Carbonatação em escala piloto de telhas de cimento reforçadas com fibras celulósicas e sintéticas

Abstract

The civil construction sector has undergone constant evolution for best practices and sustainable materials, always considering market competitiveness and sustainability. One of the topics is the addiction of cellulosic pulp in the fiber cement matrix which has an drawback because it is easily degraded due to calcium hydroxide - Ca(OH)2 in the cement matrix. Seeking the feasibility of using plant fibers in the matrix, accelerated carbonation technologies is efficient in terms of prolonging plant fibers’ durability, with the reduction of matrix pH due to the transformation of calcium hydroxide into calcium carbonate (CaCO3). The present study focus in the evaluation during carbonation, the influence of pressure, volume and relative humidity inside the chamber, and the humidity of fiber reinforced cement materials. Three steps were carried out to evaluate the proposed variables: I) evaluating the variation of the internal pressure of the chamber; II) evaluating the variation of the volume of cement material inserted in the carbonation process and III) evaluating the variation of humidity internal to the carbonation chamber and initial humidity of the material at the entrance of the process, evaluating the mechanical, physical and chemical results after the experimental steps, aiming to enable the use this methodology on an industrial scale. Stage I, accelerated carbonation process was carried out on a pilot scale, using the Fhaizer autoclave as a chamber, with a volume of 8m³, 6 hours of duration, saturated in CO2, with controlled humidity and pressures of -0.5 bar, atmospheric pressure and 5 bar. The best results are: physical (up to 8% drier and up to 4% more apparent density), mechanical (up to 15%, up to 43% and up to 22% higher than the others in terms of MOR, LOP and Specific Energy, respectively). Higher degree of carbonation was found in carbonated specimens with an overpressure of 5 bar. Stage II, the accelerated carbonation process was carried out with a reduction in the volume of occupation in the carbonation chamber by 75%, which consequently allowed a more efficient control of humidity (20% lower than in Stage I). Mechanical results up to 13% higher than Stage I, physical reduction of up to 24% of the moisture of the samples were obtained. Densification of the matrix by 8%, and an increase of 36% in the degree of carbonation were also observed. The evidence of effectiveness by reducing the internal relative humidity at the autoclave during the accelerated carbonation process were assessed. Finally, in Stage III, where the pre-drying of the fiber cement materials was carried out, results were potentiated in terms of carbonation degree values and CO2 fixation with increments of 27% and 36% respectively. The results show the significant influence of the initial moisture of the fiber cement material in the carbonation process and offer a way to apply this methodology in an industrial scale, as well as showing that the accelerated carbonation process can be an essential technique and strategy for carrying out the sequestration of CO2.