The main difference is in the composition of the stone that has been processed to obtain these metallurgical flux agents.
Quicklime has a CaO content of more than 90% and an MgO content of less than 1%. It is used in electrical furnaces for the production of slag and in the ladle refining process to encourage desulphurisation and prevent the loss of heat by forming an insulating barrier on the slag line.

Calcined dolomite is made of a combination of CaO (a maximum of 60%) and MgO (a maximum of 40%). This product is used in electrical furnaces to provide MgO with the aim of preventing the wear and tear of basic refractories and extending their useful life by creating a basic slag.

No. The reactivity test uses water to calculate the temperature reached, in degrees centigrade, in a certain time. This type of test is very important for applications in the chemical industry or for soil stabilisation. However, there is a certain correlation between the quality of the lime for the iron and steel industry and the reactivity test due to the chemical reactions noted at high temperatures in electrical furnaces. The best limes are those that have a low content of sulphur, silica, CO₂ (loss by calcination) and the right granulometry. These impurities have an influence on the speed with which lime dissolves during the fusion process of the metal or iron mineral. FeO is what most encourages the lime to melt, followed by silicon and aluminium oxides.

The amount of lime depends on the quality and quantity of metal and the acid compounds that this gives off, such as SiO₂ and Al₂O₃. The consumption of lime fluctuates betweens 20 and 50 kg/t of steel produced, which allows a typical basicity index of 3 to be maintained, starting from indices of 1.5 to 1.9.

The essential factor is the generation of iron oxide (FeO) as the main flux agent, in the same way that magnesium oxide (MgO) combined with the temperatures and basicity of slag has an influence on reducing the melting temperatures of lime.

The basicity of the slag is an important factor in reducing phosphorous in the converter. However, increasing the amount of lime would drastically increase the basicity of the slag until reaching a point where, with no flux agent, the slag would become less viscous, preventing it from mixing with the steel (the phase that allows the phosphorous to be eliminated). As the iron oxide content in the slag is very low at this point, the silica acts as the flux agent for the lime.