Salts in Reused Fired Clay Bricks: Content and Related Challenges

The present work sheds light on the missing information of active soluble salts in CE-marked reused fired clay bricks and examines the content and related challenges. The salt content in twenty and nineteen CE-marked, reused fired clay bricks from the two largest suppliers in Denmark was examined, and the existing limited results from previous examinations of CE-marked fired clay bricks and historical bricks were included to provide a more general picture. A systematic approach to measuring ion content at realistic, relevant locations in bricks was used, yielding results for total ionic content (electrical conductivity and summed single-ion contents) and for single ions (both anions and cations). To discuss the severity of the ionic content, the measured ionic contents were compared with various approaches (ÖNORM B 3355-1, WTA Merkblatt 4-5-99/D, experience-based DK, experience-based B). Dependent on the assessment approach, 16–45% of the CE-marked reused fired clay bricks had ionic content that was too high, ranging from just above the limit to significantly higher. While a discussion of appropriate threshold values for CE-marked reused fired clay bricks is needed, some of the bricks contained levels above all threshold values, indicating a problematic high salt content. This paper is a contribution to the SWBSS2026 Conference.