(271i) Manufacture of Sustainable Light-Weight Concrete Blocks By Utilizing Industrial Solid Waste

The demand for green buildings is growing rapidly because of rising global-level environmental concerns. Light weight or aerated concrete has been approved as an eco-friendly building material which is generated from solid wastes, such as fly ash, ground granulated blast furnace slag (GGBFS), and silica fumes, which are industrial byproducts, well known for their cementitious properties. The construction materials can be established as secondary industry in the area of solid waste and recycling. The rate of solid-wastes generation, during handling in automated aerated-concrete industries and in subsequent transportation is estimated to be approximately 4 to 10 % of the total production rate.

We have developed a novel route to make light-weight aerated concrete using colloidal gas aphrons (CGAs) as an aerating medium. CGAs are micro-bubbles of typically 10 to 100 μm diameters, having a very high interfacial area, flow properties similar to those of water, and high stability, which makes it a good aerating medium to manufacture the light-weight concrete. High energy efficiency is one of the defining characteristics of aerated concrete made by this new route of colloidal gas aphrons. CGAs-based light-weight slurry can be utilized to make ultra-light blocks as well as to incorporate industrial solid waste, such as different types of fly ash and the solid waste of automated aerated concrete industries.

Solid wastes of aerated concrete industries have been studied as an absorbent for various materials, such as water, used engine oil, diesel fuel, but these are mostly sold as filler materials in the construction industry at throwaway prices. Considering the magnitude of this problem, we reincorporated the crushed autoclaved aerated concrete (CAAC) wastes upto 25% of the total solids in new aerated concrete blocks. CAAC can be utilized in two ways depending upon the air hold-up in CGAs. Typically CGAs have an air hold-up of 0.65-0.70, which can be further increased by changing certain parameters in the CGAs-generation process, which in turn help in obviating the density differences between the AAC (autoclaved aerated concrete) solid wastes and aerated slurry, thus facilitating inclusion of wastes. In addition, the autoclaving may be completely replaced by the less expensive steam-curing process, while still meeting the standard specifications for the product, with a reduction in associated costs of the overall process of manufacture.

This method of inclusion of industrial solid wastes in aerated concrete provides an economical solution to the pursuit of a zero-waste manufacturing process for the aerated-concrete products.

Keywords: Supplementary cementitious material; Solid-waste utilization; CGAs based aerated concrete.