Building materials - Concrete

Concrete has been used as a building material since the Mesopotamian ages and became very popular with Greek and Roman builders. It withstands immense pressure and has a high durability. It can be poured into almost any shape and, when reinforced with steel, it can bridge wide distances. Micro-XRF allows for fast measurements of large areas, with high spatial resolution in short times. The individual element distributions can be visualized and extracted quickly. Fundamental parameter-based quantification allows for a quick assessment of the composition of the sample. Smart analysis of mapping allows for semi-quantitative analysis of Cl and K concentration in the matrix. As concrete is a mixture of many complex chemical compounds its durability depends on environmental conditions. It can last thousands of years under suitable conditions, but nowadays we frequently find images of cracked and weathered concrete. Saltwater, for example, leads to chemical reactions that change the volume and lead to stress and strain in the concrete structure.

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The Pantheon in Rome. For two thousands years this structure is the largest unreinforced concrete dome in the world.

The dam at Votna lake (Norway) is exposed to seawater. This 5 cm long drill core taken from the sea side of the dam clearly shows a gradient in Cl concentration. The false color presentation depicts this even more clearly. The line profile, extracted from the area scan, shows that the Cl diffused more than 1 cm into the concrete.

Drawing out a series of objects allows for some (semi-)quantitative analysis: The HyperMap data can be used to tell the aggregates apart from the cement and quantify the cement composition into the depth of the sample. Here, the Cl concentration goes from 1 wt.% to 0 wt.% within the first 10 mm. The K concentration is anticorrelated to the Cl (leaching). The sum of SiO2 and CaCO3 is stable at about 85 wt.%.