Abstract
In this paper, lime, gypsum, NaOH, and Na2SO4 are mainly used to study the activation degree and activation mechanism of fly ash, and L9 (34) orthogonal table is used for the orthogonal test. The influence of different activators on the rheological and strength properties of slurry was analyzed. The microstructure and hydration products of fly ash cement cementitious body were studied by SEM and XRD. The results show that the bleeding rate of slurry containing activator fly ash system is between 2.24% and 3.37%, which is much higher than that of pure cement slurry (9.25%). Therefore, the addition of this system can improve the fluidity of slurry, and the optimal scheme is a3b2c2d2. The results show that the compressive strength of cement with activator fly ash system is much lower than that of pure cement, but the increase of strength is between 31% and 85%, which is much greater than that of pure cement (35%–46%). The optimal scheme is A2B2C3D3 or A3B2C3D3 at 3 days and A1B3C2D3 at 28 days. According to the scanning results of SEM and XRD, the addition of activator can significantly improve the hydration degree of fly ash and form a more complex network structure without obvious gap.
Highlights
TWith the development of mining technology, filling method is considered a future development direction for an increasing number of large, medium, and small mines, and the reduction of filling cost has always been the research emphasis of scholars all over the world [1, 2]
Fly ash mainly refers to fine particles generated from coal combustion, the particle size of which is 1–100 m and the main chemical compositions are SiO2 and Al2O3 [3]
If the fly ash is released into the air, it will seriously affect the air quality, but if it is stacked on the ground, it will pollute the local environment and inevitably cause a waste of resources
Summary
TWith the development of mining technology, filling method is considered a future development direction for an increasing number of large, medium, and small mines, and the reduction of filling cost has always been the research emphasis of scholars all over the world [1, 2]. As an inert material, fly ash can substitute cement as much as possible only when its internal potential activity is fully stimulated For this purpose, it is affirmatively necessary to study the excitation principle and mode of fly ash. As for the chemical excitation mode, different fly ash excitants are added to stimulate the internal potential activity of fly ash [12]. Excitant is added to increase the concentration of OH- in the slurry [17], so that the reaction speed between fly ash and Ca(OH) is improved. It has a certain promoting effect on the early strength of gelatin. Notes: the ratio of cement to fly ash is 1 : 1; the water-cement ratio is 0.5
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