IDENTIFYING MAT FAULTS Reading the Mat IDENTIFYING MAT FAULTS TAKING THE CORRECT REMEDIAL ACTION

Too Many Experts! They Cause Confusion & Make a Mess of Things

Reading the Mat Mission Statement “Produce a Blemish Free Mat Free From Lines (Steps), Streaks, Dragging (Tearing), Segregation, and/or Texture Differential.”

Identifying Blemishes in the Mat Reading the Mat Identifying Blemishes in the Mat Terminology: - Severe Marks - Texture Differential - Segregation - Steps,Miss Matched Lines - Voids - Streaks - Dragging (Tearing) - Crushing Aggregate - Cracking

SEVERE MARKING OF THE MAT READING THE MAT SEVERE MARKING OF THE MAT

Counter this with Screed Lock Mat Marks Counter this with Screed Lock When Paver Stops: Screed Weight Becomes the Dominant Factor

Showing up on Profilograph READING THE MAT Severe Mark in Mat Showing up on Profilograph Cause 1. Paver stopped due to lack of material 2. Roller stopped too close to paver Remedy 1. Good material delivery 2. Minimize paver stops 3. Balance paver & roller speeds with material delivery 4. Roller to stop on previously compacted mat

Texture differential caused by screed extensions being too high. Known as ‘Double Screeding’

Shadow

Shadow Problem

Mat quality beginning to change

Left side mat quality greatly improved

Mat quality on completion

Mat quality on completion

READING THE MAT Cause Remedy 1. Adjust extension height Mat Shadows (Texture differential) Cause Uneven distribution of screed weight over mat area Remedy 1. Adjust extension height 2. Decrease angle of attack of extensions

SEGREGATION THROUGH THE PAVER READING THE MAT

Cool mix is being segregated by the augers

Segregation & cooling is caused by multiple handling of the material

Segregation through paver READING THE MAT Segregation through paver Cause 1. Poor material 2. Use of pick up machine with no hopper insert 3. Material breaking up in augers Remedy 1. Avoid segregation at plant during loading 2. Dump material en-masse in to hopper or use MTV with hopper insert 3. Keep hopper full, set flow gates and augers at optimum position 4. Refer to road institute/NAPA publications

CENTER LINE STREAKING READING THE MAT

Any paver with a center drive auger box may cause center line streaking when using certain materials Adjustment must be made to the tractor and the screed to eliminate these marks

Insufficient material getting under auger drive box READING THE MAT Center line streak Cause Insufficient material getting under auger drive box Remedy 1. Raise augers & flow gates 2. Check condition and position of kick back auger flights 3. Adjust side arm to rearmost position at tow point to move screed further back

STEPS OR SCREED MARKS IN MAT READING THE MAT

Stone caught at screed causing dragging of the mat What’s wrong here ?

Forward Mounted Extensions What's Wrong? EXTENSIONS TOO HIGH!

Front Mounted Extensions What's Wrong? EXTENSIONS TOO LOW!

Rear Mounted Extensions Extensions Too High! What's Wrong?

Rear Mounted Extensions Extensions Too Low! What's Wrong?

2. Extension Angle of Attack What's wrong? 1. Cold Extension 2. Extension Angle of Attack

What's wrong? Transition Lines Made by Extension Being Incorrectly Set to Main Screed

Incorrectly set up screed or screed twisting READING THE MAT Steps or lines in mat Cause Incorrectly set up screed or screed twisting Remedy 1. Ensure screed is set up up correctly prior to work starting 2. Adjust screed as necessary on the fly 3. Be aware of your screed gauges 4. Do not chase lines that come and go

HOLES OR VOIDS IN THE MAT READING THE MAT

READING THE MAT Holes in the mat Cause Hopper running out of material between truck loads (head of material fault) Remedy Keep hopper 30% full at all times Install material level indicator kit

INSUFFICENT THICKNESS OF MATERIAL READING THE MAT DRAGGING AND TEARING & INSUFFICENT THICKNESS OF MATERIAL

Dragging & Crushing rock through laying too thin

Maximum Thickness Approximately Angle of Attack Too Low Maximum Thickness Approximately 4 to 5 x Nominal Rock Size Minimum Thickness 1.5 to 2 x Nominal Rock Size (3 x For Superpave) Mat Dragging & Crushing Rock Due to Insufficient Angle of Attack Base or Lower Surface

READING THE MAT Dragging and tearing of the mat & crushing rock Cause 1. Cold screed 2. Paving speed 3. Poor material quality 4. Laying too thin Remedy 1. Heat screed correctly to the desired temperature 2. Reduce paving speed 3. Have plant check out material quality 4. Increase angle of attack

READING THE MAT SUMMARY Whenever a fault appears in the mat, trace it back to the screed and tractor and investigate the cause. Consider screed operation and adjustment, paver operation, set-up or adjustment, material quality and temperature and foreign objects. Determine the cause and take the correct remedial action.