Current industry standards for evaluating concrete durability in wastewater environments, such as ASTM C267, rely almost exclusively on mass loss as the primary performance indicator. This study demonstrates that mass change alone can be an ambiguous metric that does not fully characterize the structural degradation of advanced cementitious binders. Through a comprehensive physical, chemical, and mechanical evaluation of 27 binary and ternary mixtures (totalling 486 specimens), we identify four limitations of mass-based standards: (1) The Slag Anomaly, where excellent surface mass preservation masks a significant loss of internal structural capacity, indicating potential internal structural softening. (2) The Sewage Anomaly, where specimens in active biogenic environments exhibit mass gain (up to +1.21%) despite continuous chemical attack. (3) Non-Linear Scaling, where 5% “accelerated” acid tests fundamentally alter degradation kinetics compared to realistic 1% environments. (4) The Maturation Conflict, where extended curing (56 days) significantly improves the physical resistance of slow-reacting pozzolans (cyment) while increasing the mass loss of high-performance ternary blends (MK/SF), likely linked to the exhaustion of their chemical buffering capacity. Current standards relying solely on mass loss may not capture internal degradation in slag-based cements that remain geometrically intact. We propose residual flexural strength as a necessary complementary metric.
Affes et al. (Thu,) studied this question.