Chemical Analysis of Hardened Concrete

Chemical analysis of hardened concrete can provide a wealth of information about the mix constituents and possible causes of deterioration. Standard methods can be used to find the cement content and original water/cement ratio, but many other properties can also be established .

• Cement Content and Aggregate Cement Ratio - This analysis can be carried out using the method given in BS1881:1988 and can include chloride content, sulphate content and alkali metals content on either a general sample or a matrix rich sample (a hand separated sample rich in cement).This method can be used to analyse both lump and dust samples
• Cement Content and Pulverised fuel ash/fly ash (pfa) content - This analysis involves an acid digestion followed by a hot alkaline digestion to remove the cement and a subsequent grading of the insoluble material to determine the pfa content. The cement content is then determined using the standard method
• Cement Content and Slag content - This analysis involves the determination of the slag content by means of its sulphide content and determining the cement content.
• Water/Cement Ratio - This is determined using a method based on BS1881:1988 and involves measuring the capillary porosity and cement content of the sample.
  If reference materials are available they can be analysed along with the concrete sample to give a more accurate result of the determinations. If reference materials are not available the assumptions of their values can be made.
• Aggregate Grading - This method involves the digestion of the cement by an acid and hot alkaline process and the subsequent drying and sieving of the aggregate.
• Determination of the presence of High-Alumina Cement (HAC) - This method involves a hot extraction followed by the determination of alumina to check for high-alumina cement (HAC). If this is found to be present further analysis using a differential thermal analysis (DTA) technique can be used to determine the degree of conversion of the high-alumina cement. This method can be used to analyse both dust and lump samples.

Tests are carried out to BS, EN and ASTM standards. The laboratory is also equipped to undertake a wide range of non standard analysis of concrete samples.