Effect of water absorption of coarse aggregate on permeability, durability, and microstructure of concrete

Coarse aggregate water absorption significantly affects the durability of hydraulic concrete. We investigated concrete mixes incorporating aggregates with low (0.7%), medium (3.8%), and high (7.85%) water absorption, assessing mechanical properties, permeability, and interfacial transition zone (ITZ) microstructure via scanning electron microscopy. Increased water absorption led to reduced compressive and splitting tensile strength, decreased impermeability and frost resistance, and higher chloride ion permeability. Microstructural analysis demonstrated that high-absorption aggregates caused thickening and increased porosity of the ITZ, particularly in the region extending up to 160 μm from the aggregate surface. A strong linear correlation (R 2 > 0.9) between water absorption and ITZ porosity was observed, linking microstructural changes to macroscopic performance degradation. These findings highlight that limiting aggregate water absorption is an effective strategy for enhancing concrete durability in hydraulic engineering.