Use of marble dust containing filler mixture in composite slab production: Relationship between roasting conditions and physical properties of the slab

Abstract

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.

Phase variation and mechanical properties of waste calcium carbonate to substitute quartz in composite slab production

“…Calcite mineral, the sole crystalline phase of MD, starts to calcine around 700 • C, and CaO formation is expected to be completed around 1000 • C. 46,47 Baş et al 19 proposed that the calcination of calcite in the MD-quartz mixture and the formation of Ca-silicate sinter phases did not complete below 1200 • C. Therefore, sintering roasting of the mixture was applied at 1200 • C to achieve complete calcination of MD present in the mixture and to fulfill the roasting process releasing new xCaO⋅ySiO 2 complex sintered phases with higher hardness than calcite. Figure 6 shows SEM images of roasted filler mixtures and elemental distribution for 3 h roasting at 1200 • C for 25, 50, and 75 wt% MD.…”

“…Larnite and calcioolivine phases were the dominating reaction products at higher calcite/silica molar ratios, 19,28 whereas wollastonite is the synthetic, stable roasting phase at a low calcite/silica ratio. 19,29,30 The findings in the literature and in practice have shown that there is good potential to mitigate the environmentally adverse effect of MD generated at uncontrollable rates by utilizing it in slab production as filler material, which is the motivation behind this research. In this study, MD was tested with micronized quartz, both in its natural form and after roasting at 1200 • C. Effects of roasting of the mixture of quartz and MD on morphological changes, phase distribution, and mechanical properties of the produced composite slab were demonstrated by spectroscopic and physical analyses.…”

“…Borselline et al 7 proposed that MD adversely affected the mechanical behavior and porosity of the produced slabs due to the soft and brittle characteristics of constituting mineral-calcite-of MD. In order to overcome the hardness problem related to calcite, MD, and micronized quartz-containing, Baş et al 19 investigated the effect of sintering roasting temperature on the density and phase variation of sintered filler mixture and their effect on the physical properties of composite slab. As roasting is the way to obtain the different Ca-silicate (xCaO⋅ySiO 2 ) phases (e.g., spurrite, calcioolivine, larnite, and wollastonite) with acceptably high hardness as compared with that of MD 11,13,20,21 of which, hardest phase is larnite (β-Ca 2 SiO 4 ) with about 6 in Mohs scale.…”

“…The roasting at low temperatures also supports the formation of larnite, but complete phase conversion does not occur. 26,27 Baş et al 19 demonstrated that the calcination of calcite and formation of hard Ca-silicate phases did not complete at low temperatures, which caused retrogressed physical properties of the produced slabs below 1200 • C. Roasting at 1200 • C enhanced the formation of Ca-silicates. Larnite and calcioolivine phases were the dominating reaction products at higher calcite/silica molar ratios, 19,28 whereas wollastonite is the synthetic, stable roasting phase at a low calcite/silica ratio.…”

“…26,27 Baş et al 19 demonstrated that the calcination of calcite and formation of hard Ca-silicate phases did not complete at low temperatures, which caused retrogressed physical properties of the produced slabs below 1200 • C. Roasting at 1200 • C enhanced the formation of Ca-silicates. Larnite and calcioolivine phases were the dominating reaction products at higher calcite/silica molar ratios, 19,28 whereas wollastonite is the synthetic, stable roasting phase at a low calcite/silica ratio. 19,29,30 The findings in the literature and in practice have shown that there is good potential to mitigate the environmentally adverse effect of MD generated at uncontrollable rates by utilizing it in slab production as filler material, which is the motivation behind this research.…”