تحلیل آزمایشگاهی دوام و رفتار مکانیکی بتن خودتراکم حاوی متاکائولن در محیط‌های سولفاتی با رویکرد کاهش مصرف سیمان و حفاظت از محیط‌زیست
محورهای موضوعی : فنآوری های نوین در منابع طبیعی و محیط زیستکرار عبدالامیر ناهی 1 , محمد امیر شرافتی 2 , هادی فاطمی 3
1 - عمران ، مهندسی ، دانشگاه آزاد اسلامی واحد شیراز ، شیراز ، ایران
2 - گروه عمران دانشگاه ازاد اسلامی شیراز
3 - عمران ، مهندسی ، دانشگاه آزاد اسلامی واحد شیراز ،شیراز، ایران
کلید واژه:
چکیده مقاله :
|
Introduction: In recent years, the construction industry has been recognized as one of the largest consumers of natural resources and producers of greenhouse gases. One of the most important materials used in this industry is Portland cement, the production of which consumes significant amounts of energy and emits carbon dioxide (CO₂) one of the main greenhouse gases into the atmosphere. This issue not only affects air quality and human health but also accelerates global warming and climate change. Moreover, cement production relies heavily on raw materials such as limestone and clay, and excessive extraction of these materials leads to depletion of non-renewable natural resources and threatens environmental sustainability. Materials and Methods: This study aimed to investigate the effect of partially replacing cement with metakaolin in self-compacting concrete (SCC) and to evaluate the performance of this concrete in sulfate-rich corrosive environments. For this purpose, SCC samples were prepared with three different metakaolin replacement levels: 5%, 15%, and 25% by weight of cement. To simulate corrosive environmental conditions, samples were exposed to four sulfate solutions containing sulfate ions from sodium sulfate (Na₂SO₄), magnesium sulfate (MgSO₄), calcium sulfate (CaSO₄), and ammonium sulfate ((NH₄)₂SO₄). These sulfate ions were selected due to their destructive effects on concrete structures, particularly in industrial and marine environments, to accurately assess the concrete's resistance under realistic conditions. |
|
|
Results and Discussion: Laboratory results demonstrated that incorporating metakaolin significantly improved the characteristics of self-compacting concrete. Among the tested samples, the mixture containing 15% metakaolin exhibited the best performance. This mixture showed a notable increase in compressive strength compared to the control sample (without metakaolin). Additionally, water absorption decreased, indicating reduced porosity and increased density of the concrete microstructure. SEM images confirmed greater cohesion and fewer voids within the internal structure of the concrete. The 15% metakaolin concrete also exhibited higher resistance to sulfate environments, particularly against magnesium and ammonium ions, with less surface deterioration and cracking observed. Furthermore, the partial replacement of cement with metakaolin reduced the CO₂ emissions associated with concrete production, contributing effectively to minimizing the environmental impact of this widely used construction material. Compressive strength tests at various ages showed that the 15% metakaolin mixture performed better not only at 28 days but also at early (7 days) and late (90 days) stages, indicating good pozzolanic reactivity and long-term microstructural development. Reduced water absorption also implies lower permeability to aggressive ions, thereby decreasing long-term degradation. Stress–strain analysis showed that metakaolin-containing samples had higher stiffness (elastic modulus), reflecting increased concrete hardness and resistance to sudden deformations under cyclic loads. |
|
|
Conclusion: Based on the obtained results, it can be concluded that the optimal use of 15% metakaolin not only enhances the mechanical properties and durability of self-compacting concrete against sulfate ion attack but also plays a significant role in reducing environmental pollution by lowering cement consumption. The use of metakaolin aligns with sustainable development approaches, potentially extending the service life of structures under harsh environmental conditions. |
