The resistivity of pore water solution - A decisive parameter of rebar corrosion and repair methods

Although the resistivity of mortar and concrete is of major importance for rebar corrosion and repair methods, e.g. cathodic protection, there is a lack of fundamental research. This paper gives an overview of some of the more mechanistic aspects of the ionic conductance of mortar and concrete. It has been shown that not all water in mortar or concrete is conducting. The fractional volume of paste makes it possible to take into account the geometrically reduced cross-section of the conducting path due to the presence of aggregates. The influence of the pore structure of the paste itself and the chemical and physicochemical interactions of the water with the cement paste surface is much stronger than the geometrical effects. The combination of the above mentioned factors leads to an overall formation factor between the resistivity of concrete/mortar and the pore water in the paste of abo ut 900 to 5000. The moisture content is much more important for the resistivity as well as for the corrosion rate than the chloride content. Copyright (C) 1996 Elsevier Science Ltd.