Preparation, properties of foamed basic magnesium sulfate cements and their foaming mechanisms with different activators

Balancing mechanical and thermal properties of inorganic foamed composites has been a practical and technical challenge for decades. In this paper, we present a systematical investigation about the effects of different activators on the foamability and foaming mechanisms, pore characteristics and performance of foamed basic magnesium sulfate cement (FBMSC) by using hydrogen peroxide as foaming agent. The results reveal that the activators at a small amount have no tangible impact on the crystal growth of 5 Mg(OH)(2)center dot MgSO4 center dot 7H(2)O (5.1.7 phase) in FBMSC. Besides crystalline 5.1.7 phase that is responsible for high mechanical strength, the pore characteristics and thermal insulation of FBMSC are dependent on the foamability. Compared with KMnO4 and MnO2, FBMSC with the presence of KI exhibits a more gentle foaming process and a better pore structure. Thus the mechanical strength and thermal resistance of KI-FBMSC with lower densities can meet the criteria of Autoclaved Aerated Concrete (AAC, GB 11968-2006 of China Standard) and Foamed Concrete (FC, Chinese Building Materials Industrial Standard JG/T 266-2011) with higher densities. The excellent performance and environmental friendliness, simple synthesis procedure with energy saving of FBMSC make it appealing to prefabrication insulation panel industry.