Week 6 Lecture-Introduction to Asphalt Concrete PDF

CIVL 1012- Civil Engineering Materials​ Week 6 Introduction to Asphalt Binders & Asphalt Mixtures Dr. Raheleh Alizadeh Angelo DelZotto School of Construction Management  Learning o...

CIVL 1012- Civil Engineering Materials​ Week 6 Introduction to Asphalt Binders & Asphalt Mixtures Dr. Raheleh Alizadeh Angelo DelZotto School of Construction Management  Learning objective In this chapter you will learn about: Types of Asphalt Cement Products Asphalt Distillation Process and Chemistry Uses of Asphalt Classification of Asphalts Grades of Asphalt Cement Asphalt Characteristics Additives and Fillers https://images.app.goo.gl/yMnecv1f9ruUXS8Q9 Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 2  Introduction to Bituminous Materials Before mid-1850s from natural pools (Trinidad lake asphalt, etc.) Later, produced from refining petroleum Nowadays, practically all asphalt cement is from refined petroleum Bituminous materials Asphalt Tar - Usually refined from petroleum oil - By destructive distillation of bituminous coal or by cracking - Used in pavements, sealing and petroleum vapors waterproofing agents. - Used for waterproofing, for pavement treatments such as parking lots and airport aprons. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 3  Asphalt Distillation Process Petroleum is heated then piped into a distillation column; Different Products separate at different temperatures; Asphalt is a lower valued product than other components of crude oil. Quantity and quality of asphalt depends on crude petroleum source and refining method. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 4  Asphalt Chemistry Bituminous materials are hydrocarbons. Major Minor Compounds Heteroatoms Compounds Very complex chemical composition Carbon Sulfur, Nitrogen, depends on the oil source and refining. Oxygen method. Hydrogen Trace metals Mostly hydrogen & carbon atoms Asphalt Molecular structure affects the physical and aging properties of aggregate. Asphalt Cement Asphaltenes: dark brown friable solid, responsible for viscosity and adhesive property Maltenes: resins and oils, dark, semisolid or solid, with a viscosity largely affected by temperature. Acts as agents to disperse asphaltenes in the oils. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 5  Asphalt Cement Products for Pavements A blend of hydrocarbons of different molecular weights. ASPHALT CEMENT Semi solid at room temperature, must be heated to apply as a binder (Asphalt binder) Used for Hot Mix Asphalt (HMA), Warm Mix Asphalt (WMA), patching Most common Produced by dissolving asphalt cement in a lighter molecular weight ASPHALT CUTBACK hydrocarbon solvent (Liquid asphalt product) Used for Cold Mix & maintenance applications. In past, widely used for pavement construction Produced by dispersing asphalt in water as emulsion (60%-70% asphalt ASPHALT EMULSION cement, 30%-40% of water and a fraction of a % of emulsifying agent) (Liquid asphalt product) Emulsifying agents are usually a soap material Used for cold mix & maintenance applications Note: Liquid asphalt is more convenient, but they cannot produce a quality of asphalt concrete comparable to what can be produced by heating neat asphalt cement and mixing it with carefully selected aggregate Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 6  Asphalt Cement (Binder) Adheres well to most rocks Waterproof Fairly durable Resistant to reaction with most acids, alkalis, and salts Temperature sensitive Asphalt binder is a visco-elastic material Viscous at high temps, like a fluid Elastic at low temps, like a solid Its characteristics depend on both temperature and loading rate Subgrade Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 7  Asphalt Cutback Cutback is sprayed on a pavement or mixed with aggregate, the solvent Asphalt Asphalt evaporates, leaving the asphalt Solvent Cement Cutback residue as the binder. Cold mix maintenance, patching, chip seals, crack sealing and surfacing low volume roads Advantage Easy to apply Disadvantages Not cost-effective because solvents are produced from petroleum and expensive Hazardous, volatile solvents Hydrocarbons are released into atmosphere Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 8  Asphalt Emulsion Asphalt Emulsifying Asphalt Cement Water Agent Emulsion Many of the same uses as cutback, Emulsion is preferred over cutback because of followings: ▪ Safer ▪ Environmentally better ▪ Might be slightly more economic (solvents are cheaper) ▪ Used with damp aggregates Minute droplets of asphalt cement dispersed in a water medium 9  Hot Mix Asphalt Fog Seal Chip Seal Mamlouk/Zaniewski,Materials Mamlouk/Zaniewski, MaterialsforforCivil Civiland andConstruction ConstructionEngineers, Engineers,Fourth FourthEdition. Edition.Copyright Copyright©©2016 2017Pearson PearsonEducation, Education,Inc. Inc. 10  Temperature Susceptibility of Asphalt The consistency of asphalt is highly affected by temperature ✓ Gets hard and brittle at low temperature ✓ Gets soft at high temperature Thermal Cracking Too brittle  Thermal cracking Too soft  Rutting Rutting Slope indicates degree of asphalt’s temperature susceptibility The steeper the slope, the higher the temperature susceptibility of the asphalt 11  Temperature Susceptibility of Asphalt Asphalt comes in different grades (soft and hard) The grade of the asphalt cement should be selected according to the climate of the area (optimum range for annual area’s temperature range. Soft grade asphalt Hard grade asphalt (low viscosity) (high viscosity) Used in cold climates Used in hot climates to avoid thermal to avoid rutting cracking Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 12  Softening Point, Flash Point, Fire Point Softening Point: The temperature at which an asphalt sample can no longer support the weight of a 3.5 g small steel ball. Helps to find the temperature up to which a bitumen binder should be heated for different road applications. https://images.app.goo.gl/6NrXKgjAMDkvsZgv9 Flash point: Fire Point: At high temperature, asphalt can flash/ignite in The lowest temperature at presence of open flame or spark. Flash point is the which the vapor of bitumen lowest temperature at which vapor of bitumen binder binder will continue to burn catches fire in the form of flash under certain conditions for at least five seconds after of the test. At this point, just a flash will appear for a ignition by an open flame of fraction of second and fire will not last longer standard dimension. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 13  Asphalt Age Hardening Asphalt age hardening (asphalt durability): The viscosity of asphalt binder increases when asphalt ages and asphalt binder becomes stiffer and more brittle. It may happen due to oxidation, heat, UV light,.. Asphalt aging affects its durability and results in high potential for cracking. Two stages of aging: First stage: happens when asphalt mixture is produced at a very high temperature at a very fast rate (short-term aging). During this stage, a very thin film of asphalt is exposed to air at elevated temperatures, leading to a significant change in the rheological properties of the asphalt binders. Second Stage: happens when the asphalt is exposed to environment for example under the service; especially when pavement is subjected to a relatively lower temperature for a long period of time. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 14  Asphalt Grading 1. Asphalt binder Current Performance grading (PG) Penetration grading (PEN) History Viscosity grading (AC) Aged residue grading (AR) Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 15  Superpave & Performance Grade Binders Strategic Highway Research Program (SHRP) in 1987 began developing a new system for specifying asphalt materials and designing asphalt mixes. SHRP To extend the life of asphalt pavement Objectives Reduce the life-cycle costs of asphalt pavements Reduce maintenance costs Minimize premature failures SHRP research program produced Superpave (Superior Performing Asphalt Pavements) mix design method for asphalt concrete Performance Grading method for asphalt binder specification Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 16  Asphalt Binders Performance Grading (PG) Grading based on binder performance in the field. Intended to improve pavement performance by reducing the potential to: Permanent deformation Fatigue cracking Low-temperature cracking Excessive aging from volatilization PG # - # Pumping and handling Low-temperature grade High-temperature grade Performance Graded Starts with PG followed by 2 numbers: max & min pavement service temperatures in Celsius PG 52-28: designed for 52oC to -28oC High is measured 20 mm (3/4") below pavement surface, low is measured at surface Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 17  Asphalt Binders Performance Grading Adjustment Binder grades in Performance Grade Specifications Number of increases in high-temperature grade for Design ESALs Traffic Speed km/h different combinations of traffic loads & speeds (million) 70 30 2 1 1 First design based on temperature: PG 64-22 10 million ESALs & 50 km/h speed: PG 70-22 ESAL: (Equivalent Single Axel Load) pavement design factor used in the design of 40 million ESALs & 15 km/h speed? pavement, considers traffic volume and loads. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 18  Asphalt Binders Penetration Grades (PEN) 40-50 60-70 85-100 120-150 200-300 #-# maximum penetration minimum penetration Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 19  Penetration Test Measures consistency of binder using a weighted needle loaded for 5 sec (in 25˚ C). https://images.app.goo.gl/xGdo9TTcJ1Z2J5hbA The depth of penetration is measured in units of 0.1 mm and reported in penetration units Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. www.controls-group.com/eng/bitumen-testing-equipment/penetrometer-fully-automatic-model-_-pivot_.php 20  Asphalt Binders Viscosity (AC) Grades Grade Absolute Viscosity (Pa.s) AC-2.5 AC-5 50±10 AC-10 100±20 AC-20 200±40 AC-30 300±60 AC-40 400±80 AC- # 1/10 of midpoint of the allowable viscosity range (e.g., AC-20, viscosity range 160-240 Pa.s) Asphalt cement Note: High viscosity asphalt cement has a high designation number. Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 21  Asphalt Binders Viscosity of Aged Residue (AR) grades Grade Absolute Viscosity (Pa.s) AR-10 AR-20 200±50 AR-40 400±100 AR-80 800±200 AR-160 1600±400 AR- # 1/10 of midpoint of viscosity after aging (e.g., AR-40, viscosity range 300 to 500 Pa.s) Aged Residue Based on the absolute viscosity of the asphalt after it has been conditioned to simulate the effects of the aging that occur when the asphalt cement is heated to make asphalt concrete Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 22  Asphalt Grading 2. Asphalt Cutbacks Types of RC: Rapid Curing 5-10 min Cutbacks MC – # MC: Medium Curing few days SC: Slow Curing few months Viscosity M = medium curing, R = rapid curing, Viscosity at 60⁰C: 30, 70, 250, 800, & 3000 S = slow curing (higher grade is higher viscosity), result of varying amount and type of solvent. RC-70 RC-250 RC-800 RC-3000 MC-30 MC-70 MC-250 MC-800 MC-3000 SC-70 SC-250 SC-800 SC-3000 Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 23  Asphalt Grading 3. Emulsion Grading by setting time and viscosity: RS: rapid setting: 5-10 min CMS – 1 h MS: medium setting : several hours SS: slow setting: few months h: hard asphalt residue 1,2: indicates emulsion viscosity Viscosity = 1 or 2 (2 is high viscosity of the MS: medium set, R:rapid, S: slow emulsion) C = cationic, HF = high float Anionic – negative charge Cationic – positive charge h: hard MS – 1 h h: hard asphalt residue 1,2: indicates emulsion viscosity CSS1 MS: medium set, R:rapid, S: slow CSS1H Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 24  Asphalt Concrete Asphalt Asphalt Aggregate Binder Concrete Aggregate and asphalt binder mixed together at a high temperature and placed and compacted on the road while still hot. HMA Mixed at temperature of 135-160°C High energy cost Environmental concerns WMA Mixed at temperature of 110- 130°C Asphalt Concrete is produced in batch or drum plants Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 25  Warm Mix Asphalt, advantages WMA is produced and applied at a temperature around 20 – 40 °C lower than an equivalent “Hot Mix Asphalt Less energy and fuel consumption to heat the mix Lower green house gases Less oxidation of the asphalt binder Pave at lower temperature Extending the paving season since the asphalt can be compacted at lower temperature 26  Asphalt Concrete Desirable Properties Stable: Resistant to thermal Resist permanent Fatigue resistant: cracking: deformations under load Due to contraction at low Under repeated loading and high temperature temperatures Resistant to hardening or Resistant to moisture aging: induced damage: Skid resistant: During production and in Stripping of asphalt from By texturing surface service aggregate Workable: Ease of mixing, placing, Economical compacting Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 27  Asphalt Concrete Mix Design To determine the design asphalt content using the available asphalt and aggregate Varies for: material types, material properties, loading level and environmental conditions Evaluation of Selection of design Selection of design Determine design moisture sensitivity aggregate structure asphalt grade binder content of mix Typical design asphalt contents: 4-7% by weight of total mix. Not enough binder: All aggregate particles will not be coated with asphalt: less stable & less durable pavement Too much binder: Too much lubrication between aggregate and particles move under load: less stable material Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 28  Asphalt Concrete Mixing Methods Mixing Methods Marshall Hveem Method Method Superpave Method ASTM D1559 ASTM D1560 Marshall and Hveem: Commonly used before Superpave method development; Marshall was more common compared to Hveem, because of its simplicity and ability to use for field control; They are not adoptable to new conditions, such as modified binders, large- sized aggregate and heavier traffic loads Superpave: It is performance based and more rational than Marshall and Hveem 29  Superpave Mix Design: Aggregate Selection Source properties Soundness Toughness Stockpiles evaluated Deleterious materials Consensus properties (depends on traffic level and depth) Gradation ▪ Curve must pass through control points Blend requirements ▪ Blend stockpiles Coarse aggregate angularity (min. % crushed particles) Fine aggregate angularity Flat & elongated particles: max. Sand equivalency: need clean aggregates Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 30 Aggregate Blend Requirements 31  Aggregate Blend Requirements Course Fine Aggregate Aggregate Flat and Sand Angularity Angularity Elongated Equivalency Design Level (% min) (% min) (% max) (% min) Light Traffic 55/- — — 40 Med. Traffic 75/- 40 10 40 Heavy Traffic 85/80 45 10 45 Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 32  Superpave Mix Design: Binder Selection Based on service temperatures mainly and modify for traffic volume and traffic speed: Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 33  Specimen Compaction for Mix Design Superpave and Marshall asphalt concrete mix design methods use different types of compaction: Marshall hammer Superpave Mix Design : Gyratory compactor Marshall Mix Design: Marshall hammer Gyratory compactor Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 34  Superpave Mix Design: Evaluate moisture susceptibility Using Design Aggregate Structure and Design Binder Content prepare six compacted samples Three specimens are conditioned by vacuum saturation and freezing-thawing, three other samples are not conditioned Measure indirect tensile strength by Marshal stability machine Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc.  Marshall Stability Test Marshal stability of asphalt concrete: The maximum load the material can carry when tested in the Marshall apparatus at the temperature of 60°C Marshal Flow: The deformation when loads start to decrease, reported in units of 0.25 mm 2𝑃 𝜎𝑡 = 𝜋𝑡𝐷 𝜎𝑡 : 𝑡𝑒𝑛𝑠𝑖𝑙𝑒 𝑠𝑡𝑟𝑒𝑛𝑔𝑡ℎ P: Load at failure t: thickness of specimen D: diameter of specimen Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 36  How to improve TSR? Increasing asphalt content Altering Using a higher aggregate viscosity gradation If asphalt content TSR8% => permeability problems Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2016 Pearson Education, Inc. 42  Additives Improve properties of asphalt binder or asphalt concrete/to add special properties to asphalt concrete mix Lab and field tests to evaluate effect of additive and justify cost 1. Fillers Improve gradation, stability, binder-aggregate bond, or to fill voids Crushed fines, Portland cement, lime, fly ash, & carbon black 2. Extenders To reduce amount of asphalt and therefore its cost Sulfur & lignin 3. Antistripping Agents Improve bond between asphalt binder and aggregates specially for moisture resistance Lime or Portland cement Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 43  Additives 4. Polymer Modified Asphalt Rubber based: Increase elasticity and stiffness, increase the bond between aggregate and asphalt Natural rubber, SBS (styrene-butadiene-styrene), recycled tire rubber, etc. Plastic based: Increase stiffness of the mix, reducing the rutting potential, may reduce the temperature susceptibility and improve its performance at low temperature polyethylene, polypropylene, polyvinyl chloride (PVC), etc. 5. Others To improve strength and stiffness Fibers, oxidants, antioxidants, hydrocarbons Mamlouk/Zaniewski, Materials for Civil and Construction Engineers, Fourth Edition. Copyright © 2017 Pearson Education, Inc. 44  Videos: Superpave Gyratory Compactor Process https://www.youtube.com/watch?v=WGFrWlG29Ak Marshal Stability Test https://www.youtube.com/watch?v=1P7-6lJUITo 45 Questions?