Definition of optimal parameters for supercritical carbonation treatment of vegetable fiber-cement composites at a very early age

•Extruded vegetable fiber-cement composites are treated by supercritical carbonation.•Carbonation parameters and age of the composites are defined for optimized curing.•The best parameters: 24h of initial hydration and 1h of supercritical carbonation.•The bleached cellulose pulp is a key point for the composite mechanical behavior. This paper presents a study of cellulose pulp fiber-cement composites subjected to supercritical carbonation at a very early age. The raw materials used for the creation of cementitious composite mixes include: Portland cement, limestone filler, and cellulose pulp. Composites were produced by a slurry vacuum dewatering process and subjected to curing conditions which studied the effect of supercritical carbonation concentration (0% and close to 100% of CO2), the effect of cellulosic pulp (unbleached or bleached), and durability. All samples were subjected to mechanical, physical, and microstructural tests. The initial period of thermal curing (varying from 24h to 48h) and exposure time to carbonation (from 1h to 2h), did not have a statistically significant effect on the mechanical performance of the composites. However, the flexural test results of carbonated composites reinforced with bleached pulp showed a statistically significant improvement when compared to unbleached pulp reinforcement (24% increased average modulus of rupture). Thus, for cementitious composites cured with supercritical carbonation, the use of bleached cellulosic pulp, 24h of thermal hydration and 1h in an environmental chamber provided the optimal curing conditions and the most desirable properties in this study.