硅酸盐学报2026，Vol.54Issue(5)：1501-1511,11.DOI:10.14062/j.issn.0454-5648.20250046
半干法碳化对硅酸盐水泥水化及微观结构的影响
Effect of Semi-dry Carbonation on Hydration and Microstructure of Portland Cement
摘要
Abstract
Introduction With the ongoing expansion of global housing and infrastructure,cement as an essential component of concrete is projected to reach a global demand of 468 million tonnes by 2050,contributing approximately 6%-7%of total CO2 emissions.Reducing carbon emissions in cement and concrete production is thus critical for achieving carbon neutrality goals.In the central and western regions of China,a growing demand for large infrastructure projects such as dams,tunnels,and mountain bridges increasingly relies on the use of mass concrete.However,a great heat release from cement hydration with a low thermal conductivity leads to internal heat accumulation and significant temperature differentials.These thermal gradients increase cracking risk and compromise long-term durability.Conventional strategies like low-heat cement,mineral admixtures,and chemical retarders are adopted to mitigate early hydration heat.Nevertheless,these approaches are limited due to high production costs,reduced strength,or insufficient control over heat evolution rate.Recently,carbon capture,utilization,and storage(CCUS)technologies,particularly semi-dry carbonation,show a promising potential for reducing carbon emissions and regulating hydration heat,especially for high-alkaline materials.In this study,semi-dry carbonation pretreatment was applied to Portland cement,forming a surface layer of CaCO3 that serves as a physical barrier to suppress early hydration.The effect of semi-dry carbonation on the hydration behavior and microstructure was investigated.The results could provide some insights into applying CCUS technology for hydration heat control in cement-based materials. Methods A P·I 42.5 Portland cement(Fushun Cement Co.,Ltd.,China)was used.Semi-dry carbonation was performed in a NELD-CA070 carbonation chamber using simulated kiln gas containing 20%CO2 at a RH of(70% ± 5%)and a temperature of(20 ± 2) ℃.The cement was loosely spread in trays and carbonated for 2,4 h,or 8 h,respectively,under manually stirring for every 30 min.The resulting samples were designated as C2,C4,and C8,respectively,while the uncarbonated sample was labeled as C0.All the samples were dried at 40 ℃for 24 h after carbonation. Cement pastes were prepared at a water-to-cement ratio of 0.4 and cured under standard conditions(i.e.,20 ± 1 ℃,95 ± 5%RH).For the determination of compressive strength,cube specimens(40 × 40 × 40 mm)were tested at 1,3,7 d,and 28 d,respectively.For the microstructural analysis,fresh pastes were cast in sealed vials,demolded after 24 h,immersed in water,and cured until the specified age.Hydration was stopped by solvent exchange with isopropanol,followed by vacuum drying and grinding to a fine powder with the particle size below 80 μm. The early hydration heat evolution was measured by isothermal calorimetry(TAM Air).The phase composition was determined by isothermal calorimetry,thermogravimetric analysis(TGA),X-ray diffraction(XRD),and Fourier transform infrared spectroscopy(FTIR).The pore solution alkalinity was assessed through pH measurement and elemental analysis by inductively coupled plasma optical emission spectrometry(ICP-OES).The pore structure was characterized by mercury intrusion porosimetry(MIP),and the microstructure was determined by scanning electron microscopy(SEM). Results and discussion The semi-dry carbonation alters the phase composition and microstructure of cement.The TG analysis shows a weakened gypsum decomposition peak and an intensified CaCO3 decomposition,indicating that gypsum participates in carbonation.The mild carbonation(i.e.,2-4 h)increases CH content due to enhanced pre-hydration.CO2 sequestration reaches 1.60%,2.27%,and 3.62%after 2,4 h,and 8 h,corresponding to 3.62%,5.16%,and 8.23%CaCO3 formation,respectively.As carbonation progresses,C3S,C2S,C3A,C4AF,and gypsum decrease,while calcite and amorphous silica increase,driven by reactions with CO2 and moisture.The FTIR spectra show strengthened C—O stretching(1410 cm-1),weakened H2O peaks(3527 cm-1),and intensified SO42-bands(1124 cm-1 and 1197 cm-1),indicating interactions among gypsum,CO2,and alkali oxides.The SEM images reveal roughened clinker surfaces caused by the deposition of carbonation products such as calcite and silica gel. The semi-dry carbonation significantly reduces early compressive strength,with 1-d reductions of 31.2%,77.5%,and 89.6%after 2,4 h,and 8 h,respectively.However,this effect diminishes over time,with less than 5.4%strength loss at 28 d.Carbonation extends the induction period and reduces hydration heat,lowering cumulative heat by 67.2%at 10 h.Early hydration degrees and chemically bound water also decrease,corresponding to reduced CH content and early strength.Despite this,hydration products at<400 ℃are largely unaffected,having the minimal difference in 28-d strength.Early-age pore solution alkalinity declines significantly.In the C8 group,Na+and K+concentrations at 1 d are reduced by 60%and 40.7%,and the pH value is decreased from 13.52 to 13.18.At 28 d,the pH value becomes 13.5,indicating no risk to reinforcement passivation.At this age,total porosity increases slightly from 21.1%to 22.8%,with a minor rise in capillary and gel pores.The SEM images and MIP analyses confirm similarly dense microstructures across all the samples,indicating that the calcite layer is eventually penetrated and has no adverse long-term effect. Conclusions This study showed that emi-dry carbonation could alter the phase composition and microstructure of Portland cement.After 2-h,4-h,and 8 h-carbonation,CO2 sequestration increased to 1.60%,2.27%,and 3.62%,respectively,accompanied by a reduction in clinker minerals and gypsum and formation of amorphous silica and calcite layers on cement particle surfaces.These calcite layers could effectively suppress early hydration by reducing the contact area between water and reactive clinker phases.As a result,cumulative heat release at 3 d was decreased by 14.7%,35.1%,and 58.1%,respectively,leading to a lower early compressive strength,a pore solution alkalinity,and a looser microstructure.However,the long-term effect was limited.At 28 d,the continuous formation of hydration products penetrated the calcite layer,and hydration degree and product quantity were reduced by less than 7%,and the compressive strength,pH value,and porosity were altered by no more than 5.4%,0.1,and 8.1%,respectively.关键词
半干法碳化/硅酸盐水泥/水化/微观结构Key words
semi-dry carbonation/Portland cement/hydration/microstructure分类
化学化工引用本文复制引用
周晓丰,张苏辉,於成龙,谢涛,李雪双,元强..半干法碳化对硅酸盐水泥水化及微观结构的影响[J].硅酸盐学报,2026,54(5):1501-1511,11.基金项目
国家重点研发计划(2024YFE0210400) （2024YFE0210400）
中国中铁股份有限公司科技研究开发计划项目(2023-重大-08) （2023-重大-08）
中南大学研究生科研创新项目(1053320231007). （1053320231007）
