scholarly journals Low-Carbon Binder for Cemented Paste Backfill: Flowability, Strength and Leaching Characteristics

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 707 ◽  
Author(s):  
Jingping Qiu ◽  
Yingliang Zhao ◽  
Hui Long ◽  
Zhenbang Guo ◽  
Jun Xing ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Orthogonal Experiment ◽  
Solid Content ◽  
Raw Material ◽  
Cemented Paste Backfill ◽  
Low Carbon ◽  
Optimum Parameters ◽  
Paste Backfill ◽  
Activated Slag ◽  
Furnace Slag

Blast furnace slag was used as the main raw material to prepare the alkali activated slag (AAS), a low-carbon binder, for cemented paste backfill (CPB). The optimum parameters for preparing the AAS binders using an orthogonal experiment were obtained. Under the optimum conditions (NaOH content was 3 wt. %, Ordinary Portland cement (OPC) content was 7 wt. %, and gypsum dosage was 4 wt. %), the 28 days compressive strength of the binder was 29.55 MPa. The flow ability of the fresh CPB slurry decreased with solid content due to the increased yield stress, while the flow ability increased when rising the binder dosage. A predictive model for the compressive strength of CPB samples was reached through multivariate analysis and the R2 values were higher than 0.9. Sensitivity analysis showed that the solid content is the most important parameter which influences on the development of the CPB strength with a correlation coefficient of 0.826. From the Toxicity Characteristic Leaching Procedure (TCLP) tests, the leaching concentrations of Pb and Cd were below the threshold. As a result, the AAS has potential application as an alternative binder and cemented paste backfill.

scholarly journals Substitution of Cement with Granulated Blast Furnace Slag in Cemented Paste Backfill: Evaluation of Technical and Chemical Properties

Minerals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1068
Author(s):  
Soili Solismaa ◽  
Akseli Torppa ◽  
Jukka Kuva ◽  
Pasi Heikkilä ◽  
Simo Hyvönen ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Blast Furnace ◽  
Mine Tailings ◽  
Blast Furnace Slag ◽  
Partial Substitution ◽  
Cemented Paste Backfill ◽  
X Ray ◽  
Granulated Blast Furnace Slag ◽  
Paste Backfill ◽  
Furnace Slag

Cemented paste backfill (CPB) offers an environmentally sustainable way to utilize mine tailings, one of the largest waste streams in the world. CPB is a support and filler material used in underground mine cavities, which consists of mine tailings, water, and binder material that usually is cement. Replacing cement with secondary raw materials like granulated blast-furnace slag reduces the total CO2 emissions and strengthens the internal microstructure of the CPB. This study characterizes the total- and soluble contents of CPB starting materials and five CPB specimens containing different levels of slag substitution. In addition, phase composition (mineral liberation analysis, MLA) and internal structure (X-ray tomography) of five CPB specimens is documented, and measurements of compressive strength are used to evaluate their suitability as backfill material. Mine tailings and CPB specimens used in this study are rich in sulphates and arsenic, but low in sulphides. Stronger As leaching of ground CPB specimens compared with ground mine tailings is related to the elevating pore water pH during the cement hydration. The hydration product ettringite is found in all CPB specimens and its content is the lowest in the slag containing specimens. X-ray tomography revealed vertically differentiated density structures in the CPB specimens. The lower parts of all specimens are denser in comparison with the upper parts, which is probably due to the compaction of the solid particles at the base. The compressive strength test results indicate that partial substitution of cement with slag improves the strength of the CPB. The total replacement of cement with slag reduces the early strength but gives excellent strength and lower porosity over longer time intervals. The results of the study can be utilized in developing more durable and environmentally responsible CPB recipes for gold mines of similar mineral composition and gold extraction method.

scholarly journals Strengthening Behavior of Cemented Paste Backfill Using Alkali-Activated Slag Binders and Bottom Ash Based on the Response Surface Method

Materials ◽  
2020 ◽  
Vol 13 (4) ◽  
pp. 855
Author(s):  
Qi Sun ◽  
Xueda Wei ◽  
Tianlong Li ◽  
Lu Zhang
Keyword(s):  
Response Surface ◽  
Bottom Ash ◽  
Hydration Product ◽  
Cemented Paste Backfill ◽  
Alkali Activated Slag ◽  
Surface Method ◽  
Optimal Mix ◽  
Paste Backfill ◽  
Activated Slag ◽  
Alkali Activated

A new type of cemented paste backfill (CPB) was prepared by using the bottom ash (BA) from a thermal power plant as an aggregate, alkali-activated slag as a binder, and an air-entraining agent as an admixture. Based on the central composite design (CCD) response surface method, the mix ratio was optimized, and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) was performed on the optimal mix ratio. ImageJ software was utilized to determine the porosity of the experimental samples at various curing ages. The results indicate that the optimal mix ratio of the aggregate-binder ratio is 3.28, the alkali dosage is 3%, the solid content is 67.44%, and the air-entraining agent dosage is 0.1%. As the curing age increases, the porosity of CPB gradually decreases. A calcium aluminosilicate hydrate (C-A-S-H) gel is the main hydration product of alkali-activated slag. At the beginning of the hydration reaction, the slag gradually dissolves, and the C-A-S-H product binds the BA together. At 14 d, complete calcium hydroxide (CH) crystals appeared in the hydration product. Finally, the degree of C-A-S-H crystallization increased further to form a dense structure.

Low carbon binder modified by calcined quarry dust for cemented paste backfill and the associated environmental assessments

2021 ◽  
Vol 300 ◽  
pp. 113760
Author(s):  
Yingliang Zhao ◽  
Jingping Qiu ◽  
Shiyu Zhang ◽  
Zhenbang Guo ◽  
Pinqi Wu ◽  
...  
Keyword(s):  
Cemented Paste Backfill ◽  
Low Carbon ◽  
Environmental Assessments ◽  
Paste Backfill ◽  
Quarry Dust
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