LECTURE ON BITUMINOUS PAVING MIX

KINDS OF PAVEMENT 1.Rigid-Type Pavement -Concrete Pavement -Concrete Mix -Cement + aggregates + water -Design Mix2.Flexible Type Asphalt Pavement -Asphalt Pavement - Bituminous Mix - Asphalt + mineral aggregates - Job Mix

ASPHALT PAVEMENTS - pavements consisting of a surface course of mineral aggregate coated and cemented together with asphalt cement on supporting course such as asphalt bases, crushed stone, slag or gravel or on Portland cement concrete brick or block pavement. ASPHALT OVERLAY - one or more courses of asphalt construction on an existing pavement. -generally includes a leveling course to correct the contour of the old pavement followed by uniform course or courses to provide needed thickness - when overlaying rigid type pavement the overlay should be not less than four inches to minimize reflection of cracks and joints through the overlay. - greater thickness of overlay may be required depending upon conditions of old pavement and traffic to be served.

COURSES OF ASPHALT AGGREGATE MIXTURE 1.ASPHALT BASE COURSE A foundation course consisting of mineral aggregate, bound together with asphaltic material.2.ASPHALT INTERMEDIATE COURSE (BINDER COURSE) - a course between a base course and an asphalt surface course.3 ASPHALT SURFACE COURSE (WEARING COURSE) - the top course of an asphalt pavement.4.ASPHALT LEVELING COURSE - a course (asphalt-aggregate mixture) of variable thickness used to eliminate irregularities in the contour of an existing surface prior to superimposed treatment or construction.

ASPHALT PAVEMENT STRUCTURES(Flexible Pavement Structure)- courses of asphalt aggregate mixtures plus any non-rigid courses between the asphalt construction and the foundation or sub-grade. FLEXIBLE - The term sometimes used in connection with asphalt pavements denotes the ability of such a pavement structure to conform to settlement of foundation.

TYPES OF ASPHALT PAVEMENT 1.DENSE-GRADED HOT MIX ASPHALT - hot mix asphalt pavement, the highest quality among the different types. - consists of well graded aggregate and asphalt cement which are heated and blended together in exact proportions at a hot mix plant. WELL-GRADED AGGREGATES- aggregate that is graded from the maximum size down to filler with object of obtaining an asphalt mix with controlled void content and high stability. 2.OPEN-GRADED SURFACE AND BASE COURSES - one containing little or no mineral filler or in which the void spaces in the compacted aggregates are relatively large. 3.STONE-FILLED MIXES - a sheet of asphalt containing up to 25 percent coarse aggregate.

TYPES OF ASPHALT PAVEMENT 4. SAND HOT MIX ASPHALT - a mixture of sand and asphalt cement or liquid asphalt prepared with or without special control of aggregate grading, with or without mineral filler. -either mixed-in-place or plant-mix construction may be employed. -use in construction of both base and surface courses. 5.SHEET HOT MIX ASPHALT - a hot mix of asphalt cement with clean, angular, graded sand and mineral filler. -its use is ordinarily confined to surface course usually laid on an intermediate or leveling course. 6.ASPHALT EMULSION MIXES (COLD MIXES) -cold mix pavements use asphalt emulsion or cutback asphalt. - require little or no heating of materials and can often be produced at the construction site without a central plant.

1.COARSE AGGREGATE (CA)-retained 2.36 mm ( No. 8) sieve-maybe obtained from gravel deposits or stone quarries. 2.FINE AGGREGATE (FA)- passing 2.36 mm (N0. 8) sieve and retained on 0.75 mm (N0. 200) sieve.-sources of fine aggregate are natural deposits of bank, beach or river sand or size between coarse and fine aggregate is 2.36 mm ( N0.8). 3.MINERAL FILLER (MF) -passing 0.075 mm (No. 200) sieve- may consist of finely ground limestone, rock powder, naturally occurring silt, Portland cement, hydrated lime or similar clean non-plastic finely divided mineral matter.-it may occur naturally in the fine and coarse aggregate as mineral dust or it may be added as a separate ingredient.- normally range 0.5 to 1.0 mass percent dry aggregate basis; hydrated lime is used, lower percentage limit is applicable to aggregate which are predominantly calcareous. AGGREGATE FRACTIONS:

COURSES OF ASPHALT AGGREGATE MIXTURE 1. ASPHALT BASE COURSE - a foundation course consisting of mineral aggregate, bound together with asphaltic mate 2. ASPHALT INTERMEDIATE COURSE (BINDER COURSE)- a course between a base course and an asphalt surface course. 3. ASPHALT SURFACE COURSE (WEARING COURSE)-the top course of an asphalt pavement. 4. ASPHALT LEVELING COURSE- a course (asphalt-aggregate mixture) of variable thickness used to eliminate irregularities in the contour of an existing surface prior to superimposed treatment or construction.

1. ASPHALT - is the binder of the aggregates -normally ranges from 5 8 % mass percent on the basis of total dry aggregate. - grade of asphalt cement normally ranges from 60/70 to 200/300 penetration.The service performance of an asphalt pavement is greatly influenced by the grade and quantity of asphalt it contains.The grade selected for each project is influenced by climatic conditions, traffic, and strength of the road foundation.Hot climates use lower penetration grades or hard asphalts.Cold Climates - use higher penetrates grades or softer asphalts.COMPOSITION OF BITUMINOUS MIX

2.MINERAL AGGREGATE -important ingredient - normally ranges from 92 to 96 percent of the weight of mixture.

1.Strength2. Particle shape3. Surface texture4. Absorption5.Gradation6.Cleanliness7.Specific Gravity8. Affinity for water9. Soundness IMPORTANT PROPERTIES OF AGGREGATES

1. ROAD MIX (MIXED-IN-PLACE) - an asphalt course produced by mixing mineral aggregate and liquid asphalt at the road site by means of travel plants, motor graders, drags or special road-mixing equipment.2.PLANT-MIX - a mixture produced in an asphalt mixing plant which consist of mineral aggregates uniformly coated with asphalt cement or liquid asphalt. 2.1Cold Mix - Plant mixes which may be spread or compacted at atmospheric temperature. - cold-laid - used only for patching 2.2 Hot Mix - Plant mixes which must be spread and compacted at an elevated temperature.- hot-laid- both the aggregate and asphalt - cement are heated prior to mixing for giving origin to the term hot mix .- higher durability and stability than cold mix. TWO TYPES OF BITUMINOUS MIX

SIGNIFICANT PROPERTIES OF BITUMINOUS PAVING MIXTURESTABILITY - it is defined as resistance to displacement under sustained or repeated loadings. -it implies resistance to shoving and rutting by the action of vehicular traffic and involves resistance to shearing stress.FACTORS AFFECTING STABILITY1.Gradation of the Mineral Aggregate2.Shape and Surface Texture of Aggregate Particles3.Hardness of Aggregate Particles4.Maximum Size of Coarse Aggregate5.Quantity and Consistency of the Bituminous Binder6.Degree of Compaction

TESTS FOR STABILITY1. Hubbard- Field2. Marshall3. Hveem Stabilometer4. Unconfined Immersion-Compression5. Triaxial Compression

2. DURABILITY - it is defined as resistance to disintegration or deterioration due to the detrimental effects of traffic, water, air and temperature changes. FACTORS AFFECTING DURABILITY1. Density of the compacted mixture2. Properties of mineral aggregates3. Properties of the Bituminous Binder4. Quantity of the Bituminous Binder

3. FLEXIBILITY - it is defined as the ability of the pavement to bend repeatedly without cracking and to conform to variations of the underlying base.FACTORS AFFECTING FLEXIBILITY 1. Quantity of Bituminous Binder 2. Quantity of Mineral Filler 3. Viscosity and Temperature Susceptibility of the binder.

SKID RESISTANCE - it is the resistance offered by the pavement to slipping or skidding of the vehicle tires.

FACTORS AFFECTING SKID RESISTANCE 1.Excess asphalt at pavement surface 2.Surface Roughness of Aggregate Particles

PERMEABILITY - it means porosity or perviousness the mixture, principally dependent on pore size, a dense graded mix prevents water from entering the base through the surface. FACTORS AFFECTING PERMEABILITY 1. Density of the compacted mix 2. Temperature of the mix

6. WORKABILITY - the ease by which the material can be placed to its desired uniformity and compacted to the required density.

FACTORS AFFECTING WORKABILITY 1. Gradation of Aggregate 2. Consistency of the bituminous binder 3. Temperature of the mix

7. FATIGUE RESISTANCE - ability to withstand repeatedly flexing caused by the passage of the wheel loads.FACTORS AFFECTING FATIGUE RESISTANCE 1. Quantity of the Bituminous Binder 2. Gradation of Aggregate

MINIMUM OF TESTING REQUIREMENTS1- Quality Test for every 130 M. T. of fraction thereof size of sample : 20 kgDIFFERENT TESTS ON BITUMINOUS MIX

1.EXTRACTION - quantitative determination of asphalt content in bituminous paving mixtures.Calculation: wt. of original wt. of sample after extraction% Asphalt Content = - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -x 100 (by wt. of mix) wt. of original sample wt. of original wt. of sample after extraction% Asphalt Content = - - - - - - - - - - - - - - - - - - - - -- - - - -- - - - - - - - --x 100 (by wt. of agg.) wt. of sample after extraction

2. BULK SPECIFIC GRAVITY - Bulk specific gravity of the compacted bituminous mixtures are used in calculating unit weight of the mixture. The specific gravity or density is an important data in the determination of the degree of compaction of a newly constructed asphalt pavement.Calculation: A Bulk Specific Gravity, Gmb = --------- B - C where : A = mass of specimen in air, g B = mass of surface-dry specimen, g C = mass of specimen in water, g

3. GRADING - determining the relative proportions of various particles sizes of mineral aggregates in a mix, if it conforms with the Job Mix Formula/Specifications.

4. STABILITY (IMMERSION-COMPRESSION METHOD) - this method covers measurement of the loss of cohesion resulting from the action of water on compacted bituminous mixtures.

4.1DRY STABILITY compressive strength of freshly molded and cured specimens.4.2WET STABILITY - compressive strength of duplicate specimens that have been immersed in water under prescribed conditions. CALCULATIONS:Index of Retained Strength (IRS) - calculate numerical index of resistance of bituminous mixtures to the detrimental effect of water as the percentage of the original strength that is retain after the immersion period. Wet StabilityIndex of retained strength, %= ------------------- x 100 Dry Stability

JOB MIX FORMULAJOB-MIX FORMULA - primary quality control mechanism for the production of asphalt mixtures with a high degree of uniformity that will satisfy job requirements. The Job-Mix Formula with the allowable tolerances becomes the job control grading band. The job control grading band, however, must be within the boundaries of the specification grading band .

Each Job-Mix Formula submitted shall proposed definite single values for : 1. The percentage of aggregate passing each specified

sieve size. 2. The percentage of bituminous material to be added. 3. The temperature of the mixture delivered on the road. 4. The kind and percentage of additive to be used. 5. The kind and percentage of mineral filler to be used.

After the job-mix is established, all mixture furnished for the project shall conform thereto within the following ranges of tolerances :Passing No. 4 and larger sieve + 7 %Passing No. 8 to No. 100 sieve + 4 %Passing No. 200 sieve + 2 %Bituminous Material + 0.4 %Temperature of Mix + 10 0 C

The mixture shall have a minimum dry compressive strength (dry stability) or 1.4 Mpa (200 psi) or 1400 kN/m2 or kPa.The mixture shall have a mass percent air voids with the range of 3 to 5.The mixture shall also have an index of retained strength of not less than 70%.At least three weeks prior to production, the contractor shall submit in writing a job-mix formula each mixture supported by laboratory test data along with sample and sources of the components and viscosity temperature relationship to the Engineer for testing and approval.Should a change in source of material be proposed or should a job-mix formula prove unsatisfactory, a new job-mix formula shall be submitted by the contractor in writing and be approved by the Engineer prior to production.Approval of a new job-mix formula may require laboratory testing and verification.

ACCEPTING, SAMPLING AND TESTING OF FINISHED ASPHALT PAVEMENTThe contractor shall cut full depth sample as directed from the finished pavement. Samples shall be neatly cut by a saw or core. At least one, but no more than three samples shall be taken for each full days operation. The contractor shall supply and finished new material to back fill voids left by the samples taken.The samples obtain will be used to test the density of compacted pavement. The compacted pavement shall have a density equal to or greater than 95 mass percent of the density of a laboratory specimen.

ASPHALT CORE

TESTING OF DRILLED CORES FROM AN ASPHALT PAVEMENTSIGNIFICANCE AND USE-Core tests determine the thickness and density of compacted asphalt pavement.SAMPLING :1.Specimens shall be taken from the pavement with a core drill, diamond or carborundum saw, or by other suitable means.2.Care shall be taken to avoid distortion, bending or cracking of specimen during and after removal from the pavement.3.Specimens shall be free from foreign materials such as seal coat, tack coat, foundation material, soil, paper or foil.4. Specimens for thickness and density determination.Sawed specimen : at least 150 mm x 150 mmCored specimen : 100 mm dia. full depth

Recommend that :1.The diameter of cylindrically molded or cored specimens, or the length of the sides of, sawed specimens, be at least equal to four times the maximum size of the aggregates.2.That the thickness of the specimens be at least one and one-half times the maximum size of the aggregates.OBTAINING OF CORE SPECIMENSCase 1. At least one but no more than three (3) samples shall be taken for each full days operation. To ascertain the degree of compaction of the asphalt pavement, more than one (1) core sample but not greater than three (3) maybe taken for each days operation. When 2 or 3 cores are taken, each core should represent a specific pavement area completed within a day. Averaging of the thickness and density of the 2 or 3 cores should not be done.

Case 2. If no core was taken at the end of each days operation and the project has already been completed, core shall be taken for every 100 linear meters per lane or fraction thereof of the completed pavement. Each core shall represent 100 LM of the asphalt pavement. Averaging of the thickness and density of the core should not be done.

TESTS ON ASPHALT CORE1.DENSITYCALCULATION : Density (d) = Gmb x Density of WaterWhere:Density of water = 1.0 gm/cm3 Gmb = Bulk Specific Gravity

CALCULATION OF BULK SPECIFIC GRAVITY ( Gmb) A Gmb = - - - - - - - - - B - CWhere: A - mass of specimen in air, gB - mass of surface dry specimen, g C - mass of specimen in water, g the compacted pavement shall have a density equal to or greater than 95 mass percent of the density of a laboratory specimen

CALCULATION: Field Density % COMPACTION = ---------------------------------- Lab. Compacted Density

2. THICKNESS 1.make four (4) measurements at approximately quarter points on the periphery of cores or at the approximate midpoint of each of the four sides of rectangular sawed specimens. (See figure) 2.the average of these measurements is the thickness (t) of the specimen.METHOD OF MEASUREMENTBituminous mixture will be measured by the tonne. The quantity to be paid shall be the number of tones of bituminous mixture in the accepted pavement computed based on the cores taken by applying the thicknesses and densities of the cores obtained therein to the width and length of the pavement represented by the core; otherwise, core samples shall be taken from the completed pavement for every 100 L. M. per lane to determine the corresponding thicknesses and densities.Batch weights will not be permitted as a method od measurement.

COMPUTATION : QUANTITY TO BE PAID l w t dW = ________________ 10 6Where: W = weight of mixture, tonne l = pavement length represented by the core, cm w = pavement width represented by the core, cm t = pavement thickness, cm d = density of the core, gm/ cm 3Note: The division 10 6 converts the unit of weight from gram to tonne.

Illustration Case I :In the construction of a 380 linear meter asphalt road, with a designed thickness of 5 cm, a width requirement of 3.05 m and a programmed quantity for bituminous mix of 135 tonnes, an asphalt core was taken after each full days operation. Results of thickness and density tests are as follows:PavingPaving Length Thickness DensityDaterepresented, m M gm/cm3Day 1120 5.3 2.262Day 2140 5.1 2.311Day 3120 5.0 2.221The computation for the quantity of bituminous mixture that should be paid is as follows:

Converts units of length and width to cm 12,000 (305) (5.3) 2.262 W1 = ------------------------------- = 43.88 tonnes 106 14,000 (305) (5.1) 2.311 W2 = ------------------------------- = 50.33 tonnes 106 12,000 (305)(5.0)2.221 W3 = ------------------------------- = 40.64 tonnes 106 WT = 134.85 tonnes In the preceeding case, only the quantity corresponding to 134.85 tonnes shall be paid.

Illustration Case 2 :For the same stretch of road, no core test was conducted at the end of each days operation. Thus, core were taken for every 100 linear meters of the completed pavement. Results of thickness and density tests are as follows :Paving Length Thickness DensityRepresented, m cm gm/cm3100 5.3 2.262100 5.1 2.311100 5.1 2.22580 5.0 2.226

The computation for the quantity of bituminous mixture that should be paid is as follows:Converts units of length and width to cm 10,000 (305) (5.3) 2.262 W1 = ------------------------------- = 36.56 tonnes106 10,000 (305) (5.1) 2.311 W2 = ------------------------------- = 35.95 tonnes106 10,000 (305)(5.1)2.225 W3 = ------------------------------- = 34.61 tonnes106 8,000 (305)(5.0)2.225 W4 = ------------------------------- = 27.16 tonnes106 WT = 134.28 tonnes

Only the quantity corresponding to 134.28 tonnes shall be paid. `

Daghang Salamat