Efeito do tratamento com sulfato de alumínio e hidróxido de cálcio nas propriedades de compósitos cimentícios produzidos com polpas quimiotermomecânicas

Abstract

The aim of the present study was to evaluate the effect of mineralization of Pinus pulps, originating from the chemothermomechanical pulping process, by adding different percentages of aluminum sulfate and calcium hydroxide, on the physical-mechanical properties of extruded fiber-cements. For the production of fiber-cements, Portland CPV-ARI cement, agricultural limestone, 5% Pinus spp. pulp, Hydroxypropyl Methylcellulose (HPMC), and polycarboxylic ether (ADVA) were used. The pulps were treated with aluminum sulfate at concentrations of 9 and 18% (m/m) and with calcium hydroxide at concentrations of 4.5 and 9% (m/m), in an experimental plan with five treatments. The control was composed of untreated pulps. The mixture was added with 30% limestone, 1% HPMC, and 1% ADVA. The water-to-cement ratio was 0.40. Test specimens (7 repetitions per treatment) were produced by the extrusion process. Mechanical, physical, and microstructural properties were determined. It was observed that treating the cellulose pulp with the combined use of aluminum sulfate and calcium hydroxide resulted in an increase in the mechanical strength of the fiber-cements. However, for concentrations with only aluminum sulfate, the average values of MOR (Modulus of Rupture) and MOE (Modulus of Elasticity) remained close to those of fiber-cement produced without treated pulps. Extruded composites with pulps treated with a combination of 9% aluminum sulfate and 4.5% calcium hydroxide showed superior properties.