Tratamento de fibras de sisal com lignosulfonato para aprimoramento das propriedades dos compósitos de fibrocimento

Abstract

Aiming to reduce the environmental impact caused by the production of fiber cement, the use of loading with sisal fiber comes and is highlighted, in view of what in addition to satisfactory mechanical properties is a renewable resource, but plant substances degrade in the alkaline environment. As lignosulfonate has binding properties and is made up of polar and non-polar groups, it is believed that it can improve fiber-matrix adhesion in addition to waterproofing the fiber surface, preventing the basic alkali content of concrete degrading the plant cell. Within this context, this work aims to study the behavior of fiber reinforced cementitious composites with pure sisal fiber and impregnated with lignosulfonate aqueous solutions containing 1%, 2% and 4% of lignosulfonate in mass with respect to the treated fiber mass. The mechanical properties of the composites (CPs) were evaluated and the morphological characteristics of CPs and fibers were investigated. For this, tests were performed on the fibers and CPs by SEM and EDS, and by water absorption and bending tests of the CPs at 28 days (wet curing) and at 90 and 180 days (natural aging). The SEM images indicated that the fibers were impregnated with lignosulfonate, the EDS results indicate a decrease in the calcium content in the composites as the concentration of the lignosulfonate increases. The mechanical results showed that composites with fibers impregnated with 1% lignosulfonate solution have greater modulus of rupture (8Mpa) and less water absorption (2%) in the initial ages (28 days), even so, all had a decrease in Tensile Strength at 90 and 180 days. In this period, the CP prepared with fiber impregnated with 4% lignosulfonate solution has the greatest modulus of rupture (5%) in comparison to the other CPs and a greater water absorption (15%), showing the improvements of the lignosulfonate effect over time. There was also a 75% gain in toughness in CP with fiber impregnated with 1% lignosulfonate and 60% in CP with impregnation of 4% lignosulfonate compared to pure fiber in aged age. Thus, the treatment is efficient in terms of fiber preservation for CPs impregnated with 4% lignosulfonate.