Over the years, a number of methods have emerged involving calculations to determine the relative corrosivity of water. 

·        The Marble Test (Baylis Curve) looks at the change in alkalinity after a defined addition of calcium carbonate.

·        Caldwell Lawrence diagrams can be used to estimate corrosivity, but require the use of pre-made graphs dependent on specific temperature and solids concentrations.

·        Ryznar’s Stability Index (RSI) primarily uses pH as an indicator of corrosivity given that other factors remain static. The index centers roughly on 7 with values higher indicating potentially corrosive conditions.

·        CCPP (Calcium Carbonate Precipitation Potential) is the most accurate indicator of the group, but also the most time consuming and complicated method involving a number of calculations.

·        The Langelier Index is the most commonly used indicator. Similar to RSI, Langelier uses a system based on 0 where negative values are corrosive and positive values are scaling.

When I design concrete exposed to chemical action (groundwater, exposure class AX1, AX2, AX3), I take into account the type, minimum amount of cement, minimum class of concrete and maximum w/c. Never heard of Ryznar index.

The intrusion of chloride ions, present in salts and seawater, into reinforced concrete can cause steel corrosion if oxygen and moisture are also available to sustain the reaction. The corrosion level of water to reinforced concrete structures depend on the chlorides concentration in water. The attached Table 1 shows the maximum permissible water soluble chloride-ion content for reinforced concrete in various exposure conditions (ACI 318 2002).

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