CIV3703 Transport Engineering
CIV3703 Transport Engineering Module 5 Design of Bituminous Surfaces – Part B
Dr. Andreas Nataatmadja
5.5 Design of Asphalt Surfacings
5.5.1 Design Objectives Dense Graded Mixes dense grading of aggregate particles sufficient binder to coat particles & waterproof small volume of air voids (3 to 7%) workable mix (laying; compaction) Open Graded Mixes permeability, stability important noise or spray reduction Gap Graded Mixes durable mix
Grading & Mix Component
Why Spray Reduction?
5.5.2 Design Procedure 1. Selection of mix type. 2. Combination of aggregates. 3. Binder content estimation. 4. Manufacture and compaction of trial mixes. 5. Testing of trial mixes. 6. Evaluation of test results. 7. Adjustment of mix design. 8. Job mix.
Aggregate Blending – Graphical Method
Numerical Check
Aggregate Blending – Computerised Method
Combined Material: % passing at sieve size of 1 mm = 0.7 x 24 + 0.3 x 51 = 32.1
Asphalt Volumetric Model
Binder Estimation (Table 5.10)
Preparation of Test Specimens - Marshall Method Mix compacted in cylindrical moulds 100 mm diameter compacted height approximately 64 mm adjustment factors used for height variations compaction: drop hammer: 4540 g; free fall 457 mm; 35, 50 or 75 blows per face gyratory compactor
Filling the Mould
Compacting Specimen
Marshall Test Specimen preparation specimens measured for height and mass specimens heated to 60°C for 30 to 40 min in a water bath Testing specimen placed in compression heads force applied diametrically - rate 51 mm/min test time must be < 30 secs (cooling) load and deformation measured.
Marshall Test Machine
Breaking head
Test Results
Marshall Stability = maximum load taken by the specimen (kN) Marshall Flow = deformation at maximum load (mm)
Other Test Results Bulk density Maximum Theoretical Density (voidless) Air Voids Percentage Voids filled with binder (VFB, % of voids in the mineral aggregate filled with binder) Voids in mineral aggregate (VMA)
Example:
Evaluation of Test Results Test results graphed to show values and trends with increasing bitumen content by mass. Stability, flow, air voids, voids in the mineral aggregate and bulk density vs Bitumen content by mass
Binder Content Selection Final binder content selected should give: close to maximum stability close to maximum bulk density close to minimum VMA air voids within specified limits flow within specified limits
5.5.3 Current Trends A lot of work worldwide in last decade looking at design of asphalt mixes. Australia - joint research by state road authorities, ARRB and asphalt industry. Mix design based on traffic loading: 3 levels - light, medium and heavy traffic mixes
Light traffic mixes (< 500,000 ESA) design concentrates on correct volumetric proportion. Medium traffic mixes ensures mix has suitable mechanical properties (creep, fatigue, modulus). High traffic mixes (> 5,000,000 ESA) checks mix has suitable properties after very high compaction.
Materials Testing Apparatus (MATTA)
Source: IPC
Fatigue Test
5.7 Other Forms of Bituminous Surfacing Sprayed seals & asphalt are the two most commonly used forms of bituminous surfacings. Several other methods/techniques developed - some well tried, some fairly new.
5.7.1 Polymer Modified Binders (PMB) Bitumen suitable for most surfacing applications. Bitumen properties may be enhanced by addition of polymer. PMBs used for wide variety of applications: spray seals: crack control, aggregate retention asphalt: rutting resistance; fatigue resistance; cracking resistance
Binder Relative Performance
(A = asphalt, S = sprayed seal, M = multigrade, C = Class, E = elastomer, P = Plastomer, R = crumb rubber)
Source: RMS-NSW
PMB in Sprayed Seals Strain Alleviating Membrane (SAM) PMB seal coat with 10 or 14 mm aggregate. Strain Alleviating Membrane Interlayer (SAMI) PMB seal interlayer between cracked pavement and new asphalt. Highly Stressed Seals (HSS) PMB seal in situations of high stress (high speeds, winding alignment, etc.)
5.7.2 Geotextile Seals Geotextile spread then normal seal applied. Large range of geotextiles available polyester, needlepunched preferred.
5.7.3 Fibre Reinforced Seals Polymer modified emulsion binder with glass fibres to reinforce binder. Alternative to geotextile seals and SAM/SAMI/HSS. Fibredec system: spray emulsion, spread chopped fibre glass strands, spray second emulsion coat, spread aggregate.
5.7.4 Surface Enrichment
Light application of bituminous binder to an existing seal. Also known as enrichment seal, or fog coat. Used when aggregate is OK, but binder has deteriorated. Binder: cutback bitumen, or bitumen emulsion (more common).
5.7.5 Stone Mastic Asphalt (SMA) Gap graded mix with high coarse aggregate content. Aggregate interlocks to form strong aggregate skeleton. Good resistance to rutting and shoving. Usually small % fibres also added.
5.7.6 Asphalt and Geogrid Asphalt reinforced with geogrid. Geogrid: self-adhesive glass fibre grid, or combination polypropylene/ grid geotextile.
www.geofabrics.com.au
5.7.7 Bituminous Slurry Surfacing Proprietary technique. Mix: bitumen emulsion mineral aggregate mineral filler Spread as thin layer on pavement surface. Life expectancy: 4 to 6 years. Also: microsurfacing or microasphalt
Slurry Surfacing Process
Slurry Surfacing
www.betterroads.com
5.7.8 Novachip (Safepave) Proprietary process developed in France. Hot mix asphalt of 10 or 14 mm nominal size - relatively open graded. Mixed hot and laid on emulsion spray. Spraying and laying done by one machine. Layer is between 1 and 2 stones thick. Stability depends on stone to stone contact.
5.7.9 Recycled Asphalt Reclaimed asphalt pavement (RAP) used for many years previously for aggregate. Asphalt recycling based on assumption that rheological properties of binder can be restored to near new May add rejuvenating agent or softer binder Now up to 20% RAP is often used without accounting for different binder properties Plant production allows up to 50% RAP due to emission restriction
Recycling Types Hot Plant Recycling - uses mixing plant. Hot in-place recycling. Cold in-place recycling. Increasing regulation to use recycled material including RAP and tyres.
Hot In-Place Asphalt Recycling (HIPAR)
End Module 5, Part 2
Dr. Andreas Nataatmadja
5.5 Design of Asphalt Surfacings
5.5.1 Design Objectives Dense Graded Mixes dense grading of aggregate particles sufficient binder to coat particles & waterproof small volume of air voids (3 to 7%) workable mix (laying; compaction) Open Graded Mixes permeability, stability important noise or spray reduction Gap Graded Mixes durable mix
Grading & Mix Component
Why Spray Reduction?
5.5.2 Design Procedure 1. Selection of mix type. 2. Combination of aggregates. 3. Binder content estimation. 4. Manufacture and compaction of trial mixes. 5. Testing of trial mixes. 6. Evaluation of test results. 7. Adjustment of mix design. 8. Job mix.
Aggregate Blending – Graphical Method
Numerical Check
Aggregate Blending – Computerised Method
Combined Material: % passing at sieve size of 1 mm = 0.7 x 24 + 0.3 x 51 = 32.1
Asphalt Volumetric Model
Binder Estimation (Table 5.10)
Preparation of Test Specimens - Marshall Method Mix compacted in cylindrical moulds 100 mm diameter compacted height approximately 64 mm adjustment factors used for height variations compaction: drop hammer: 4540 g; free fall 457 mm; 35, 50 or 75 blows per face gyratory compactor
Filling the Mould
Compacting Specimen
Marshall Test Specimen preparation specimens measured for height and mass specimens heated to 60°C for 30 to 40 min in a water bath Testing specimen placed in compression heads force applied diametrically - rate 51 mm/min test time must be < 30 secs (cooling) load and deformation measured.
Marshall Test Machine
Breaking head
Test Results
Marshall Stability = maximum load taken by the specimen (kN) Marshall Flow = deformation at maximum load (mm)
Other Test Results Bulk density Maximum Theoretical Density (voidless) Air Voids Percentage Voids filled with binder (VFB, % of voids in the mineral aggregate filled with binder) Voids in mineral aggregate (VMA)
Example:
Evaluation of Test Results Test results graphed to show values and trends with increasing bitumen content by mass. Stability, flow, air voids, voids in the mineral aggregate and bulk density vs Bitumen content by mass
Binder Content Selection Final binder content selected should give: close to maximum stability close to maximum bulk density close to minimum VMA air voids within specified limits flow within specified limits
5.5.3 Current Trends A lot of work worldwide in last decade looking at design of asphalt mixes. Australia - joint research by state road authorities, ARRB and asphalt industry. Mix design based on traffic loading: 3 levels - light, medium and heavy traffic mixes
Light traffic mixes (< 500,000 ESA) design concentrates on correct volumetric proportion. Medium traffic mixes ensures mix has suitable mechanical properties (creep, fatigue, modulus). High traffic mixes (> 5,000,000 ESA) checks mix has suitable properties after very high compaction.
Materials Testing Apparatus (MATTA)
Source: IPC
Fatigue Test
5.7 Other Forms of Bituminous Surfacing Sprayed seals & asphalt are the two most commonly used forms of bituminous surfacings. Several other methods/techniques developed - some well tried, some fairly new.
5.7.1 Polymer Modified Binders (PMB) Bitumen suitable for most surfacing applications. Bitumen properties may be enhanced by addition of polymer. PMBs used for wide variety of applications: spray seals: crack control, aggregate retention asphalt: rutting resistance; fatigue resistance; cracking resistance
Binder Relative Performance
(A = asphalt, S = sprayed seal, M = multigrade, C = Class, E = elastomer, P = Plastomer, R = crumb rubber)
Source: RMS-NSW
PMB in Sprayed Seals Strain Alleviating Membrane (SAM) PMB seal coat with 10 or 14 mm aggregate. Strain Alleviating Membrane Interlayer (SAMI) PMB seal interlayer between cracked pavement and new asphalt. Highly Stressed Seals (HSS) PMB seal in situations of high stress (high speeds, winding alignment, etc.)
5.7.2 Geotextile Seals Geotextile spread then normal seal applied. Large range of geotextiles available polyester, needlepunched preferred.
5.7.3 Fibre Reinforced Seals Polymer modified emulsion binder with glass fibres to reinforce binder. Alternative to geotextile seals and SAM/SAMI/HSS. Fibredec system: spray emulsion, spread chopped fibre glass strands, spray second emulsion coat, spread aggregate.
5.7.4 Surface Enrichment
Light application of bituminous binder to an existing seal. Also known as enrichment seal, or fog coat. Used when aggregate is OK, but binder has deteriorated. Binder: cutback bitumen, or bitumen emulsion (more common).
5.7.5 Stone Mastic Asphalt (SMA) Gap graded mix with high coarse aggregate content. Aggregate interlocks to form strong aggregate skeleton. Good resistance to rutting and shoving. Usually small % fibres also added.
5.7.6 Asphalt and Geogrid Asphalt reinforced with geogrid. Geogrid: self-adhesive glass fibre grid, or combination polypropylene/ grid geotextile.
www.geofabrics.com.au
5.7.7 Bituminous Slurry Surfacing Proprietary technique. Mix: bitumen emulsion mineral aggregate mineral filler Spread as thin layer on pavement surface. Life expectancy: 4 to 6 years. Also: microsurfacing or microasphalt
Slurry Surfacing Process
Slurry Surfacing
www.betterroads.com
5.7.8 Novachip (Safepave) Proprietary process developed in France. Hot mix asphalt of 10 or 14 mm nominal size - relatively open graded. Mixed hot and laid on emulsion spray. Spraying and laying done by one machine. Layer is between 1 and 2 stones thick. Stability depends on stone to stone contact.
5.7.9 Recycled Asphalt Reclaimed asphalt pavement (RAP) used for many years previously for aggregate. Asphalt recycling based on assumption that rheological properties of binder can be restored to near new May add rejuvenating agent or softer binder Now up to 20% RAP is often used without accounting for different binder properties Plant production allows up to 50% RAP due to emission restriction
Recycling Types Hot Plant Recycling - uses mixing plant. Hot in-place recycling. Cold in-place recycling. Increasing regulation to use recycled material including RAP and tyres.
Hot In-Place Asphalt Recycling (HIPAR)
End Module 5, Part 2
