Assessment of changes in physical characteristics due to leaching of hydration products from concrete

It is well known that changes in concrete properties such as the increase in porosity of the surface layer and reduction in strength occur because of material transfer due to dissolution and diffusion of hydration products when concrete comes into contact with water. The present study was an experimental investigation of test methods that can detect damage in cement composites, by immersion in highly acidic medium and measuring hot water permeability, capillary, water absorption and compressive strength. The applicability of immersion tests of cement paste were investigated and a model of change for physical properties such as porosity and strength due to leaching were constructed. The results indicated that the porosity could be calculated from the solid-phase calcium concentration, and the changes in the compressive strength, flexural strength, permeability coefficient and diffusion coefficient could be predicted for the degradation phenomenon caused by leaching. It was concluded that the porosity of paste after degradation caused by leaching can be predicted by the Powers' model, the model in which the increase in porosity through leaching is added.