Chloride testing is mainly carried out on reinforced concrete using test methods given in BS 1881. Chloride can be present in the concrete either as added calcium chloride used to accelerate the setting time of the concrete or as a contaminant of the aggregate. Post-construction contamination can come from chloride salts, used for de-icing, that have dissolved in water and subsequently permeated the concrete or from a marine environment. Chloride salts, in the presence of moisture, can cause the accelerated corrosion of the reinforcing steel within the concrete, resulting in an expansive rusting reaction of the reinforcement and subsequent spalling of the concrete.
The aim of the chloride testing is to establish the level of chlorides within the concrete structure, either as an overall level or, via the taking of incremental samples, as a profile through the depth of the structure.
Chloride testing can also be used to establish a coefficient of chloride diffusion either on new concrete or on an existing structure. The diffusion coefficient is calculated by carrying out analysis to determine a chloride profile after exposure of one face of a specimen to a chloride solution.
Chloride testing in conjunction with a visual survey and a survey to establish the depth Chloride testing, in conjunction with a visual survey and a survey to establish the depth of carbonation and cover to reinforcement, can give an indication of the condition of the structural concrete within a building and the potential for future performance.
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