Engineering properties of controlled low strength materials using flyash and waste gypsum wall boards

• Proportioning of CLSM using waste gypsum wallboard sheets and quarry dust.
• Ternary binder blend of cement, fly ash and waste gypsum wallboard sheets.
• Reduced compressive strength was observed for all mixes after 28 days.
• Reduction in H2S emissions at landfills due to drywalls use in CLSM.
• Phenomenological models generated save time and effort to design CLSM mixes.

The discarded gypsum wallboards (drywalls) dumped at landfills, release hydrogen sulfide gas, a harmful substance, to the atmosphere along with the leachate at the landfill. In this paper, the discarded drywalls were utilized as secondary cementitious materials in controlled low strength materials (CLSM) with flyash and cement. Quarry dust, a stone industry waste was used as fine aggregates. CLSM mixes were produced for varying water contents, drywall and flyash to cement ratios by weight. Spread flow, Marsh flow time and fresh density properties at fresh state, and un-confined compressive strength, settlement and density properties at 3, 7, 28 and 56 days for hardened state, were investigated. Reduced compressive strengths at later ages due to use of drywalls were observed. Flow and strength phenomenological models were generated using wide range of experimental data and validated for separate set of experimental data, to encourage production of CLSM using waste drywalls, of required parameters instead of conventional trial and error process.