ABSTRACT
To promote the widespread use of fly ash (FA) and coal gasification slag (CGS) in mine filling, reducing the amount of cement and promoting the sustainable development of mining enterprises are essential. In this study, decarbonized CGS (DCGS) was prepared from CGS through decarbonization. A new DCGS-FA filling material was prepared using DCGS, FA, cement (3 wt.%), sodium sulfate (SS), and aeolian sand (AS). The effects of different mass ratios (1/9-5/5) of DCGS/FA on the properties of new filling materials were investigated. The results indicate that CGS can be used with FA to prepare filling materials after decarbonization. The flow performance of the DCGS-FA filling material is positively correlated with the mass ratio of DCGS/FA, while the mechanical properties are negatively correlated. The 28-day unconfined uniaxial compressive strength (UCS) of all specimens met the mechanical requirements (UCS ≥ 1.0 MPa). The types of hydration products were determined through X-ray diffraction, scanning electron microscopy, and energy-dispersive spectroscopy. The main hydration products of DCGS-FA filling materials are ettringite (AFt) and C-S-H gel. The results of the TG/DTG test of 28 days revealed that an increase in the DCGS/FA mass ratio would reduce the content of hydration products in filling materials. When the mass ratio increased from 1/9 to 5/5, the content of hydration products in the filling material decreased by 54.5%. This study provides a new concept for the resource utilization of CGS and FA in mine filling, which can significantly reduce the amount of cement in filling materials and promote the sustainable development of mine filling.
Subject(s)
Coal Ash , Coal , Coal Ash/chemistry , X-Ray DiffractionABSTRACT
With the wide application of the filling mining method, it is necessary to consider the influence of rock activity on the filling body, reflected in the laboratory, that is, the influence of loading rate. Therefore, to explore the response characteristics of loading rate on the mechanical and damage characteristics of aeolian sand paste filling body, DNS100 electronic universal testing machine and DS5-16B acoustic emission (AE) monitoring system were used to monitor the stress-strain changes and AE characteristic parameters changes of aeolian sand paste filling body during uniaxial compression, and the theoretical model of filling sample damage considering loading rate was established based on AE parameters. The experimental results show that: (1) With the increase in loading rate, the uniaxial compressive strength and elastic modulus of aeolian sand paste-like materials (ASPM) specimens are significantly improved. ASPM specimens have ductile failure characteristics, and the failure mode is unidirectional shear failure â tensile failure â bidirectional shear failure. (2) When the loading rate is low, the AE event points of ASPM specimens are more dispersed, and the large energy points are less. At high loading rates, the AE large energy events are more concentrated in the upper part, and the lower part is more distributed. (3) The proportion of the initial active stage is negatively correlated with the loading rate, and the proportion of the active stage is positively correlated with the loading rate. The total number of AE cumulative ringing decreases with the increase in loading rate. (4) Taking time as an intermediate variable, the coupling relationship between ASPM strain considering loading rate and the AE cumulative ringing count is constructed, and the damage and stress coupling model of ASPM specimen considering loading rate is further deduced. Comparing the theoretical model with the experimental results shows that the model can effectively reflect the damage evolution process of ASPM specimens during loading, especially at high loading rates. The research results have significant reference value for subsequent strength design of filling material, selection of laboratory loading rate and quality monitoring, and early warning of filling body in goaf.
