Morphological, physico chemical, mineralogical and geochemical properties of vertisols used in bricks production in the Logone Valley (Cameroon, Central Africa)

Abstract

A detailed knowledge of soils is a prerequisite for their valorization and their suitable use. In the present paper, vertisols of the Logone Valley have been characterized on morphological, physico chemical, mineralogical and geochemical point of view, in view of their promotion as good building materials. These studies show that those vertisols are characterized by dark color, clayey texture, massive structure, deep, open superficial desiccation cracks and micro-reliefs (gilgai). They are neutral to slightly basic (6.4 to 7.4), with low organic matter content, an average cation exchange capacity (CEC ~ 22,8 meq/100g) and a high C/N ratio (up 39%) suggesting the organic matter is not well mineralized. Their exchangeable cations are dominated by Ca and K. They are constituted mainly by smectites associated to some amount of kaolinite, illite, quartz and feldspars, and they display high content in SiO2 (61.07 – 77.78 %), average content in Al2O3 (7.08 – 15.54) and low amount in Fe2O3 (1.78 – 6.92). The Si/Al ratio is greater than 2 and the mineralogical indice of alteration is higher than 60%. All those characters suggest that bisiallitisation is the main cristallo chemical process acting in the studied region. The clayey character of the studied vertisols can be judiciously exploited in view to promote competitive crude earth bricks.