Study of the degradation of non-conventional MgO-SiO2 cement reinforced with lignocellulosic fibers

This paper assesses the use of low alkaline composites based on magnesium oxide and silica (MgO-SiO₂) cement and reinforced with cellulose fibers for the production of thin elements to resist bending loads. The strategy adopted was to study the durability of lignocellulosic fibers in a lower pH environment than the ordinary Portland cement (OPC), by comparing the flexural performance of samples at 28 days and after 200 accelerated ageing cycles. Two types of vegetable fibers were used: eucalyptus and pine pulps. For both types of fibers, composites made out of MgO-SiO₂ cement after ageing treatment show a better mechanical performance than OPC samples (modulus of rupture of ～10.5 and 9 MPa respectively). When used in MgO-SiO₂ cement matrices, eucalyptus fibers offer excellent specific energy (SE) values (～5 kJ/m²) compared to OPC samples in which SE drastically decreases after ageing from 4.97 kJ/m² to 0.14 kJ/m². The preservation of the reinforcing capacity of the composite materials after ageing was also proved by SEM techniques. In the light of the results, the use of MgO-SiO₂ cements is an effective way to apply cellulosic fibers as reinforcement in fiber-cement products since no signs of degradation were found, even improving flexural properties over time.