A comparison between the influence of superplasticizer and organosilanes on different properties of cemented paste backfill

The water repellency influence of non-polar organosilanes (vinyl and methyl) and polycarboxylate superplasticizer were studied and compared on flow behavior, strength development, and microstructural properties of cemented paste backfill (CPB) composed of sulfidic and non-sulfidic tailings. The addition of water-repellent admixtures affects the water requirement and hence the total performance of cementitious materials. Based on the uniaxial compressive strength (UCS) test and slump height measurements, the addition of vinyl silane to CPB provided a higher UCS value and reduced the required amount of water for a specific slump height. The addition of vinyl and methyl organosilanes, however, was less advantageous on CPBs composed of sulfidic tailings since reduced the early strength development. The achieved differential thermogravimetric (DTG), mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) results implicated that the use of vinyl silane was more efficient to densify the CPB matrix due to the hydration improvement and the formation of additional C-S-H gel specifically in non-sulfidic CPBs.