The Use of Weathered Ignimbrites for the Production of Stabilized Earth Blocks (Seb): Case of Dschang (Western Cameroon)

Abstract The weathered mantle developed on welded ignimbritic formations of Dschang (Western Cameroon) constitute for population living in the vicinity, the raw material use to manufacture building blocks. However, many defects have been noticed on houses built using these blocks such as cracking, swelling and low compressive resistance of blocks.

The purpose of this study is to investigate the physical and geotechnical properties of these soil materials and their suitability in manufacturing Stabilized Earth Blocks (SEB) for optimized local constructions by testing their physico-mechanical characteristics. Results of these investigations, reveal two major types of soil profiles: the soil profile from top hill (Meka’a Profile) and the soil profile of downhill (Mingou Profile). These soil profiles are well-developed with three main horizons (A, B and C). The surrounding population has been using materials from B horizons (middle unit of soil profiles) for the manufacture of SEB. These materials are mainly composed of quartz (12 – 31%), goethite (17 – 22%), kaolinite (8 –18%) and gibbsite (23 – 44%). They display high value of moisture content (48 – 61%) and are very porous (47%). Grain size analysis classified these materials as fine-grained particles (47 – 65%) and so do other geotechnical classifications systems such as HRB, GTR and LCPC. The Atterberg limits reveal that they have high plasticity in nature with plasticity index ranges from 39 to 53.8%.

Satisfactory results were obtained when the weathered materials was stabilized with cement (CPJ 35) above 6%. Flexural strength tests ranged from 2.11 – 2.44 MPa and compressive strength ranged from 2.68 – 3.53 MPa. Nevertheless, some corrections are necessary to enhance these characteristics. This can be carried out by grain size distribution correction or the use of any type of chemical stabilizer.

However, some more detailed specific tests are still required in a bid to optimize the suitability of weathered ignimbrites for stabilized earth blocks production.

Keywords Ignimbrites-Local materials-Geotechnical classification-SEB-Valorization

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