Influence of Fly Ash and Recycled AAC Waste for Replacement of Natural Sand in Manufacture of Autoclaved Aerated Concrete

Currently in Vietnam, the source of natural sand used in construction in general and in production of autoclaved aerated concrete (AAC) in particular is increasingly exhausting, so finding new sources of raw materials to replace natural sand has important role to ensure the maintenance of construction material production activities as well as towards sustainable construction development. Autoclaved aerated concrete (AAC) is one of the lightweight concretes that commonly used in construction. AAC is relatively light in weight, having lower thermal conductivity, higher heat resistance, lower shrinkage, and faster in construction process when compared to the conventional concretes. This paper aims to research, use and compare the use of recycled AAC waste and fly ash to replace natural sand in AAC concrete brick production factory. The new developed AAC was conducted by replacing sand with recycled AAC and fly ash in ratio of 0%, 5%, 10%, 15%, 20%, 30%, 40% and 60, 80 and 100%. Mechanical tests such as density, compressive strength have been carried out. Research results show that it is possible to take advantage of recycled AAC waste products with a maximum content of 5% and fly ash with a content of up to 100% to replace the natural sand in the manufacture of AAC bricks. In terms of economic and technical efficiency, the use of fly ash is more optimal, because it allows reducing the volumetric density, enhancing compressive strength and minimizing the grinding cost as well as contributing to environmental protection, aiming to sustainable construction.