 A sufficient thickness of concrete cover is thus required in order to slow down the carbonatation process towards the rebar.The minimum concrete cover will depend on the environmental conditions encountered and must be thicker when the concrete is also exposed to moisture and chloride (proximity to the sea, use of de-icing salt for bridges or roads, ...).A high quality concrete made with a low water-to-cement (w/c) ratio will have a lower porosity and will be less permeable to water and to the ingress of corrosive species (dissolved oxygen, chloride, ...).