A novel approach for the preparation of low thermal conductivity foam concrete with γ-C2S carbonation and aragonite-reinforced pore walls

In the preparation of foam concrete (FC), reconciling the contradiction of porosity (or thermal conductivity) and mechanical strength poses a significant challenge. In this paper, the strategy of regulating the carbonation of γ-2CaO·SiO 2 (γ-C 2 S) to form aragonite whiskers for strengthening the pore wall was proposed, thereby achieving the highest possible total porosity while meeting the required compressive strength. The controlled formation of aragonite and its strengthening mechanism of pore wall, as well as the optimum preparation conditions of FC formed by γ-C 2 S carbonation were studied. The results indicated that the CaCO 3 in the pore walls predominantly existed in the form of whisker-like aragonite under the action of modifier MgCl 2 ·6H 2 O, and the mass content of aragonite achieved 53.4 %, almost without calcite. Under the optimum preparation conditions, the thermal conductivity and compressive strength of aragonite foam concrete (AFC) were 0.0496 W/m·K and 0.5 MPa, respectively. Compared with calcite foam concrete (CFC) formed without the regulator, the compressive strength was increased by 150 % and the thermal conductivity was decreased by 5.2 %, it showed that thermal conductivity and mechanical strength were reconciled. Based on pore structure analysis, the formation of aragonite reduced the pore wall porosity (PP) and refined the most probable pore size. Furthermore, the CO 2 absorption rate reached 45.4 % under the carbonation of 84 h. This provides a new perspective for the preparation of low thermal conductivity FC with CO 2 sequestration functionality.