Development and Application of a High-Volume Recycled Powder Solidifying Material for Waterworks Sludge

Abstract

Recycled powder (RP) is produced as a by-product during the process of recycling construction and demolition (C&D) wastes, presenting a low additional value. Using RP-based solidifying material can not only improve its utilization efficiency, but also reduce the cost of commercial solidifying materials. To date, this is the best solidifying material utilized to dispose the original waterworks sludge (OWS) with high moisture contents (60%), and the product could be used to fabricate non-fired bricks. This has become a new environment-friendly technology of “using waste to treat waste”. In this paper, the influence of different particle sizes and dosages of RP on the prepared solidifying material was studied. Besides, unconfined compression strength (UCS), volume stability, chemical composition, and heat of hydration, pore structure of the solidifying material were characterized. Then, non-fired bricks were prepared by using the solidifying material, recycled aggregate, and original waterworks sludge. The UCS and softing coefficient (SC) of the non-fired bricks were evaluated. As a result, the 28-day UCS of the solidifying material with optimal (M30) was 35.40 MPa, which could reach 84.37% of Portland cement (PC). The addition of RP increased the volume stability of the solidifying material. The addition of a large amount of RP reduced the heat flux and cumulative heat release of the solidifying material, while its porosity increased. The UCS of non-fired brick (NF20) in 28 days was 15.19 MPa and the SC after 28 days was 78.35%. In conclusion, the preparation of solidifying material using RP could be a promising approach and has a great potential in disposal of original waterworks sludge.