This research has examined the optimum particle size of crumb rubber, used as an additive to concrete that would provide maximum freeze-thaw protection whilst minimising the compressive strength loss. The crumb rubber as used in the paper was divided into five batches, with increasing particle size, graded in increments of 0.5mm, from 2.5mm. The primary properties of the concrete investigated were; air content, freeze-thaw durability and compressive strength. These were tested using standard test methods. The range of tests used were conclusive in that the <0.5mm crumb rubber particle size, provided the greater degree of air entrainment. The freeze-thaw cycle results suggested that crumb rubber provided freeze-thaw protection, as the plain concrete deteriorated compared to the concrete with crumb rubber additions. There was no definitive correlation between the compressive strength and the crumb rubber particles size, although the rubberised concrete had an average strength loss of 5.24% after 28 days. This research indicates that crumb rubber graded up to <0.5mm is the optimum size to use, when crumb rubber granules are used to provide freeze-thaw protection in concrete.