Understanding the role of calcium formate towards hydration and deformation property of light-burned magnesia cement

Abstract Light-burned magnesia (LBM) cement is an advanced material to compensate for thermal shrinkage of concrete. Its deformation property is related to the hydration of MgO. The effect of additives on the hydration of LBM cement is worthy of exploration but always ignored. This paper systematically studied the effect of calcium formate (CF) on the hydration of LBM cement. Results showed that in LBM-H2O system, CF inhibited the hydration and setting of LBM; however, in Cement-LBM-H2O system, CF accelerated the hydration of LBM and increased its expansion efficiency. Combine with Monte Carlo simulation, this phenomenon can be explained as follows: CF is adsorbed on cement surface and accelerates hydration of cement phase at first; secondly, this reaction releases OH− to accelerate the hydration of MgO. Besides, SEM figures show that incorporation of CF leads to the formation of fibrous C-S-H gel and promotes the formation of hexagonal Mg(OH)2.