AAC blocks or Autoclaved Aerated Concrete blocks, one of lightweight building material, made up of sand, calcined gypsum, lime, water, aluminium powder and cement which is heated under pressure in autoclave. These blocks are used for both interior and exterior construction. It is greyish-white in color and has thermal efficiency three times higher than clay bricks. It is 50% lighter than red bricks and also one-third of cost those bricks. Its sound insulation is approximately 42b and water absorption of about 10% of its weight. Get more informative here.