MICHAELIS was a German chemist who played a very important role in the development of concrete. He discovered in 1893 that some metasilicates can become very hard when dry. In the early 20th century, he built instruments to calculate the parameters of reinforced concrete.

This chart allows you to work with three input parameters. One of the inputs is the diameter of round iron used in reinforced concrete. It appears along the curved portion of the instrument.

The selection of the diameter of iron is made by positioning the crosshair cursor on the selected value. One should then read the sought value on the intersections between the reticle and the lines corresponding to other parameters.