A comparative study assessing the validity of water absorption methods when applied to secondary fine aggregates

The valorization of secondary sands is crucial for fostering a circular economy within the construction sector. One significant obstacle in this endeavor stems from the high water absorption (WA) rates commonly reported for secondary sands. This high WA leads to increased water and cement demand in cementitious mixes and elevates costs. The only widely standardized method to measure the WA of fine aggregates is the cone method, which has proven ill-suited for fine aggregates with angular particles or a high content of fines. This study undertakes a comparative evaluation of the cone method and seven alternative methods: immersion, centrifugation, paper sheet, colorimetric, volumetric flask, continuous drying, and electrical conductivity. Tests were performed on natural river sand and three types of secondary sand. Findings reveal that the continuous drying and electrical conductivity methods demonstrates the greatest potential in terms of reliability and applicability. Also the volumetric flask and centrifugation methods show some potential, provided that critical refinements are made to the corresponding test protocols. •Flaws of water absorption methods for secondary sands are exposed.•Caution should be taken in the interpretation of water absorption data from the literature.•There is an urgent need for improved water absorption assessment of secondary sands.•Electrical conductivity and continuous drying methods are recommended.