Caractérisation des argiles de la région d'Ouagadougou: application à la construction en terre crue au Burkina Faso

Abstract

The replacement of earthen buildings by concrete represents a comfort and financial issue in Burkina Faso. Through a cooperation and development project, this work aims to valorize earth material in the form of Compressed Earth Blocks (CEB) in order to reintroduce it into Burkinabè architecture. This work consists in the construction clays identification, their characterization and the reserves localization and assessment. After a sampling phase in Ouagadougou, clays granulometry studies (laser, sieving granulometry and sedimentometry), plasticity studies (Atterberg’s limits) and mineralogy studies (XR diffraction, TGA, DTA) from four sites (Kamboinsé, Kossodo, Pabré and Saaba) enabled to characterize earth in Ouagadougou. The different areas are located along a north-west-south-east line. Materials are mainly silty and kaolinite-rich, except for Pabré. Kaolinite contents increase towards south whereas illite follows the opposite trend. This antagonistic behavior is related to the climatic zonation of Ouagadougou region. These clay minerals come from soils chemical alteration (hydrolysis) and are common under tropical latitudes. Other components originate from the bedrock (quartz, muscovite, anorthite). Goethite and hematite are related to the omnipresent lateritisation process. The distinct mineralogical composition of the Pabré clays (kaolinite-poor, illite and quartz-rich) is linked to its environmental context (backwater), which is different from the three other sites (peneplains). All the sampled clays have the granulometric, plastic (to be experimented) and mineralogical properties needed for CEB production and use.