Aggregate production with microwave sintering

In this thesis, spherical pellets were formed by mixing red soil (terra rossa) with alkalis and water. The pellets dried in different environments were rapidly sinte-red in the microwave oven to produce aggregates. In order to reach high temperatures in the microwave oven, the pellets were placed in the microwave oven in a silicon car-bide (SiC) coated insulated container and the microwave oven power was kept high (1200 W). Temperatures of 840, 980 and 1200℃ were achieved in 6, 12 and 18 mi-nutes, respectively. As the sintering temperature increased, the color of the aggregates changed from red to brown. In the aggregates produced by using 10% Na2CO3 by weight of red soil, excess alkali accumulated on the aggregate surface and carbonated. Since the aggregate pel-lets dried in an oven at 80 ₒC for one day were drier and stronger than those dried in the laboratory, the cracks formed during the sintering phase decreased and their comp-ressive strength increased. The highest compressive strength (3.69 MPa) was obtained in aggregates using 2.5% NaOH by weight of red soil, dried in an oven and sintered for 18 minutes. When more alkali (5% NaOH) was used, due to the increase in the glassy phase; the aggregate expanded by 127%, unit weight (0.67 g/cm3) and the compressive strength (0.474 MPa) decreased.