The problem with understanding the properties of polypropylene fibres in concrete is that there are many types of fibre, with many suggested properties and conflicting claims made by both manufacturers of polypropylene fibres and researchers in the field of material science as to the effects of fibres on compressive strength, flexural strength, post crack performance, absorption reduction and freeze/thaw durability of concrete. From an initial pilot study, utilising standard BSI and ASTM tests and devised non-standard tests, including measurement of grout resistivity an extensive test programme was conductec to determine the effect of polypropylene fibres on the freeze/thaw behaviour of concrete.