Department of Civil Engineering, Mehran University of Engineering & Technology, Jamshoro, Sindh, 76020, Pakistan.
Department of Civil and Environmental Engineering, Universiti Teknologi PETRONAS, 32610 Bandar, Seri Iskandar, Perak, Malaysia.
Environ Sci Pollut Res Int. 2021 Sep;28(35):49074-49088. doi: 10.1007/s11356-021-13918-2. Epub 2021 Apr 30.
Research for alternative binders has become a necessity due to cement's embodied carbon, climate change, and depletion of natural resources. These binders could potentially reduce our reliance on cement as the sole binder for concrete while simultaneously enhancing the functional characteristics of concrete. Theoretically, the use of finer particles in the cement matrix densifies the pore structure of concrete and results in improved properties. To validate this hypothesis, current research was designed to investigate how the value-added benefits of nano-silica (NS) and metakaolin (MK) in fly ash (FA)-blended cement affect the mechanical and durability characteristics of concrete when used as ternary and quaternary blends. Additionally, the cost-benefit analysis and environmental impact assessment were conducted. It was observed that the synergy of MK and NS used in FA-blended cement had a greater impact on enhancing the functional characteristics of concrete, while 10% MK as ordinary Portland cement (OPC) replacement and 1% NS as an additive in FA-blended OPC concrete was the optimum combination which achieved 94-MPa compressive strength at the age of 91 days and showed more than 25% increment in the flexural and splitting tensile strengths compared to the control mix (MS00). The ultrasonic pulse velocity and dynamic modulus of elasticity were significantly improved, while a significant reduction in chloride migration of 50% was observed. In terms of environmental impact, MS100 (30% FA and 10% MK) exhibited the least embodied CO emissions of 319.89 kgCO/m, while the highest eco-strength efficiency of 0.268 MPa/kgCO·m with respect to 28-day compressive strength was exhibited by MS101. In terms of cost-benefit, MS00 was determined the cheapest, while the addition of MK and NS increased the cost. The lowest cost of producing 1 MPa was exhibited by MS01 with a merely 0.04-$/MPa/m reduction compared to MS00.
由于水泥的碳排放量、气候变化和自然资源的枯竭，寻找替代粘结剂已经成为必要。这些粘结剂有可能减少我们对水泥作为混凝土唯一粘结剂的依赖，同时提高混凝土的功能特性。从理论上讲，在水泥基体中使用更细的颗粒可以使混凝土的孔结构更加致密，从而提高性能。为了验证这一假设，目前的研究旨在研究纳米二氧化硅（NS）和偏高岭土（MK）在粉煤灰（FA）-掺合水泥中的附加值如何影响作为三元和四元混合物的混凝土的机械和耐久性特性。此外，还进行了成本效益分析和环境影响评估。结果表明，MK 和 NS 的协同作用在提高混凝土的功能特性方面具有更大的影响，而 10%MK 替代普通波特兰水泥（OPC）和 1% NS 作为 FA-掺合 OPC 混凝土的添加剂是最佳组合，在 91 天龄期达到 94-MPa 的抗压强度，与对照（MS00）相比，弯曲和劈裂拉伸强度提高了 25%以上。超声波脉冲速度和动态弹性模量有了显著提高，而氯离子迁移率降低了 50%。在环境影响方面，MS100（30%FA 和 10%MK）表现出最小的 CO 排放量为 319.89kgCO/m，而 MS101 的 28 天抗压强度的生态强度效率最高，为 0.268MPa/kgCO·m。在成本效益方面，MS00 是最便宜的，而添加 MK 和 NS 则增加了成本。MS01 生产 1MPa 的成本最低，与 MS00 相比仅减少了 0.04-美元/MPa/m。
