Kallimani Rajvardhan, Minde Pravin
Dr. Vishwanath Karad MIT World Peace University, Pune, India.
Environ Sci Pollut Res Int. 2025 Mar;32(13):8201-8218. doi: 10.1007/s11356-025-36210-z. Epub 2025 Mar 8.
Concrete is the most used material globally, with cement production causing 8% of emissions. Waste-based supplementary cementitious materials (SCMs) offer a partial cement replacement to address climate goals. The present study explores using Ground Granulated Blast Furnace Slag (GGBS) and biochar as SCMs to elevate concrete's sustainability while maintaining structural performance. GGBS, sourced from steel production, was used at 20% and 40%, while biochar, derived from wood waste through pyrolysis, was incorporated at 3%, 4%, and 5% by weight of cement. The effects of these replacements were evaluated through compressive strength tests at 7 and 28 days, as well as microstructural analyses employing scanning electron microscopy (SEM) and energy-dispersive X-ray analysis. Findings revealed that GGBS enhanced workability due to its finer particles and pozzolanic activity while aiding long-term strength development. However, including biochar, particularly at higher percentages, led to a reduction in compressive strength, attributed to its porous structure and high carbon content, which weakened the interfacial transition zones (ITZ) and increased voids in the matrix. SEM analysis confirmed the highly porous nature of biochar, which interfered with the formation of calcium silicate hydrate (C-S-H), while EDAX showed a significant presence of carbon in biochar and GGBS, further explaining the dilution of strength. At 7 days, the compressive strength of concrete decreased by 29.4% (22.84 MPa) for 20% GGBS with 3% biochar, and up to 52.1% (15.49 MPa) for 40% GGBS with 5% biochar, compared to the control mix (32.34 MPa). At 28 days, the reduction ranged from 26.7% (25.02 MPa) for 20% GGBS with 4% biochar to 54.6% (15.49 MPa) for 40% GGBS with 5% biochar, relative to the control mix (34.14 MPa). Despite the reduction in early strength, the GGBS and biochar blends offer promise for applications focused on long-term durability and sustainability. This research highlights the need for careful optimization of mix proportions to find a middle ground between environmental benefits and mechanical performance.
混凝土是全球使用最多的材料，水泥生产产生的排放量占8%。基于废弃物的辅助胶凝材料（SCMs）可部分替代水泥，以实现气候目标。本研究探索使用粒化高炉矿渣（GGBS）和生物炭作为SCMs，在保持结构性能的同时提高混凝土的可持续性。来自钢铁生产的GGBS的用量为20%和40%，而通过热解从木材废料中获得的生物炭，按水泥重量的3%、4%和5%掺入。通过7天和28天的抗压强度试验，以及使用扫描电子显微镜（SEM）和能量色散X射线分析的微观结构分析，评估了这些替代物的效果。研究结果表明，GGBS因其更细的颗粒和火山灰活性提高了工作性，同时有助于长期强度发展。然而，加入生物炭，尤其是较高比例时，会导致抗压强度降低，这归因于其多孔结构和高碳含量，削弱了界面过渡区（ITZ）并增加了基体中的孔隙。SEM分析证实了生物炭的高度多孔性，这干扰了硅酸钙水合物（C-S-H）的形成，而能谱分析（EDAX）显示生物炭和GGBS中大量存在碳，进一步解释了强度的降低。与对照混合料（32.34MPa）相比，在7天时，含20%GGBS和3%生物炭的混凝土抗压强度降低了29.4%（22.84MPa），含40%GGBS和5%生物炭的混凝土抗压强度降低了52.1%（15.49MPa）。在28天时，相对于对照混合料（34.14MPa），强度降低范围从含20%GGBS和4%生物炭的26.7%（25.02MPa）到含40%GGBS和5%生物炭的54.6%（15.49MPa）。尽管早期强度有所降低，但GGBS和生物炭混合物在注重长期耐久性和可持续性的应用中具有潜力。本研究强调需要仔细优化混合料比例，以在环境效益和力学性能之间找到平衡点。
