Traditional brick productions in Madagascar: From raw material processing to firing technology

Bricks are the most common building materials of Madagascar due to the large availability of clayey raw material,the simple technology of production and the ease of use. The brick production is mainly organised in localworkshops close to supplying site of clayey deposit where sediments are extracted, moulded in bricks, dried andthen fired in open-air furnaces. Fuel varies from peat soils to wood depending on the local availability.Correspondingly, firing time varies from few days in wood furnaces to some weeks in peat fired furnaces.Samples of bricks and raw materials as well as peat fuel, from four workshops located in central and southwesternMadagascar were collected and analysed to infer the technological skills of the Malagasy traditionalbrick manufacture. Central Highlands Madagascar workshops use clayey lateritic soils formed from in situweathering of basement rocks. The main plastic component of these deposits is kaolinite. Also the clayey sedimentsfrom southwestern Madagascar have kaolinite along with low-ordered clay minerals and carbonatessuch as calcite and minor Sr-rich dolomite.As far as fired bricks are concerned, experimental data evidenced quite low firing temperatures (below600 °C) in the two different furnaces, regardless the type of fuel. As far as peat fuel is concerned, its low calorificvalue along with a large amount of furnace energy dispersion does not allow to achieve the temperatures requiredto produce good quality bricks, notwithstanding long firing time (some weeks). On the other hand,firewood powdered furnaces, although providing much higher energy and a consequent much shorter firingprocess (few days), also suffer of diffuse heat dispersions which concur to the bad quality of the final product.The specific energy input calculated for type 1 furnace (peat fuel) ranges between 0.09 MJ/kg and 0.18 MJ/kg of clayey material thus confirming a rather inadequate firing process for the production of good qualitybricks, and a rough estimate indicates that volume ratios between peat and clayey material as low as 1:1 shouldbe used in order to reach “modern” specific energy inputs.