Compressive strength behaviour of plant fibre adobes based on fibre volume fraction

Owing to variations in density, optimal per cent weight additions of plant fibres may not always improve the mechanical properties of adobes. Optimal weight additions of low-density plant fibres may cause the excess fibres to tangle and overlap, weakening the soil–fibre composite and lowering the adobes’ compressive strength. To overcome the limitations arising from variations in plant fibre density, this study evaluates the role of plant fibre addition on the compressive strengths of adobes in terms of per cent volume fraction (v_f). Analysis of data from the literature showed that straw and fruit fibre volume fractions ≤2% define the critical fibre volume fraction (v_f,critical) for the adobes. Fibre additions ≤2% lead to increase in compressive strength, while v_f values >2% caused reduction. In addition, fibre-reinforced adobes with porosities ≤31% exhibit a positive change in compressive strength; adobes with porosities >31% exhibit lower compressive strengths than their unstabilised counterparts. The findings importantly indicate that adobes with straw and fruit fibre inclusions achieve increased strength when their dry densities (apparent densities) are ≥1.84–1.86 g/cm³.