An aerial view of Outlack Quarry taken May 2001

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In-house Testing




In-house testing is now carried out at Outlack Quarry. Situated near the office, the new laboratory is able to carry out specific tests on our products to ensure their quality for our customers. Aggregate grading and Bituminous tests are the main tests carried out in the new laboratory, however we do intend on introducing new equipment to be able to carry out other tests as well in the near future.

Bituminous materials are tested for PSD (Particle Size Distribution) and Bitumen (Binder) content

How is our Asphalt and Bitmac Tested?

A number of samples are taken daily from lorries after the load has been discharged from the Asphalt Mixing Plant in specifically designed boxes. These are then kept warm in an oven with a set temperature until needed.

The samples are then reduced in size using a method called riffling or by quartering. The reduced sample of asphalt or bitmac is weighed on calibrated electronic scales and the weight recorded. Where the remainder is either dispatched to a waste pile or to a UKAS accredited laboratory so that final test results can be checked and compared.

Asphalt or bitmac samples are placed into a sampling basket and covered. These are then placed in the Carbolite« Asphalt Binder Analyser which determines the asphalt binder content of hot mix asphalt/bituminous mixtures by the loss on ignition method. Not only does using this equipment cut out health hazards with working with chemicals but it is also environmentally friendly. After the test is complete the results are printed, the sample removed and allowed to cool.

A sample being placed into a Carbolite« Analyser.

Once the sample is cooled to room temperature it is again weighed to check that the weight complies with the analyser results  and placed in a tray. The sample is submersed in water for a period of 24 hours to help break down lumps of fine aggregate.

The next day the water is removed by passing the saturated sample through a 63Ám sieve fitted with a guard sieve under running water so as to make sure the sample is clean. Clean samples are placed in the oven to dry out completely.

Washed samples are then ready to go through the aggregate grading process. This is done by putting a sample through a number of different sized sieves stacked with the largest size to the top, a collecting pan at the bottom and a lid on top are also added so that no aggregate can escape. The stack of sieves are then placed on a sieve shaker and shook for approximately 10 minutes.

Sieves stacked on a sieve shaker

The aggregate in each sieve is weighed and recorded and checked as to whether it passes specifications set by British Standards. It is then given a grade A, B or C. The bitumen content is also graded. Grades are recorded and filed.


How is our Aggregate tested?

This is done using the same aggregate grading process as detailed above. This time samples are taken from in most instances quarry stockpiles and storage bins on a weekly basis for sieve analysis and on a quarterly basis to test the aggregate shape, flakiness index and crushed particle index.


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Last modified: 10/20/05