Microstructural and chemical investigations of cemented paste backfills

Ramlochan, T; Grabinsky, Murray; Hooton, RD

doi:10.1201/9780203021637.ch35

Cited by 10 publications

(3 citation statements)

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“…For instance, the W/C ratio in concrete research usually ranges between 0.3 and 0.6, while W/C ratios in CPB are significantly higher to reach a desired pumping consistency. Thus, 2.5-7 are common W/C ratios for CPB (Ramlochan et al 2004). Despite this difference, CPB and concrete are alike in terms of their gradual transition from a nonNewtonian fluid to a solid of quantifiable strength.…”

Section: Introductionmentioning

confidence: 94%

Characterizing stiffness development in hydrating mine backfill using ultrasonic wave measurements

et al. 2011

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Ultrasonic velocity measurements have previously proven valuable in measuring the development of stiffness of cement mixtures. We have successfully applied this technique to "cemented paste backfill" (CPB), an engineered mine backfill material having significantly higher void ratio and lower binder content than conventional mortars and concretes. The development of P-and S-waves was measured for samples containing 3% and 5% Portland cement, for a 1 week period after mixing. Two sets of samples were tested; one stored in air and one submerged in water. For the air-dried samples, a declination in P-wave velocity was seen due to moisture loss, followed by a small increase in velocity due to continued cement hydration. The submerged samples showed constant P-wave velocity. The S-wave velocity increased for both sets of samples, showing greater increase for the air-dried samples, which reflects the effect of the suction developed on stiffness. However, the effect of binder content variation on stiffness is less significant in air-drying CPB than in submerged CPB. The results compare well with the trends reported for hydrating materials as well as natural soils, suggesting that ultrasonic wave measurements can be used as a nondestructive test to be correlated with other forms of laboratory testing.Résumé : Les mesures de vitesse ultrasoniques ont prouvé leur utilité pour la mesure de la rigidité de mélanges de ciment. Nous avons appliqué cette technique au "remblai cimenté en pâte", un matériau de remblayage minier qui comporte un indice des vides plus élevé et un contenu en liant plus faible que les mortiers et bétons conventionnels. Le développement des ondes P et S a été mesuré pour des échantillons ayant 3 % et 5 % de ciment Portland, et ce, pendant une période d'une semaine suivant le mélange. Deux séries d'échantillons ont été testées : une série d'échantillons conservés à l'air et une série d'échantillons submergés dans l'eau. Pour les échantillons séchés à l'air, une diminution de la vitesse des ondes P a été observée en raison de la perte d'humidité, suivie par une faible augmentation de la vitesse due à la poursuite de l'hydratation du ciment. Les échantillons submergés ont présenté une vitesse constante des ondes P. La vitesse des ondes S a augmenté pour les deux séries d'échantillons, avec une augmentation plus élevée pour les échantillons séchés à l'air, ce qui démontre l'impact de la succion développée sur la rigidité. Cependant, l'effet de la variation du contenu en liant sur la rigidité est moins significatif pour les RCP séchés à l'air que pour les RCP submergés. Les résultats se comparent bien avec les tendances rapportées pour les matériaux hydratants ainsi que pour les sols naturels, ce qui suggère que les mesures de vitesse des ondes ultrasoniques peuvent être utilisées comme essai non destructif pouvant être corrélé aux autres types d'essais en laboratoire.

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Section: Introductionmentioning

confidence: 94%

Characterizing stiffness development in hydrating mine backfill using ultrasonic wave measurements

et al. 2011

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“…The widely used mix proportion of CPB uses cement binder approximately 3%-7% by dry weight and tailings approximately 70%-85% by total weight (Landriault 1995;Orejarena and Fall 2011). The CPB with 2.5%-7% water to cement ratio has better flowability without clogging the pipeline (Ramlochan et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

Temperature Effect on Mohr–Coulomb’s Effective Strength Parameters of Paste Backfill

Hasan

Ting

2022

Front. Mater.

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In-stope paste backfill monitoring at different mine sites showed anomalous increase in total stress during rest periods. One of the explanations according to a recent laboratory- model experiment was attributed to volumetric expansion caused by temperature increase within the backfill. This paper extends the understanding whether the Mohr–Coulomb’s effective strength parameters are affected by such temperature increase. The effects are explained through evaluating the apparent cohesion and the effective internal and interfacial friction angles under different temperature conditions. A series of modified direct shear tests were performed on saturated specimens under three controlled temperature levels: 25°C, 50°C, and 70°C. The specimens consist of cemented paste backfill and uncemented paste backfill. The results show that the effective internal and the interfacial friction angles increase as the temperature increases, depending on the type of material and the shearing condition, whereas the temperature increase does not significantly affect the apparent cohesion. The findings serve as a reference for engineers and academics in explaining the stress anomaly and to better understand the shear behavior of paste backfill under different temperature conditions for mine stope backfill design.

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“…Numerous researchers [43][44][45][46][47][48][49] also investigated experimentally the influence of binder type and rate, water-to-cement ratio, consolidation, and mineral and chemical admixtures on strength, rheology and pore structural properties of CTB or CPB samples. One can observe from those works that the ultimate mechanical strength and durability of CTB samples are greatly affected by its mineralogical and microstructural evolution after binder hydration during the curing process.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of Viscosity, Strength and Microstructural Properties of Cemented Tailings Backfill

2018

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In this study, the particle size distribution and chemical composition of gold mine tailings were examined experimentally. A series of viscosity and uniaxial compressive strength (UCS) tests were used to study the relations between the viscosity of cemented tailings backfill (CTB) slurry, the solid content (SD), and the cement-to-tailings ratio (c/t). Relations between UCS performance of CTB and SD, c/t, and curing time (CT) were discussed while examining the microstructure of 28-day cured backfill with different solid contents. Results illustrate that a major increase in CTB viscosity by increasing the SD leads to the formation of tailings grains for a skeleton formation, which is formed due to consolidation and gravitational forces. The CTB’s strength increases with the increase of c/t, SD, and CT, due to a decrease in water-to-cement ratio and porosity, and an increase in hydration products over time. The SEM micrographs show how CTB’s microstructure is affected by the SD, generating ettringites and calcium silicate hydrates in the backfill matrix. The findings of this study will lead to an efficient CTB mix design for reaching the higher performance in underground mining structures, thereby reducing expenses related to the backfill.

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Microstructural and chemical investigations of cemented paste backfills

Cited by 10 publications

References 0 publications

Characterizing stiffness development in hydrating mine backfill using ultrasonic wave measurements

Characterizing stiffness development in hydrating mine backfill using ultrasonic wave measurements

Temperature Effect on Mohr–Coulomb’s Effective Strength Parameters of Paste Backfill

Evaluation of Viscosity, Strength and Microstructural Properties of Cemented Tailings Backfill

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