Clay raw materials for cement production

Clay raw materials are used to provide alumina and silica to the charge for the cement kiln and thus counterbalance too high content of CaCO₃ in limestones and marls. The optimum content of CaCO₃ in the kiln charge is 75-80%. When CaCO₃ exceeds these values, various mineral additions are added to reduce its content at the advantage of SiO₂, Al₂O₃ and Fe₂O₃.

Clay raw materials are qualified to the law raw materials group. According to the classification used in cement industry: law raw materials contain <42% CaO (<75% CaCO₃), normal raw materials contain 42-45% CaO (75-80% CaCO₃) and high raw materials contain >45% CaO (>80% CaCO₃).

The advancements in development and current exploitation of these raw materials are relatively low. This is due to the two main factors: (1) attempts to achieve the optimum composition of mined major raw material (in this case – limestones and marls) and, in this way, to diminish the problems with its correction, usually made by the operators at the development stage, that is at the stage of works performed to open a mineral deposit for exploitation, and (2) replacement of natural clay raw materials with mineral waste raw materials such as ash from heat and power plants, blast furnace slag and similar ones.

Lithologically the explored deposits of raw materials for the cement industry represent loams, clays, loesses and silts.

In 2016 anticipated economic resources of clay raw materials deposits for the cement industry increased by 0.279 million tonnes (0.1%) in comparison with 2015 and were reported to be equal 276.81 million tonnes (table 1).

In 2016 there were resources of raw materials for production of cement kiln as co-occurring raw material documented – below the bottom of sand deposit Lechówka dz.86 (+0.294 million tonnes of clays and silts).

Table 1. Clay raw materials for cement production - million tonnes

Deposits of clay raw materials for cement production (together with building ceramics raw materials) are presented on the map.

Exploitation of deposits described in this chapter has been carrying out only in Lubelskie Voivodeship area for Chełm cement factory. In 2016 the output was recorded only for Lechówka dz. 102/1, 99 from which 0.006 million tonnes of raw materials were produced.

For cement production in Chełm cement factory there were also used about 0.052 million tonnes (0.026 million m³) of clayey raw material from Buśno deposit (Lubelskie Voivodeship) which is still placed in the chapter “Building ceramics raw material” – according to the way of raw material using described in the geological documentation. Nevertheless, in 2012 the production of building ceramics was abandoned and the raw material started to be used as a component for cement production. In 2016 there were about 52 thousand tonnes (26 thousand m³) produced from this deposit.

The Kujawy cement plant also uses – as so-called “law raw material” – sands from the Barcin-Piechcin-Pakość deposit (Kujawsko-Pomorskie Voivodeship), which is placed in the chapter "Quartz sands for production of cellural concrete and lime-sand brick". The output amounted to 50 thousand tonnes (30 thousand m³) in 2016.

Table 2. List of clay raw materials for cement production deposits - thousand tonnes

Prepared by: Wojciech Szczygielski