The following outlines the general procedure for the wet-chemical analysis of concrete, mortar and plaster samples by atomic absorption spectroscopy (AAS). The estimation of the cement content of a concrete is usually based on the determination of the amount of soluble calcium oxides or soluble silica. Unless the composition of the cement is provided, the average compositions for these oxides listed in ASTM C1084 are used. A few factors must be considered:

• Aggregates containing calcareous compounds, such as limestone or dolomite, bias the calcium procedure to erroneously high values.
• Concretes containing Fly Ash add-mixtures similarly bias the soluble silica procedure.
• The acid extraction can be done with coarsely crushed or pulverized sample. The former is slower but more accurate, while the latter is quicker but less accurate because aggregate may enter the solution.
• Concretes exposed to seawater or very soft natural water may have lost some of the lime from the cement by leaching; therefore, the lime (calcium) content is not a measure of the original cement content.
• To reduce the reactivity of the HCl used in the acid extraction, it is diluted and chilled to below 5deg C; this acts to reduce the unwanted solution of aggregates.
• The final treatment involves an alkali hydroxide to ensure solution of any gelatinous silica produced, which is insoluble in acid treatment.

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