Cementitious composites reinforced with kraft pulping waste

Abstract

Kraft pulping is currently the most widely used technique in the production of cellulose pulp, and the production process generates large amount of lignocellulosic residues. Looking to add value to this residue, the aim of this study was to evaluate the physical and mechanical properties of extruded cementitious matrices reinforced with lignocellulosic waste from the kraft pulping of Eucalyptus spp wood. The experimental design were consisted of 3 treatments with 5 samples for each treatment, as follows: 1) 70% Portland cement (by mass) with 30% ground carbonate (by mass) - T1; 2) 66.5% of Portland cement, 28.5% ground carbonate and 5% residual pulp fibers - T2, and 3) 69.5% Portland cement, 25.5% metakaolin and 5% residual pulp fibers - T3. The mass for extrusion was prepared with the addition of hydroxypropyl-methylcellulose (HPMC) and polyether carboxylic (ADVA) as rheology modifiers, with water:cement ratio of around 0.3. After mixing, the mass was taken to an extruder where the specimens were obtained. Apparent porosity (AP), bulk density (BD), water absorption (WA), modulus of rupture (MOR), fracture toughness (KIC) and fracture energy (EF) were evaluated. There was statistical difference between the treatments for AP, BD, WA, KIC and EF values, and the treatment with the metakaolin showed the lowest values for BD and the highest values for AP, WA and FE. The treatment with ground carbonate and residual pulping showed intermediate results when compared to the other treatments. No statistical differences were found between the fiber-cement treatments for MOR values.