Abstract
The influence of admixtures on the engineering properties of fly ash-based cemented tailings backfill (CTB) is a topic of significant practical interest, as it affects the backfilling cost and the environmental effect of mining operation. This paper presents results of an experimental study on the influence of different activators on the engineering properties of the CTB containing fly ash. CTB samples are mixed with different contents of calcium formate, sodium sulfate, and cement clinker (4%, 8%, and 12% by mass of total binder) and cured in a cubic chamber (at 20°C and RH 90 ± 5%) for 3, 7, and 28 days. Specimen tests were performed to assess the slump height, setting time, leaching water rate, vertical settlement, and strength development. Furthermore, the XRD analyses were conducted on the hydration products of fly ash-based CTB mixtures. The results show that activators can cause decrease in the slump height, leaching water rate, and vertical settlement of fly ash-based CTB mixtures. However, inclusion of cement clinker ranging from 8%–12% of total binder can reduce the slump height, setting time, leaching water rate, and vertical settlement to an acceptable range. Addition of calcium formate in the fly ash-based CTB caused negligible change in compressive strength. The compressive strength improved with higher content of sodium sulfate and cement clinker at the age of 28 days. XRD analyses showed considerable intensity counts of C-S-H gel, calcium hydroxide, and ettringite, resulting from the addition of sodium sulfate and cement clinker. This study also shows that an understanding of the effect of activators on the engineering properties of fly ash-based CTB is crucial for designing a cost-effective and workable CTB with reduced environmental impact.
Highlights
Mine tailings is the main waste from mineral processing with an annual output of about 300 million tons in China alone [1]. erefore, safe disposal of tailings has been a big challenge in the mining industry, mainly due to its toxicity and potential risk to human health, ambient ecological environment, etc. e tailings storage facilities are the traditional method to disposal of these tailings, such as dams, embankments, and dry stacking on surface land
Water leaching from the slurry results in volume shrinkage. e shrinkage of the slurry induced vertical settlement of the slurry and generation of cracks in the upper layer of the slurry. e vertical settlement was measured in terms of settlement ratio in a column mould by a laser ranger apparatus. e settlement ratio represents the value of total amount of settlement to the initial height (h0), which may cause unfilled mined-out area in underground stope, as shown in Figure 2. e settlement ratio (β) is calculated as follows: β hs × 100%. h0 (3)
Small pieces were obtained from the dried samples and sprayed with Au before scanning electron microscopy (SEM) observations. e microstructure morphology characteristics of the cemented tailings backfill (CTB) specimens were investigated by a Quanta 250 FEG SEM with a solution of 1.0 nm and an accelerating voltage of 30 kV. e X-ray diffraction (XRD) and SEM tests were performed on the CTB samples CC4%, CC12%, and control cured for 28 days
Summary
Mine tailings is the main waste from mineral processing with an annual output of about 300 million tons in China alone [1]. erefore, safe disposal of tailings has been a big challenge in the mining industry, mainly due to its toxicity and potential risk to human health, ambient ecological environment, etc. e tailings storage facilities are the traditional method to disposal of these tailings, such as dams, embankments, and dry stacking on surface land. The findings reported in the above studies illustrate that the proper alkali activator and appropriate proportion can significantly alter the mechanical properties of fly ash-based concrete These observations mainly focused on the properties of modified concrete containing fly ash, and the results cannot be directly suitable for CTB. Is study aims to investigate the properties of alkaliactivated fly ash-based cemented tailings backfill through various experimental tests, which assess the slump height, setting time, leaching water rate, settlement, and compressive strength. It will recycle fly ash as a binder for the cleaner production of mineral resource and reduce the binder cost of cemented backfilling
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
