The cyclic wetting and drying characteristics of treated and untreated concrete substrates were studied. During the absorption cycle, specimens were exposed to both water and sodium chloride solution. The testing programme used relatively simple, non-destructive methods to quantify the efficacy of the treated surf ace; in particular, cumulative volume gain and surface resistivity measurements. Destructive testing was used to investigate the depth of impregnation of the surface treatment and the penetration of chlorides into the substrate. Copyright © 1996 Elsevier Science Ltd.