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Chapter3 road pavement
 

Chapter3 road pavement

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    Chapter3 road pavement Chapter3 road pavement Presentation Transcript

    • CHAPTER 3 : PAVEMENT MATERIALS• Road surface or pavement is thedurable surface material laiddown on an area intended tosustain vehicular or foottraffic, such as a road or walkway.• In the past cobblestones andgranite setts were extensively used,but these surfaces have mostly beenreplaced by asphalt or concrete. 1
    • MATERIAL USED IN HIGHWAY CONSTRUCTIONI. Aggregateii. Bitumen and asphaltiii. Tariv. Cementv. Steel reinforcement. 2
    • AGGREGATE•Coarse particulate material used inconstruction, including sand, gravel, crushedstone, slag, recycled concrete and geosyntheticaggregates.•Aggregates are a component of composite materialssuch as concrete and asphalt concrete•Aggregate serves as reinforcement to add strength to theoverall composite material.•Due to the relatively high hydraulic conductivity value ascompared to most soils, aggregates are widely used indrainage applications such as foundation and frenchdrains, septic drain fields, retaining wall drains, and roadside edge drains.•Aggregates are also used as base material underfoundations, roads, and railroads. 3
    • • Has been widely used since 1920–1930.•The terms asphalt and bitumen are often used interchangeably tomean both natural and manufactured forms of the substance. BITUMEN In AND ASPHALTAmerican English, asphalt (or asphalt cement) is the carefully refinedresidue from the distillation process of selected crude oils. Outsidethe U.S., the product is often called bitumen.•The viscous nature of the bitumen binder allows asphalt concrete tosustain significant plastic deformation, although fatigue from repeatedloading over time.• Most asphalt surfaces are laid on a gravel base.• In areas with very soft or expansive subgrades such as clay or peat,thick gravel bases or stabilization of the subgrade with portlandcement or lime may be required.•Asphalt is categorized as hot mix asphalt (hma), warm mix asphalt,or cold mix asphalt.•Hot mix asphalt is applied at temperatures over 300 F• Warm mix asphalt is applied at temperatures of 200 to 250 degreesF•cold mix asphalt is often used on lower volume rural roads, wherehot mix asphalt would cool too much on the long trip from the asphaltplant to the construction site.•Advantages: low noise, relatively low cost comparedwith other paving methods, and perceived ease of repair.• Disadvantages:less durability than other pavingmethods, less tensile strength than concrete, the tendencyto become slick and soft in hot weather and a certain amount ofhydrocarbon pollution to soil and groundwater or waterways. 4
    • CEMENT•Cement is a binder, a substance that sets and hardensindependently, and can bind other materials together.•The word "cement" traces to the romans 5
    • PORTLAND CEMENT•Cement is made by heating limestone (calcium carbonate) withsmall quantities of other materials (such as clay) to 1450 C in akiln.•The resulting hard substance, called clinker, is then ground witha small amount of gypsum into a powder to make OrdinaryPortland Cement, the most commonly used type of cement (oftenreferred to as OPC).•Portland cement is a basic ingredient of concrete, mortar andmost non-speciality grout.•The most common use for Portland cement is in the production ofconcrete. 6
    • STEEL REINFORCEMENT•Also known as reinforcingsteel, reinforcement steel, or a deformedbar, is a common steel bar, and iscommonly used as a tensioning device inreinforced concrete and reinforcedmasonry structures holding the concrete incompression.•usually formed from carbon steel, and isgiven ridges for better mechanicalanchoring into the concrete.•Rebar is available in different grades andspecifications that vary in yieldstrength, ultimate tensilestrength, chemical composition, andpercentage of elongation.•The grade designation is equal to theminimum yield strength of the bar in ksi(1000 psi) for example grade 60 rebar hasa minimum yield strength of 60 ksi. Rebaris typically manufactured in grades 740, 60, and 75.
    • Types And Grades Of AggregateThree main types of rock are used to producecrushed rock aggregates:IgneousSolidified molten rocks (eg basalt, granite)Sedimentary Created by settlement of particles (eg gritstones) ororganic remains (eg limestone) in ancient seasMetamorphic Created by heat or pressure (eghornfels, quartzites) 8
    • TYPES OF TESTS ON MATERIALSa.Aggregate Impact Value Testb. Polished Stone Value Testc. Aggregate Crushing Value Testd. Flakiness Index Teste. Elongation Testf. Penetration Testg. Softening Testh. Viscosity Testi. Flash and Fire Point Testj. Ductility Testk.Floatation Testl. Soundness Test. 9
    • Aggregate Impact Value Test BS 812: Part 112: 1990• Determine aggregate resistance due to impact.• Size aggregate : passing sieve 14mm and retain 10 mm.• Agregate were filling into mould in one layer and will bedriven by rod in 25 times.• Aggregate mass will be taken.•Hammer with 13.5 to 14 kg will be release from the heightof 380mm and will driven in a 15 times on aggregate.• After finished, aggregate will be sieve with size of sieveis 2.36 mm.• AIV were determine with a formulae :AIV = mass of aggregate passing sieve of 2.36 mm x 100% total mass< 30 % - pass>30 % fail 10
    • Polished STone Value Test• Only conducted on aggregate that be used as a wearing coarse.• Polishing value of aggregate show of aggregate resistance due towheel vehicles.• Polishing level affect skid resistance of pavement.• This test consist 3 stages:i. Sample preparationii. Polishing sampleiii. Skid resistance measurement. 11
    • Aggregate Crushing Value Test BS812 : Part 110 : 1990• To determine the strength of aggregate resistance to crushingunder the applied compressive load.• Normal size : passing 14 mm sieve and 10 mm retain ( 3000 g )• Aggregate were fill into mold in three layers and each layer weredriven by 25 times.•Then inserted into the compression machine for 10 minutes andwill be compress by 400 KN load.• Aggregate will be sieve in in 2.36 mm sieve and the mass will bedetermined.ACV = mass of aggregate passing sieve of 2.36 mm x 100 % total mass 12
    • Elongation Index BS812 : Part 1: 1975• To determine the percentage of the longest aggregate.• Classified longest when longest dimension is more than 1.8times from average size.• Aggregate size to be tested is 63 mm to 6.3 mm.EI = Retain mass x 100 % Total mass 13
    • Flakiness Index Test BS 812 : Section 105.1 : 1989•Purpose : To determine percentage of flat aggregate.• Classified as flat when the thickness is less than 0.6 of average size.• Aggregate to be tested is in size of 63 mm to 6.3 mmFI = Mass of aggregate passing x100 % Total mass 14
    • Penetration Test (AASHTO T49-84)•To determine the hardness of the material.•Defined as the distance (in 1 / 10) standard needle punctureof the time, load and temperature are known.•Using a standard needle under the load of 100 grams for 5seconds at a temperature of 20 degrees celsius.•High penetration value indicates the material is soft. 15
    • SOFTENING TEST•To determine the temperature at whichphase changes occur in the bitumen.•Soft spot is defined as the temperature atwhich bitumen is unable to support thesteel ball and began to soften. 16
    • VISCOSITY TESTTo determine the viscosity of the bitumen.Defined as the resistance of a fluid to flow.Two types of viscosity : absolute ordynamic viscosity and kinematic. 17
    • Flash and Fire Point TestWhen the bitumen is heated at hightemperatures, the vapor will be liberatedand embrace if any sources of ignition.Flash point indicates the temperature atwhich bitumen can be heated withoutdanger of fire generated in the presence ofthe fire.The method used is the Cleveland opencup method. 18
    • DUCTILITY TESTThis test is done to determine the ductilityof distillation residue of cutback bitumen,blown type bitumen and other bituminousproducts as per IS: 1208 – 1978. Theprinciple is : The ductility of a bituminousmaterial is measured by the distance in cmto which it will elongate before breakingwhen a standard briquette specimen of thematerial is pulled apart at a specifiedspeed and a specified temperature.The apparatus required for this test:i) Standard mouldii) Water bathiii) Testing machine 19
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    • Objectives of asphalt mix designThe design of an asphalt mix is largely a matter ofselecting and proportioning materials to optimisethe engineering properties in relation to the desiredbehaviour in service.Procedures for designing asphalt mixes have beengenerally developed around testing of dense gradedmixes and determination of optimum bindercontent, although most tests can be used for other mixtypes with suitable interpretation of results.The overall objective for the design of dense gradedasphalt paving mixes is to determine (within thelimits of project specifications) a cost-effectiveblend and gradation of aggregates and binder thatyields a mix 21
    • Characteristics of asphaltic concrete mix1.Sufficient binder to ensure a durable pavement;2. Sufficient mix stability to satisfy the demands oftraffic without distortion or displacement;3. Sufficient voids in the total compacted mix to allowfor a slight amount of in place compaction by traffic andbitumen expansion due to temperature increases,without flushing, bleeding and loss of stability;4. A maximum void content to limit the permeability ofharmful air and moisture into the mix;5. Sufficient workability to permit efficient placementof the mix without segregation and without sacrificingstability and performance;6. For surface mixes, proper aggregate texture andhardness to provide sufficient skid resistance. 22
    • An overview of the design processAsphalt mix design involves the following basic stepsthat are similar in concept, regardless of the actualtests and procedures used:1. Selection of mix type.2. Selection of component materials.3. Combination of aggregates to meet target grading.4. Selection of target binder content or range.5. Mixing and compaction of asphalt mix to a densitythat is representative of in-service conditions.6. Measurement of volumetric properties ofcompacted mix.7. Mechanical testing of compacted samples, ifrequired.8. Verification of design properties on samples ofmanufactured asphalt, if required.9. Selection of Job Mix. 23
    • MARSHALL MIX DESIGN METHOD- Developed by Bruce Marshall & the U.S.Corps ofEngineers.Objective: To determine the optimumasphalt content fora particular aggregate blend and asphalt tobe used. 24
    • PROCEDURES:1. Prepare asphalt concrete specimens (4 inches indiameter & 2.5 inches in height) for a range of asphaltcontent at and near the estimated optimum asphaltcontent.(A) Mixing temperature:at asphalt viscosity of 170 20 cSt(B) Compaction temperature:at asphalt viscosity of 280 30 cSt(C) Compactive Effort:35, 50 or 75 blows with a Marshall hammer(10 lbs, 18 inches drop) on each side of the specimen.(D) Number of Samples:3 replicates at each asphalt contentTypically, 5 different asphalt contents are used. 25
    • ADDING ASPHALT TO AGGREGATE 26
    • MIXING OF AGGREGATE AND ASPHALT 27
    • Placing asphaltmixture in acompactionmold 28
    • Proving RingFlowmeter Breaking Head 29
    • 4. Plot(A) Marshall Stability v.s. % Asphalt(B) Marshall Flow v.s. % Asphalt(C) % Air Voids v.s. % Asphalt(D) Bulk Density v.s. % Asphalt(E) % VMA v.s. % Asphalt(F) % VFA v.s. % Asphalt5. Obtain % Asphalt at 4% air voids 30
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    • % AC at 4% air voids: 6.76. Verify mix design criteria at the optimumasphalt content. The five mix criteria tocheckagainst are:(A) Marshall stability(B) Marshall flow(C) Air Voids(D) VMA(E) VFA 32
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