Authors: Rafraf, G; Belem, T; Mrad, H; Gélinas, L-P; Krichen, A

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Rafraf, G, Belem, T, Mrad, H, Gélinas, L-P & Krichen, A 2023, 'Experimental validation of a prediction model of the compressive strength of cemented rockfills', in GW Wilson, NA Beier, DC Sego, AB Fourie & D Reid (eds), Paste 2023: Proceedings of the 25th International Conference on Paste, Thickened and Filtered Tailings, University of Alberta, Edmonton, and Australian Centre for Geomechanics, Perth, pp. 841-852,

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Underground mine backfilling promotes solid waste to be returned as cementitious material either in the form of cemented paste backfill – CPB – (using tailings) or in the form of cemented rock fill – CRF – (using crushed waste rock, WR). The cement or binder addition is intended to develop a required unconfined compressive strength (UCS) value to ensure ground stability during mining operations. While CPB is the most common type of mine backfill used in underground mining operations, CRF is only used when high compressive strength is required to increase productivity. Despite the performance of CRF, this type of backfill is not much studied or optimised. The main objective of this study is to validate experimentally a newly developed semi-empirical model for predicting the UCS of CRF. This model considers various physical parameters of CRF materials such as the types of binder (e.g. general use Portland cement –GU, GU-fly ash, GU-ground granulated blast furnace slag, etc.) and their mass proportion (binder rate Bw), the water-to-cement ratio (W/C), the type of WR (according to its relative density DR) and the grain size distribution, and the curing time (t). To this end, numerous cylindrical CRF specimens are prepared by varying the W/C, the type of binder, the binder rate Bw (4–8%), the type of WR and the average diameter (d) of the particles. Preliminary results show that the accuracy of the predicted UCS values of various laboratory-prepared CRF mix recipes is satisfactory with a high coefficient of correlation (R 0.9). Therefore, it is reasonable to adopt the proposed CRF strength prediction model for laboratory-prepared specimens that can be scaled up in situ bydeveloping an efficient CRF preparation quality control (QC) procedure.

Keywords: unconfined compressive strength, cemented rockfill, semi-empirical prediction model, experimental validation, quality control

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