High-toughness M-S-H cement composites reinforced with cellulose fibers through CO2 curing

Abstract

This work evaluates the influence of a CO2-saturated curing environment on thin (5 mm thick) boards of magnesium silicate hydrated (M-S-H) cement composites reinforced with cellulose fibers (CF). The first stage of the work consists of the optimization of the curing temperature when samples are subjected to high CO2 curing conditions. By means of XRD, the optimal carbonation temperature was set at 45 °C, at which a higher peak intensity attributed to nesquehonite (MgCO3·3H2O) was reached. At the selected temperature, the carbonation reaction was assessed by TGA. Carbonation conditions promoted the formation not only of hydrated magnesium hydroxicarbonates (HMHC) crystals, but also of other poorly crystallized compounds. As a consequence, carbonation increased the total amount of hydrated phases present in the matrix. Mercury intrusion porosimetry (MIP) tests were performed in order to evaluate a modification of the pore structure after carbonation. In this regard, carbonation reduced total cumulative intrusion by up to 38%. Finally, bending tests revealed that carbonation increases the strength of the composites while preserving their high. This results also into unprecedented toughness values (8.78 kJ/m2) considering only the deflection up to the modulus of rupture (0.17%). Therefore, carbonation is presented as a curing technique able to leverage the potential of CF in fiber reinforced cementitious composites (FRCC).