The immediate stability at the design water and binder content must be determined using the IBI test in accordance with BS EN 13286-47. The IBI value must be taken as the average of a set of 3 test specimen results.
Strength is taken as the average of at least 3 specimens. The mean of the test results must be greater than the specified strength (C1.5/2 or C3/4) and no individual result can fall below 67% of the strength requirement class. In addition, the mean of the test results must not exceed C9/12.