calibration

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HM Plant Calibration,
Laying, Compaction,
and Testing
BY
CHANDRA SEKHAR PASUPULETI

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Objective
 What is calibration of Hot Mix Plant
 How to do the calibration
 How to set the crushing pattern
 Various steps to take care of good Laying,
compaction.
 The Factors affecting the compaction
 Quality control

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HM PLANT
CALIBRATION

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HOT MIX PLANT

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What is calibration?
The calibration of HM plant is not only checking the
weighing scales, setting up appropriate cold bin feeding
as well as crusher quarry are also comes under this
chapter. Because…..
HM plant calibration

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Plant capacity:
• Plant capacity = f(Pug mill size)
• Hourly rate = f(batch size, cycle time)
• What else affect the plant capacity??
(Here, output is plant capacity)
Input Process Output
HM plant calibration

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Input:
• Material storage
• Cold feed
• Dryer
• Screening unit
• Hot bin setting
• Environmental conditions etc
HM plant calibration

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Material storage:
• Proper stacking
• Protection from rain and foreign matters etc.
HM plant calibration

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What is cold bin and hot bin?
Cold feed
• Cold bin aggregate
Sizes : 28 mm, 20 mm, 10 mm, Q/D
• Hot bin aggregate
Sizes : 16-24 mm, 8–16 mm, 4–8 mm, 0-4
mm, R/Filler
Which of the above two is base for mix design?
HM plant calibration

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HM plant calibration
How to fix the cold bin feeding?
 Individual grading
 Blending
 Calibration of cold feeders

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Individual gradation and blending
1. Correct sampling and number of samples
2. Careful grading and blending to fix the necessary
proportions.
E:presentation 27.07.06plant calibrationindividual
grading.xls
HM plant calibration

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Calibration of cold feeder:
• Cold feeding =
f(conveyer belt speed, gate opening)
• Conveyer belt speed (s), m/sec
• Select any one size
• Check the moisture content (w), %
• Keep the gate opening at certain scale
HM plant calibration

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• Run the plant and take the material collected in
1 m length of belt, take the weight (Wm),kg.
• Dry weight (Wd) = Wm / (1+w) per m
• material per second, W = Wd X s
• Determine the ‘W ’ for different openings.
HM plant calibration

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• Establish a graphical relation b/n gate opening
vs. dry weight of material delivered per second
• Do the same for all sizes
• From the graphs select the required opening to
feed different sizes as per the mix design
blending proportions.
E:presentation 27.07.06plant calibrationindividual
grading.xls
HM plant calibration

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Relation ships established:
1. 28mm: y = 0.0043x - 2.2363, R2 = 0.9967
2. 20mm: y = 0.0047x - 5.4685, R2 = 0.9985
3. 10mm: y = 0.0033x - 0.5832, R2 = 0.9984
4. Q/dust: y = 0.0035x - 0.125, R2 = 0.9992
Where y = opening size and
x = weight in gm
HM plant calibration

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Say, required production is 100 ton /h,
Total mix = 100 ton.
Total aggregate, if bitumen is 4.5%
= 100-100*.045 = 95.5 ton
Based on blending proportions are:
40 mm : 0 % 20 mm = 36%
10 mm = 23% C/Dust = 41%
HM plant calibration

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20mm required per hour = 95.5*0.36 = 34.4 ton
Belt run in 1 h = 1.3920*60*60 m = 5011.2 m
Material required per meter run = 34.4/5011.2 = 6865
gm
Therefore, from eq.2,
gate opening, y = 0.0047x6865 - 5.4685 = 27
Likewise gate openings for all the sizes can be
calculated.
HM plant calibration

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HOT BIN PROPORTIONING:
• It is very much necessary to set the hot bin
openings in such a way that all the cold feed
material is consumed at any point of time.
Procedure:
• Empty all the hot bins cleanly and close.
• Close all the cold feed, and release only one size.
• Run the material at certain opening for certain time.
HM plant calibration

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• Let all the material screen through various sizes of
screens in the drum
• Check the material collected in different bins
• Take the weights of each bin.
• Calculate the % of material collected in each bin.
HM plant calibration

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Cold feed vs. Hot bins
0 – 4
(6.4+38.2=
44.6)
28 mm (0 %)
4 – 8
(7.5+1.9+1.4
=10.8)
8 – 16
(9.1+25.8=
34.9)
16 – 24
(0 + 8.3 =
8.3)
20 mm (36%)
Q/Dust (41%)
10 mm (23%)
R/Filler
(1.4)
7.5% 92.5%
5.4% 71.7% 22.9%
27.7% 32.6% 39.6%
3.4%
93.3%
3.3 %

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Therefore, hot bin proportions to be set at
• 16 – 24 = 8.3%
• 8 – 16 = 34.9%
• 4 – 8 = 10.8 %
• 0 - 4 = 44.6 %
• R/Filler = 1.4%
These are the proportions, according to the cold bin
feeding
Set the crusher production to meet cold feed or
vise versa
Cold feed vs. Hot bins

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Summary of Advantages of calibration:
•No overflow from hot bin
•No segregation in the mix
•Increases the production capacity
•Correct job mix
•Balance with quarry production
•Reduction in re_handling
HM plant calibration

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Laying, Compaction,
and Testing

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Laying and compaction of the mix is the process to
which all the other operations are directed.
Planning and preparation
Prime coat / Tack coat
Paver: It spreads the mixture in a uniform layer of
desired thickness and shape, or finishes the layer to the
desired elevation and cross section, ready for
compaction.
Laying

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Laying
Paver:
Working speed, width, thickness
Various forces acting on the screed
To achieve better compaction and level with paver
•The forces acting on the screed must be constant
To take care of these forces
•Material feeding in the hopper must be consistent
and adequate.

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Laying
Paver:
•Material should be dumped with uniform thickness
•Sensor forces and the compacting forces on the
screed should not be vary
Starting wooden blocks may be used to set the paver
initially.
Maximum size of the aggregate must be 1/3 of
compacted thickness
Screed heaters also should be used initially, but not
during the paving

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Laying
Trucks:
Take care of hydraulic oil leakages
Tarpaulin should be used during cool weather and long
hauling. The procedure to spread the tarpaulin also
important.
Backing of loaded trucks to the paver.
Truck must be totally loaded at a time.
Trucks must be clean and free from foreign materials
before loading.
Trucks may be coated with some releasing agents to
avoid the sticking of mixture.

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Laying
Visual inspections:
Is there any blue smoke on the mix ( in the truck)
Shape of the mix in the truck (dome, flat)
Rate of temperature decrease in the mix
Dull appearance of the mix
Contamination of the mix at the bottom due to excess of
releasing agents. Bleeding may occur due to this.

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Laying
Joints:
These are the main causes of early distresses due to
poor density at joints.
Joint in the first lift and second lift should not be
coincided.
Transverse joints must be vertically cut before starting
from there.
Rolling must be parallel to the joint.
150mm increments of roller from the old pavement.

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Laying
Longitudinal joints must be treated carefully be
cleaning, tack coating and then over lap of paver about
25mm at least.
Coarse aggregates near the joints must be removed
and wasted.
Hot longitudinal joints generally have no problems.

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Compaction – general mechanism
General mechanism:
Compaction = f( Compressive force, restricting force
incl. confinement)

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Compaction
Factors affecting compaction:
1. Mix properties and characteristics of the
ingredients.
2. Environmental condition
3. Lift thickness
4. Sub grade base

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Compaction
1. Mix properties and characteristics of the
ingredients:
Effect of maximum size of aggregate
Texture, contact area of aggregate
Grading type (Open grade may need more effort)
Crushed or natural aggregate
Compaction temperature should be more than 85oC

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Compaction
1. Mix properties and characteristics of the
ingredients:
Rolling at less than 85oC will rather reduce the density
Temperatures of various construction activities must be
established

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Compaction
2. Environmental conditions:
Wind velocity,
Humidity,
Ambient temperature
Temperature of the surface on which paving to be done.

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Compaction
3. Lift thickness:
To get better compaction thickness should be more or
less in bituminous mixes??
.

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Compaction
4. Sub grade base and confinement:
These must be good enough to take the forces of
vertical and horizontal to get better compaction
.

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Compaction
Cold weather paving:
Need to take the following precautions:
• Lift thickness
• Mix temperature
• Hauling distance
• Plant speed
• Number of rollers
• Distance b/n roller and paver
• Paver speed
• Insulate the trucks

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Compaction
Rollers: Should be self-propelled
Steel wheeled static roller
Pneumatic roller
Vibratory roller

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Compaction
Steel wheeled static roller
Min. wt. 9 ton for heavy duty works
Wt. Can be changed by adding/removing ballasts
Can be used for break down , intermediate, and finished
rolling.
Should be free from grooves, pits, worn etc.
Position power wheel and tiller wheel (Normal and
steep grade pavements)

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Compaction
Steel wheeled static roller:
Advantages of power wheel moving ahead.
• Higher diameter
• Heavier relatively

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Compaction
Pneumatic roller:
Wheels oscillates
Same effect on the pavement like traffic.
Can be used for break down, intermediate, and also to
condition the asphalt surface.
Conditioning helps in reducing permeability and
increase the resistance to abrasion.
Tyre pressure should not be vary more than 35 Kpa

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Compaction
Pneumatic roller:
Sub grade must be good enough as the pressure
exerted would be more than the static steel wheel
roller.
For rolling
Min wt per wheel. : 1360 to 1590
Min dia : 510 mm
Tyre inflation pressure : 486 to 517 Kpa

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Compaction
Pneumatic roller:
For conditioning
• Min wt. Per wheel : 680
• Min dia : 380 mm
• Tyre inflation pressure : 345 - 415 Kpa
Kneading type rolling can be performed for more
than two weeks also, which will increase the surface
performance and not at all density.

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Compaction
Vibratory roller:
• Weight
• Frequency
• Amplitude
How vibrations are created in the roller?
• Off-centric load

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Compaction
Vibratory roller:
What is frequency?
• No of cycles per minute
• More the spinning speed more the load exerted,
more the eccentric load more the load exerted.

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Compaction
Vibratory roller:
Amplitude
• More the eccentric load more the amplitude,
more the impact load
• Keep the speed and the frequncy matched to get
better surface.
• At least 10 vibrations per feet

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Compaction
Vibratory roller:
• For thin layers – low amplitude – max frequency
• For thick layers – high amplitude – max
frequency

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FOR ANY ROLLER. INCREASE THE NUMBER
OF PASSES BY INCREASING SPEED,
WILL NEVER GIVE THE BETTER COMPACTION
Compaction
IRRESPECTIVE OF ROLLER TYPE,
THE SPEED SHOULD BE : 5 – 8 KMPH

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Where to control the quality?
• Plant
• Field – before laying
• Field – after laying
Quality Control

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What is to be controlled at plant?
• In coming material quality check
• Cold-bin and hot-bin proportioning
• Gradation
• Bitumen content
• Temperature
Quality Control

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Quality Control
Control tests at site?
• Temperature check at various operations.
• Paving and compaction by paver
• Thick ness
• Levels
• Fixing of censer with compaction factor
• Rolling (number of passes need to be established)

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Quality Control
Tests on finished surface?
• Levels (+ 6 )
• Density ( Min : 98%)
• Surface un evenness
• Roughness

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Quality Control
Inspection and Test Plan (ITP)
bitum mix designlaying com distressDBM ITP.xls

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THAN Q
ANY QUESTIONS ?????