三乙醇胺对液体无碱速凝剂“促-抑”水泥早期水化的调控机理研究

Study on Regulation Mechanism of Triethanolamine to Liquid Alkali-free Accelerator on ‘Accelerating-Inhibiting’ of Early Hydration of Cement

三乙醇胺(TEA)作为水泥混凝土中常用的早强组分,对早期强度发展有显著的促进作用。近年来随着喷射混凝土和液体无碱速凝剂的快速发展,三乙醇胺以其优良的早强特性逐渐得到广泛应用。然而,不同条件下由三乙醇胺制备的速凝剂性能不尽相同,甚至截然相反,其对水泥早期水化的影响规律及作用机理亟待明确。本工作制备了不同TEA比例的液体无碱速凝剂,从凝结时间、早期强度、水化放热行为、水化物相、热分析等方面详细研究了液体无碱速凝剂中TEA对水泥早期水化的影响规律。结果表明,当TEA占液体无碱速凝剂质量的0.25%时,凝结时间最短,初凝109 s,终凝324 s,1 d强度最高,达到12.32 MPa,满足喷射混凝土用速凝剂的国标要求。TEA在低掺量时能够加速液体无碱速凝剂对水泥早期水化的促进作用,而TEA在高掺量下会对水泥早期水化有明显的削弱和抑制。此外,通过电导率、核磁氢谱等手段研究了TEA与铝相的络合机制,揭示了TEA对液体无碱速凝剂“促-抑”水泥早期水化的调控机理:(1)低TEA掺量时,TEA络合偏铝酸根离子,参与加速C_(3)A的早期水化;(2)高TEA掺量时,会生成大量钙矾石和TEA-Ca络合物,覆盖在C_(3)A表面抑制水化。本工作系统探究了不同TEA掺量的液体无碱速凝剂对水泥早期水化的影响规律和调控机理,为开发高性能液体无碱速凝剂提供了重要的研究基础和科学指导。

Triethanolamine(TEA),as a commonused component in cement concrete for early strength,which can significantly promote the development of early strength.In recent years,with the rapid development of shotcrete and liquid alkali-free accelerator,triethanolamine has been widely used due to its excellent early-strength characteristics.However,the performance of accelerator prepared from triethanolamine under different conditions are not the same or even the opposite.Its influence law and action mechanism on early hydration of cement need to be clarified.In this study,liquid alkali-free accelerator with different proportions of TEA was prepared.The influence of TEA in the alkali-free accelerator on the early hydration of cement was investigated in detail from the aspects of setting time,early strength,hydration exothermic behavior,hydrate phase and thermal analysis.The results show that when TEA accounted for 0.25% of the mass of alkali-free accelerator,the setting time was the shortest,the initial setting was 109 s,the final setting was 324 s,and the strength was the highest at 1 d,reaching 12.32 MPa,which meets the national standard requirements of accelerator for shotcrete.TEA can accelerate the accelerating effect of alkali-free accelerator on early hydration of cement at low dosage,while it can significantly weaken and inhibit early hydration of cement at high dosage.In addition,the complexation mec-hanism between TEA and aluminum phase was studied by means of conductivity and nuclear magnetic hydrogen spectroscopy,and the regulation mechanism of TEA to liquid alkali-free accelerators on the ‘accelerating-inhibiting' early hydration of cement was revealed:(ⅰ) when the content of TEA is low,metaaluminate ions complex with TEA and participate in accelerating the early hydration of C_(3)A;(ⅱ) high TEA content will produce a large amount of ettringite and TEA-Ca complex,which will cover the surface of C_(3)A and inhibit hydration.This study systematically explores the influence and regulation mechanism of liquid alkali-free accelerator with different TEA contents on early hydration of cement,which provides an important research basis and scientific guidance for the development of high-performance liquid alkali-free accelerator.