磷酸钠对碱矿渣水泥水化行为影响研究

发布时间：2018-11-21 19:41

【摘要】：碱矿渣水泥是利用碱金属化合物激发冶金工业废渣形成的一种水硬性胶凝材料,具有优良的物理力学性能及抗化学侵蚀性能。然而,碱矿渣水泥凝结速度过快,现场施工困难。Na3PO4对碱矿渣水泥凝结时间有显著影响,但影响规律存在争议,作用机理尚不明确。本文研究了水胶比0.29为条件下,Na3PO4与Na OH水玻璃(模数固定为2.5)组成的复合碱组分碱矿渣水泥的凝结时间、流动度经时损失和强;采用TAM air微量热仪测试了复合碱组分碱矿渣水泥的水化放热行为。应用Knudson水化热模型及Jander方程,分析了复合碱组分对碱矿渣水泥水化动力学过程。采用XRD和SEM测试手段,分析了复合碱组分碱矿渣水泥的水化产物及微观结构。探讨了Na3PO4碱矿渣水泥水化行为机理。研究表明:复合碱组分中,Na3PO4相对掺量对碱矿渣水泥凝结时间有显著影响。Na3PO4-Na OH复合碱组分中,Na3PO4相对掺量低于20%,增强矿渣颗粒间连续性,碱矿渣水泥表现为缓凝;相对掺量高于80%,Na3PO4与Na OH共同析出,碱矿渣水泥表现为促凝。Na3PO4-水玻璃复合碱组分中,Na3PO4相对掺量低于20%,降低碱矿渣水泥早期水化程度,碱矿渣水泥表现为缓凝;相对掺量高于80%,Na3PO4与水玻璃共同析出,碱矿渣水泥表现为促凝,并导致水泥浆长时间不硬化。复合碱组分中,Na3PO4相对掺量对碱矿渣水泥水化过程有重要影响。Na3PO4-Na OH复合碱组分中,Na3PO4相对掺量低于20%,复合碱组分中水化放热速率小。从水化动力学参数可知,加速期反应速率小,反应由致密层扩散控制,增大了碱矿渣水泥早期水化反应阻力,减速期与衰减期由多孔扩散和致密扩散双重控制;相对掺量高于80%,碱矿渣水泥水化放热量小,碱组分对矿渣激发效果弱。Na3PO4-水玻璃复合碱组分中,Na3PO4相对掺量低于20%,削弱了诱导前期放热峰,延长加速期开始时间。从水化动力学参数可知,碱矿渣水泥加速期受致密扩散控制,减速期与衰减期由多孔扩散和致密扩散双重控制,反应速率常数随反应的进行而逐渐增大;相对掺量高于80%,碱矿渣水泥无法正常水化。Na3PO4复合碱组分碱矿渣水泥早期水化产物中无Ca3(PO4)2晶体生成。Ca3(PO4)2不是引起碱矿渣水泥缓凝的原因。
[Abstract]:Alkali slag cement is a kind of hydraulic cementitious material which is formed by using alkali metal compounds to excite metallurgical industrial waste slag. It has excellent physical and mechanical properties and chemical erosion resistance. However, the setting speed of alkali slag cement is too fast and the field construction is difficult. Na3PO4 has a significant influence on the setting time of alkali slag cement, but the law of influence is controversial, and the mechanism of action is not clear. Under the condition of water-binder ratio 0.29, the setting time and fluidity loss and strength of alkali slag cement composed of Na3PO4 and Na OH sodium silicate (fixed modulus 2.5) were studied. TAM air microcalorimeter was used to measure the hydration heat release behavior of alkali slag cement. Knudson hydration heat model and Jander equation were used to analyze the hydration kinetics of alkali slag cement. The hydration products and microstructure of alkali-mixed slag cement were analyzed by means of XRD and SEM. The hydration mechanism of Na3PO4 alkali slag cement was discussed. The results show that the relative content of Na3PO4 has a significant effect on the setting time of alkali slag cement in the compound alkali component, and the relative content of Na3PO4 in the Na3PO4-Na OH compound alkali component is lower than 20%, which enhances the continuity between the slag particles, and the alkali slag cement exhibits retarding coagulation. The relative content of Na _ 3PO _ 4 and Na OH precipitated together, and the alkali slag cement showed accelerated coagulation. In the compound alkali component of Na3PO4- water glass, the relative content of Na3PO4 was lower than 20, which reduced the hydration degree of alkali slag cement at early stage, and the alkali slag cement showed retarding coagulation. When the relative content of Na _ 3PO _ 4 is higher than 80% Na _ 3PO _ 4 and sodium silicate precipitate together, the alkali slag cement can accelerate coagulation and cause the cement slurry not to harden for a long time. The relative content of Na3PO4 plays an important role in the hydration process of alkali slag cement. The relative content of Na3PO4 is lower than 20 in the composition of Na3PO4-Na OH, and the hydration heat release rate is small in the compound alkali component. From the kinetic parameters of hydration, it can be seen that the reaction rate in accelerated period is small and the reaction is controlled by dense layer diffusion, which increases the resistance of early hydration reaction of alkali slag cement, and the deceleration period and attenuation period are both controlled by porous diffusion and densification diffusion. The hydration heat release of alkali slag cement is small, and the activation effect of alkali component on slag is weak. The relative content of Na3PO4 is lower than 20% in Na3PO4- sodium glass compound alkali component, which weakens the exothermic peak in the early stage of induction and prolongs the start time of acceleration period. According to the hydration kinetic parameters, the accelerated period of alkali slag cement is controlled by densification diffusion, the deceleration period and attenuation period are controlled by porous diffusion and densification diffusion, and the reaction rate constant increases gradually with the reaction. The alkali slag cement can not be hydrated normally when the relative content is higher than 80%. There is no Ca3 (PO4) _ 2 crystal formation in the early hydration product of Na3PO4 compound alkali slag cement. Ca3 (PO4) _ 2 is not the cause of the retarding of alkali slag cement.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ172.1

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