Acid Degradation of Recycled-Aggregate Concrete from Sub-Saharan Demolition Waste: Dataset, Kinetics and Aggregate Screening Index

The acid durability of recycled-aggregate concrete (RAC) remains largely undocumented in sub-Saharan Africa, and the small, collinear datasets of such campaigns are rarely released. Three concretes (natural, partially recycled and fully recycled) were cast with quarry aggregates or aggregates from two demolition-waste sources in Yaoundé, Cameroon, characterized to French and European standards. After 90 days of water curing (25.4 to 25.9 MPa), specimens were immersed in nominally 5% sulfuric or hydrochloric acid, and residual compressive strength and mass loss were measured on one specimen per age after 7, 14, 21, 28 and 90 days of immersion. After 90 days in sulfuric acid, the natural concrete retained 64% of its strength and the recycled concretes 31% and 27%; in hydrochloric acid, retention was 44%, 44% and 55%. At nearly equal mass loss, the recycled concretes retained 7.4 MPa in sulfuric acid against 12.6 MPa in hydrochloric acid, consistent with an expansive mechanism but also with the higher acid dose of the sulfuric bath; reaction products were not analysed. Mix-descriptor collinearity is quantified, degradation kinetics are described by monotonic trends and simple empirical laws, and aggregate sources are pre-qualified by an anchored multi-criteria screening index. The dataset is released with the article.