ABSTRACT
This is the first part of a two-part paper providing an experimental and analytical evaluation of the influence of natural fibres on the axial compressive behaviour of cement mortar matrices. This paper shows how the addition of sisal and coconut fibres in various volume fractions and lengths affected the compressive stress-strain behaviour of two mortar matrices. The influence of these fibres on the fracture process of mortars in compression is also evaluated. The use of undensified silica fume and blastfurnace slag as partial replacement of ordinary Portland cement (OPC) is also investigated. The results indicate that the addition of natural fibres reduced the compressive strength of the matrix by about 18 to 32, slightly reduced its elastic modulus and did not change significantly the Poisson's ratio. On the other hand, the fibres confined the material thereby delaying the first crack propagation and increasing the post-peak ductility. The results also indicate that the effect of sisal and coconut fibres reinforcement on the fracture behaviour of mortar up to failure stress is similar to the characteristics imparted by the increase in sand content in the mortar matrix. The partial replacement of OPC by slag and silica fume led to mixtures with a compressive strength slightly higher than those made with OPC. The cement replacement resulted in both decrease and increase in the elastic modulus, whereas the Poisson's was not significantly changed.
Key words:
composite materials; compressive strength; sisal fibres; coconut fibres; mortar; stress-strain curves