ABSTRACT
Brick represents one of the most used materials for the construction of buildings, but the rising demand of building materials and increased construction and demolition wastes has encouraged the development of new building materials. However, the traditional brick production causes several environmental and human health impacts, so there is a clear need of searching and replacing for more efficient and durable alternatives far beyond the limitations of the conventional brick production. Geopolymer that emerged as an eco-friendly alternative to cement binders has distinct advantages such as excellent mechanical properties, low energy in its production and emits fewer dioxides. This project work is an attempt to discover an eco-friendly brick for the development purposes by totally replacing the normal brick components by wastes from many industries. For the investigation purpose, we made geopolymer bricks by utilizing fly ash as the binder (fly ash is the by-product from burning coal in electric power generating plants and it is wealthy in silica and alumina), foundry sand as the fine aggregate which is the by-product from ferrous and non-ferrous metal casting industries, bentonite as an additive for improving its properties and finally the alkaline arrangement (blend of NaOH and Na2SiO3). Fly ash combines with alkalis such as Sodium Hydroxide (NaOH) and Sodium Silicate (Na2SiO3) creating alumino silicate gel, that shows properties similar to that of cement and it can be used as the binding material. Also, there is no carbon dioxide emission as in the case of cement production. Here water is needed only for making sodium hydroxide solution from solid pellets of NaOH. As fly ash is a fine material, it has more surface area for reacting with the chemicals, thereby increasing the pozzolonic activity and hence there will be an increase in compressive strength. Also, a combination of foundry sand and bentonite is very good for moulding purposes. In ordinary brick making, kiln burning is needed for curing purposes and huge energy is consumed during this process. But when it comes to geopolymer brick, only 24 hours oven drying at 1100°C is required. The remaining curing processes are under normal air temperature. The mix design was obtained to be 10 M for NaOH and the ratio of solutions to fly ash is 0.5. The ratio of Na2SiO3 to NaOH is 1.5. The geopolymer bricks were then produced and the blocks were held under rest period for about 3 days after moulding. The demoulded bricks are dried under oven for about 24 hours and henceforth the strength parameters such as compressive strength, water absorption, efflorescence, sound test and hardness were tested on the brick on the day after oven drying, 7th day, 14th day and 28th day. Hence the final results were made by comparing these properties with ordinary clay brick. From the experimental results, it is seen that the geopolymer bricks presented a high compressive and a low-water absorption capacity. The bricks were rated as slight-effloresced without any flaking of brick surfaces. The presence of efflorescence is ultimately due to the presence of alkali. Accordingly, 10 M solution can be taken as the design mix because as molarity increases there will be more efflorescence and at the same time as molarity decreases there will be decrease in compressive strength.
