Effect of chemical and mineral foaming agents on expansion, insulation, strength features, and microstructure of foam backfill

Composed of large numbers of bubbles, foam creates an insecure system and is efficiently used in cementitious materials, including cemented tailings backfill (CTB). Foam-CTB (FCTB) retains some benefits of little density/thermal conductivity, and high workability/fire resistance. However, the behavior of FCTB is governed by its unique microstructure, which heavily relies on types and features of the foam used in mine fill. In this study, a novel arrangement of expansion and thermal insulation-based FCTB was created by tailings, foaming agents (FA) and cement as raw material. The study investigated the effects of expansion features, strength, thermal insulation and microstructure of FCTB using expansion tests, uniaxial compression, thermal conductivity measurements, and analyses via XRD, FTIR, and SEM-EDS. Lab findings certify that adding three diverse FA (i.e., SDS: sodium dodecyl sulphate, anionic surfactant; ADC: azodicarbonamide, chemical foaming agent; and DTAB: dodecyl trimethyl ammonium bromide, cationic surfactant) significantly increased the expansion rate of slurry, and DTAB-0.8 increased by 14.6 %. By rising FA dosage, UCS of FCTB dwindled as a whole, but the strength of ADC and DTAB increased by 45.15 % and 28.21 % respectively at 0.2 % content. In chorus, FA pointedly improved FCTB’s peak strain, enhancing its ductility. Addition of FA also significantly diminished FCTB’s thermal conductivity. As content of DTAB was 0.8 %, thermal conductivity dropped to 0.5726 W/(m·K), enriching fill’s thermal insulation ability. FA also promoted the formation of hydration yields. By rising FA content, porosity increased, and hydration yields adhered to fill surface. FCTB has superb thermal conductivity and strength properties, which afford a novel idea for source use of solid waste such as tailings, and provide a potential technical way for the development of efficient filling thermal insulation materials.