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Laboratory mixture design procedure for HBM

The producer must design the mixture in accordance with the procedure described here to meet the compressive strength of A10.2.17.
The composition of HBM must be based on mixture design testing carried out using a minimum of 3 binder contents and a minimum of two water contents at each binder content.
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.
The effect of immersion in water on compressive strength must be assessed in accordance with BS 1924-2 as follows:
  1. y1 and y2 = 20°C for mixtures containing cement or 40°C for mixtures not containing cement
  2. RRc must be ≥80
  3. On completion of the immersion stage (y2) the test specimens must show no signs of cracking or swelling
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.
HBM must be non-frost susceptible. Material is classed as non-frost-susceptible if:
  1. the compressive strength class is C3/4 minimum, or
  2. the mean heave is 15 mm or less, when tested in accordance with BS 812-124, with the sample preparation in accordance with BS 1924-2.