## 1 Introduction  
Fiber-cement products are nowadays widely used in the world because of their versatility for manufacturing construction materials such as lightweight roof tiles, ceilings, decorative components, and floors, which are used in most houses in developing countries as well as in agricultural and industrial buildings [1,2]. The fiber-cement industry has grown rapidly because of increased demand. As such, the rheological [3,4] and mechanical [5,6] properties of fiber-cement composites have been extensively studied. However, the cement industry is the third-largest source of carbon dioxide emissions. One of the considered strategies to mitigate CO2 emissions is carbon dioxide capture and storage (CCS) [7]. The current storage methods focus on enhanced oil recovery, underground geological storage, and disposal in deep oceans [8]. Alternatively, optimization of fiber-cement composites by 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%.