Estudo de compósitos de cimento Portland com polpa kraft de celulos modiicados com látex natural e metacaulim

Abstract

In this work the reinforcement of Portland cement matrices with cellulose kraft pulps was studied. It is known that the alkalinity of the cement paste deteriorates the fiber. In this sense, we tried to produce a less aggressive matrix to the fibers by adding natural latex and replacing part of the Portland cement for metakaolin. Flexural strength tests and water absorption were made on composites at 28 days of age. After the flexural tests, the samples were submitted to X-ray diffraction and scanning electron microscopy. The influence of the analyzed parameters (percentage of cellulose, percentage of latex and percentage of metakaolin) on the mechanical and physical properties of the composites was evaluated through a experimental design. From this design it was possible to develop a model of equations that optimized the results of toughness, modulus of rupture, modulus of elasticity and water absorption. The composite with 1.252% cellulose, 1.126% latex and 37.06% metakaolin presented the best modulus of elasticity, equal to 21.89 GPa at 28 days of age. The best flexural strength and toughness was presented by the composite with 8.5% cellulose, 0.21% latex and 34% metakaolin, with a modulus of rupture of 14.42 MPa and a toughness of 1.68 kJ/m² at 28 days of age. Analyzing the results obtained by attenuated total reflection and by contact angle, it was possible to prove that the latex was possibly adhered to the pulp, hydrophobising it. Therefore, it was concluded that it is possible to use the natural latex emulsion in the cellulosic pulp and metakaolin for the production of cementitious composites.