Performance and Properties of Alkali-Activated Blend of Calcined Laterite and Waste Marble Powder

This contribution reports on some preliminary studies on the use of lateritic soils from Cameroon as raw materials for the production of alkali-activated binders. These soils contain about 40–60% kaolinite and variable amounts of quartz, hematite, and other minor phases. After calcination at 800 °C, this material is blended with up to 30% waste marble powder, which is produced in large amounts during quarrying, cutting, and processing of marble. The results of our tests show that a careful mix design allows a good mechanical performance to be achieved, with the values of the cubic compressive strength larger than 30 MPa after 28 days. The role of Fe on the performance of this material is investigated by comparison with Fe-free blends of commercial metakaolin, waste marble powder, and quartz. Calorimetric data suggest that the use of alkanolamines as Fe chelating agents may accelerate the early-age reactivity, depending on dosage, although the effect on the development of mechanical properties is minor. It is argued that alkali-activated calcined laterite represents a viable option for the development of sustainable binders, especially for the African market, where it could be used, for example, to produce compressed stabilized earth blocks, in substitution of masonry units based on Portland cement or fired clay bricks. The use of waste marble powder adds further environmental value to this material.