Most of the states government planned to ban clay bricks. Because, clay bricks require plastering and heavier in weight. Thermal conductivity & water absorption for clay bricks are 1.25 – 1.35 W/m2 ºC & 20-25%, whereas thermal conductivity & water absorption for fly ash bricks are 0.90-1.05 W/m2 ºC & 6-12%. Fly Ash bricks are alternative to burnt clay bricks in the construction sector in India. Fly ash bricks are nowadays mostly used for construction and gaining its popularity over builders and engineers because of its high strength, uniformity and less consumption of mortar plastering. Great future for fly ash brick manufacturer in India for coming decade.
Not good for areas of the world with extreme temperature fluctuation though are they? And extremely porous and apt to degrade much faster than a clay fired brick in an exposed enviroment? Although if you are plastering over both substrates than i guess its not that important from that standpoint.....
That's all well and good as long as the fly ash is from low sulfur coal, if not one runs into the scenario of Chinese drywall and the ill effects it had on many homes across the US. They mixed high sulfur fly ash in with the gypsum as a filler. The sulfur once released corrodes metal plumbing pipes, HVAC systems, gives off a foul odor and in some instances made the homeowners sick. The sulfur in the fly ash became "active" due to the varying humidity and temperatures from inside to outside as the seasons changed. It was bad stuff that was allowed into the country and often rebranded as a US made product.