**2. Materials**

The material used in the research was a domestic clay calcined at 850 ◦C with the loss on ignition equal to 9.20%. The material was classified as a low-quality clay due to the fact that it only contains 26% Al2O3 [2]. The main associated mineral, except for kaolinite and muscovite, found in the raw clay by XRD was quartz, Figure 1. A previously analyzed aggregate from igneous rocks with medium reactivity (aggregate reactivity class R1 according to [13,14]) was selected for the reference aggregate. Ordinary Portland cement (CEM I 42.5R) with a high alkali content (Na2Oeq = 1.12%) was used in this research. A detailed chemical composition of the raw clay and cement determined by XRF is shown in Table 1.

**Figure 1.** Mineral composition of the raw and calcined clay.


