硅酸盐学报2025，Vol.53Issue(4)：816-827,12.DOI:10.14062/j.issn.0454-5648.20240635
煅烧条件对硅灰石晶相和碳化活性的影响
Impact of Calcination Condition on Phase Composition and Carbonation Reactivity of Wollastonite
摘要
Abstract
Introduction Cement industry continues to face significant environmental challenges due to its substantial CO2 emissions,primarily stemming from carbonate decomposition in raw materials and fossil fuel combustion during production.Carbonatable binders and carbonation curing technologies have a promising potential for CO2 reduction in cement production,and the existing methods involve the calcination of calcareous and siliceous raw materials to produce low-lime silicates for their emission reduction limits.Natural wollastonite,primarily composed of calcium silicate(CS),has an attractive alternative due to its abundant reserves and ease of extraction.Utilizing natural wollastonite as a carbonatable binder can eliminate both fossil fuel combustion and the need for calcareous raw materials,thereby avoiding the carbonate decomposition entirely.However,its application is currently limited due to its low carbonation reactivity.This study was to investigate the enhancement of carbonation reactivity of natural wollastonite via optimizing calcination activation to develop a high-performance carbonatable binder. Methods Natural wollastonite was calcinated under various calcination activation condictions(i.e.,temperature,time,and cooling regimes).The activated wollastonite powder was mixed with water and compressed at 4 MPa to form the samples with different two dimensions(i.e.,20 mm × 20 mm × 20 mm and 20 mm × 80 mm × 20 mm).These samples underwent carbonation curing for 24 h before characterization.The mechanical properties were evaluated through compressive and flexural strength tests.The phase composition was characterized by X-ray diffraction(XRD)on both the wollastonite powder and carbonated samples before and after calcination activation.The structure of the samples was determined by Fourier-transform infrared spectroscopy(FT-IR)to analyze both the calcination activation effects and the resulting carbonation products.The microstructural evolution was determined by scanning electron microscopy(SEM).CO2 uptakes were analyzed by thermogravimetric analysis(TGA). Results and discussion This study reveals that calcination activation significantly enhances the carbonation hardening performance of natural wollastonite via increasing carbonation reactivity.Optimal conditions are identified at a calcination temperature of 1200 ℃,effectively transforming Para-CS and β-CS into metastable α-CS.The effective calcination time for the complete transformation is 60 min,while preserving the material valuable fibrous structure.Water quenching is found to be the most effective cooling method,retaining higher concentrations of crystal defects in the metastable α-CS.The transformation from a chain structure to a ternary ring structure at 1200 ℃ results in an increased structural distortion,thus leading to an enhanced carbonation reactivity of α-CS.The carbonation analysis reveals the extensive formation of carbonation products,primarily calcium carbonate and highly polymerized silica gel,resulting in a dense microstructure.Note that the preservation of the fibrous structure through calcination activation allows unreacted wollastonite to serve as a fibrous reinforcement within the carbonation hardening system,contributing to enhanced mechanical properties. Conclusions The results showed that calcination temperature exhibited a dominant effect,followed by calcination time and cooling regime.The optimal calcination temperature of 1200 ℃ led to the improvements in compressive strength,flexural strength,and CO2 uptakes of the carbonated samples.The calcination time was critical in ensuring a complete phase transformation,while maintaining structural integrity,and a rapid cooling could preserve crystal defects that enhanced carbonation reactivity.The resulting carbonatable binder developed a carbonation hardening system comprising calcium carbonate,highly polymerized silica gel,and unreacted wollastonite fibers that could serve as an effective reinforcement within the carbonation hardening system.These findings could provide a promising pathway for the large-scale utilization of natural wollastonite in sustainable construction materials,having a potential for reducing the environmental impact of cement industry.关键词
天然硅灰石/煅烧活化/固碳胶凝材料/碳化活性/微观结构Key words
natural wollastonite/calcination activation/carbonatable binder/carbonation reactivity/microstructure分类
建筑与水利引用本文复制引用
刘松辉,李东林,张欣雨,李根深,朱建平,管学茂..煅烧条件对硅灰石晶相和碳化活性的影响[J].硅酸盐学报,2025,53(4):816-827,12.基金项目
国家自然科学基金(52108208) （52108208）
河南省科技攻关项目(242102231063) （242102231063）
河南理工大学项目(J2023-6,T2023-5,B2020-11). （J2023-6,T2023-5,B2020-11）
