Clay raw materials for cement production
Clay raw materials are used for the production of the cement clinker as a supplement adjusting of a kiln input. The basic compound of a kiln input are carbonate rocks: limestones and marls. The optimum content of CaCO3 in the raw material for the clinker baking is 75-80%. In the case when the composition of the basic raw material differs from these values, various mineral additions are used. Clay raw materials reduce the CaCO3 content and increase the content of SiO2, Al2O3 and Fe2O3.
According to the classification used in a cement industry, clay raw materials are qualified to the law raw materials group. The law raw materials contain <42% CaO (<75% CaCO3), the normal raw materials contain 42-45% CaO (75-80% CaCO3) and the high raw materials contain >45% CaO (>80% CaCO3).
The advancements in a development and current exploitation of the clay raw materials for cement production are relatively low. Already at the stage of the documentation and exploitation of the raw materials for the cement industry deposits, the aim is to optimize the raw material composition. It reduces the necessity of the composition correction. There are also the waste raw materials widely used: the dusts, the ashes, the blust furnace slags, the clayey mining wastes and others.
Lithologically the explored deposits of raw materials for the cement industry represent mainly clays and clayslates, but also loams, loesses and silts.
The anticipated economic resources of clay raw materials deposits for the cement production as of the end of 2019 amount to 279.458 million tonnes. They decreased by 0.183 million tonnes (0.1%) in comparison with 2018 (Table 1).
In 2019, there was one new deposit documented – Lechówka II. The resources of loams and silts (0.139 million tonnes) for the cement production are the accompanying raw material, whereas the main raw material are sands (natural aggregates). For the loessial loams deposit Buśno, there was a new documentation with recalculated resources approved – it updated the resources and the deposit boarders (the resources drop by 0.150 million tonnes).
Deposits of clay raw materials for the cement production (together with building ceramics raw materials) are presented on the map.
In the reporting year, there were 2 deposits in Lubelskie Voivodeship exploited: Buśno and Lechówka. The raw material was used by the Chełm cement plant. The output amounted to 0.165 million tonnes and increased by 30.9% in comparison with the previous year. In the Kujawy cement plant, as the law raw material, there have been quartz sands from Barcin-Piechcin-Pakość deposit (Kujawsko-Pomorskie Voivodeship) used for many years. Such sands are recorded in the chapter Quartz sands for production of cellular concrete and lime-sand brick but in 2019 the deposit was not exploited.
The clayey rocks, of the potential to be used for the cement production, occur commonly in Poland and the relatively low quality requirements are not the barrier to the prospecting process. The existing resources base exceeds the current domestic demand. Moreover, for the cement production, there can also be used the clayey raw materials documented for other purposes e.g.: for the building ceramics production, which are not used in line with the intended use*.
The figure below shows changes in resources and output of clay raw materials for cement production in Poland in the years 1989-2019.
Prepared by: Wojciech Szczygielski
* Szczygielski W., Walentek I., 2020 - Surowce ceramiki budowlanej (building ceramics raw materials), surowce do produkcji kruszyw ceramicznych i cementu (mineral raw materials for production of clay aggregates and cement clinker). In: Bilans perspektywicznych zasobów kopalin Polski wg stanu na 31.12.2018 r. (eds. Szamałek K., Szuflicki M., Mizerski W.): 239-257. PIG-PIB, Warszawa.