Testing of industrial products - Aggregates for construction

The Dutch Static Compression test method

The principle of the method

The DSC test is carried out on a size fraction d/D mm (where D = 1.414 d). The size of the test specimen is determined as the mass of this size fraction of the aggregate required to fill a one-half litre measure.

The test is performed by crushing the aggregate in a compresion testing machine using a cylindrical steel mould. The load is increased from zero to 200 kN over 60 seconds, and then maintained at 200 kN for a further 30 seconds.

The test specimen is then sieved on a test sieve with aperture size d/2 mm. The result of the test, the DSC value, is the amount of the test specimen that passes the test sieve, expressed as a percentage by mass of the mass of the test specimen.

The test is carried out on two test specimens, and the average of the DSC values for two test specimens is reported as the crushing strength.

History of the test

About fifty years ago, with a need for a more dense infrastructure, and with growing traffic in the Netherlands, more and more aggregates were needed, and it was necessary to introduce specifications that included several levels of strength and of polishing resistance, and a variety of grading requirements. For that reason, among others, a strength test for coarse aggregates was developed based on a static compression test used in the United Kingdom. Over the years, some minor changes have been made to the British test, and the result is now the Dutch Static Compression Test. This has proved to be a simple, quick and nevertheless reliable test.

The following paragraphs were taken from the second draft of NEN 6245 Crushed aggregates for bituminous mixtures and surface dressings. Determination of the crushing percentage under static load. They were translated and adapted for the cross-testing programme.

Equipment and aids

  1. Sieves according prEN 993 part 2.
  2. A sample divider according prEN 932 part 1.
  3. A drying oven (110 ± 5) °C.
  4. A cylindrical metal measuring cup with a wall thickness of at least 5 mm and an inner diameter equal to the height of (86,0 ± 0,3) mm and a volume of (0,50 ± 0,06) dm3.
  5. A balance, reading accuracy 1 g.
  6. A cylindrical stainless steel mould with an inner diameter of (112,8 ± 0,5) mm, a height of (112,8 ± 0,2) mm and a wall thickness of (6,0 ± 0,5) mm. Inner surface of the mould (100,0 ± 0,5) mm2 equipped with a matching base plate with a thickness of (6,0 ± 0,5) mm under the edges and a thickness of (11 ± 1) mm within the inner surface of the mould.
  7. A stainless steel stamp with a diameter of (110,8 ± 0,5) mm and a thickness of (16 ± 1) mm equipped with an upgoing central part with a diameter of (90 ± 1) mm and a height of (97 ± 1) mm. Total height of the stamp (113 ± 1) mm.
  8. A compressing machine equipped for gradually increase a load to (200 ± 2) kN and to maintain this load during (30 ± 1) s.

Procedure.

Sieve the sample out by wet sieving on the prescribed sieves and dry the acquired fraction to constant mass.

Conduct the following density measurements:

Fill the measurement cup with the dry fraction material while compacting by pushing the cup with the material with short heavy movements on a flat surface. After compaction fill the cup with some particles in such a way that a flat surface is obtained which in average complies with the upper side of the cup.

Weigh the material in the cup with an accuracy of 1 g. Carry out this density measurement at least 3 times using - if possible - new material for each measurement. Calculate the average of this measurements with an accuracy of 1 g. (m0)

Weigh m0 material and pour this into the mould, without compaction, in such a way that the material forms a more or less even plane. Put the stamp on the material in the mould and put the whole in the compression machine.

Increase the load gradually in (60 ± 1) s to (200 ± 2) kN and maintain this load for (30 ± 1) s.

Remove the crushed material out of the mould and sieve it out by dry sieving on a sieve half the size of the lower fraction limit and weigh the mass of the material on that sieve with an accuracy of 1 g. (m1)

Carry out this crushing test twice using m0 g new material. If the results differ more than 3 % (m/m) increase the number of tests to 4.

Calculation

Calculate the crushing percentage of each determination with an accuracy of 1 % with the following formula:

Vp = 100 (m0 - m1)/m0

where:

Vp = the crushing percentage

m0 = the mass of the material in the mould

m1 = the mass of the material on the prescribed sieve.

Calculate the test result as the average of the 2 or 4 measurements with an accuracy of 1 % (m/m).