Behaviour of fibre-reinforced cemented sand under flexural tensile stress

Abstract

In soil improvement, the insertion of cement to the soil matrix provides an increase in strength and rigidity of the material, whereas fibre addition provides an increase in ductility, reducing post-peak loss in strength. This research aims to experimentally analyse the mechanical behaviour of unreinforced and fibre-reinforced cemented sands under flexural tensile monotonic loading conditions. In order to do so, an experimental program was planned using silty sand (Arenito Botucatu), early strength Portland cement – CPIII, and polypropylene fibres 24 mm long and 0.023 mm thick. Three different dry unit weights (γd) (18, 19 and 19.7 kN/m³), three cement contents (3, 5 and 7%), and two fibre contents (0 and 0.5%) were chosen. Analysing the results, an increase in cement content generates an increase in flexural strength (qf) for all concentrations and the increase in γd generated smaller qf gains, especially for lower cement contents. The addition of fibres generated a qf increase for lower γd but at higher γd there was a reduction in the influence of fibre addition on strength gain. The reduction can be attributed to an entanglement of the fibres in higher compaction strengths, disrupting the formation of cementitious bonds. However, based on a qualitative assessment, there was a noticeable reduction in post-peak strength loss due to fibre insertion. The parameter porosity/volumetric cement content (η/C_iv^0.28) was considered suitable to predict the qf mechanical behaviour of the studied composite.