Effect of fibre type on the compressive and tensile strength of a soft soil chemically stabilised

This study compared the performance of steel and polypropylene fibres, with a dosage of 50 kg/m³, used to reinforce a soft soil chemically stabilised for a constant binder quantity of 375 kg/m³. The experimental programme is comprised by the study of four kinds of fibres with four types of tests, to evaluate the unconfined compressive strength, direct tensile strength, split tensile strength and flexural strength. The results indicate that the reinforcement with fibres decreases the brittleness of the composite material and that the highest ductility is obtained with the use of poltpropylene fibres. The experiments show that the effect of the inclusion of fibres in the soil–binder paste depends on the type of fibre and the failure mechanism, i.e., the strain level imposed by each kind of test. Thus, although the use of any type of fibres has a detrimental impact (17 to 32%) on the compressive strength, but it has a positive effect on the tensile strength when evaluated by flexural strength tests (25 to 147%). However, if the tensile strength is characterised by split tensile strength tests, the addition of steel or polyproylene fibres has a negligible or a positive impact (2 to 47%), respectively, while the results of direct tensile strength tests indicate the positive impact of steel fibres (16 to 27%) and a detrimental effect of the polypropylene fibres (35 to 45%).