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, clays 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 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.
Anticipated economic resources of clay raw material deposits for the cement industry decreased in 2015 by 0.01 million tonnes (in comparison with 2014) and were reported to be equal 276.53 million tonnes (table 1).
There was a not new deposit documented in 2015 but Borki - hałda deposit was crossed out from “The balance…”. The deposit was formed by the mound of wastes of iron ore mine Łęczyca I. In the 1994-1996 period the ore was used for cement production in Działoszyn. According to “The balance…” the resources of raw material declined from 300 thousand tonnes calculated in mine management plan to only about 8 thousand tonnes.
Deposits of clay raw materials for cement production (together with building ceramics raw materials) are presented on the map.
Exploitation has been carrying out only in Lubelskie Voivodeship area for Chełm cement factory. In 2015 the output was not recorded from deposits described in this chapter (table 2). However, in 2012 it was replaced (in Chełm factory) by the loess raw material which was exploited from Buśno deposit (Lubelskie Voivodeship). Before 2012, this raw material had been used for ceramic brick production (according to the geological documentation of the deposit). Therefore, Buśno deposit is covered in the chapter “Building ceramics raw material”. In 2015 the output amounted to 100 thousand tonnes (50 thousand m3).
The Kujawy cement plant also uses sands from Barcin-Piechcin-Pakość deposit (Kujawsko-Pomorskie Voivodeship), which is placed in the chapter "Quartz sands for production of cellular concrete and lime-sand brick" (classification according to the geological documentation). The output amounted to 31 thousand tonnes (18 thousand m3) in 2015.
Prepared by: Wojciech Szczygielski