**1. Introduction**

In 2021, worldwide emissions from the cement industry reached almost 2.9 billion tons of CO2, which is more than 7% of the total global CO2 emissions [1]. For the production of 1 Mg of Portland cement clinker, about 1.7 Mg of natural resources are used, mainly carbonate raw materials, such as limestone and marl [2]. About 60% of the total CO2 emissions released by a cement plant come from the calcination of carbonates in the raw material bulk. The remaining 40% of all CO2 emissions in a cement plant are derived from the burning of fossil fuels. Therefore, the world cement industry has to meet the constantly growing environmental requirements, which mainly concern the reduction in CO2 emissions [3].

One way to reduce CO2 emissions is the production of multicomponent cements CEM II-CEM V according to the PN-EN 197-1 standard [4] using significant amounts of main ingredients other than Portland clinker, mainly granulated blast furnace slag or siliceous fly ashes. Cements containing significant amounts of these components are characterized by low hydration heat, higher compressive strength, longer curing periods, and higher resistance to chemical aggression [5–10].

The PN-EN 197-5 standard [11] defines the framework conditions for a significant reduction in the clinker content of cements. It extends the range of Portland multicomponent cements (the possibility of using several main components in the composition of cement) by a group of Portland multicomponent cements CEM II/C-M with a minimum content of Portland clinker of 50% and a newly created group of multicomponent cements CEM VI, in which the share of non-clinker components can reach 65% at a maximum.

This paper presents the results of research into the properties of the CEM II/C-M cements with a mixture of granulated blast furnace slag and siliceous fly ashes at 20 and 15% or 30 and 15%, respectively, and the CEM VI cement containing 40% granulated

**Citation:** Tkaczewska, E.; Malata, G. Properties of the Cement, Slag and Fly Ash Mixture Composition Corresponding to CEM II/C-M and CEM VI. *Mater. Proc.* **2023**, *13*, 11. https://doi.org/10.3390/ materproc2023013011

Academic Editors: Katarzyna Mróz, Tomasz Tracz, Tomasz Zdeb and Izabela Hager

Published: 14 February 2023

**Copyright:** © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/).

blast furnace slag and 15% siliceous fly ashes. Cement tests were performed to analyze the compressive strength, linear changes, phase composition, and microstructure after a specified period of time.
