添加爐石和飛灰對石灰石水泥混凝土之耐久性研究

Abstract

本研究旨在探討石灰石水泥系統中摻配爐石與飛灰等礦物摻料對混凝土力學性能與耐久性之影響，進一步評估其作為低碳建材於實務工程中之可行性與永續應用潛力。隨著全球面對氣候變遷與淨零碳排的壓力日益加劇，建築材料產業積極尋求低碳轉型。水泥工業長期為高碳排放源，其燒製過程中熟料階段約貢獻全球二氧化碳總排放量的 7% 至 8%。石灰石水泥因可降低熟料用量，減少能耗與碳排放，已成為具發展潛力之替代型水泥材料。然而，其耐久性表現仍具高度變異，尤其於暴露於氯離子滲透與硫酸鹽侵蝕等嚴苛環境下，其微觀反應行為與長期穩定性尚待驗證。 本研究採用石灰石水泥與卜特蘭I型水泥，搭配不同比例之爐石與飛灰，分別製備多組混凝土與水泥砂漿試體，並設計不同水膠比（0.4、0.5、0.6）及石灰石粉細度變化作為主要變因。系統性評估其新拌混凝土性質（工作度、泌水率、含氣量等）、力學性質（抗壓強度、劈裂抗張強度、彈性模數）及耐久性（RCM、RCPT、硫酸鹽浸泡、乾燥收縮等指標）。其中，核心比較對象為三元混合膠結材料系統（CS35F15M、LS35F15M），即以 35% 爐石與 15% 飛灰取代水泥，藉此探討其與石灰石水泥共同作用下之反應行為與性能表現。 試驗結果顯示，石灰石水泥因具填充效應與成核效應，能有效促進早期水化反應，儘管早期抗壓強度略低於I型水泥，但於28天後展現良好後期強度發展潛力。尤其搭配飛灰與爐石摻配後，能有效補足石灰石水泥稀釋效應所造成之反應性不足，顯現出材料間的協同效應。RCM與RCPT試驗顯示，三元系混凝土之氯離子傳輸係數可降至 10⁻⁸ cm²/s 以下，具優異之抗滲性與緻密結構。硫酸鹽侵蝕試驗亦顯示，複合摻料可顯著提升體積穩定性與抗劣化能力，減少裂縫與重量損失，且隨石灰石粉細度增加，其耐硫酸鹽性能亦同步提升，顯示細度控制對微觀反應結構具正面影響。 此外，乾燥收縮結果指出，石灰石與爐灰摻配可有效降低毛細水逸散與孔隙連通性，改善早期乾縮與開裂風險。整體而言，石灰石水泥與爐石、飛灰三者之複摻系統不僅具良好工作性、力學性與長期耐久性，更能有效降低水泥用量與碳排放，符合現今低碳建材發展趨勢。 本研究成果可作為石灰石水泥與複合礦物摻料應用於混凝土材料設計之實驗依據，亦有助於未來永續建築與基礎設施中之實務推廣與標準制定，為綠色工程與低碳社會發展貢獻一份助力。

This study investigates the effects of incorporating slag and fly ash into limestone cement systems on the mechanical and durability performance of concrete, aiming to evaluate the feasibility and long-term sustainability of such blends as low-carbon construction materials. In response to the global push for carbon neutrality and sustainable development, the cement industry—responsible for approximately 7–8% of total global CO₂ emissions, primarily from clinker calcination—has become a key target for decarbonization. Limestone cement, which reduces clinker consumption and energy use, offers promising environmental benefits. However, concerns remain regarding its durability, especially under aggressive conditions such as chloride ingress and sulfate attack. In this study, domestic Type I Portland cement and limestone cement were used in combination with various proportions of ground granulated blast-furnace slag (GGBS) and fly ash to produce multiple series of concrete and mortar specimens. Key variables included water-to-binder ratio (0.4, 0.5, 0.6), mineral admixture type and content, and limestone fineness. A comprehensive experimental program was conducted to evaluate fresh properties (slump, bleeding rate, air content), mechanical properties (compressive strength, splitting tensile strength, and modulus of elasticity), and durability indicators including rapid chloride migration (RCM), rapid chloride permeability (RCPT), sulfate immersion, and drying shrinkage. The core comparative focus was placed on ternary blended binders (CS35F15M and LS35F15M) containing 35% slag and 15% fly ash, to examine the synergistic effects within the limestone cement matrix. Experimental results revealed that although limestone cement exhibited slightly lower early-age strength, its filler effect and nucleation ability effectively accelerated hydration. With the addition of slag and fly ash, the later-age strength improved significantly, indicating a strong synergistic interaction among the mineral components. RCM and RCPT tests demonstrated that ternary mixes achieved chloride migration coefficients below 10⁻⁸ cm²/s, highlighting excellent impermeability and pore structure densification. Sulfate immersion tests also showed improved dimensional stability and resistance to chemical degradation, particularly for mixes with finer limestone particles, which enhanced long-term durability. Furthermore, drying shrinkage tests indicated that incorporating limestone powder and supplementary cementitious materials reduced capillary water loss and pore connectivity, helping to mitigate cracking risks at early age. Overall, the ternary system combining limestone cement with slag and fly ash provided a favorable balance between workability, strength development, and long-term durability, while also contributing to substantial clinker reduction and carbon savings. The findings of this study provide experimental support for the design of green concrete mixtures using blended cements and supplementary cementitious materials. They also offer practical insights for the promotion of sustainable building practices and the development of standards for low-carbon infrastructure, contributing meaningfully to the advancement of environmentally friendly construction and carbon-neutral engineering.