*2.3. Methods*

Determination of the effect of hydroxyethyl methyl cellulose on the setting processes of cement and cement-lime composites was carried out using three methods, which included:


Using the first method, mortar samples were tested, whereas, using the second method, paste samples were tested. In each case, the experiments were carried out for the first 48 h of material maturation. Additionally, using X-ray diffraction analysis, measurements after 40 days of maturation were made to verify whether there are differences in the leaven hydration products compared to the results obtained after two days.

The setting process was determined using the ultrasonic wave velocity method by an IP-8 Ultrasonic Measuring System (UltraTest GmbH, Achim, Germany). The essence of the study consisted in passing the ultrasonic wave through the material from one end to the other and recording its velocity over time. Ultrasonic heads and a temperature sensor were mounted on both sides for all forms. Each time, a sample of fresh mortar was taken (a cylindrical sample with a height of 5 cm and a diameter of 5 cm), which was placed for the entire duration of the test in the sampler (Figure 1). The upper surface of the tested material was protected with a glass plate to limit its water loss through drying. The change in the velocity of the ultrasonic wave and the temperature inside the samples were recorded every 60 s for a period of 48 h of measurements and saved automatically in the computer's memory.

**Figure 1.** Mortar sample during ultrasonic testing.

The BT2.15CS low-temperature differential scanning microcalorimeter by SETARAM (SETARAM, Plan-les-Ouates, Geneva, Switzerland) was used for micro-calorimetric measurements. Binder samples (with admixture or without it) were mixed with distilled water and put into small PE zip-bags and, immediately after mixing, placed in the calorimeter. Calorimetric curves were recorded with an electronic measuring unit, connected to a personal computer.

XRD images were obtained in an X-ray diffractometer Empyrean (PANalytical, Almelo, Netherlands), equipped with a copper lamp. FT scanning was carried out at a 2θ range of 5–65◦ and the step length was 0.0167◦. The PANalytical XRD analysis software HighScore 4.6 (PANalytical, Almelo, Netherlands) with the International Center for Difration Data (ICDD) database PDF-2 was used for phase identification. X-ray diffractometric studies were carried out on powdered samples of pastes after the time of 2 and 40 days of setting.
