Sorptivity tests alone cannot accurately predict the service life of concrete. As we have shown, sorption rates can strongly depend on the degree of saturation and any estimate of service life must make reasonable assumptions about the exposure of the concrete specimen to a variety of weather conditions and wetting-drying cycles. A more general approach may be to consider the capillary diffusivity [5], [22] (see appendix) which relates the rate of sorption to the degree of saturation. Such information may then be used in models to predict moisture transport which account for the environmental exposure of concrete. However, in the determination of capillary diffusivity, we have shown that care must be taken to correctly account for surface effects. Also, estimates of capillary diffusivity made from measurements made over short time intervals will not properly take into account the effect of smaller pores which appear to dominate sorption at long times. Nevertheless, since the sorptivity of a material should be inversely correlated with its degradability, sorption measurements performed on uniformly prepared concrete and mortar specimens can provide useful information concerning quality control and the determination of which samples are likely to have a longer service life. For instance, sorption measurements could be useful for the determination of frost resistance of concrete by predicting how easily critical saturation is reached.
In addition, our studies indicate that in many cases, sorptivity may be the main controlling factor determining the service life of building materials like concrete. For materials subject to wetting/drying cycles, capillary transport may provide a more rapid means of ingress of chlorides than diffusion and, further, sorption appears to be less sensitive to the curing period than diffusion implying that sorption remains a more robust transport process over time.