2.2. Mix design
Concrete mix design was undertaken by using the method
documented in the ‘Design of Normal Concrete Mixes’ (Teychenne
et al., 1997) published by the Building Research Establishment.
This design method is based on the determination of the material
proportions.
The mix design of the reference concrete in this paper aimed to
achieve a target mean strength of 53 MPa (often referred to grade
C40/50) at 28 days with a slump value of 60e180 mm. A w/c ratio of
0.37 was determined according to the target mean strength, the
cement strength class and the type of aggregates. The amount of
free water used to achieve the designed w/c ratio was determined
according to the desired slump, the maximum size and the type of
aggregate. Cement content was calculated by the values of w/c ratio
and the amount of free water. Different sizes of rubber aggregates
were used to replace 20% of the fine aggregates by volume. The
amount of coarse, fine and rubber aggregates of each concrete
mixture were calculated.
Five concrete mixtures were produced to study the effect of
rubber particle sizes and their distribution: REF, CRA20, CRB20,
CRC20 and CCSR20. All mix design parameters were kept constant
throughout the experiment programme except for the fine
aggregate constituent. The mixture proportions are presented in
Table 2