Investigation of the AFm-Cl system: Fe-to-Al solid solution, thermal behavior and carbonation

IF 10.9 1区工程技术 Q1 CONSTRUCTION & BUILDING TECHNOLOGY

Cement and Concrete Research Pub Date : 2024-10-15 DOI:10.1016/j.cemconres.2024.107696

Aurore Lechevallier , Mohend Chaouche , Jérôme Soudier , Evelyne Prat , Guillaume Renaudin

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Abstract

Due to increasing interest in reducing CO₂ emissions, new hydraulic binders are emerging, many of which contain significant amounts of iron and aluminum oxides. The reactivity of such binders can be activated using CaCl₂. It thus appears essential to investigate mixed Al/Fe-Cl hydrates to better characterize the hydration products and hydration processes of these new hydraulic binders. AFm-Cl phases with varying proportions of Al³⁺ and Fe³⁺ trivalent cations were synthesized and characterized. Carbonation of AFm-Cl samples is unavoidable at ambient atmosphere and leads to phases with Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O general composition (samples were synthesized for x = 0, 0.17, 0.33, 0.50, 0.67, 0.83 and 1). A complete solid solution between the two Ca₂Al(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O and Ca₂Fe(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O endmembers was demonstrated. Two hydration states were identified with characteristic interlayer distances of about 7.8 Å and 6.8 Å for, respectively, the Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O hydrate and the Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15 dehydrated phase. Thermal studies indicated a similar succession of thermal events for Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O regardless of the nature of the trivalent cation; the presence of iron however decreasing the degradation temperatures. Finally, the Ca₂Al_1-xFe_x(OH)₆·Cl_0.7(CO₃)_0.15·2H₂O phase was investigated in the presence of carbonate anions, showing a progressive exchange of chloride for carbonate within the interlayer to form Ca₂Al_1-xFe_x(OH)₆·(CO₃)_0.5·3H₂O before degrading into calcite.

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AFm-Cl 系统研究：铁-铝固溶体、热行为和碳化

由于人们对减少二氧化碳排放的兴趣与日俱增，新型液压粘合剂不断涌现，其中许多都含有大量的铁和铝氧化物。使用 CaCl2 可以激活此类粘合剂的反应活性。因此，研究 Al/Fe-Cl 混合水合物以更好地描述这些新型液压粘合剂的水化产物和水化过程显得至关重要。我们合成并表征了具有不同比例 Al3+ 和 Fe3+ 三价阳离子的 AFm-Cl 相。AFm-Cl 样品在环境气氛中不可避免地会发生碳化，从而形成具有 Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 基本成分的阶段（合成了 x = 0、0.17、0.33、0.50、0.67、0.83 和 1 的样品）。结果表明，Ca2Al(OH)6-Cl0.7(CO3)0.15-2H2O 和 Ca2Fe(OH)6-Cl0.7(CO3)0.15-2H2O 两种内含物之间存在完整的固溶体。确定了两种水合状态，Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 水合物和 Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15 脱水相的特征层间距离分别约为 7.8 Å 和 6.8 Å。热研究表明，无论三价阳离子的性质如何，Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 都会发生类似的连续热事件；但铁的存在会降低降解温度。最后，在碳酸根阴离子存在的情况下对 Ca2Al1-xFex(OH)6-Cl0.7(CO3)0.15-2H2O 相进行了研究，结果表明在降解为方解石之前，氯离子在层间逐渐交换为碳酸盐，形成 Ca2Al1-xFex(OH)6-(CO3)0.5-3H2O。

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来源期刊

Cement and Concrete Research 工程技术-材料科学：综合

CiteScore

20.90

自引率

12.30%

发文量

318

审稿时长

53 days

期刊介绍： Cement and Concrete Research is dedicated to publishing top-notch research on the materials science and engineering of cement, cement composites, mortars, concrete, and related materials incorporating cement or other mineral binders. The journal prioritizes reporting significant findings in research on the properties and performance of cementitious materials. It also covers novel experimental techniques, the latest analytical and modeling methods, examination and diagnosis of actual cement and concrete structures, and the exploration of potential improvements in materials.