增强作为胶凝补充材料的氢形沸石的水胶凝反应活性

IF 10.8 1区 工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY
Atolo A. Tuinukuafe , David X. Rademacher , Tina M. Nenoff , Jessica M. Rimsza
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引用次数: 0

摘要

富含二氧化硅和氧化铝的毛细管与石灰反应形成胶结化合物,并作为胶凝补充材料(SCM)掺入硅酸盐水泥中。然而,由于水胶合反应的速度慢于硅酸盐水泥的水化速度,其在现代建筑中的应用因早期强度不足而受到限制。因此,有必要采用能够加快水胶合反应速度的替代性 SCM,包括合成沸石,因为合成沸石具有高比表面积和高纯度成分,这表明其具有快速水胶合反应的可能性。通过离子交换和原位 X 射线衍射实验,评估了不同阳离子组成(Na-沸石、H-沸石)、SiO2/Al2O3 比率和框架类型的合成沸石在消耗 Ca(OH)2 后的水胶凝反应性。由于 Na+ 和羟基占据了酸性位点,Na-沸石与 KOH 和 Ca(OH)2 的交换反应有限。与此同时,H-沸石通过在布氏酸位点与 H+ 进行阳离子交换或在空闲的酸位点吸附阳离子,很容易从氢氧化物溶液中吸附 K+ 和 Ca2+。通过吸附阳离子,H-沸石降低了 pH 值,增加了 Ca2+ 的溶解度,从而在 Ca(OH)2 溶解/扩散是限制速率因素的体系中促进了水青石反应。高 H 型沸石反应性导致每 1 克沸石在反应 16 小时后消耗 0.8 克 Ca(OH)2 而每 1 克 Na 型沸石消耗 0.4 克 Ca(OH)2。H- 沸石调节了孔隙流体的碱度,并通过类似于两步 C-S-H 成核实验的机制产生了低密度无定形硅酸盐相。控制这些反应机制是开发具有与波特兰水泥相当的水化速率的下一代水青石胶凝体系的关键。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Enhanced pozzolanic reactivity in hydrogen-form zeolites as supplementary cementitious materials
Pozzolans rich in silica and alumina react with lime to form cementing compounds and are incorporated into portland cement as supplementary cementitious materials (SCMs). However, pozzolanic reactions progress slower than portland cement hydration, limiting their use in modern construction due to insufficient early-age strength. Hence, alternative SCMs that enable faster pozzolanic reactions are necessary including synthetic zeolites, which have high surface areas and compositional purity that indicate the possibility of rapid pozzolanic reactivity. Synthetic zeolites with varying cation composition (Na-zeolite, H-zeolite), SiO2/Al2O3 ratio, and framework type were evaluated for pozzolanic reactivity via Ca(OH)2 consumption using ion exchange and in-situ X-ray diffraction experiments. Na-zeolites exhibited limited exchange reactions with KOH and Ca(OH)2 due to the occupancy of acid sites by Na+ and hydroxyl groups. Meanwhile, H-zeolites readily adsorbed K+ and Ca2+ from a hydroxide solution by exchanging cations with H+ at Brønsted acid sites or cation adsorption at vacant acid sites. By adsorbing cations, the H-zeolite reduced the pH and increased Ca2+ solubility to promote pozzolanic reactions in a system where Ca(OH)2 dissolution/diffusion was a rate limiting factor. High H-zeolite reactivity resulted in 0.8 g of Ca(OH)2 consumed per 1 g of zeolites after 16 h of reaction versus 0.4 g of Ca(OH)2 consumed per 1 g of Na-zeolite. The H-zeolite modulated the pore fluid alkalinity and created a low-density amorphous silicate phase via mechanisms analogous to two-step C-S-H nucleation experiments. Controlling these reaction mechanisms is key to developing next generation pozzolanic cementitious systems with comparable hydration rates to portland cement.
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来源期刊
Cement & concrete composites
Cement & concrete composites 工程技术-材料科学:复合
CiteScore
18.70
自引率
11.40%
发文量
459
审稿时长
65 days
期刊介绍: Cement & concrete composites focuses on advancements in cement-concrete composite technology and the production, use, and performance of cement-based construction materials. It covers a wide range of materials, including fiber-reinforced composites, polymer composites, ferrocement, and those incorporating special aggregates or waste materials. Major themes include microstructure, material properties, testing, durability, mechanics, modeling, design, fabrication, and practical applications. The journal welcomes papers on structural behavior, field studies, repair and maintenance, serviceability, and sustainability. It aims to enhance understanding, provide a platform for unconventional materials, promote low-cost energy-saving materials, and bridge the gap between materials science, engineering, and construction. Special issues on emerging topics are also published to encourage collaboration between materials scientists, engineers, designers, and fabricators.
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