A comparison of methods of assessing frost susceptibility

Frost heave damage in Britain is prevented by ensuring that all unbound materials, usually sub-base aggregates, within 450 mm of the road surface are non-frost susceptible as judged by the TRRL test. In the recently revised test, cylindrical specimens, compated by vibration hammer, are subjected to 96 hours freezing in a self refrigerated unit (SRU) rather than to a 250 hour freezing period in a cold room as formerly. When additional temperature monitoring is undertaken, parameters can be derived which are analogous to those obtained from USACRREL and French frost susceptibility tests. Data is presented from TRRL tests on a dozen aggregates at various gradings. There appears to be broad agreement between the classification systems used in Britain, the USA and France.