Theoretical Density
The density of the compacted briquette
is used as the specified Lab Test
Maximum Density (LTMD ) for
comparison to determine the relative
compaction
13. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
LTMD California Kneading Compactor
Hveem Method
• Mechanically Compacts Briquettes in steel molds using the
California Kneading Compactor.
• Mix Design based on optimum asphalt content that yields
air voids in the compacted briquettes between of 4%
when comparing briquette density to Rice Theoretical
Density
The density of the compacted briquette
is used as the specified Lab Test
Maximum Density (LTMD ) for
comparison to determine the relative
compaction
14. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Common Practice – Specifying
Relative Compaction
Theoretical Maximum Specific Gravity:
– Specify a minimum in place relative compaction equal to 92% of the Theoretical
Maximum Specific Gravity, commonly referred to as the Rice Test
– Field Tests are performed by Nuclear Gauge or Cores
– % Relative Compaction is the ratio expressed as a percentage between the in
place density of the compacted pavement and the Rice maximum specific gravity.
Agencies May specify a maximum in
place relative compaction on the order
of 96 to 97% to preserve stability in
areas of heavy traffic
15. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Theoretical Maximum Specific
Gravity - Rice
• Measures the specific gravity of a loose mixture of
the HMA after all of the air in the mix has been
removed under vacuum.
• Used in all mix design methods to select the
design asphalt content that yields air voids in
compacted briquettes between 3 and 5%
16. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Gyratory Compactor
Super Pave Method
• Mechanically Compacts Briquettes in larger steel molds
using the Gyratory Compactor.
• Mix Design based on optimum asphalt content that yields
air voids in the compacted briquettes of 4% when
comparing briquette density to Rice Theoretical Density.
• Specifies a Minimum VMA – stiffer mixes
Theoretical Maximum Specific Gravity
(Rice) test used for comparison to field
density to determine the relative
compaction
17. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
YOUR QUESTIONS
Thank you for your attention.
18. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Hamburg Wheel Tracking Device
Super Pave Method
Editor's Notes
Good afternoon, my name is Ed Lyon and I am a registered civil engineer and registered geotechnical engineer in California. I am thrilled to be here today to discuss compaction of hot mix asphalt pavements. This is a very broad subject so this afternoon I will be focusing my presentation on three areas. First I want to spend some time discussing the importance of compaction and its impact on the long term performance of a pavementSecond I will be discussing aggregate gradation and its impact on compaction and pavement performance And Finally I am going to review the common practice in use to specify relative compaction and how they are used to achieve long term pavement performance.
First lets start off with a good working definition of compaction. Read definition:Compaction is the process of rearranging the aggregate and binder in the loose mix into a dense interlocking matrix while driving air out of void spaces the mix increasing the density or unit weight of the mix and creating a stable finished surface
It has been said that compaction is the single most important factor that determines long term pavement performance. That is due to the fact that the degree of compaction accomplished affects many of the key pavement properties that drive performance.Compaction will affect the Satbility / Strength of the pavemnetIt has a direct relationship to the pavements ability to resist repetitive fatigue loadsIt will directly affect the pavements durability or resistance to weathering and it ability to resist moisture damage and proper compaction will prevent raveling of the pavement.To understand how compaction can positively or negatively impact these quality characteristics lets go back to our definition
Compaction is the process by which the volume of air in the HMA Mixture is reducedSo essentially the extent to which the HMA is compacted in the field will determine the volume of air left in the completed pavementsPoorly compacted pavements will have a high volume of air remaining in the completed mixDensely compacted pavements will have a low volume of air in the completed mix
And the volume of air in an HMA pavement is really the characteristic that drives the long term performance of the pavementSo when we talk about compaction and how it affects pavement performance we are really talking about the volume of air, or air voids, in the completed pavements and how that will affect the long term performance of the pavement
A densely compacted pavement will have low in place air voids the benefits of low in place air voids have been demonstrated through numerous studies and they include: Improved Fatigue resistance: The tensile strength of the pavement is derived from the binder and in order to resist fatigue loads the pavement needs good tensile strength and the horizontal stresses imposed on the bottom of the pavement layer are pulling stresses that result in fatigue cracking. To more the mix is compacted the fewer air voids are present allowing the binder to carry those forces and remain elastic.Durability or the pavements resistance to weathering is improved by low air voids as it has been shown that low air voids slow the rate of hardening of the binder and extends the time during which the pavement remains flexible extending the life and performance of the pavement Poorly compacted mixes have a high volume of air that can lead to raveling. Studies have shown that raveling begins to become an issue at 8% air voids. Well compacted mixes will have less than 8% air and will not be subject to raveling Finally sensitivity to moisture damage can be improved by proper compaction
However you can have to much of a good thing. There are negative affects to driving the air voids out of the mix or over compacting a pavement.Stability is the pavements ability to resist lateral deformation under vertical loads. It is primarily derived from the shear strength of the aggregates. As you begin to compact an HMA pavement from a loose state you increase the stability and strength of the mix as you force the aggregate into a tight matrix.As you continue to compact a pavement to low air void content, lower than 3%, the binder is called to carry larger portions shear strength and the pavement will experience reduced stability and reduced resistance to rutting.Therefore, to achieve long term pavement performance it is important to find balance between the positive benefits of low air voids and the air voids required to ensure the stability and strength of the mix
Understanding the importance of air voids in the mix we can also demonstrate how aggregate gradation will impact the performance of the pavements and the effort required to compact the pavement. The FHWA Power 45 Curves define the ideal gradation that will yield the greatest density when compacted. These curves represent the aggregate gradation that will most easily combine as each of the various particle sizes in the mix interlock and the smaller fractions ideally fill the voids between the larger particles resulting in the tightest spacing possible between coarse to fine for a given maximum aggregate size.Mixes designed with gradations that fall along these curves will be very easy to compact in the field and will have low oil demands as the tight arrangement of the aggregates removes leaves a low volume of air remaining to be filled by binderAs with compaction though we again can have too much of good thing. Mixes that are designed along these lines may have too few voids to provide the necessary volume of air in the pavement to ensure stability.So some agencies will specify a minimum VMA to force the gradation away from the ideal curves
The VMA or Voids In Mineral Aggregate is the volume of voids in the aggregate including the volume occupied by air voids and the volume filled by binder that was not absorbed by the aggregate.So in order to ensure that the mix contains sufficient voids to provide a stable mix agencies specify a minimum VMA. The higher the VMA the further away from the ideal power 45 curves the gradation will fall meaning that the aggregates will not interlock as well and will therefore be more difficult to compact.High VMA Mixes will be harsh or stiff mixes that tend to have higher stability but they will be more difficult to compact in the field Low VMA mixes will be densely graded they may have lower stability but they will be much easier to compact in the field The design aggregate gradation selected based on a VMA specification is driven by the same goals for long term pavement performance and the need for balance between stability and durability. Compaction of the pavement is the final step that determines how well we achieve that balance.
So how are the specifications that we work with every day set up to verify that this balance have been achieved?Our specifications call out Relative Compaction. We defined compaction as the process of compacting the pavements and reducing the air content of the mix, but what is relative compaction.Percent relative compaction is the ratio between the field in place density So when we talk about relative compaction it is important to ask the question Relative to What ??
There really are two general ways that our specifications have been developed The first is a two step process where we specify air voids in the lab and then specify relative compaction in the field based on a Lab Test Maximum Density In the mix design stage we compact briquettes at varying oil contents and compare the their density to whats called the maximum theoretical specific gravity to select the oil content that results in 4% air in the lab During construction we see specifications that require tests to determine the air voids and limit them to 2 to 5% We then we use the density of the compacted briquettes as the lab test max density the LTMD and compare that to the field densityto determine relative compaction
There are three common mix design procedures in use today that include the marshall method, the hveem method and the super pave method of mix design.
The maximum specific gravity is the combined specific gravity of the aggregate which are typically 2.6 to 2.8 and the binder which are typically 1.01 so the values are inversly related to binder content. The higher the percent binder the lower the maximum theoretical specific gravity.This test never compacts the mix – in fact its important that the test be run on a sample that is loose so that the air in the mix can be removed easily. The test measures the maximum specific gravity by removing all of the air in the mix under vacuum. It can be a sensitive test and it is driving the evaluation of the overall long term performance of the pavement so it is important that the test be run carefully.It is sensitive to the time that the test is run. It needs to be run long enough to completely remove the air from the test vessel, any air remaining in the container will be included in the calculated volume of the materials tested.All of our mix design procedures use the Maximum theoretical specific gravity test, commonly referred to as the Rice test, to determine the maximum density that defines the percent air voids in the mix.