This paper presents the outcome of a comprehensive experimental program undertaken to study the performance of cellulose pulp and synthetic PVA (polyvinyl alcohol) based fiber-cement composite under both carbonated and non-carbonated curing conditions at early age. The composites were produced at different rolling pressures (2.5 to 9.0 bar) and subjected to various curing conditions in which the effects of CO 2 pressure (1 to 3 bar) and curing time (3 to 9 h) were studied. The mechanical

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... ies (modulus of elasticity (MOE), modulus of rupture (MOR), and toughness), as well as the physical properties (porosity, bulk density, and water absorption), were measured for all samples. Scanning electron microscopy (SEM) was used to investigate the effect of carbonation on porosity change and adhesion of fiber-matrix. A parametric investigation of the effects of the carbonation curing period, CO 2 pressure, and rolling pressure on the improvement of the physical and mechanical properties during carbonation curing was performed. Results showed that fiber-cement composites cured with an elevated CO 2 pressure of 3 bar, rolling pressure of 3 bar, and 5 h of curing time provided optimal curing conditions resulting in the most desirable mechanical and physical properties. However, toughness was greatly reduced with the increase of the CO 2 pressure, curing time, and rolling pressure. Additionally, the carbonation curing improved the bonding between the fiber and the cement matrix because of the precipitation of calcite particularly in the pores of the interfacial transition zone (ITZ) between the cement matrix and the fibers. 2 of 21 curing at elevated CO 2 conditions could, on the one hand, enhance the mechanical properties and on the other hand reduce carbon dioxide emissions. Many researchers point out that the carbonation process offers several benefits including durability improvement, reduction of porosity [9], reduction of the average pore size [10] associated with the increased densification of the matrix through the precipitation of CaCO 3 , which is a denser and more stable product than Ca(OH) 2 [11] , and strength gain [12] . Therefore, such a technology can reduce carbon dioxide emission from major point sources while developing a value-added product at the same time. However, the carbonation of cementitious composites leads to a decreased alkalinity of the cement matrix due to a lower portlandite content, which can cause faster corrosion of steel reinforced concrete [13] . The atmospheric CO 2 diffuses into concrete and reacts with calcium hydroxide, the main hydration product of cement, resulting in a decrease of pH, which leads to the initiation of corrosion of steel reinforcement bars (loss of the passivation layer at lower pH). This phenomenon, called passive carbonation of concrete, is a major deterioration mechanism of reinforced concrete structures. Another negative effect is carbonation-induced shrinkage which is sometimes mentioned in the literature [13] . Carbonation processes can be classified into two types: carbonation of hardened cementitious materials, or carbonation curing of fresh cementitious materials in which CO 2 reacts with the anhydrous phases and hydration products to form calcium carbonate [14, 15] resulting in a stronger composite [14, 16] . Carbonation curing of fresh materials including accelerated CO 2 curing has been considered to be a beneficial and economical process, which offers a possibility to help to reduce the dominant greenhouse gas CO 2 by capturing it in stable carbonate forms, and resulting in enhanced mechanical properties. Among the various cementitious products such as precast, non-reinforced concrete, bricks or concrete products with non-metallic reinforcements [17] , and fiber-cement composites that can be used in the accelerated CO 2 curing process, the fiber-cement composites, in particular, are chosen in this study because they do not have any steel bars (which poses a threat for long-term performance). Moreover, the thickness of the fiber-cement products in our case is very thin (4-5 mm), which could increase the carbonation degree as the permeation of CO 2 can be very fast along the depth. There are a lot of factors influencing the carbonation. The concentration of CO 2 is the dominant factor as the carbonation reaction rate is significantly influenced by the CO 2 concentration. In atmospheric conditions in which the CO 2 concentration level is around 0.03%-0.04%, the rate is slower than in accelerated curing conditions in which the concentration could be up to 100%. In natural conditions, the complete carbonation of engineering sized components takes many years but only a few hours or days under laboratory conditions by increasing the CO 2 concentration, especially in case of application of a pressure gradient to facilitate transport processes and dissolution of CO 2 [14, 18] . Controlling surrounding relative humidity (RH) is very important to accelerate the carbonation process. Walton et al. showed that carbonation was more rapid at a relative humidity of 50-70% and decreased at higher and lower relative humidity [19, 20] . The increase of temperature (up to 60 • C) increases the CO 2 uptake due to the leaching of Ca 2+ ions from the solid phases [21] . Finally, the initial conditions of the cementitious materials are also important such as the water to cement ratio, the initial porosity, and density. In this study, we changed the initial physical characteristics of the specimen by changing the rolling pressure during the Hatschek process. The Hatschek process consists of producing fiber-cement sheets by stacking thin laminas made from a suspension of cement, fibers, mineral admixtures, and water. Consequently, there are many parameters (e.g., CO 2 concentration, temperature, and relative humidity) to be optimized in the accelerated carbonation curing process to obtain a high-performance composite. Only a few studies have been reported in the literature in which accelerated CO 2 curing is considered for fiber-cement composites under different conditions. Almeida et al. [22] studied carbonated cementitious specimens reinforced with bleached eucalyptus pulp, with a climate chamber set to 60 • C temperature, 90% RH, and atmospheric CO 2 concentration (15 vol %) for two days. The results showed that the mechanical properties were better for the composites subjected to accelerated carbonation at early stages of hydration and carbonated samples presented higher values of