Marble dust generated during slab cutting as reject causes significant environmental problems due to increased reactive surface area. It has closer size distribution with micronized quartz filler used in composite slab. Owing to its high hardness, micronized quartz production is an energy intensive process. This study was conducted to investigate the applicability of marble dust in composite slab production together with micronized quartz as filler. The filler mixture was roasted to mitigate drawback arising from low hardness of marble dust. XRD characterization revealed that phases in roasted filler were wollastonite, larnite, calcio olivine, quicklime and free quartz depending on the roasting temperature and time. Physical tests were applied to clarify the effect of sinter phases on slab properties. Physical properties were determined to retrogress as the roasting temperature increased to 1100°C possibly due to rate of free lime in roasted filler, and then improved again reaching peak point at 1200°C. They ameliorated by increasing roasting time at 1200°C. Larnite and quartz were determined to be effective on improved physical properties than wollastonite and calcio olivine.

Owing to the fast‐emerging nature and rapid advancements in the construction industry, huge volumes of marble dust (MD) are generated as reject during slab cutting in marble processing, causing significant environmental hazards. Nowadays, quartz composite slabs have increasingly been preferred in building works due to their excellent hygienic property and mechanical strength. Composite slab is produced using micronized quartz as filler, the grinding of which is an energy‐intensive process. Substitution of micronized quartz with MD at different percentages was investigated in natural form and after roasting. Natural MD offered appreciable physical properties closer to those of a quartz composite slab. Physical properties slightly retrograded by quartz supplementation in the raw form. Roasting the filler led to the formation of rounded Ca–silicate. Wollastonite was the first phase formed after sintering at the lowest MD percentage and shortest roasting times. Larnite became dominating phase first by increasing MD percentage and roasting time, and then calcio‐olivine formed. Physical characterization test results demonstrated that hardnesses of new phase and particle shape were the key parameters that improved slabs’ mechanical properties of. Hard rounded larnite particles improved mechanical behavior of slabs having the synergic effect of quartz, whereas wollastonite did not show a significant effect.