Mechanical and thermal properties of cemented tailings materials at early ages: Influence of initial temperature, curing stress and drainage conditions Liang Cui, Mamadou Fall ⇑ Department of Civil Engineering, University of Ottawa, Ottawa, Ontario K1N 6N5, Canada highlights  Cemented paste backfill (CPB) is extensively used in underground mining as a construction material.  Initial backfill temperature affects its thermal and mechanical properties.  Curing stress affects the thermal and mechanical properties of CPB.  Drainage conditions affects the thermal and mechanical properties of CPB. article info Article history: Received 11 April 2016 Received in revised form 17 August 2016 Accepted 21 August 2016 Keywords: Cemented paste backfill Tailings Cement Mechanical properties Thermal properties Multiphysics abstract The cementitious construction material, cemented paste backfill (CPB), is extensively used in under- ground mining operations worldwide. After the CPB is placed in the field, the evolution of its mechanical and thermal properties strongly affects its stability and the heat transfer within it. An experimental setup is designed to enable the curing of CPB samples under different stresses, filling rates, initial temperatures and drainage conditions as well as the monitoring of the changes in capillary pressure, temperature, amount of drained water and electrical conductivity in the CPB samples during curing. Furthermore, extensive testing is carried to investigate the combined effects of initial temperature, curing stress and drainage on the mechanical, microstructural and thermal properties of CPB. The obtained results reveal that these properties are strongly influenced by the initial backfill temperature, curing stress and drai- nage conditions, and their interactions. These can significantly affect the cement hydration, capillary pressure development and pore structure of CPB. Ó 2016 Elsevier Ltd. All rights reserved. 1. Introduction During underground mining operations, large quantities of mine waste, such as tailings, are produced. However, the surface disposal of tailings is not only a significant expense, but may also give rise to potential long-term environmental issues, such as acid mine drainage (AMD) [1–4]. As an alternative to surface tailings disposal, cemented paste backfill (CPB), which comprises a mixture of tailings, binder and water, is an innovative cementitious mate- rial (however, CPB is different from concrete) used for under- ground mine backfilling and mine waste management [5,6]. CPB reduces the volume of surface tailings and other pertinent environ- mental issues when it is placed into the mined-out space of an underground mine, which is commonly known as stopes [7–9]. Moreover, CPB can also provide ground and wall support, limit the possibility of caving, and prevent subsidence [6,10,11]. Conse- quently, the application of CPB technology significantly improves safety in underground mine operations and increases productivity. Due to its environmental, financial and safety benefits for the min- ing industry, CPB technology is now regarded as a standard prac- tice in mining operations worldwide [12,13]. Mechanical properties are considered to be a key factor for the safe and effi- cient design of CPB structures, such as the unconfined compressive strength (UCS), stress–strain behavior and shear strength parame- ters [2,14–16]. These properties are required to properly assess the mechanical stability of CPB, which must demonstrate acceptable mechanical properties to ensure the safety of miners. Moreover, early age mechanical properties are particularly important for the mechanical stability of backfill structures at the early ages, reduction in the liquefaction risks of CPB and the optimization of http://dx.doi.org/10.1016/j.conbuildmat.2016.08.080 0950-0618/Ó 2016 Elsevier Ltd. All rights reserved. ⇑ Corresponding author at: Department of Civil Engineering, University of Ottawa, 161 Colonel By, Ottawa, Ontario K1N 6N5, Canada. E-mail address: mfall@uottawa.ca (M. Fall). Construction and Building Materials 125 (2016) 553–563 Contents lists available at ScienceDirect Construction and Building Materials journal homepage: www.elsevier.com/locate/conbuildmat