MAKING TEST CUBES FROM FRESH CONCRETE:
Concrete cubes are made on site to check that the strength of the concrete is above the
minimum strength which has been specified.
Making, curing and testing cubes should be carried out in the correct manner. Even
small deviations from the standard procedures will usually lead to compressive strength
results which are lower than the true strength of the concrete. For example, for each 1%
air entrapped there will be a 4 to 5% loss of strength. The procedures for concrete cube
making are given in British Standard (BS) 1881:1983 Testing Concrete and Hong Kong
Construction Standard (CS 1:1990) Testing Concrete.
The sections applicable to site cubes are:
- CS1:1990:Section 1: Sampling fresh concrete on site
- CS1:1990:Section 7: Making test cubes from fresh concrete.
- Sample tray;
- Mould for making test cube;
- Steel float or trowel;
- Compacting bar;
- Vibrating hammer or vibrating table;
- Cleaning rags;
- A bucket or barrow for transporting the samples;
- Polythene sheeting;
- Curing tank.
Some of the tools and equipment required for cube making.