Natural iron-aluminosilicate as potential solid precursor for supplementary cementitious materials: A comparative study with other aluminosilicates.

The objective of this study was to investigate the impact of the geographic and climatic conditions on laterites properties and on geopolymerization based-laterite. Four different laterite deposits in the four geographical zones of Cameroon were studied. This included the center, north, south and west corners of Cameroon, having chemical composition of SiO + AlO + FeO = 88.94, 87.6, 89.13 and 78.97%, respectively. The center and south laterites from the black forest, with high pluviometry and relative humidity, show significant amounts of FeO. While the west laterite from grass field - mountainous areas and the north-laterite from plain arid and semi-arid climate still show lower iron concentrations. The IR absorption bands of the different laterites appear between 1007 and 1047 cm; characteristic bands of aluminosilicate. The BET (Brunauer-Emmett-Teller) Specific surface area values are comprised in the range of [21.9, 24.1 m/g] for non-calcined laterite and between [45.6 and 123.5 m/g] for laterites calcined at 550 °C and 575 °C. The main particle size values are 5.71, 6.37, 7.43 and 8.45 μm for center-laterite, west-laterite, north laterite and south-laterite, respectively. Although, they differ in the degree of laterization, all the laterites present almost total conversion to geopolymers, due to the presence of amorphous kaolinite and reactive goethite. However, the iron content has significant impact on the globular microstructure. The particle size of laterites, their high values of BET surface area and their significant reactivity make them promising substitutes to metakaolin and other supplementary cementitious materials.