Spontaneous electrical effects in masonry affected by capillary water rise: The role of salts

The investigation of the electrical effects accompanying capillary water rise from ground in old masonries is of great practical interest, as such effects might be exploited for both measurement purposes (determination of moisture and soluble salts) and for dehumidification purposes (techniques based on electrokinetic principles).In the present paper, the spontaneous dc voltages arising in a real-scale masonry model subject to a steady-state capillary flux of saline solutions (0.05 M sodium chloride and 0.05 M sodium sulphate in water) were measured. The resulting voltage depends on the amount and distribution of salts, rather than on moisture content in the masonry.

► One-brick-thick masonry model was built with fired clay bricks.
► A steady-state capillary flux of water with chloride and sulphate was attained.
► Moisture, salts and spontaneous potential were measured at different heights.
► The role of salts was highlighted.
► The results are consistent with the electrical double layer theory.