Environmental potential assessment of MSWI bottom ash-based alkali-activated binders

Area of Science:

• Materials Science
• Environmental Science
• Civil Engineering

Background:

• Alkali-activated binders (AABs) offer a sustainable alternative to ordinary Portland cement (OPC).
• Residue-based AABs may pose toxicity risks due to hazardous compounds in alkaline media.
• Environmental risk assessment is crucial for validating AABs in construction.

Purpose of the Study:

• To environmentally assess AABs made with different fractions of weathered bottom ash (WBA).
• To evaluate the leachate toxicity and ecotoxicity of AA-WBA under service life and end-of-life scenarios.
• To determine the correlation between metal(loid) concentrations and ecotoxicity.

Main Methods:

• Preparation of AABs using 0-30 mm and 8-30 mm fractions of weathered bottom ash (WBA).
• Granular and monolithic leaching tests simulating end-of-life and service life scenarios.
• Acute toxicity tests using *Daphnia magna* as model organisms.

Main Results:

• AABs with the 0-30 mm WBA fraction exhibited higher metal(loid) concentrations.
• Service life leaching tests revealed multiple metal(loid)-release mechanisms.
• A 48h EC50 value near 10% indicated moderate toxicity; coarser WBA fractions enhanced metal(loid) immobilization.

Conclusions:

• The fraction size of WBA significantly impacts the metal(loid) leaching and ecotoxicity of AABs.
• Coarser WBA fractions (8-30 mm) are preferable for reducing environmental risks.
• A correlation between specific metal(loid) concentrations and ecotoxicity was established.