Compression Strength Test

The Compression Test measures the concrete strength in the hardened state & shows the best possible strength a concrete block can reach in perfect conditions. The testing is done in a laboratory off-site & the only work done on-site is to make a concrete cylinder for the compression test.
The strength is measured in Megapascals (MPa) and is commonly specified as a characteristic strength of concrete measured at 28 days after mixing. The compressive strength is a measure of the concrete’s ability to resist loads which tend to crush it.

Tools:
Cylinders (100mm diameter x 200 mm high or 150 mm diameter x 300 mm high)
(The small cylinders are normally used for most testing due to their lighter weight)
Small Scoop
Bullet-nosed rod (600 mm x 16 mm)
Steel Float
Steel Plate

Methods:

  • Clean the cylinder mould and coat the inside lightly with form oil. Then place on a clean, level and firm surface, (i.e.), the steel plate.
  • Collect a sample.
  • Fill the ½ the volume of the mould with concrete then compact by rodding 25 times. Cylinders may also be compacted by vibrating using a vibrating table.
  • Fill the cone to overflowing and rod 25 times into the top of the first layer, then top up the module till overflowing.
  • Level off the top with steel float and clean any concrete from around the mould.
  • Cap, clearly tag the cylinder and put it in a cool dry place to set for at least 24 hours.
  • After the mould is removed the cylinder is sent to the laboratory where it is cured and crushed to test the compressive strength.