LIGHTWEIGHT AGGREGATE PRODUCTION by RAPID SINTERING TERRA ROSSA-NaOH MIXTURES in MICROWAVE OVEN

In this study, the use of microwave ovens (MO) in the production of lightweight aggregates (LWA) with rapid sintering method was investigated. Sintering temperatures up to 1200 C° was obtained by using SiC coated microwave kiln in MO. LWA were produced by rapid sintering terra rossa (TR)-NaOH mixtures at MO. Alkali amount (2.5, 5 and 7.5% NaOH by weight of TR), drying type (no drying, drying in laboratory at 20 ₒC or in oven at 80 ₒC for one day) and sintering time (8, 12 and 18 min) on the physical, mechanical and microstructure of aggregates were investigated. The aggregate pellets dried in oven were stronger than those dried in the laboratory. Thus the sintering cracks diminished and the compressive strengths were enhanced for aggregates. The highest compressive strength (36.96 kg/cm2) was obtained in aggregates using 2.5% NaOH by weight of TR, dried in oven and rapid sintered for 18 minutes. When more alkali (5% NaOH) was used, due to the increase in flux content; the aggregate shell formed earlier and had more time to expand up to 127%. Thus the unit weight (0.67 g/cm3) and compressive strength (4.74 kg/cm2) of the aggregate were decreased.

Keywords:

Rapid sintering, Microwave, Terra rossa Lightweight aggregate, Compressive strength,

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