Study of preparation for autoclaved aerated concrete with low-silicaironore tailings

Abstract

To investigate how properties will impact on by the fineness and content of low-silica iron ore tailings that used as the main raw material of autoclaved aerated concrete (AAC), testing methods such as mechanical properties testing, XRD, and FE-SEM were used in this research. Results shows that the decreased fineness of iron ore tailingsmake hydration reactions occur more quickly, with more hydration products being generated and the product’s compressive strength increases. However, it may generate extra fine residues of unreacted raw materials that would be difficult to form good foam structures, so that the compressive strength decreases. A higher proportion of iron ore tailings helps increase the amount of tobermorite that turns from a needle or schistose shape to a short fibrous shape. The tobermorite then forms a network structure by interweaving with each other. In this respect, the product’s compressive strength is raised. On the other hand, if there are too much content of iron ore tailings, they will loosen the integration of hydrate products and lower the bulk density. The resulted AAC shows a bulk density of 588­kgm^-3and a compressive strength of 4.20MPa, which is in line with the requirement of A3.5, B06-class AAC products regulated by antoclaved aerated concrete building blocks (GB 11968-2006). The main mineral phases of the products are 0.9nm tobermorite, 1.1nm tobermorite, 1.4nm tobermorite, C-S-H hydration products, ferrotschermakite, anhydrite, calcite, dolomite and residual quartz. The resulted AAC intensity mechanism analysis shows that the strength of the product is obtained by cementing the C-S-H gel, tobermorite and unreacted compositions.