Sewage sludge ash characteristics and potential for use in bricks, tiles and glass ceramics

TLDR

The study reviewed global literature to assess sewage sludge ash characteristics for use in bricks, tiles, and glass ceramics. Sewage sludge ash shows chemical similarity to conventional ceramic materials, enabling densification, strength gains, and reduced absorption; it can partially replace clay with only modest performance loss, lowers firing temperatures, and its glass ceramics surpass natural stone in strength and durability while keeping heavy metal leaching low, as confirmed by practical case studies.

Abstract

The characteristics of sewage sludge ash (SSA) and its use in ceramic applications pertaining to bricks, tiles and glass ceramics have been assessed using the globally published literature in the English medium. It is shown that SSA possesses similar chemical characteristics to established ceramic materials and under heat treatment achieves the targeted densification, strength increases and absorption reductions. In brick and tile applications, technical requirements relating to strength, absorption and durability are achievable, with merely manageable performance reductions with SSA as a partial clay replacement. Fluxing properties of SSA facilitate lower firing temperatures during ceramics production, although reductions in mix plasticity leads to higher forming water requirements. SSA glass ceramics attained strengths in excess of natural materials such as granite and marble and displayed strong durability properties. The thermal treatment and nature of ceramic products also effectively restricted heavy metal leaching to low levels. Case studies, predominantly in bricks applications, reinforce confidence in the material with suitable technical performances achieved in practical conditions.