Transcript HMA Construction Program

HMA Construction Program
Module 8 – Compaction
Module 8 Objectives
• Objective of Compaction
• Engineering Properties Related to
Compaction
• Factors Affecting Compaction
• Types of Rollers
• Considerations for Selecting Rollers
Module 8 Objectives (cont’d)
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•
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Compaction Variables
Roller Maintenance
Roller Productivity
Operating Techniques
Definitions
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Density
Compaction
Pass
Coverage
Time Available for Compaction
(TAC)
Importance of Compaction
• Improve Mechanical Stability
• Improve Resistance to Permanent
Deformation
• Reduce Moisture Penetration
• Improve Fatigue Resistance
• Reduce Low-Temperature Cracking
Potential
Factors Affecting Compaction
• Properties of the Materials
• Environmental Variables
• Laydown Site Conditions
Properties of the Materials
• Aggregate
• Asphalt Cement
• Mix Properties
Hot Mix Compaction
• Asphalt binder holds particles together
– Provides lubrication at high temperatures
– Provides cohesion at in-service temperatures
• Prevents air and water intrusion into mat
Environmental Variables
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Layer thickness
Air and base temperature
Mix laydown temperature
Wind velocity
Solar flux
Time for Mat to Cool to 80°C, Minutes
0
25
50
75
100
120, 10
120, 0
120, -10
150, 10
150, 0
150, -10
Mix Base °C
50
40
30
20
10
0
125
150
Mat Thickness, millimeters
175
200
Major Factors
Affecting Rolling
Time
allows
MORE
time
allows
LESS
time
Mat Thickness
THICK
THIN
Mix Temperature
HIGH
LOW
Base Temperature
HIGH
LOW
Compaction Temperature Range
85 °C
(185 °F)
150 °C
(300 °F)
Laydown Site Conditions
• Lift thickness versus aggregate size
• Lift thickness uniformity
• Base Conditions
Types of Rollers
• Static Steel Wheel
• Pneumatic – Rubber Tired
• Vibratory
How Do Rollers Compact?
By applying their load
over a given area!
(Contact Pressure)
Static Steel Wheel Roller
• Contact Pressure
• Operation
Kilograms Per
Linear Millimeter
(kg/mm)
Kilograms Per Linear
Millimeter (kg/mm)
• Example:
– A 10.9 tonne roller with two, 1.3 meter wide
drums.
– In this case, 60% of the mass is on the drive
drum and 40% is on the guide drum.
– Calculate the kg/mm
Kilograms Per Linear
Millimeter (kg/mm)
• Example Solution:
1 tonne = 1,000 kg 1 meter = 1,000 mm
10.9 tonne x 1,000 kg = 10,900 kg
1 tonne
1.3 m x 1,000 mm = 1,300 mm
1 meter
60% x 10,900 kg / 1,300 mm = 5.0 kg/mm
40% x 10,900 kg / 1,300 mm = 3.4 kg/mm
Contact Pressure
Roller Contact Pressure
Roller Contact Pressure at Penetration Depths
(in kPa)
Static Roller(depth, mm)
1.6 3.2 12.5 19.0
10.9 tonnes(with ballast)
910 607 317 248
Travel
Nonpowered
drum
W R
Powered
Drum
R
W
Frictional force
turns trailing drum
Pneumatic Tired Rollers
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Wheel load
Tire design
Inflation pressure
Contact area
Tire Inflation Pressure
Versus
Ground Contact Pressure
Inflation Pressure and Ground
Contact Pressure at Various
Wheel Loads and Ply Ratings
Example
A
B
C
Ply
Rating
14
14
14
14
10
14
Wheel
Load
kg
567
1,270
1,043
1,043
1,270
1,270
Tire Contact
Ground
Pressure Area Contact Pressure
kPa
mm2
kPa
896
896
241
896
621
896
10,323
19,355
26,452
16,774
24,516
19,355
538
634
386
607
503
634
Vibratory Rollers
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Amplitude
Frequency
Impact Spacing
Operation
Movement
Down
Up
Amplitude
(A)
Time
Time (T) For Full Cycle
Frequency, f = the number of hertz (cycles/s)--a single cycle
is one full rotation of the eccentric weight. Frequency = 1/T
Amplitude, A = the maximum deviation from position at
rest -- one-half the total movement.
AMPLITUDE
Low Frequency
High Frequency
Impact Spacing
FREQUENCY
DIRECTION OF TRAVEL
Typical Data for Vibratory
Tandem Rollers
Vibratory
Oper. Drum Drum Static Dynamic VPM Nom.
Steel Tandem Wt.
Diam. Width Drum Drum
Amp.
tonne
kg
m
m
kg/mm kg/mm
mm
5.4-7.3
6,668
1.1
1.4
2.3
4.6
2,900
0.64
8.6-10.0
9,299
1.2
1.7
2.8
6.8
2,600
0.76
> 11.8
13,608
1.5
2.1
3.3
7.5
2,400
0.76
Roller Maintenance
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Water Systems
Hydraulic Systems
Mechanical Systems
Vibratory Systems
Rolls, Tires, Pads, Scrapers
FORM 8-1 ROLLER MAINTENANCE CHECKLIST Page 1 of 1
Roller ID#:_________________________________ Date:____________________________
CHECK DAILY

(1)
COOLING SYSTEM - (a) Check coolant level; (b) Check radiator core for
plugging with dirt or oil; (c) Check hoses for cracking and leaking; (d) Check
belts for proper tension; (e) Check fan for loose bearings. Fill, adjust and/or
replace as needed.

(2)
ENGINE LUBE SYSTEM - (a) Check engine oil level; (b) Check for any leakage
on or around engine; (c) Report any discolorations (milky) or overfilled conditions
right away.
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(3)
FUEL SYSTEM - (a) Check sediment bowl for dirt or water and clean as needed;
(b) Check for any leaks around lines and fittings. DO NOT OVERTIGHTEN.
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(4)
HYDRAULIC SYSTEM - (a) Check oil level; (b) Check and look for any leaks
around pumps, lines, fittings, and filters. DO NOT OVERTIGHTEN.
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(5)
ELECTRICAL SYSTEM - (a) Look at the wiring and connections for being loose
or oily. If oily, spray with contact cleaner. (b) Look at battery cable connections
and clean if starting to corrode.
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(6)
ROLLS & TIRES - (a) Check rolls for uneven wear; (b) Check tires for uneven
wear and maintain at ___ kPa. air pressure (cold/hot); (c) Check scrapers and
mats (replace as necessary).

(7)
WATER SYSTEM - (a) Check fill areas for debris; (b) Check filters for
contamination and clean; (c) Test system to see if all nozzles are clear and
operational.
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(8)
INSPECTION - (a) Look for loose bolts and tighten right away when found; (b)
clean out scraper and mat areas after each day’s run; (c) Keep top deck and
operator’s station clear; (d) Check for other oil or grease leaks from gear boxes,
transmission, differential, axle hubs, and report to shop immediately.
CHECK WEEKLY

(1)
BRAKE SYSTEM - (a) Check master cylinders for hydraulic brake fluid level.
Keep filled to proper level.

(2)
ELECTRICAL SYSTEM - Batteries: (a) Check water level and maintain level
above the plates. If one or more cells keeps going dry, it means the battery is
near the end of its life.

(3)
TRANSMISSION - Gear boxes and pump drive housing: (a) Check grease
levels and fill as needed to proper level.
Compaction Variables
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Roller Speed
Number of Coverages
Rolling Zone
Rolling Pattern
Typical Range of Roller Speeds
(km/hour)
Type of Roller
Breakdown
Intermediate
Finish
Static Steel Wheel
3.2 to 5.6
4 to 6.4
4.8 to 8
Pneumatic
3.2 to 5.6
4 to 6.4
6.4 to 11.3
Vibratory
3.2 to 4.8
4 to 5.6
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One Coverage
How many passes of the roller are needed
to cover the width of the mat one time ?
75 m
15 m
Paver
Rolling Zone
(conventional HMA)
Operating Techniques
• Transportation
• Test Strip Construction
• Establishing Roller
Patterns
• Breakdown Rolling
– Transverse Joints
– Longitudinal Joints
• Intermediate
Rolling
• Finish Rolling
• Re-watering
• Concluding
Operations
Test Strip Construction
• Simulating Actual Conditions
• Establishing Roller Patterns
• Calculating Effective Roller Speed
Establishing Roller Pattern
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Selecting compaction equipment
Width of paving
Width of roller
Number of coverages needed
Nuclear gauge
Roller Types by Application
(tonnes)
Breakdown Rolling
Static (3 Wheel
and Tandem)
Pneumatic
7.3 to 9.5
7.3 to 10.9
9.1 to 12.7
508 mm rim
607 mm rim
Vibratory (Static)
9.1 to 10
> 11.3
5.4 to 7.3
Roller Types by Application
(tonnes)
Intermediate Rolling
Static (3 Wheel
and Tandem)
Pneumatic
7.3 to 10.9
9.1 to 12.7
381 mm rim
508 mm rim
607 mm rim
Vibratory (Static)
5.4 to 7.3
9.1 to 10
> 11.3
Roller Types by Application
(tonnes)
Finish Rolling
Static (3 Wheel
and Tandem)
Pneumatic
7.3 to 9.5
7.3 to 10.9
9.1 to 12.7
381 mm rim
508 mm rim
Vibratory (Static)
5.4 to 7.3
9.1 to 10
> 11.3
5
4.5
4
3.5
3
2.5
2
1.5
1
0.5
0
4.88 m
4.27 m
3.66 m
3.05 m
1.
2
1.
3
1.
4
1.
5
1.
6
1.
7
1.
8
1.
9
2.
0
2.
1
2.
2
2.
3
2.
4
Number of Passes for One
Coverage
Drum Width vs. Lane Width
Drum Width (m)
One Roller Coverage
1
CROWN
2-lanes @
3.7 meters
2
3
6
5
4
Drum Width
= 1.8 meters
How Many Repeat Coverages
to Assure Density?
High
Passing
Density
Density
Low
1
2
3
4
5
Roller Passes
6
Thermometers
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Types
Uses
Potential problems
Calibrating
Actually using one
Roller Production Rate
Problem
Balancing Production
HMA
Facility
Trucking
Paving
Compaction
Breakdown Rolling
• Determine the rolling zone by:
– Experience
– Estimating
Calculating Your Rolling Zone
• Effective Compaction (C-Rate) Production
Rate equals 8.5 meters per minute.
• TAC from Environmental Variables chart
equals 10 minutes for 50 mm thick mat
with mix temperature of 121 oC and base
temperature of 10 oC.
• C-Rate times TAC = 8.5 mpm x 10 minutes
= 85 meters
Compacting
Transverse
Joints
Compacting
Longitudinal
Joints
Cold
Hot
OOPS!
Intermediate
Rolling
Finish
Rolling
Re-Watering During Paving
Concluding
Operations
Opening
to
Traffic
Module 8 Objectives Review
• Objective of Compaction
• Engineering Properties Related to
Compaction
• Factors Affecting Compaction
• Types of Rollers
• Considerations for Selecting Rollers
Module 8 Objectives (cont’d)
•
•
•
•
Compaction Variables
Roller Maintenance
Roller Productivity
Operating Techniques