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废弃水泥石等固体废弃物碳酸化不仅能够永久固碳,还可实现固体废弃物的再利用,减少对环境的污染。水化硅酸钙(C-S-H)是最主要的可碳化成分之一。合成了钙硅(C/S)比为1.50的C-S-H,研究了加速碳化对其显微结构的影响。用Rietveld全谱拟合的方法和热重-质谱联用的方法对碳化产物进行定量分析,用扫描电镜、N2吸附和29Si固体核磁共振对碳化前后的显微结构进行表征。结果表明:在99.9%CO2,0.2 MPa压力下加速碳化2 h之后,生成了3种不同晶型的碳酸钙和硅胶,碳酸钙从300℃开始分解,文石和球霰石具有较低的分解温度,结晶良好的方解石分解温度较高;多孔结构硅胶具有更高的吸附能力,但C-S-H碳化后的平均孔径从10.33 nm减小到6.69 nm,比表面积由85.6 m2/g减小到67.7 m2/g,这是由于大量的结构致密的碳酸钙晶体堆积造成的;C-S-H双层硅氧链之间的Ca–O层逐渐脱去与CO2反应,硅氧四面体被质子化或与邻近的硅氧四面体链接,形成了聚合度更高的Q3和Q4结构。
Waste cement and other solid waste carbonation not only permanently fixed carbon, but also to achieve solid waste recycling, reduce environmental pollution. Calcium silicate hydrate (C-S-H) is one of the most important carbonizable components. The C-S-H with a C / S ratio of 1.50 was synthesized and the effect of accelerated carbonization on its microstructure was investigated. The carbonation products were quantitatively analyzed by Rietveld full-spectrum fitting method and TG-MS method. The microstructures before and after carbonization were characterized by scanning electron microscopy, N2 adsorption and 29Si solid-state nuclear magnetic resonance. The results showed that after accelerated carbonization at 99.9% CO2 and 0.2 MPa for 2 h, three different types of calcium carbonate and silica gel were formed. Calcium carbonate began to decompose at 300 ℃. Aragonite and vaterite have lower decomposition temperature, However, the average pore size of CSH after carbonization decreased from 10.33 nm to 6.69 nm, the specific surface area decreased from 85.6 m2 / g to 67.7 m2 / g, This is due to the accumulation of a large number of densely packed calcium carbonate crystals; the Ca-O layer between CSH double-walled silicon and oxygen chains gradually decays to react with CO2, and the silicon tetrahedra is protonated or intercalated with adjacent silicon tetrahedron Link, forming a higher degree of polymerization Q3 and Q4 structure.