Leaching of concrete : the leaching process : extrapolation of deterioration : effect on the structural stability

Författare

Göran Fagerlund

Summary, in English

The leaching process when water attacks concrete, and the effect of leaching on the strength and durability of a concrete structure, is analysed theoretically. Technique for prediction of the future leaching

and structural stability is outlined. The analysis is to a certain extent supported by data from literature. The leaching process is divided in five different types: 1: Pure surface leaching 2: Surface leaching involving erosion

3: Homogeneous leaching over the entire structure

4: Semi-homogeneous leaching over the entire structure

5: Leaching in defects within the structure

For each type, the physical leaching process is outlined. Consideration is taken to the increase in

permeability caused by leaching making it theoretically possible to predict the future leaching from an

analysis of the water flow and degree of leaching at the time of inspection of the structure.

The effect of leaching on strength and E-modulus of the concrete is analysed showing that the effect can

be substantial.

A short discussion is made on the effect of leaching on the structural stability and on the changes in

structural stability in the future. Important mechanical factors discussed are changes in compressive

strength, tensile strength and bond strength between reinforcement and concrete. The increased risk of

reinforcement corrosion and frost damage in leached concrete is discussed and found to be big. The

effect of changes in the internal uplift pressure in dams due to changed flow paths inside the dam and the

effect of these changes on the dam stability are mentioned.

Finally, in an APPENDIX, a simple method is outlined for how to assess the concrete strength from

information of the physical composition of the cement paste. By this theory it is also possible to assess

the effect of leaching on the concrete strength.

Avdelning/ar