تأثير ضايعات پودر مرمر و ميكروسيليس در عملكرد مكانيكي، زيست‌محيطي و اقتصادي بتن

THE EFFECT OF WASTE MARBLE POWDER an‎d SILICA FUME ON THE MECHANICAL, ENVIRONMENTAL an‎d ECONOMIC PERFORMANCE OF CONCRETE

پژوهش حاضر يك مطالعه‌ي آزمايشگاهي بر روي خصوصيات مكانيكي 16 طرح اختلاط بتن حاوي پودر مرمر )0، 5، 10 و 20 درصد( و ميكروسيليس (0، 5/2، 5 و 10 درصد) است، كه جايگزين بخشي از سيمان شده‌اند. نسبت آب به مواد سيماني ثابت و برابر با 45/0 بوده است. آزمايش‌هاي اسلامپ، وزن مخصوص، مقاومت فشاري، مقاومت كششي و مدول كشساني به منظور ارزيابي خصوصيات بتن انجام شده است. در نهايت، تمامي طرح‌هاي اختلاط از ديدگاه‌هاي زيست‌محيطي، اقتصادي و مكانيكي بررسي و مشخص شد كه خواص مكانيكي بتن حاوي پودر مرمر، براي نسبت‌هاي جايگزيني بيش از 10٪ تمايل به كاهش دارند. نتايج رضايت‌بخشي براي نسبت‌هاي جايگزيني پودر مرمر تا 10٪ به دست آمده است. در خصوص استفاده از ميكروسيليس مشاهده شد كه كاستي‌هايي كه در مقايسه با بتن‌شاهد در خواص مكانيكي بتن حاوي پودر مرمر به وجود آمده است، جبران مي‌كند. مقايسه‌ي طرح‌هاي اختلاط بتن از ديدگاه‌هاي مختلف نشان داده است كه طرح اختلاط بهينه، زماني ايجاد مي‌شود كه پودر مرمر و ميكروسيليس به طور همزمان استفاده شوند.

One of the most widely used materials in the construction industry is concrete and one of its main constituent elements is cement. Cement production, in addition to consuming non-renewable natural resources, emits greenhouse gases and pollutes the environment. Waste marble powder (WMP) is an industrial by-product that the marble factory generates considerable amounts during stone processing. WMP mostly not used in the industry nor being recycled and causes serious environmental problems. Silica fume (SF), also known as micro silica, is an ultrafine powder collected as a by-product of the silicon and ferrosilicon alloy production. This paper presents the results of an experimental investigation of mechanical properties carried out on the concrete mixes containing WMP and SF as a partial replacement of Portland Cement (PC). In all concrete mixtures, a constant water/binder ratio was used and concrete mixtures with a target initial slump of 80±10 were prepared. All of the concrete mixtures were assessed in terms of environmental, economic and mechanical aspects. Global warming potential, fossil fuel depletion potential and acidification potential were considered as environmental indicators of concrete mixtures production. Finally, it was observed that the mechanical properties of concrete containing WMP are improved for replacement ratios up to 10%. The use of SF improved the performance of all mixing designs and compensated for the shortcomings in the mechanical properties of concrete containing high percentages of WMP. Mechanically, the best percentages for simultaneous use of WMP and SF are 5% and 10%, respectively. From an environmental point of view, replacing 20% of WMP and 10% of SF with PC, not only leads to the production of concrete with suitable mechanical properties but also reduces the use of cement by 30% and the resulting environmental pollution. The combined index designed in this study showed that the optimal mix design in terms of mechanical, environmental and economic belongs to a mixture in which 5% WMP and 5% SF are used simultaneously.