ارزيابي خواص مكانيكي، دوام و ريزساختار نمونه‌هاي ملات حاوي خاك‌هاي رس با درجه‌ خلوص مختلف كائولينيت كلسينه‌شده و سنگ‌آهك به‌عنوان جايگزين‌هاي سيمان

eva‎luation of the mechanical properties, durability, an‎d microstructure of mortar specimens containing different grades of calcined kaolinite clays an‎d limestone as cement replacements

مهندسي عمران

The cement industry, in its pursuit of greater sustainability an‎d improved performance of construction materials, is increasingly required to adopt innovative binders that not only reduce environmental impacts but also lower production costs an‎d enhance durability. Considering the substantial share of the cement sector in global CO₂ emissions an‎d the urgent need to mitigate these emissions through advanced technologies, the development an‎d use of low-clinker cements an‎d effective supplementary materials have become critically important. Among these alternatives, Limestone Calcined Clay Cement (LC3) has emerged as a promising solution. However, its production using locally available raw materials in Iran, as well as the eva‎luation of its thermal performance an‎d durability at the national scale, has not yet been explored. Moreover, addressing the early-age strength limitations of LC3 through an optimized mix design an‎d proposing strategies to further reduce its carbon footprint by incorporating industrial waste materials have not been comprehensively investigated at the global level. This research aims to bridge these knowledge gaps by conducting a comprehensive study on LC3 production using Iranian clay deposits with low-to-medium kaolinite purity, as well as waste clay materials. Clays extracted from various regions of Iran, along with limestone powder, were thoroughly characterized, an‎d a series of LC3 formulations were developed an‎d eva‎luated. The influence of kaolinite purity on pozzolanic reactivity, microstructural evolution, an‎d durability was systematically examined. To enhance early-age strength, a modified mix design incorporating alkaline salts an‎d calcium hydroxide was proposed. A detailed thermal performance assessment was also carried out up to 800 °C, focusing on residual compressive strength, porosity changes, an‎d post-heating microstructural characteristics. Additionally, to improve both the economic an‎d environmental sustainability of LC3, the feasibility of using ceramic an‎d tile waste powder as a partial replacement for calcined clay was eva‎luated. The effects of different substitution levels on mechanical properties, durability performance, an‎d microstructure were assessed. The results revealed that clays with higher kaolinite purity, through greater formation of pozzolanic gels an‎d enhanced matrix densification, significantly improved compressive strength, reduced alkali–silica reaction (ASR), an‎d exhibited superior thermal resistance at elevated temperatures. The optimized formulation containing 30% calcined clay, 15% limestone powder, an‎d 1% alkaline additives delivered the highest short-term an‎d long-term strength. Furthermore, incorporating 10% ceramic waste together with 15% limestone powder not only reduced the greenhouse-gas emissions associated with LC3 production but also decreased ASR-induced expansion by more than 50% an‎d further enhanced microstructural densification. Overall, the findings highlight that leveraging locally available mineral resources an‎d industrial waste materials for LC3 production offers an effective pathway toward developing sustainable, economical, an‎d high-performance construction materials in Iran.

7

149813