Effect of sisal fiber hornification on the adhesion with portland cement matrices

Aiming a reduction in the water absorption capacity of lingo-cellulosic fibers, wetting and drying cycles are usually performed in the industry of paper and cellulose. This procedure stiffens the polymeric structure of the fiber-cells (process known as hornification) resulting in a higher dimensional stability. In the present work it was investigated if the dimensional stability, obtained from the hornification process, can imporove the adhesion of the sisal fiber in a Portland cement matrix. In order to study the fiber-matrix bond adhesion pull-out tests were performed in embedment lengths of 25mm and 50mm. Furthermore, it was investigated the influence of the hornification in the physical behavior (dimensional variation and water absorption), mechanical (behavior under tensile loading) and microstructural (surface modifications of the fiber and changes in the fiber-cell structure). The results indicate a higher dimensional stability, reduction in the water absorption capacity, increase in the tensile strength and strain capacity and reduction in the modulus of elasticity with the hornification. The pull-out load increased which indicates a higher bond strength in the hornified fiber with the cementitious matrix.