Soil Recycling Geopolymers Fabricated from High Power Ultrasound Treated Soil Slurry in the Presence of Ammonia

Abstract

Soil slurry was recycled to prepare a geopolymer after treatment with high-power ultrasound (US) in the presence of NH3, HCl, and NaOH. Under 28 kHz US, 0.1 M NH3 additives effectively decarbonized the slurry, eliminating 72.2% of the carbon content from the original soil. The US-treated soils were used as raw materials for the geopolymer, as they contained Si and Al components in the range of 25–30 and 8–10 wt.%, respectively. The geopolymer was prepared with a Na2SiO4/NaOH aqueous solution at a ¼ weight ratio at 80 °C for 24 h. The resultant geopolymers from the NH3-treated soil showed the best compressive strength of 3 MPa after 1 day of curing, with a low carbon content, when NH3 was used as an additive as opposed to HCl and NaOH under 1200 US exposure.