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.