Commonwealth of Pennsylvania
Department of Transportation
PA Test Method No. 637
October 2013
9 Pages
LABORATORY TESTING SECTION
Method of Test for
CALIBRATION OF MOBILE MIXERS USED FOR
LATEX MODIFIED MORTAR (LMM) AND LATEX MODIFIED CONCRETE (LMC)
1.
PURPOSE
1.1
2.
EQUIPMENT
2.1
3.
This method provides a procedure for the calibration of mobile mixers used in
placing latex modified mortar and concrete.
Necessary equipment includes 8 L (2 gal.), 76 L (20 gal.), and 114 L (30 gal.)
containers. A balance meeting the requirements of AASHTO M-231, Class G2.
PROCEDURE
3.1
Cement:
3.1.1 Check the aggregate bins to insure that they are empty and clean.
3.1 2 The ground strap shall be down.
3.1.3 Run cement out of the bin to the charge belt.
3.1.4 Begin recording masses and times when the cement mass is close to 43.5
kg (95.88 lbs.) and is consistent.
3.1.5 Record masses and times on the Field Calibration Sheet (Field Calibration
Sheet is appended to this PTM).
NOTE 1- If the calibration of cement is performed with aerators on, these
aerators must be on during placement.
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October 2013
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3.2
Fine Aggregate (F.A.):
3.2.1 Load the fine aggregate bin(s).
3.2.2 Run the fine aggregate out of the bin to the charge belt.
3.2.3 Check the bin(s) to insure aggregate is flowing evenly and is not packing or
"hanging up".
3.2.4 Determine the F.A. discharge rate (mass/sec.) as follows:
Total design mass / Number of bags = mass/bag
Mass/bag + F. A. moisture mass = Actual mass
F. A. moisture mass = mass/bag x % moisture
Actual mass / time = mass/sec
NOTE 2 - This mass of fine aggregate is the saturated surface dry mass
(S.S.D.) and must be adjusted to include aggregate moisture (% moisture
from CS-4220A, Batcher-Mixer Slip).
3.2.5 Record the first mass under SAND on the Field Calibration Sheet (Field
Calibration Sheet is appended to the PTM) when it nears the required
amount of fine aggregate as calculated under Section 3.2.4 above.
3.2.6 Run the aggregate until at least three (3) consecutive trials are consistent
and acceptable (refer to the design and specification for allowable
tolerances).
3.2.7 Record the fine aggregate mass and corresponding time on the Field
Calibration Sheet.
3.2.8 Record the dial settings on the Field Calibration Sheet.
3.2.9 Insure that the settings are secured.
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October 2013
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3.3
Coarse aggregate (C.A. when the F.A. bin is emptied) applies to Latex Modified
Concrete:
3.3.1 Empty the mobile mixer of fine aggregate.
3.3.2 Load the coarse aggregate bin.
3.3.3 Run coarse aggregate out of the bin to the charge belt.
3.3.4 Check the bin to insure aggregate is flowing evenly and is not packing or
"hanging up".
3.3.5 Determine the C.A. discharge rate (wt./sec.) similar to the F.A. procedure
as stated in Section 3.2.4.
3.3.6 Record the first mass under STONE on the Field Calibration Sheet (Field
Calibration Sheet is appended to this PTM) when it nears the required
amount of coarse aggregate as determined in Section 3.3.5 above.
3.3.7 Run the aggregate until at least three (3) consecutive trials are consistent
and acceptable (refer to the design and specification for the allowable
tolerances).
3.3.8 Record the coarse aggregate mass and corresponding time on the Field
Calibration Sheet.
3.3.9 Record the dial setting on the Field Calibration Sheet.
3.3.10 Insure that the setting is secured.
NOTE 3 - Masses of both fine and coarse aggregates are saturated surface
dry (S.S.D.) masses and must be adjusted during calibration to include
moisture (% moisture from CS-4220A, Batcher-Mixer Slip).
3.4
Coarse Aggregate (C.A.) when the F.A. bin is not emptied: applies to Latex
Modified Concrete:
3.4.1 Leave the F.A. bin intact or recharge if necessary.
3.4.2 Load the coarse aggregate bin.
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October 2013
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3.4.3 Run aggregate out of the bin to the charge belt and insure that the
aggregate is flowing evenly and is not packing or "hanging up".
3.4.4 Start with the last dial setting as a guide if available or applicable.
3.4.5 Determine the aggregate discharge rate (wt./sec).
3.4.6 Determine the required aggregate mass (C.A. and F.A.) for calibration
(Suggest using 10 sec.).
3.4.7 Record the first mass under STONE on the Field Calibration Sheet when it
nears the required amount of aggregate as calculated by calibration
(Section 3.3.6. above).
Note 4- (After STONE, that mass includes sand and stone).
3.4.8 Run the aggregate until at least three (3) consecutive trials are consistent
and acceptable. (Refer to the specification for allowable tolerances).
Important: Adjust only the coarse aggregate dial.
3.4.9 Record the aggregate mass and corresponding time on the Field
Calibration Sheet.
3.4.10 Record the stone dial setting on the Field Calibration Sheet.
3.4.11 Insure that the dial setting is secured.
NOTE 5 - Masses of both fine and coarse aggregates are saturated surface
dry (S.S.D.) and must be adjusted for calibration to include moisture
(% moisture from CS-4220A, Batcher-Mixer Slip).
3.5
Latex:
3.5.1 Set the gauge to design the discharge rate (liters/min.) (gals/min.)
determined from the design and cement discharge time recorded in
Section 3.1.
3.5.2 Weigh the latex to insure that the gauge is accurate.
3.5.3 Discharge the latex until at least three (3) trials are consistent.
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October 2013
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3.5.4 Record the latex gauge settings on the Field Calibration Sheet.
3.6
Water:
3.6.1
Run the water flow meter at settings between 0 and 7.5 L/min. (0 and 2
gpm).
3.6.2
When the flow has stabilized, insert the container in midstream and start
timing. At the end of prescribed time, remove the container from the flow.
3.6.3
Weigh the water to insure accuracy of the flow meter.
3.6.4
Run at least three (3) trials at this flow rate (liters/min) (gals/min).
3.6.5
Record the rate on the Field Calibration Sheet.
NOTE 6 – The R.P.M. of the mobile mixer shall be maintained at the
operating speed throughout calibration (obtained from the metal plate on
the truck).
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October 2013
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PTM No. 637
October 2013
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CS-4342
M (1-96)
EXPLANATORY NOTES
(1)
From approved Mix Design (TR-4221-A), Mix Design Worksheet
(2)
Mass/cu.meter X % moisture in sand = Sand Moisture Mass
(3)
Adjust the dial setting until the masses for 3 consecutive trials (minimum) are
consistent and compare to the calibration mass within the tolerances stated in the
special provisions.
(4)
Mass/cu.meter X % moisture in stone= Stone Moisture Mass.
(5)
Use the TIME from the cement calibration to the nearest second.
(6)
Acceptable if within the tolerances given in the special provisions as compared to the
calculated mass and are consistent for 3 trials minimum.
(7)
Selected gauge setting shall be between the minimum and maximum flow rates (kg./
minute) as determined from the modified CS-4220A, Batcher-Mixer slip form.
(8)
Calculation of the Maximum, Minimum, and Design Water Gauge Setting:
Design Water based on the average of Maximum and Minimum Water-Cement ratios.
Maximum
Design
Water-Cement ratio X mass of Cement/ cubic meter = Total mass of
Minimum
Water
Total kg. of water
kg. of latex X % water in latex
Total aggregate moisture
=
= – __________
= – __________
Maximum
= kg. Design Water to be
Minimum added
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October 2013
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EXPLANATORY NOTES (CONTINUED)
Maximum
kg. Design
water to be added X 60
Minimum
–––––––––––––––––––––––––––––––– =
kg. of cement X Calibration time for kg.
of cement
Maximum Water
kg. p.m. Design
Gauge
Minimum Setting
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