Concrete Diagnostics

On Site Carbonation Testing, Core Sampling and Depth of Carbonation Determination

In today's business environment, preventative maintenance of ageing structures is becoming far more preferable to the construction of new structures once original design lives have been exceeded. In response to a strong market demand, DPA has developed an experienced professional team dedicated to concrete diagnostics.

Since the early 1990's DPA has been a leader in the field of concrete diagnostics. The use of specialised imported diagnostic equipment with data logging capabilities allows large volumes of data to be collected on site in a relatively short time frame. This data is then processed through advanced computer software and superimposed to produce an accurate statistical corrosion model of the structure or element being analysed, often presented in the form of three-dimensional spatial plots. This modelling allows for the accurate prediction of future durability, serviceability and the remnant life of the structure.

In addition, concrete samples, usually in the form of cores, are extracted from representative areas of the structure. These cores provide information pertaining to the physical properties of the concrete matrix, for example, compaction, aggregate distribution and porosity. Samples are then usually extracted from these cores and analysed in DPA's laboratory. The results obtained from this testing allow for the determination of contamination profiles. These profiles provide information regarding the type of contamination, the extent of contamination and the extent of penetration of this contamination into the concrete matrix.

All resulting information is combined to provide a comprehensive corrosion model of the structure. Should it be found that remedial action is necessary, various remedial options can then be formalised for the client's consideration. These remedial options will then be optimised, based on the developed corrosion model, the client's requirements and economic considerations.

Our quantity surveying department assists in the vital task of the compilation of accurate budget estimates for the various remedial options which, together with DPA's technical recommendations, allow the client to make an informed decision regarding the refurbishment of the structure.

Once a decision has been reached as to the remedial option best suited to the client, DPA, as multi disciplinary consultants, offer services ranging from (but not limited to) project management to site construction monitoring and full time quality auditing.

Our diagnostic services include:

Full Visual Surveys: Visual surveys conducted by experienced staff are an integral component of an investigation and assist in identifying potential problems that form the focus of diagnostic and analytical procedures.

Electro-Potential Mapping (EPM): The EPM technique is used to identify areas where the highest potential for reinforcement corrosion exists.

Cover Measurement: Electromagnetic determination of the location of the rebar in relation to the surface of the concrete is carried out over pre-defined areas.

Carbonation/sulphation testing: Carbonation/Sulphation testing involves the determination of the depth of a high risk reduction in alkalinity of the cover concrete due to the effects of exposure to acidic gases.

Non-destructive measurement: On site, non-destructive compressive and tensile strength measurement.

Destructive measurement: Destructive compressive strength measurement on concrete samples.

Concrete resistivity measurement: The electrical resistivity of cover concrete is determined and this data is used when considering the potential for rebar corrosion.

Stray current testing: Stray current testing is employed when corrosion may be the result of the presence of stray currents. This aspect can often be mistakenly overlooked in the planning and implementation of diagnostic investigations.

Concrete sampling: Sampling provides an indication of the physical properties of the concrete such as compaction, aggregate size and distribution. Samples are usually extracted from cores and are used in the testing for contaminants such as chlorides and sulphates in the cover concrete.

Analytical laboratory testing: Laboratory testing is carried out on crushed core samples to determine levels of contamination within cover concrete at various depths. Typical contaminants analysed include chlorides and sulphates, both of which typically contribute to severe rebar corrosion in industrial plants.

Durability index testing: DPA has the ability to carry out DI testing on old and new structures with its specially developed test apparatus to effectively assess durability concerns. DI testing includes Oxygen Permeability, Sorptivity and Chloride Conductivity testing.