Abstract
The content, mineralogy and crystallinity of iron oxides were correlated with the strength of iron-rich materials in different environmental soil conditions. A predominance of goethite, hematite, or both was observed in the hard materials and kaolinite in the soft material of the laterite. The mean crystallite dimension of goethite and hematite showed a positive linear relationship with the strength of the materials. The degree of Al substitution was higher in the softer materials. Large crystals of goethite were observed by SEM in the harder materials. A suitable crystallization environment allowed the formation of large crystals, especially of the goethite type and in large amounts, that link together to form a rigid network and thereby cause the hardening of iron-rich materials. (Author's abstract)