CIV3703 Transport Engineering
CIV3703 Transport Engineering Module 7 – Part 2 Road Construction and Maintenance
Dr. Andreas Nataatmadja
7.8 Pavement Construction Pavements are usually constructed of: Gravel or crushed rock: Granular pavement Bituminous concrete: Asphalt pavement Cement concrete: Concrete pavement Combination of the above materials
7.8.1 Gravel and Crushed Rock Pavements Pavement materials hauled to site in trucks. Spread by grader or paver. Compacted by rollers. Pavement layers determine smoothness of final riding surface.
7.8.2 Asphalt Pavements Material manufactured in large permanent plant, or smaller mobile plant. Hauled to job site in trucks. Placed by paving machine. Compacted using rollers. Pavement may be up to 500 mm asphalt, although commonly around 300 mm (depending on the traffic load and operating temperature) Final layer (wearing surface) is thin, for good riding quality.
7.8.3 Cement Concrete Pavements Material manufactured in a ready-mixed concrete plant. Hauled to job in trucks. Spread by paver. Compacted by internal/external vibration.
7.9 Placement of Road Surfacing Final wearing surface may consist of: Gravel (unsealed) Sprayed seal Asphalt Cement concrete Purpose (except for gravel) is to waterproof pavement and provide a durable, skid resistant, dust-free surface with good riding qualities.
7.9.1 Construction of Sprayed Bituminous Surfacings Prior to surfacing, pavement should be: Adequately compacted; Trimmed to desired shape; Clean; and Have all defects patched. Primed surfaces: prime should be dry before sealing
Step 1 Sweeping Sweeping to remove all loose dirt, stones and foreign material. Use: Drawn rotary brooms; or Hand sweeping Brooming should extend 300 mm beyond seal area.
Delamination Issues Delamination may be attributed to: Inadequate cleaning or inadequate prime/tack coat before placement of bituminous surfacing Seepage of water through bituminous surfacing/Asphalt (especially in cracks) to break bond between surface and lower layers Weak, loose layer immediately underlying seal Adhesion of surface binder to vehicle tyre
Step 2 Preparing Binder Binder delivered by: Rail (20 to 40 tonne capacity wagons). Road tankers (capacities up to 20,000 litres). Drums (200 litres, for liquid bituminous materials).
Step 3 Preparing Flux or Cutback Bitumen
Refinery cutbacks available. More commonly, fluxing and cutting are carried out in the field. Required amounts pumped from drums into tanker and mixed.
Step 4 Incorporating Adhesion Agent Adhesion agents usually of amine type. Lose effectiveness if maintained at high temperature for long period. Therefore added just prior to spraying.
Step 5 Preparing Aggregate Supply of aggregate arranged well in advance of spraying work. If aggregate to be precoated all particles must be completely and thinly coated. Precoat application about 6 to 12 litres per cubic metre.
Step 6 Spraying Binder Pavement temperature should be > 15 deg. C. Spraying should not proceed if rain threatening. Edge line should be marked. Start & finish of each run should be clearly marked.
Sprayer positioned so as to reach correct speed before spraying commences. To obtain uniform distribution, sprayer driven at constant speed. Driver must check: Edge guideline Road speed Pump speed
Step 7 Applying the Aggregate Spreading coordinated with spraying, so hot bitumen covered before excessive cooling. Most common spreaders: Truck mounted fantail or cockerel types.
Truck travels backwards -> Safety concerns! Application rate governed by speed of truck. Successful spreading depends on skill of driver and gate operator.
Self-propelled Spreaders Lower safety risk.
Step 8 Rolling Rolling assists particles reach their correct orientation. Rolling should commence immediately after spreading.
Step 9 Drag Brooming To improve aggregate distribution and correct spreading unevenness (assist compaction).
Traffic Control Aim: Protection of workers, public, plant, work. Spraying: all traffic must be stopped ensure delays are kept to a minimum New work limit traffic speeds: stop/go signs pilot vehicles
Recording of the Work Provide a record of work done. Comparison of work done and work performed. Provide information for future design. Determine quantities of materials used for payment purposes. Provide info for updating road inventories.
Binder Distribution Issues
Spray Bar Setting
Source: “Chipsealing in New Zealand”
Calibration
Nozzle Issues
Source: “Chipsealing in New Zealand”
7.9.2 Manufacture of Asphalt Process: Heat and dry aggregates. Mix aggregates in correct proportions. Mix with bitumen.
Two types of mixing plants: Batch plants Continuous plants
7.9.3 Asphalt Paving
Generally laid with a paving machine. Manual method usually produces rough finish. Steps: 1. Prepare the surface 2. Transport and delivery of the mix 3. Placing the mix 4. Compacting the mix
1. Preparing the Surface Repair pavement (free of defects). Sweep pavement. On a new surface: use prime. On an existing asphalt surface: mill as required and use tack coat. (Tack coat = light coat of bitumen emulsion)
2. Transport and Delivery of the Mix Minimise: Heat loss Segregation Contamination Delivery best at a uniform rate. Transport: Tip trucks, steel bodies. Minimum capacity 6 t. Cool or wet weather – cover load Communication necessary.
Asphalt Paver
Source: Caterpillar Australia
3. Placing the Mix Self-propelled asphalt pavers. Support screed using blocks at the start Heat screed plate. Check spreading depth. Ensure weather warm and no rain.
http://www.pavementinteractive.org/article/asphalt-paver/
4. Compacting the Mix Compaction seeks to achieve: Void content for durability and impermeability Uniform density Stability of mix so no deformation under traffic. Temperature of the mix a critical factor in achieving compaction. Rolling: 3 phases Breakdown or initial rolling Intermediate rolling Finish rolling
Compaction Phases 1.
2. 3.
Breakdown rolling: compacts the mix beyond the compaction imparted by the screed and obtains most of the required density. Commonly using vibratory steel or 500 kPa pneumatic tyred rollers. Intermediate rolling: further densifies and seals the surface. Using heavy static steel-wheeled rollers. Finish rolling: removes roller marks and other blemishes left from previous rolling. Use light static steel-wheeled rollers or 350 kPa pneumatic tyred rollers.
Air voids that are either too great or too low can cause a significant reduction in pavement life. Air voids between 3 and 8 percent generally produce the best compromise of pavement strength, fatigue life, durability, ravelling, rutting and moisture damage susceptibility.
Asphalt Paving Train
7.10 Placement of Road Furniture Includes: Protective barriers Guardrail Signposts Guideposts Traffic signals Street lighting Emergency telephones, etc.
7.11 Landscaping Includes: Reshaping and contouring of land Topsoiling, turfing and mulching Stabilising drains to prevent scour Planting trees and shrubs
End of Module 7, Part 2
Dr. Andreas Nataatmadja
7.8 Pavement Construction Pavements are usually constructed of: Gravel or crushed rock: Granular pavement Bituminous concrete: Asphalt pavement Cement concrete: Concrete pavement Combination of the above materials
7.8.1 Gravel and Crushed Rock Pavements Pavement materials hauled to site in trucks. Spread by grader or paver. Compacted by rollers. Pavement layers determine smoothness of final riding surface.
7.8.2 Asphalt Pavements Material manufactured in large permanent plant, or smaller mobile plant. Hauled to job site in trucks. Placed by paving machine. Compacted using rollers. Pavement may be up to 500 mm asphalt, although commonly around 300 mm (depending on the traffic load and operating temperature) Final layer (wearing surface) is thin, for good riding quality.
7.8.3 Cement Concrete Pavements Material manufactured in a ready-mixed concrete plant. Hauled to job in trucks. Spread by paver. Compacted by internal/external vibration.
7.9 Placement of Road Surfacing Final wearing surface may consist of: Gravel (unsealed) Sprayed seal Asphalt Cement concrete Purpose (except for gravel) is to waterproof pavement and provide a durable, skid resistant, dust-free surface with good riding qualities.
7.9.1 Construction of Sprayed Bituminous Surfacings Prior to surfacing, pavement should be: Adequately compacted; Trimmed to desired shape; Clean; and Have all defects patched. Primed surfaces: prime should be dry before sealing
Step 1 Sweeping Sweeping to remove all loose dirt, stones and foreign material. Use: Drawn rotary brooms; or Hand sweeping Brooming should extend 300 mm beyond seal area.
Delamination Issues Delamination may be attributed to: Inadequate cleaning or inadequate prime/tack coat before placement of bituminous surfacing Seepage of water through bituminous surfacing/Asphalt (especially in cracks) to break bond between surface and lower layers Weak, loose layer immediately underlying seal Adhesion of surface binder to vehicle tyre
Step 2 Preparing Binder Binder delivered by: Rail (20 to 40 tonne capacity wagons). Road tankers (capacities up to 20,000 litres). Drums (200 litres, for liquid bituminous materials).
Step 3 Preparing Flux or Cutback Bitumen
Refinery cutbacks available. More commonly, fluxing and cutting are carried out in the field. Required amounts pumped from drums into tanker and mixed.
Step 4 Incorporating Adhesion Agent Adhesion agents usually of amine type. Lose effectiveness if maintained at high temperature for long period. Therefore added just prior to spraying.
Step 5 Preparing Aggregate Supply of aggregate arranged well in advance of spraying work. If aggregate to be precoated all particles must be completely and thinly coated. Precoat application about 6 to 12 litres per cubic metre.
Step 6 Spraying Binder Pavement temperature should be > 15 deg. C. Spraying should not proceed if rain threatening. Edge line should be marked. Start & finish of each run should be clearly marked.
Sprayer positioned so as to reach correct speed before spraying commences. To obtain uniform distribution, sprayer driven at constant speed. Driver must check: Edge guideline Road speed Pump speed
Step 7 Applying the Aggregate Spreading coordinated with spraying, so hot bitumen covered before excessive cooling. Most common spreaders: Truck mounted fantail or cockerel types.
Truck travels backwards -> Safety concerns! Application rate governed by speed of truck. Successful spreading depends on skill of driver and gate operator.
Self-propelled Spreaders Lower safety risk.
Step 8 Rolling Rolling assists particles reach their correct orientation. Rolling should commence immediately after spreading.
Step 9 Drag Brooming To improve aggregate distribution and correct spreading unevenness (assist compaction).
Traffic Control Aim: Protection of workers, public, plant, work. Spraying: all traffic must be stopped ensure delays are kept to a minimum New work limit traffic speeds: stop/go signs pilot vehicles
Recording of the Work Provide a record of work done. Comparison of work done and work performed. Provide information for future design. Determine quantities of materials used for payment purposes. Provide info for updating road inventories.
Binder Distribution Issues
Spray Bar Setting
Source: “Chipsealing in New Zealand”
Calibration
Nozzle Issues
Source: “Chipsealing in New Zealand”
7.9.2 Manufacture of Asphalt Process: Heat and dry aggregates. Mix aggregates in correct proportions. Mix with bitumen.
Two types of mixing plants: Batch plants Continuous plants
7.9.3 Asphalt Paving
Generally laid with a paving machine. Manual method usually produces rough finish. Steps: 1. Prepare the surface 2. Transport and delivery of the mix 3. Placing the mix 4. Compacting the mix
1. Preparing the Surface Repair pavement (free of defects). Sweep pavement. On a new surface: use prime. On an existing asphalt surface: mill as required and use tack coat. (Tack coat = light coat of bitumen emulsion)
2. Transport and Delivery of the Mix Minimise: Heat loss Segregation Contamination Delivery best at a uniform rate. Transport: Tip trucks, steel bodies. Minimum capacity 6 t. Cool or wet weather – cover load Communication necessary.
Asphalt Paver
Source: Caterpillar Australia
3. Placing the Mix Self-propelled asphalt pavers. Support screed using blocks at the start Heat screed plate. Check spreading depth. Ensure weather warm and no rain.
http://www.pavementinteractive.org/article/asphalt-paver/
4. Compacting the Mix Compaction seeks to achieve: Void content for durability and impermeability Uniform density Stability of mix so no deformation under traffic. Temperature of the mix a critical factor in achieving compaction. Rolling: 3 phases Breakdown or initial rolling Intermediate rolling Finish rolling
Compaction Phases 1.
2. 3.
Breakdown rolling: compacts the mix beyond the compaction imparted by the screed and obtains most of the required density. Commonly using vibratory steel or 500 kPa pneumatic tyred rollers. Intermediate rolling: further densifies and seals the surface. Using heavy static steel-wheeled rollers. Finish rolling: removes roller marks and other blemishes left from previous rolling. Use light static steel-wheeled rollers or 350 kPa pneumatic tyred rollers.
Air voids that are either too great or too low can cause a significant reduction in pavement life. Air voids between 3 and 8 percent generally produce the best compromise of pavement strength, fatigue life, durability, ravelling, rutting and moisture damage susceptibility.
Asphalt Paving Train
7.10 Placement of Road Furniture Includes: Protective barriers Guardrail Signposts Guideposts Traffic signals Street lighting Emergency telephones, etc.
7.11 Landscaping Includes: Reshaping and contouring of land Topsoiling, turfing and mulching Stabilising drains to prevent scour Planting trees and shrubs
End of Module 7, Part 2
