Specifying durable and sustainable concrete
Low w/c ratio concrete is much more than simply stronger concrete (Aïtcin, 1998). It cannot be speciﬁed in the same way as usual concrete because some of the consequences of the hydration reaction that do not signiﬁcantly affect the properties of usual concrete can no longer be ignored. For example, low w/c ratio concretes are very sensitive to:
• external temperature, as well as their initial temperature after batching; • the selection of the cement-superplasticizer combination (Aïtcin, 1998); • drying shrinkage (Aïtcin, 1998); • the development of autogenous shrinkage (Aïtcin et al., 1997); • the mechanical characteristics of the coarse aggregate when making a
very strong concrete or a concrete with a high modulus of elasticity (Aïtcin and Mehta, 1990; Nielsen and Aïtcin, 1992).