A team of civil engineers in Melbourne is taking aim at one of the world’s most common litter problems by putting cigarette filters into an unexpected place: fired clay bricks.
In lab testing at RMIT University, researchers blended collected cigarette filters into brick clay at 0.5%, 1%, 1.5%, and 2% by mass, then compacted, dried, and fired the samples at 1,050 degrees Celsius for three hours. They compared results against control bricks with no filter content, reporting averages from three samples per mix.
The key tradeoff was strength. Control bricks reached 48.6 megapascals (MPa) in compressive strength, while the 1% mix averaged 30.8 MPa. The researchers noted that cited minimum recommendations run from 3 to 5 MPa for non-load-bearing units and 5 to 10 MPa for load-bearing units, so the 1% brick cleared that bar even with the strength drop.
Other properties shifted in ways mason contractors will recognize on the job. Water absorption rose from 9% to 12.1%. Efflorescence was rated “slight” at 1% and “moderate” at 2%, pointing to a real-world finish risk if moisture management and detailing are not handled well.
The research also tied the mix to energy and thermal changes. Because cellulose acetate has a high calorific value, the team calculated a 10.2% firing energy reduction at the 1% mix. The bricks came out lighter, with density dropping from 2,114 to 1,983 kilograms per cubic meter, and estimated thermal conductivity falling 17% due to added voids.
For contractors, the practical next step is simple: treat any “waste-in-brick” unit like any other new unit type. Ask for compressive strength, absorption, and efflorescence test data, and confirm where the product fits in the wall assembly. The researchers also flagged that large-scale adoption hinges less on brickmaking and more on collecting and processing filters safely and consistently.
Read the full, original article from Science Blog here.