Microstructure evolution and mechanical behavior of foamed cement-based tail backfills under varying fiber types and concentrations

Abstract Industrial solid waste (mine tailings) management has emerged as the key universal ecological challenge as a result of the unceasing creation of rising waste by-products. Employing tailings makes mine fill production economical and assists resolve disposal problems. Foamed cement-based tailings backfill (FCTB) is a mine fill consisting of tailings, cement, water and foaming agent. It provides certain advantages such as lightweight, good fluidity, and thermal insulation, yet is relatively weak in strength. Additionally, FCTB’s strength properties can be intensely improved by adding fibers. A total of 3 diverse fibers: polypropylene (PP), glass (G), and basalt (B) as well as dodecyltrimethylammonium bromide (DTAB) as a foaming agent were used to prepare fiber-reinforced foamed cementitious tailings backfill (FR-FCTB). The mechanical properties, energy evolution, ductility and microstructure of FR-FCTB were elaborately investigated by uniaxial compression tests (UCS) and SEM. Laboratory findings demonstrates that reinforcing effect of three fibers on FCTB specimens: glass > polypropylene > basalt. FR-FCTB showed the best strength features as a fiber content of 0.3% was adopted in FCTB. At this time, the UCS performance of glass fiber reinforced FCTBs was 0.85 MPa increased by 18.1%. The addition of fibers can increase fill’s energy storage limit, slow down discharge of elastic strain energy within backfill, and enhance fill’s ductility and toughness. The ductility factor evaluates the degree of deterioration of filling in terms of post-peak drop, with all FR-FCTB values being greater than CTB. FR-FCTB’s chief hydration product is C-S-H gel. Fiber’s bridging effect significantly rallies crack extension and thus fill’s strength features. Lastly, the study’s main results are instructive for the industrial application of FR-FCTB used in metallic mines.