硅酸盐学报2026，Vol.54Issue(5)：1593-1610,18.DOI:10.14062/j.issn.0454-5648.20250475
超硫酸盐胶凝材料中拜耳法赤泥前驱体热活性评价方法新见解
Thermal Activity Detection Methods of Bayer Red Mud Precursors in Supersulfate Cementitious Materials
摘要
Abstract
Introduction Supersulfated alkali-activated binders(SS-AABs)have emerged as a superior alternative to Portland cement due to their extensive utilization of silicon-aluminum solid waste,sulfate solid waste,and alkaline solid waste,as well as their exceptional mechanical qualities and corrosion resistance.The primary precursors of silicon-aluminum components in SS-AABs are predominantly ground granulated blast furnace slag(GGBFS),comprising 70%to 90%of the composition.Identifying alternative industrial solid waste products that serve as superior precursors for silicon and aluminum can yield significant economic and environmental advantages.Bayer red mud(BRM)is a high-alkali,challenging silicon-aluminum by-product generated in the alumina industry.Nonetheless,the crystal structure of unactivated BRM has some challenges in engaging with the alkali-activated process of the gelling system,rendering it unsuitable as a precursor for SS-AABs.The BRM,following thermal activation treatment,can yield a more active amorphous structure,facilitating enhanced dissociation and repolymerization reactions with alkaline solid waste activators,resulting in the formation of more stable hydration products and establishing a high-quality silicon-aluminum component precursor.The rationale of the detection approach for the comprehensive activity of silicon and aluminum BRMP in SS-AABs is insufficient,hence constraining engineering applications.This paper was to examine the evolution of minerals during the thermal activation of BRM,systematically analyze the characteristics of three activity testing methodologies,i.e.,chemical dissolution methods(e.g.,inductively coupled plasma(ICP)or chemical titration),pozzolanic activity index methods,and microstructural characterization methods(such as X-ray diffraction(XRD)and Fourier transform infrared spectroscopy(FT-IR)).In addition,this paper was also to investigate the changes in activity of BRM as a silicon-aluminum precursor at varying activation temperatures and propose some insights for assessing the silicon-aluminum activity of thermally activated Bayer red mud precursors(BRMP),tailored for the preparation of SS-AABs. Methods The activity index of thermally activated red mud was analyzed in accordance with the standard GB/T 1596-2005.A specimen with the sizes of 40 mm×40 mm×160 mm was fabricated with thermally activated red mud,cement,standard sand,and water in accordance with the stated proportions.It was then cured under standard conditions(i.e.,(20±2)℃,96%RH)for 7 d and 28 d,respetively.The compressive strength of the specimens was evaluated at two ages in accordance with the standard GB/T 17671-2021.The activity index was the ratio of the 7-d and 28-d compressive strength of cement mortar specimens incorporating thermally activated red mud to the compressive strength of pure cement mortar specimens at the equivalent age.A specimen SS-AABs with the sizes of 40 mm×40 mm×40 mm was prepared with 58%heat-activated BRMP,25%desulfurization gypsum,and 17%carbide slag at a water-cement ratio of 0.6.The standard curing was conducted at(20±1)℃and 96%relative humidity for 3,7 d,and 28 d,respectively.The compressive strength of the specimens was evaluated at three ages in accordance with the standard GB/T 17671-2021.The microstructure was examined by scanning electron microscopy(SEM),its mineral composition was assessed by X-ray diffraction(XRD),and the alterations in chemical bonds were evaluated by Fourier transform infrared spectroscopy(FTIR).The solubility of Si4+and Al3+in thermally activated BRMP at various temperatures was assessed by inductively coupled plasma-atomic emission spectrometry(ICP-AES).The leaching quantity of active Si4+was ascertained by a potassium fluosilicate volumetric method,and the leaching quantity of active Al3+was evaluated by ethylenediaminetetraacetic acid(EDTA)complexometric titration method. Results and discussion The result indicates that the combined analysis of XRD-FTIR can proficiently characterize the mineral composition and alterations in chemical structure of BRMP.The pozzolanic activity index approach yields quantitative data but limits to assessing pozzolanic activity in cement systems and cannot differentiate the contributions of silicon and aluminum.The chemical titration method can quantitatively assess the dissolution rates of silicon and aluminum.However,it lacks a sensitivity to variations in ion concentration,particularly within the activation temperature range of 300-700℃,making it challenging to accurately represent changes in activity.Conversely,for precisely quantifying the dissolution concentrations of Si4+and Al3+,the ICP-AES method can quantitatively indicate the activity changes in BRMP at different activation temperatures and differentiate the dissolution behaviors of silicon and aluminum,thereby offering a more dependable foundation for the optimization of components in SS-AABs.The thermal activation at 800℃significantly enhances the breakdown of silicon and aluminum components,compared to that of unactivated BRMP. Conclusions The alteration of the mineral phase in red mud could be constrained by the activation temperature.Katoite decomposed at 400℃,chlorite and diaspore decomposed at 500℃,and grossular and nepheline decomposed at 800℃.The testing methodology for volcanic ash activity possessed specific constraints when examining the activity of BRMP.The conventional activity index approach was constrained by the gypsum concentration(<5%)in Portland cement(the standard GB 175-2023),making it challenging to precisely assess the contribution of active Al2O3 in BRMP.The chemical titration method possessed specific advantages in indicating the mineral activity of BRMP following thermal activation.The quantity of leached active aluminum in BRMP post-thermal activation could be greater than that of active silicon.The analysis by XRD-FTIR indicated that at 800℃,silicon-containing minerals could fully activate,whereas aluminum-containing minerals could disintegrate more readily.The chemical titration method could partially indicate the activation impact of BRMP.However,the detected fluctuation in silicon and aluminum leaching was limited,leading to inadequate sensitivity to changes in ion concentration.The dissolution rate of active silicon and aluminum following BRMP activation by the ICP-AES method showed that the thermally activated BRMP had considerable benefits in terms of activity.The leaching quantity of Al3+in BRMP post-thermal activation consistently exceeded that of Si4+,aligning with the leaching patterns of active SiO2 and Al2O3 determined using chemical titration.At 800℃,the activation effect could be markedly intensified,with the leaching concentration of Si4+attaining 96.4 mg/L,and the leaching concentration of Al3+reaching 167.5 mg/L.Compared with the unactivated BRMP,the dissolution of silicon and aluminum elements of activated BRMP was greatly improved by thermal activation at 800℃.关键词
拜耳法赤泥前驱体/热活化温度/火山灰活性表征法/电感耦合等离子体法/化学滴定法Key words
Bayer red mud precursor/thermal activation temperature/pozzolanic activity characterization method/inductively coupled plasma method/chemical titration method分类
建筑与水利引用本文复制引用
刘文欢,焦小玉,常宁,李辉,王思莹,郝毅,吴优..超硫酸盐胶凝材料中拜耳法赤泥前驱体热活性评价方法新见解[J].硅酸盐学报,2026,54(5):1593-1610,18.基金项目
国家自然科学基金(52472035) （52472035）
陕西重点研发计划(2024GX-YBXM-373). （2024GX-YBXM-373）
