The main purpose of the soundness test is to assess the possible risk of late expansion due to hydration of uncombined calcium oxide and/or magnesium oxide. The test uses apparatus known as Le Chatlier apparatus, which magnifies any expansion during heating to a value that can be measured. General Description And Specification The apparatus consist of a small split cylinder of spring brass or other non-corrodible metal of 0.5 mm thickness forming a mould 30 mm internal diameter and 30 mm high. On either side of the split, two indicators are brazed suitably with pointed ends made of 2 mm diameter brass wire in such a way that the distance of these ends to the centre of the cylinder is 165 mm. The split cylinder will be kept between two glass plates.