Adobe and Mud Bricks
Mud bricks are unfired bricks. When you fire bricks in a kiln you bake the clay and transforms the clay into a non temperature / air permeable material with little thermal mass. Unfired bricks keep their alternative properties of maintaining and regulating heat. The important difference between fired and unfired bricks is that fired bricks help keep the building cool in summer and warm in winter whilst fired bricks do not absorb and release heat and maintain regular temperature throughout the year by absorbing heat when its warm and releasing it when its cold.
Mud bricks have been used for building for centuries. The largest remaining adobe brick building is the Great Mosque of Djenné in Mali. This impressive structure still holds great importance in Djenné and has been declared a World Heritage site. A festival is held annually, where the community comes together to repair any structural damage caused by erosion.
How are they made?
Mud bricks are made from clay, earth, sand and straw,which is mixed with water, either by hand, foot or machine, until the mixture becomes workable but fairly stiff. Formwork is needed to keep the bricks a regular size, which is important for easy construction. Traditional bricks are 14 inches by 10 inches by 4 inches. All sides of the formwork are wet before you add the mixture, which allows the formwork to be easily removed after the mixture has been added. You add the mixture to this wet formwork and work by hand the mixture into all of the corners and smooth it over the top of the brick, removing any excess material. The formwork can now be removed and cleaned for next use. The bricks are then left in the sun for around 25 days, until they are fully dried and can be used.
Bricks can be partially stabilized by using a 6% cement mix or fully stabilized by using a 10% cement mix. However this has been found to be unnecessary as the bricks are strong enough without being cement stabilized.