Circulating Fluidized Bed Combustion Ashes as an Activator of Ground Vitrified Blast Furnace Slag

The expansive and mechanical characteristics of blends of Ground Vitrified Blast Furnace (GVBF) slag and Circulating Fluidized Bed Combustion (CFBC) ashes have been investigated at different ages. The products of hydration, and their variations over a period of time have been identified by X-ray diffraction and differential thermal analysis. The results of this investigation show that the hydration of the slag can be optimally "accelerated and reinforced" by using about 15-25% of CFBC ash. At this optimum level, according to the type of CFBC ash used, the flexural and compressive strength at 28 days can reach about 2.6-5.4 MPa and 30.7 - 54.0 MPa respectively. After 180 days, these values are about 4.3-6.5 MPa and 44.0-73.0 MPa respectively. This interesting development can be essentially attributed to the massive formation of C-S-H gel combined with certain quantity of ettringite, which produces a small amount of expansion.