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Section 9: Checking the Loader Operation

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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.

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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 Item 9 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.

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