Abstract
To study the possibility of utilizing mixed construction waste and ultrafine tailings (CW&UT) as a backfilling aggregate that can be placed underground in a mine, physicochemical evaluation, proportioning strength tests, and pumpability experiments were conducted. It was revealed that mixed CW&UT can be used as a backfilling aggregate due to the complementarities of their physicochemical properties. In addition, as the results of the proportioning strength tests show, the compressive strength of a cemented CW&UT backfilling specimen cured for 28 days, with a mass fraction of 72–74%, a cement-sand ratio of 1:12, and a CW proportion of 30%, is higher than 1.0 MPa, which meets the safety requirements and economic consideration of backfilling technology in many underground metal mines, and can also be enhanced with an increase in the cement-sand ratio. The results of the pumpability experiments show that cemented backfilling slurry based on CW&UT can be transported to the stope underground with a common filling pump, with a 16.6 MPa maximum pressure, with the condition that the time of emergency shut-down is less than approximately 20 min. All in all, the research to utilize mixed CW&UT as a backfilling aggregate can not only provide a way to dispose of CW&UT but also will bring large economic benefits and can provide constructive guidance for environmental protection.
Highlights
Construction waste (CW) represents over one-third of the total solid waste in the world [1], as a result of city modernization and development
The main purpose of this study is to explore the possibility of utilizing mixed construction waste and ultrafine tailings (CW&ultrafine tailings (UT)) as a backfilling aggregate, so the simple analysis by control variable method was selected in this research, as following: 1. The cement-sand ratio was kept 1:8, the common ratio used in backfilling technology, to study the compressive strengths of specimens cured for 28 days with the CW proportion and mass fraction were changed
The following conclusions are suggested by the results of the physicochemical evaluation (Tables 1 and 2): 1. Al2O3 and SiO2 account for 15.54% and 37.45% of the contents of the CW, respectively, as shown in Table 1, which is beneficial to the strength of the backfilling body
Summary
Construction waste (CW) represents over one-third of the total solid waste in the world [1], as a result of city modernization and development. Considering that backfilling mining technology plays a significant role in the protection of the environment during the recycling of industrial waste, such as tailings, slag, fly ash and ardealite [6,7,8], and that the requirements of strength and stability of cemented paste backfill (CPB) are relatively low, backfilling CW into the stope underground in a mine may be a good way to minimize those problems. A large amount of cement is required to improve the strength and flowability of a CPB based on CW, which greatly increases the cost of backfilling. Mixing with a widely accessible, low-cost material may be an effective way to address these issues with CW, and the best option for this would be an industrial waste
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