The proposed process is a novel, inexpensive, and eco-friendly method to convert the sunburnt bricks into second-class bricks by increasing their compressive strength and other mechanical properties through the use of solar thermal energy. This is achieved by applying black lead-free paint on the whole surface of the brick and exposing it to solar radiation for about 28-30 days. As the black body absorbs radiation, there is an increased flux of radiation energy into the pores of the clay brick, and thus it increases the compression strength of brick and other its mechanical properties. Experimental samples were prepared and tested as per the prevailing industry standards. The results obtained proved that the tested samples manufactured by this novel process qualified as second-class bricks with a compressive strength of 65-70 kg/cm2. The proposed novel process is simple, cost-effective, and environmentally friendly as there is no use of fossil fuels in the conversion process. The current invention is filed for Indian patent with application number 201941036244 as in IPO publications.
TopIntroduction
There is an increasing demand for building materials owing to the rapid rise in population and urbanization. Out of building materials, demand for bricks has increased significantly as it continues to be one of the oldest forms of masonry units used in construction. Globally, about 1500 billion bricks are produced every year wherein about 1300 billion bricks (87% of the global market share) are produced in Asia alone. Although bricks use eco-friendly materials, their product is highly energy intensive and uses fossil fuels. Typically, about 0.54MJ to 3.14MJ of energy is required for every 1kg of brick production. At the global level, about 375,000,000 tons of coal is burnt every year to meet the demand of bricks. With rapid urbanization at approximately 6%, this demand will continue to rise with subsequent increase in fossil fuel consumption. While this is one major concern, the other repercussions based on these consumptions include global warming and air pollution caused by the brick kilns. It is estimated that production of 1kg of brick yields about 0.282 kg of carbon dioxide, 5mg of CO, 1mg of particulate matter. On top of that, many small bricks manufacturers resort to other non-conventional fuels (other than coal) such as old tyres, wooden logs, saw dust, dry dung, and battery cases etc. which yield more harmful gases. Hence, there is a dire necessity to develop safe, ecofriendly and sustainable brick production processes.
Traditional bricks used are usually made of red clay. Methods of production, composition and firing temperature are the key factors, which influence the properties of bricks. The two main categories of bricks are unburnt and burnt bricks. Non-fired or unburnt bricks are the clay or mud molded bricks usually exposed directly to the sun for drying and thus increasing their strength properties. Hence, these are generally called sun-dried bricks. These are typically used for constructing temporary structures and in non-load-bearing structures. Fired bricks are the clay molded bricks exposed to high temperature in the kiln to attain the required strength, often used for load-bearing and seldom used for non-load bearing wall structures.
Red bricks are usually preferred owing to their superior strength properties, but the process involves the burning of fossil fuels or wood. This aggravates the existing increase in pollution due to non-sustainable production processes. Contrary to this, sunburnt bricks are eco-friendly as they utilize only solar thermal energy, but their strength and other properties are inferior compared to fired bricks. Sunburnt bricks are inexpensive due to a simpler method of production. However, the compressive strength of the sunburnt bricks is about 35-40 kg/cm2, whereas the compressive strength of the fired bricks is 65-105 kg/cm2. Thus, during the construction of buildings as per the prevailing building codes, these sunburnt bricks are currently restricted to only non-load-bearing structures.