Key issues related to behaviour of binders in cemented paste backfilling

Abstract

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

Estado del arte:

“…The balance is made when the quantity of the compounds present in the raw mixture is not enough to produce the clinker. Materials called "second raw materials" are used such as clay, shale, sand, iron ore, bauxite, fly ash, and slag (Benzaazoua et al, 2010).…”

A model of formulation of blended binders for use in cemented mine backfills

“…When tailings are very reactive (presence of pyrite and pyrrhotite) and/or contain higher levels of sulfate, Type V (or HS) portland cement is used for backfill preparation. However, Type V cement has mainly been supplanted by the use of Type I (GU) cement blended with GGBS or ternary blended cements containing GGBS and fly ash (Benzaazoua et al, 2010). Based on the works done by Benzaazoua et al (2004a), it must be recognised that the hardening processes in CMB are very different to those encountered in mortar and concrete.…”

“…Based on the works done by Benzaazoua et al (2004a), it must be recognised that the hardening processes in CMB are very different to those encountered in mortar and concrete. No direct transposition or extrapolation can be made between concrete/mortar and CMB in view of understanding their behaviour (Benzaazoua et al, 2004a(Benzaazoua et al, , 2010. For more details concerning the key issues related to the use of binders in CMB, see Benzaazoua et al (2010).…”

“…No direct transposition or extrapolation can be made between concrete/mortar and CMB in view of understanding their behaviour (Benzaazoua et al, 2004a(Benzaazoua et al, , 2010. For more details concerning the key issues related to the use of binders in CMB, see Benzaazoua et al (2010).…”

“…Bb = GU/GGBS or Bb = GU/FaF) must be used with reactive tailings/water for CMB preparation in order to improve the long-term strength development. It was also found that GBFS blended binder (or slag cement) up to 90% of GBFS is relatively suitable for use in all classes of sulfate conditions depending on the tailings grain size distribution (Belem et al, 2000;Belem and Benzaazoua, 2008;Benzaazoua et al, 2002Benzaazoua et al, , 2004aBenzaazoua et al, , 2004bBenzaazoua et al, , 2008Benzaazoua et al, , 2010.…”