Composition. Concrete blocks are made from cast concrete (e.g. Portland cement and aggregate, usually sand and fine gravel, for high-density blocks). Lower density blocks may use industrial wastes, such as fly ash or bottom ash, as an aggregate. Lightweight blocks can also be produced using autoclaved aerated concrete.
Also know, can bricks explode in a fire?
The short answer is that those concrete blocks are not going to explode. But if you want something permanent you should use fire bricks and fire clay as mortar so it won’t crack. Related to this issue is our use of regular bricks in the hearth of our adobe oven. Most sources suggest using fire bricks or kiln bricks.
What is a hollow block?
Concrete blocks, also called cinder blocks and cement blocks, come in a wide variety of shapes and sizes. They are made out of a mixture of Portland cement, sand, gravel and water. Generally speaking, there are two kinds of concrete block, hollow and solid.