Properties of High-Early-Strength Aerated Concrete Incorporating Metakaolin

Conventional portland cement-based aerated concrete needs autoclaved curing in order to obtain high early-stage strength. Magnesium phosphate cement-based lightweight materials, such as aerated magnesium phosphate cement and magnesium phosphate cement-based foamed concrete can achieve the high early strength without thermal curing. In this study, metakaolin was introduced to enhance the performance of aerated magnesium phosphate cement, and the compressive strength, splitting tensile strength, thermal conductivity, foamability, strength retention coefficient after water immersion, sorptivity, and hygroscopicity were measured. Experimental results indicate that the presence of metakaolin has a slight influence on thermal insulation performance, and its strength and water resistance were improved significantly. The 3-h compressive strength of metakaolin-blended aerated magnesium phosphate cement can reach approximately 3 MPa. Metakaolin slightly slows down the gas-foaming process, and a larger amount of finer pores and smaller amount of capillary interconnected pores are produced. For this reason, the height of water migration in aerated magnesium phosphate cement with metakaolin is lower than that without metakaolin. Likewise, metakaolin decreases the hygroscopic moisture content of aerated magnesium phosphate cement, and the hygroscopicity, which can be described by several classical sorption isotherm models, reveals the typical characteristics of the hygroscopic property of portland cement-based porous materials.