Many natural gravels classified as Type 2 sub-base materials in the Department of Transport Specification for Highway Works have adequate strength for roadmaking. However, some are unsuitable for use because they are frost-susceptible. Research was carried out on a frost-susceptible flint gravel to ascertain the effect of adding small amounts of hydrated lime, bentonite or Portland cement on the frost-heave of the material. The results showed that 2 per cent of cement or bentonite reduced the frost-heave to almost zero, and the same proportion of hydrated lime reduced the frost-heave by about a half. Tests were also carried out which verified that the additives at these levels did not reduce the strength of the material. (A)

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