Asphalt Pavement Laydown and Compaction Picture of plant

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Asphalt Pavement Laydown and Compaction Picture of plant Slide 2 Compaction of the asphalt mat, typically, has more affect on the life of the pavement than any other item in asphalt construction. Slide 3 Adequate Compaction Helps Reduce or Retard. Fatigue Cracking Fatigue Cracking Rutting Rutting Binder Oxidation Binder Oxidation Moisture Damage Moisture Damage Thermal Cracking Thermal Cracking Slide 4 Fatigue Cracking Slide 5 Rutting Slide 6 Asphalt Binder Oxidation - Hardening Slide 7 Moisture Damage Adequate compaction will help minimize the infiltration of water. Adequate compaction will help minimize the infiltration of water. Slide 8 Thermal Cracking Slide 9 Mixture Items that Affect Compaction Aggregate texture, hardness and shape Aggregate texture, hardness and shape Asphalt Binder Grade Asphalt Binder Grade Mixture Properties Mixture Properties Voids Asphalt Binder Content Mixture Temperature and Cooling Rate Mixture Temperature and Cooling Rate Slide 10 Field Operations that Affect the Compaction of the Bituminous Mixture Types of Rollers and Order they are used Types of Rollers and Order they are used Mode of the Steel Rollers Mode of the Steel Rollers Vibratory mode on or off High/Low Amplitude High/Low Frequency in most cases the roller should be set to high frequency and low amplitude Speed of Rollers Speed of Rollers Number of Roller Passes Number of Roller Passes Slide 11 Number of Roller Passes 13579 113579 201234 301123 401112 Number Passes to Cover Paver Width Roller Passes Minimum Passes on Critical Longitudinal Section Slide 12 Roller Speed Example Given: Plant & Paver Specifics - 12 feet wide - 500 tons per hour - 1.5 inch lift Roller Specifics - minimum 3 passes coverage - roller width is 54 inch Required What is the minimum roller speed you need to compact the mat? Slide 13 Roller Speed Answer The speed of the paver is: 500 tons per hour = 500*2000/145 = 6900 cuft per hour Pavement Cross section = 12 feet * 1.5 inch/12 = 1.5 sqft Paver speed = (6900 cuft/hr) / 1.5 sqft = 4600 ft/hour The required roller speed is: Roller Speed = 4600 ft/hour * 9 passes /5280 ft/mi = 7.8 mph Slide 14 What are the Recommended Roller Speeds ? From Chapter 18 of Hot Mix Paving Handbook Static Steel Wheel 2 3.5 2.5 - 4 3 - 5 Pneumatic 2 3.5 2.5 - 4 4 - 7 Vibratory 2 - 3 2.5 3.5 -- Type of Roller Breakdown Intermediate Finish Operating Position Range of Roller Speeds (mph) Slide 15 You Need More Than 1 Roller !!! Slide 16 Roller Settings and Roller Patterns Vibratory Steel Roller generally works best in the high frequency and low amplitude mode Vibratory Steel Roller generally works best in the high frequency and low amplitude mode Typical Rolling Pattern: Typical Rolling Pattern: Vibratory Steel Roller as break down Pneumatic Roller as intermediate Static Steel Roller as finish roller Only Pneumatic rollers should be used when the temperature of the mat is within the bituminous mixtures tender zone Only Pneumatic rollers should be used when the temperature of the mat is within the bituminous mixtures tender zone Slide 17 Vibratory Breakdown Slide 18 Pneumatic Breakdown Slide 19 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(A) Time Up Down Time (T) For Full Cycle Movement Slide 20 Amplitude Slide 21 DIRECTION OF TRAVEL Frequency Impact Spacing High Frequency Low Frequency Slide 22 Joint Compaction Compaction of the Longitudinal Joint is the Weak Link in the Paving Process Compaction of the Longitudinal Joint is the Weak Link in the Paving Process Compaction of the Both the Confined and Unconfined Edges is a Challenge Compaction of the Both the Confined and Unconfined Edges is a Challenge The Unconfined Edge Needs to be Compacted with the Edge of the Steel Roller Over-hanging the Mat by 6 Inches The Unconfined Edge Needs to be Compacted with the Edge of the Steel Roller Over-hanging the Mat by 6 Inches If a Pneumatic Roller is used in the Break Down Position, it Should not be Closer than 6 Inches to the Joint If a Pneumatic Roller is used in the Break Down Position, it Should not be Closer than 6 Inches to the Joint Slide 23 Joint Compaction Compaction of the Confined Joint is Best Achieved by Rolling on the Hot Mat and Overlapping the Cold Mat by 6 Inches Compaction of the Confined Joint is Best Achieved by Rolling on the Hot Mat and Overlapping the Cold Mat by 6 Inches Steel Rollers may Tend to Bridge from the Cold Mat and this May Impede Compaction Right at the Joint. A Pneumatic Roller will be More Effective in Reducing this Bridging. Steel Rollers may Tend to Bridge from the Cold Mat and this May Impede Compaction Right at the Joint. A Pneumatic Roller will be More Effective in Reducing this Bridging. Rolling from the Cold Side is No Longer Recommended Rolling from the Cold Side is No Longer Recommended Raking of the Joint is Not Recommended Raking of the Joint is Not Recommended Slide 24 LOWHIGH LOWHIGH THINTHICK Base Temperature Mix Temperature Factors Affecting Rolling Time Mat Thickness allows LESS time allows MORE time FACTORS Slide 25 Time for Compaction Exercise Slide 26 Paver Operations Slide 27 The primary objective of the paver is to place a bituminous mixture on the roadway, in a manner that results in mat that has an even distribution of temperature, thickness and pre-compaction, in both the longitudinal and transverse directions. The primary objective of the paver is to place a bituminous mixture on the roadway, in a manner that results in mat that has an even distribution of temperature, thickness and pre-compaction, in both the longitudinal and transverse directions. Slide 28 Mix Placement Concerns Even and steady flow of mixture into the paver hopper Even and steady flow of mixture into the paver hopper Even and steady flow of mixture to the paver Even and steady flow of mixture to the paver Even and steady flow of mixture through the paver and in front of the paver screed Even and steady flow of mixture through the paver and in front of the paver screed The appropriate angle of attack of the screed needs to be set and frequent adjustments minimized The appropriate angle of attack of the screed needs to be set and frequent adjustments minimized Slide 29 Flow of Mixture to the Paver Slide 30 Flow of Mixture into the Paver Hopper Slide 31 Paver Hopper and Flow Gates Slide 32 Flow Gates set to Allow Uniform Material Flow to the Auger Slide 33 Operating the Screed Slide 34 What Affects the Thickness of the Bituminous Being Paved If the paver speed, the height of material behind the screed, and tow point height are held constant, there is only one screed angle of attack that will give you the desired mat thickness. If the paver speed, the height of material behind the screed, and tow point height are held constant, there is only one screed angle of attack that will give you the desired mat thickness. Slide 35 Slide 36 Slide 37 Paver Schematic Slide 38 Slide 39 Slide 40 Slide 41 Slide 42 TOW POINT Slide 43 Primary purpose of automatic screed control is to produce a smooth asphalt pavement layer. Primary purpose of automatic screed control is to produce a smooth asphalt pavement layer. Smoother than a screed operator can accomplish by continually changing the setting of the thickness control cranks. Automatics Screed Controls Slide 44 Automatic Screed Functions by: Automatic Screed Functions by: maintaining the elevation of the screed tow points in relation to a reference other than that of the wheelbase of the paver itself. Elevation of the tow point is kept at a constant elevation in relation to a given grade reference. The automatics dont allow the relative position of the tow point to change even though the tractor unit is moving up and down. The automatics dont allow the relative position of the tow point to change even though the tractor unit is moving up and down. Slide 45 Slide 46 Slide 47 Automatics of the Paver The paver operator controls the angle of attack of the screed. The paver operator controls the angle of attack of the screed. The automatic controls on the paver control the tow point height. The automatic controls on the paver control the tow point height. Slide 48 Checking the Mat Thickness Slide 49 Adjusting the Thickness Slide 50 Screed Reaction Time The screed reacts to change in angle of attack over 5 tow arm lengths. The screed reacts to change in angle of attack over 5 tow arm lengths. 65% of change occurs in the first tow arm length. 65% of change occurs in the first tow arm length. 35% of change occurs in the last 4 tow arm lengths. 35% of change occurs in the last 4 tow arm lengths. Slide 51 How Long Does it Take the Screed to React to an Adjustment of the Thickness Control Screw Slide 52 What do the Automatics on a Paver do? Slide 53 Contract Special Provisions Slide 54 Slide 55 Slide 56 Slide 57 Bituminous Web Page www.mrr.dot.state.mn.us/pavement/bituminous/bituminous.a sp Slide 58 Slide 59 Slide 60 Slide 61 Slide 62 Slide 63 Slide 64 Slide 65 Common Errors When Using Spread Sheets Most common error happens when the macros are disabled due to the security setting being set to high Most common error happens when the macros are disabled due to the security setting being set to high Set the security level to low Set the security level to low Move cursor to the menu on top and under the Tools menu, pick Tools: Macro: Security In the security dialog box, set the security level to low and press OK Slide 66 Slide 67 Slide 68 Common Errors When Using Spread Sheets Problems with creating random numbers Problems with creating random numbers The two versions of the core locations spread sheets use random number functions to pick the core locations. The program must make a decisi