Optimizing the modified atmosphere parameters in the carbonation process for improved fiber-cement performance

The objective of this work was to evaluate the effect of the relative humidity on the accelerated carbonation process of the fiber-cement composites reinforced with a high concentration of vegetable fibers. The samples were produced with 10% of bleached eucalyptus pulp, in a method of fabrication similar to the commercial boards. The composites were submitted in an atmosphere with CO2 saturation, and relative humidity range of 60–90% to evaluate the effect of this parameter on the development of carbonation reaction. X-ray diffraction and thermogravimetric analysis were accomplished at different times, for monitoring the formation of carbonates along the accelerated carbonation process. Microstructure, physical and mechanical properties, and degradation were also evaluated. The composites carbonated with 60% of relative humidity presented a formation of CaCO3 significantly higher (37%) than the other concentrations of relative humidity (70, 80 and 90%) in just 4 h of carbonation. The densification of the cementitious matrix increased by 17%, and the modulus of rupture by 43% compared to non-carbonated composites. There was no statistically significant difference between the relative humidity of 60 and 70% for the physical and mechanical properties of the materials, and in general, the carbonation process preserved the reinforcement capacity of eucalyptus pulp in fiber-cement even after the accelerated aging cycles. In conclusion, this study demonstrated that the concentration of the relative humidity of the curing atmosphere is the main vehicle for diffusion and reactivity of the accelerated carbonation process. The use of the ideal relative humidity content can provide a faster and more effective carbonation reaction, in the production of fiber-cement materials. [Display omitted] •Fiber-cement composites are treated by accelerated carbonation.•The carbonation process is used with different concentrations of relative humidity.•The relative humidity of 60% allows a carbonation reaction more effective and fast.•Water is the main vehicle in the kinetics of carbonation reaction.