Role Of Fly Ash Research Articles

Discussion of “Role of Fly Ash and Aluminum Addition on Ettringite Formation In Lime-Remediated Mine Tailings” by A. M. O. Mohamed, M. Hossein, and F. P. Hassani

Discussion of “Role of Fly Ash and Aluminum Addition on Ettringite Formation In Lime-Remediated Mine Tailings” by A. M. O. Mohamed, M. Hossein, and F. P. Hassani

Role of Fly Ash and Aluminum Addition on Ettringite Formation in Lime-Remediated Mine Tailings

Abstract In this study, experiments were performed to evaluate the formation of ettringite in mine tailings samples treated with lime, fly ash type “C,” and aluminum. The success of the treated samples was evaluated based on results of X-ray diffraction and scanning electron microscopy. Using lime and fly ash, the preliminary investigation showed that addition of 5 % lime and 10 % fly ash constitutes the threshold of the treatment agents needed to form ettringite. However, long-term hydration resulted in lowering pH, and disintegration of formed ettringite. To overcome this problem, aluminum was added to the samples and formation of ettringite was monitored over a period of 660 days. Experimental results indicated that on availability of aluminum for reaction, primary and secondary ettringite minerals are formed and precipitated in these samples. Furthermore, the analysis indicated that the formed ettringite minerals remained stable during a hydration period of 660 days.

The use of fly ash in concretes subject to heat

The influence of fly ash on the basic characteristics of lightweight and ordinary concretes subject to heat treatment has been studied. The use of fly ash increases the strength of lightweight concretes, reduces cement consumption by 15 to 25%, and permits a decrease in concrete mean density (by 100 kg/m 3 on the average) and heat conduction. In ordinary concretes, the reduction of cement consumption is 40 to 70 kg/m 3, while increasing absolute and relative strength values after heat treatment. The latter is, on the average, 85% from the concrete strength at the age of 28 days. The role of fly ash as a polyfunctional ingredient which performs the functions of aggregate, active mineral admixture, plasticizer, and microfiller is also demonstrated.