Hydration and mechanical properties of magnesia, pulverized fuel ash, and portland cement blends

A study was conducted to determine the quantity of water bound by hydration, the products formed during hydration, the microstructures, and the mechanical properties as a function of the relative content of reactive magnesium oxide (magnesia, MgO), pulverized fuel ash (pfa), portland cement (PC), and water used to prepare the mixes. It was confirmed that hydration of MgO leads to the formation of brucite and that PC forms its normal hydration products, even when both materials are present together. It was found that calculated changes in porosity and consumption of water during hydration based on the proposed hydration reactions agree well with the measurements. It was also found that the stiffness and strength improve directly proportional to the PC content. It is proposed that the lower strength of mixes with high reactive MgO contents is due to a combination of their high water demand and the difference in morphology between brucite and C-S-H gel.