الفهرس | Only 14 pages are availabe for public view |
Abstract The continuous development of ornamental stone industry in Egypt due to the increasingly great demand of the Egyptian stones, led to a continuous and increasing accumulation of huge quantities of wastes in different forms. In the area of Shaq El – Thoaban only, about 70 % of these wastes is generating. The majority of these wastes are generated in the form of sludge (semi liquid) which has a hazardous effect on the surrounding environment and the sustainable development. In the present study we used the term “marble” as a commercial name comprising the whole class of carbonate rocks amenable to sawing and polishing for decorative purposes and economically valuable. The main objective of the present study is to characterize the marble and granite sludge wastes chemically, mineralogically and physically to demonstrate their possibility as a cement substitute rather than natural aggregates in cement and concrete production besides, the suitability of using the marble sludge wastes in quicklime manufacturing. The properties of cement composites, manufactured concrete products and prepared quicklime were investigated chemically, mineralogically and physico-mechanically. Regarding cement composites pastes, the marble and granite sludge were substituted for cement binder separately up to 40 % and combining up to 50% at certain proportions of 0% (control), 10%, 20%, 30%, 40% and 50%. The chemical, mineralogical, physical and mechanical properties of both fresh and hardened cement composites pastes including these wastes were determined at 3, 7 and 28 days curing according to standard test methods (ASTM and/or ECP) and the results were compared with the specification requirements of these standards. Concerning the concrete mixtures, the marble sludge waste was only used as a cement replacement at certain proportions of 0%, 10%, 20%, 30% and 40% and the hardened concrete units so produced were tested for the physical and mechanical properties after 28 days curing according to standard test methods (ASTM and/or EN BS) and the results were compared with the specification requirements of these standards. With respect to quicklime, the marble sludge was fired at 1000ºC for three soaking times (15, 30 and 120 min.). The quality of prepared quicklime samples was determined in terms of available lime index and lime reactivity and the results were compared with the specification requirements of these standards. The test results showed that the addition of marble and granite sludge as cement replacement in cement composites led to an insignificant increase in water absorption and apparent porosity and decrease in compressive strength up to 20% replacement, which becomes observable at higher replacement levels compared to the control. The physical and mechanical properties of cement composites were found to conform to the standard (ASTM and ESS). The test results of hardened concrete products showed that the addition of up to 20% marble sludge as cement replacement improved the physical and mechanical properties where water absorption and porosity decreased while the compressive and flexural strengths, abrasion resistance and freeze-thaw durability increased. At higher replacement levels these properties were affected negatively. The results showed also that the physical and mechanical properties of concrete units were found to conform with the standard (ASTM, EN BS and ESS) that enable them to be used in construction and building sectors. The results of prepared quicklime showed that the calcinations of marble sludge wastes at 1000°C for 30 min. soaking time is considered the optimum condition for quicklime production of higher available lime index more than other soaking times, consequently higher lime reactivity. All the aforementioned results indicated that the using of marble and granite sludge waste have a significant effect on the properties of cement composites, concrete products and quicklime production, meanwhile reduce their hazardous effect on the environment. The present study suggests a concrete mix comprising: marble powder waste (70 Kg/m3), Ordinary Portland cement (280 Kg/m3), coarse aggregate (1163 Kg/m3), fine aggregate (682 Kg/m3) and water (178 Kg/m3). Such mix was prepared on the production line of “The Engineering Company for Concrete Products” (Techno-Crete) and tested. |