Understanding the microstructural evolution of hypersaline cemented paste backfill with low-field NMR relaxation

Cemented paste backfill (CPB) comprising mineral tailings, binders and mixing waters is an important potential support material in the mining industry. As the mechanical properties of CPB are significantly influenced by its microstructural characteristics the development of measurement tools to better understand its pore structure evolution is important for its increased utilisation. This study reports the application of low-field nuclear magnetic resonance (NMR) relaxation time measurements to characterise the microstructural evolution of CPB materials over 56 days of hydration, contrasting common tap water and hypersaline water (~22 wt% salt) as mixing waters. Distinct NMR relaxation time populations were evidenced within each CBP sample, revealing the presence of both capillary (T1,2 ≈ 10 ms) and gel pore water (T1,2 ≈ 300 – 500 µs), with time-dependent relaxation measurements facilitating characterisation of capillary pore structure evolution over the hydration period assessed. Hypersaline samples demonstrated a time-lag in this measured capillary pore evolution, relative to those hydrated with tap water, while hydration rates were observed to increase with increased CPB binder content. Further, both T1 and T2 NMR relaxation times were found to correlate with the uniaxial compressive strength of the CPB materials investigated, facilitating the formulation of a predictive correlation function between NMR relaxation characteristics and mechanical properties.

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Microstructural evolution of cemented paste backfill: Mercury intrusion porosimetry test results

Cement and Concrete Research ◽

10.1016/j.cemconres.2007.08.016 ◽

2007 ◽

Vol 37 (12) ◽

pp. 1654-1665 ◽

Cited By ~ 90

Author(s):

Serge Ouellet ◽

Bruno Bussière ◽

Michel Aubertin ◽

Mostafa Benzaazoua

Keyword(s):

Microstructural Evolution ◽

Mercury Intrusion Porosimetry ◽

Cemented Paste Backfill ◽

Test Results ◽

Mercury Intrusion ◽

Paste Backfill

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Effects of Superplasticizer on the Hydration, Consistency, and Strength Development of Cemented Paste Backfill

Minerals ◽

10.3390/min8090381 ◽

2018 ◽

Vol 8 (9) ◽

pp. 381 ◽

Cited By ~ 31

Author(s):

Jian Zhang ◽

Hongwei Deng ◽

Abbas Taheri ◽

Junren Deng ◽

Bo Ke

Keyword(s):

Underground Mines ◽

Strength Development ◽

Strength Increase ◽

Strengthening Effect ◽

Cemented Paste Backfill ◽

Solid Concentration ◽

Resonance System ◽

Low Field ◽

Binder Ratio ◽

Paste Backfill

The strength and consistency of cemented paste backfill (CPB) are of key concerns in the stope stability and cost control for underground mines. It is common practice to use additives, such as superplasticizer, to improve the performance of CPB. This study mainly focuses on the effects of superplasticizer on the hydration, consistency, and strength of CPB. In this study, a polynaphtalene sulfonate was used as the superplasticizer. The binder is a mix of 33.3% ordinary Portland cement and 66.7% fly ash. The CPB specimens with a tailings-binder ratio of 3:1 and a solid concentration of 70% were then tested by a low field nuclear magnetic resonance system after different hydration times. Effects of polynaphtalene sulfonate on the hydration, fluidity, and strength were investigated. Results showed that the polynaphtalene sulfonate has a strong influence on short-duration hydration, which may contribute to the strength increase of CPB. It has been demonstrated that the polynaphtalene sulfonate improved the fluidity of the CPB mixture. With the increased dosage of polynaphtalene sulfonate, the slump increased. It was also found that the polynaphtalene sulfonate dosage has a negligible effect on the 1 day (d) strength while it has a strengthening effect on the 7 d, 14 d, and 28 d strength of CPB specimens.

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