Magnesium carbonate trihydrate, nesquehonite, is proposed as a precursor for the production of a construction material similar to plasterboard, in a unique carbon capture and utilisation process [1]. The hardening process is thought to follow a similar mechanism to gypsum in the manufacture of plasterboard, where the hardening is produced in the recrystallization of gypsum crystals. However, nesquehonite [2], during hardening, converts into hydromagnesite, releasing CO2 and H2O during the transformation. In this work, samples of nesquehonite were hardened by forcing their conversion into hydromagnesite in enclosed cubes [3]. The influence of the curing temperature (50 ℃-80 ℃) and time (0-72 hours) on the compressive strength has been studied and correlated to the conversion of nesquehonite into hydromagnesite [4]. Compressive strength values up to 6MPa are easily achievable in the studied conditions and it was observed that at higher temperatures time has a detrimental effect on the strength. The probable overpressure within the cubes, generated by released CO2 and water at the higher temperatures, is thought to be the main cause for the loss of strength.