Industry paper tube wastes and vermiculite for production of eco-friendly cement-based composites

Abstract

Despite the advantages of cementitious composites, such as durability and thermal insulation, their mechanical performance can be limited, especially under severe environmental conditions. To overcome this limitation, a promising approach is the reinforcement of the matrix with fibers and the addition of lightweight fillers. In this context, this work investigates the use of fibers from waste Kraft paper tube, an abundant and sustainable material, combined with vermiculite, an expansive mineral that confers lightness and insulation. The objective was to evaluate the influence of combining these materials, in different proportions, on the physical and mechanical properties and the thermal transmission of the composites, aiming to develop a more efficient material with higher sustainable added value. The experiment was designed with four treatments, evaluating different proportions of Kraft paper tube waste replacement by vermiculite (0, 10, 20, and 30%). In the production of the composites, Portland cement CPV-ARI, shredded Kraft paper tubes, expanded vermiculite, calcium chloride, and water were used. The composites were produced with a nominal density of 1.10 g/cm³, with a cement:paper waste ratio of 1:0.37, a cement:calcium chloride ratio of 1:0.06, and a cement:water ratio of 1:0.6. In the hydraulic press, the composites were cold-pressed under a stress of 8.6 kgf/cm² for 10 minutes, followed by clamping for 24 h and curing for 28 days. Furthermore, mechanical, physical, and thermal conductivity tests were performed on the composites, obtaining the modulus of rupture and modulus of elasticity from three-point bending tests; compressive strength from the parallel compression test and internal bond strength from the parallel tension test. The results showed that the replacement of 30% of the paper with expanded vermiculite increased the compressive strength by 240% compared to the composite with paper tube waste and without vermiculite. Furthermore, for the 30% replacement treatment, the composite presented a water absorption of 9.78% after 24 hours of immersion, achieving a reduction below the 10% limit required by technical standards for cementitious composites. When comparing this absorption to the mix without vermiculite, a decrease of 66% was observed at 2 hours and 42% over the total 24-hour period, and the thermal conductivity remained statically stable compared to conventional composites. Regarding thickness swelling, the same trend as for water absorption was observed. The replacement of over 20% of shredded Kraft paper tubes with vermiculite improved the mechanical properties without compromising thermal insulation. The combination of Kraft paper and expanded vermiculite is a viable technical and environmental alternative for the production of sealing and partition composites, with the potential to reduce the use of virgin resources by up to 30%. This dissertation provides valuable information on the application of shredded Kraft paper tube waste and vermiculite in fiber-cement composites and offers data support for future research in the area, which is an important contribution to the development and optimization of technologies for cement-based products.