Competing mechanisms of cement hydrates and anhydrous phases at ambient and 120 °C carbonation

IF 10.8 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement & concrete composites Pub Date : 2025-02-16 DOI:10.1016/j.cemconcomp.2025.105986

Hao Yu , Yi Jiang , Tung-Chai Ling

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引用次数: 0

Abstract

The carbonation of a fresh cement matrix involves several parallel reactions, including the hydration of anhydrous phases and the carbonation of both anhydrous phases and cement hydrates. This study aims to elucidate the competing mechanisms of anhydrous phases and cement hydrates during high-temperature carbonation. We comparatively investigate the behaviors of three representative precursors (a) fresh cement powder (as a composite system), (b) hydrated cement powder (representing cement hydrates), and (c) steel slag powder (representing anhydrous cement phases) under high-temperature (120 °C) carbonation. By differentiating the concurrent reactions occurring in the fresh cement system, the individual contribution of each material can be identified. The results show that carbonation occurs more significantly on cement hydrates than on anhydrous phases at ambient temperatures, but the trend reverses under high-temperature carbonation. Notably, dicalcium silicate (C₂S) directly reacts with CO₂ at 120 °C within the fresh cement matrix, producing calcite and a highly polymerized calcium silicate hydrate (C-S-H) gel similar to that of steel slag. This reaction not only contributes to carbonation but also facilitates hydration through its nucleation effect. In contrast, for tricalcium silicate (C₃S), hydration initiates first, followed by the carbonation of its resultant product, namely portlandite, and subsequently C-S-H.

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水泥水合物和无水相在环境和120°C碳化时的竞争机制

新水泥基质的碳酸化涉及几个平行反应，包括无水相的水化和无水相和水泥水合物的碳酸化。本研究旨在阐明高温碳化过程中无水相与水泥水合物的竞争机制。我们比较研究了三种具有代表性的前驱体(a)新鲜水泥粉（作为复合体系）、(b)水化水泥粉（代表水泥水合物）和(c)钢渣粉（代表无水水泥相）在高温（120℃）碳化作用下的行为。通过区分新水泥体系中发生的并发反应，可以确定每种材料的单独贡献。结果表明：在常温下，水泥水合物的碳化比无水相的碳化更明显，但在高温下碳化的趋势相反；值得注意的是，硅酸二钙（C2S）在新鲜水泥基体内与CO2在120℃下直接反应，生成方解石和高度聚合的水合硅酸钙（C- s - h）凝胶，类似于钢渣。该反应不仅有助于碳酸化，而且通过其成核作用促进水化。相比之下，对于硅酸三钙（C3S），首先开始水化，然后是其产物（即硅酸盐）的碳酸化，然后是C-S-H。

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来源期刊

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.