Section 9: Checking the Loader Operation
Introduction
The loading of aggregate from stockpiles into the haul trucks
is very important to the success of a seal coat application. This
operation is sometimes overlooked because it is somewhat removed from
the center of activity. Every effort should be made to watch the
loader operation activity early in the project and spot-check it
periodically thereafter.
Loader Operation Checklist
Gradation
. The loader operator should
take a representative scoop of aggregate with each bucket. Graded
aggregate will tend to segregate somewhat when it is stockpiled.
Finer particles tend to sift between the coarse particles, making
the stockpile show a greater content of coarse particles near the
top and outside. The bucket on the front-end loader should penetrate
the stockpile near the bottom and penetrate deeply enough to have
a full range of the aggregate gradation.Contamination.
The loader operator usually
tries to use every bit of aggregate available on the stockpile.
In doing so, the bucket may scrape too close to the bottom of the
stockpile allowing clay balls or grass to be picked up along with
the aggregate. Aggregate containing contaminants should not be used.
If there is grass, clay, or soil being placed in the spreader box,
the loader operation must be corrected immediately.Degradation.
The loader should be operated
carefully to avoid degradation of the aggregate. The operator should
not operate the equipment in such a manner that causes the front
wheels to roll over any of the stockpile. This will cause the larger
pieces to be crushed into smaller particles changing the aggregate
gradation.Full Trucks.
The operator should fill
every truck to its predetermined calibrated level. This will ensure
that the contractor is paid for the correct amount of aggregate,
and the aggregate is applied at the desired application rate refer
to
of the 2014 TxDOT Standard Specifications for Construction
and Maintenance for Highways, Streets, and Bridges.Excessive Dust.
Sometimes projects can
have problems with excessive dust in the aggregate stockpile. If
a cloud of dust occurs with every bucket load that is placed in
the trucks, the dust may be detrimental to the seal coat performance.
If dust is a problem, it may be reduced by lightly sprinkling the
stockpile with water. Only enough water should be used to reduce
the dust, and this is only recommended when emulsions are being
used.