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Backfilling practices become widely used by modern hard rock mines helping ore extraction as well as allowing a more integrated solid waste management. Among backfill types, cemented paste backfill is taking an increasing interest since its easy placement in the underground stopes and its capacity to use reactive sulfidic tailings. Various binder agents, including conventional manufactured cements and alternative additives, can be used in order to set the needed mechanical properties of the backfill during mining sequences. Due to the high price of binders and their sensitivity towards chemical properties of the backfill material, backfill recipe optimisation becomes capital. The key note will focus on the various sources and compositions of the most common binders in paste backfilling. The paper will also contribute in the understanding of the binder hardening processes in cemented paste; focusing particularly on i) cement hydration, ii) water demand and water chemical interactions, iii) solid mineralogy, iv) sulfate and sulfide behaviours, v) temperature role, etc. The main short-and long-terms behaviour types of cemented paste backfill will be discussed (effects of drainage-consolidation, sulfate attacks, etc.). https://papers.acg.uwa.edu.au/p/1063_30_Benazzaoua/ Key issues related to behaviour of binders in cemented paste backfilling M. Benzaazoua et al. 346 Paste 2010, Toronto, Canada Tailings % and type of sulfides Particle size Clay minerals % H 2 O Binder Ca+Mg/Si+Al % ciment % CaSO 4 Paste backfill Mixing water Sulfates Soluble lime % Binder