Assessment of Sisal Fiber Integrity as a Reinforcing Element in MgO-Based Cement Matrices

The aim of this work is to evaluate the effects of sisal fiber exposure to cement matrices with different alkalinity in order to assess their viability as reinforcing elements in cementitious composites. To improve sisal fiber durability, this study introduces the use of a different calcium (Ca)-free cement binder based on MgO and SiO2. Sisal fibers were exposed to both MgO-SiO2 and conventional Portland cement to compare chemical interactions before and after different aging conditions by TGA, XRD and SEM/EDS analysis. MgO-SiO2 cement removes the amorphous phases of sisal fibers similarly to NaOH treatments used for polymeric composites. Contrarily for cements with high Ca(OH)(2) concentration, MgO-SiO2 cement promotes the hydrolysis of the fibers only in the amorphous phase, while the cellulose content and crystallite size was hardly modified. Sisal fibers exposed to MgO-SiO2 cement do not present any extra crystalline phase related to the cement hydration products. Thus, fiber mineralization process is avoided, whereas good adherence is promoted between M-S-H gel and fibers.