Paste Backfill Strength Behaviour Using Different Binding Agents and Binder Combinations
Paste backfill system have increasingly been used by underground mines due to environmental concerns and the excellent structural support that stabilized paste backfill can provide. Stabilizing paste backfill requires use of considerable amounts of binding agent, which is usually Type 10 Normal Portland Cement (NPC). In some cases, where backfill oxidation or sulphide attack develops that can detrimentally affect its strength behaviour, special types of cement must be used that are resistant to these effects. However, the cost of these special cements, regardless of the type, is not cheap. Previous research has indicated that binder cost is the highest of all the cost items in backfilling, followed by the backfill material and placement costs. Due to the high charges associated with the use of cement as binding agent, application of alternative binding agents is often sought to minimize cost, but without jeopardizing the strength behaviour of the paste backfill as structural support.
The purpose of this paper is to present the variability of responses of paste backfill specimens that have been prepared with varying binding agent and binder combinations, when subjected to uniaxial compressive strength testing. Tailings material from an operating mine was used in combination with four binding agents, these being NPC T-10, oxidation or sulphide attack resistant binder (Binder A), replacement binder B (Binder B), and replacement binder C (Binder C). Specimens were prepared at a fixed size and tested in a Material Testing System (MTS) under constant strain rate conditions following cure times of 7, 14, 28, 56, 90, 112, 180, 240, 300 and 360 days. Paste backfill parameters, such as the peak unconfined compressive strength and modulus of elasticity, were observed. Strength characteristics will be presented and results will be normalized relative to paste backfill materials constituted using NPC T-10, a universal binding agent adopted by most mines.
Paste backfill, Peak unconfined compressive strength, Modulus of elasticity, Binding agent and binder combinations, Strength behaviour