Basic oxygen furnace (BOF) slag as an additive in sodium carbonate-activated slag cements

IF 3.4 3区 工程技术 Q2 CONSTRUCTION & BUILDING TECHNOLOGY
Laura Stefanini, Brant Walkley, John L. Provis
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Abstract

Basic oxygen furnace slag (BOFS) is a high-volume waste resulting from the production of steel from pig iron. Due to its high free lime content, BOFS is difficult to recycle and/or include into conventional cement systems. Alkali-activation technology offers a pathway to transform industrial wastes such as BOFS into low-carbon cements. Alternative precursors for cement systems are needed as the reliance on commonly used materials like ground granulated blast furnace slag (GGBFS) is becoming unsustainable due to decreasing availability. This study investigates alkali-activated cements incorporating 20 and 30 wt.% of naturally weathered BOFS as a replacement for GGBFS, in both sodium silicate- and sodium carbonate-activated systems. A fraction of BOFS subject to mechanical activation is compared against the untreated BOFS in the 20 wt.% systems. It is observed that in naturally weathered BOFS, a significant portion of the free-lime is found to convert to portlandite, which accelerates alkali-activation kinetics. In sodium silicate-activated systems, the high pH of the activator results in incomplete reaction of the portlandite present in BOFS. The sodium carbonate-activated system shows near complete conversion of portlandite, causing an acceleration in the kinetics of reaction, setting, and hardening. These findings confirm the viability of sodium carbonate activated GGBFS-based systems with only a minor loss in strength properties. BOFS can be utilised as a valuable cement additive for the production of sustainable alkali-activated cements utilising sodium carbonate as a less carbon-intensive activator solution than the more commonly used sodium silicate. Mechanical activation of BOFS offers further optimisation potential for alkali-activation.

Abstract Image

将碱性氧气炉(BOF)炉渣作为碳酸钠活性矿渣水泥的添加剂
碱性氧炉炉渣(BOFS)是生铁炼钢过程中产生的大量废弃物。由于游离石灰含量较高,碱性氧炉炉渣很难回收利用和/或纳入传统水泥系统。碱活化技术为将 BOFS 等工业废物转化为低碳水泥提供了一条途径。由于对磨细高炉矿渣(GGBFS)等常用材料的依赖日益减少,水泥系统需要替代前体。本研究调查了在硅酸钠和碳酸钠活化体系中掺入 20 和 30 wt.%天然风化高炉矿渣(BOFS)作为 GGBFS 替代品的碱活化水泥。在 20 wt.% 的体系中,经过机械活化的 BOFS 的比例与未经处理的 BOFS 进行了比较。结果发现,在自然风化的 BOFS 中,相当一部分游离石灰转化成了波长石,从而加速了碱活化动力学。在硅酸钠活化系统中,活化剂的高 pH 值会导致硅酸盐泡沫砂浆中的硅灰石反应不完全。而碳酸钠活化体系则几乎完全转化了波长石,从而加速了反应、凝固和硬化的动力学过程。这些发现证实了以碳酸钠活化的 GGBFS 为基础的系统的可行性,其强度特性仅有轻微损失。与更常用的硅酸钠相比,碳酸钠作为一种碳密集度较低的活化剂溶液,可作为一种有价值的水泥添加剂,用于生产可持续的碱活化水泥。对生物硅酸盐水泥进行机械活化可进一步优化碱活化的潜力。
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来源期刊
Materials and Structures
Materials and Structures 工程技术-材料科学:综合
CiteScore
6.40
自引率
7.90%
发文量
222
审稿时长
5.9 months
期刊介绍: Materials and Structures, the flagship publication of the International Union of Laboratories and Experts in Construction Materials, Systems and Structures (RILEM), provides a unique international and interdisciplinary forum for new research findings on the performance of construction materials. A leader in cutting-edge research, the journal is dedicated to the publication of high quality papers examining the fundamental properties of building materials, their characterization and processing techniques, modeling, standardization of test methods, and the application of research results in building and civil engineering. Materials and Structures also publishes comprehensive reports prepared by the RILEM’s technical committees.
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