*3.4. Application Properties of Mortars*

Table 9 shows the scoring of the quality of plastering mortars, the results of the assessment of the performance of the tested materials, and the methods of application of the plasters. The C-0.52MV, C-1.82HV, C50L-1.82HV, and C25L-1.82MV mortars received the highest score, followed by the C-1.82LV, C50L-0.52MV, and C50L-1.82LV mortars. The remaining plasters were of very poor quality. According to a specialist plasterer, mortars with the highest scores were those can be used as commercial products without any additional changes in their composition, whereby some of the tested mortars could be applied manually and others could be applied by machine. Mortar C50L-1.82HV was deemed a universal material, which could be applied manually or by machine. The methods of application were determined on the basis of the rheological properties. Mortars fit for a manual method of application had low plastic viscosity, whereas those fit for machine application had high viscosity. High plastic viscosity facilitates the application of the mortar, whereby the material clings to the float and does not run off the wall. Hydrated

lime also improved the flexibility of the plasters and the ease of processing. Hydrated lime and cellulose ether were essential in the case of machine-applied plasters due to the method specificity. In addition, hydrated lime facilitated plaster processing, and cellulose ether enabled longer water retention in the mortar.


**Table 9.** Application properties of mortars.

Figure 10 presents images of the walls during application (first-day assessment of application properties) and processing (second-day assessment).

**Figure 10.** Images of walls (**a**) during application, and (**b**) during processing.

Due to the fact that the point assessment did not fully reflect the properties of each mortar, the results on the point scale were supplemented with a descriptive assessment. Table 10 shows a description of the application properties of the selected mortars. Materials were also visually assessed after 28 days of setting and hardening processes. Mortars containing hydrated lime in their composition had a much lighter color, which is advantageous from a technological and economic point of view. This allows a reduction in paint consumption for coating.


**Table 10.** Descriptive assessment of the workability of selected mortars.

Figure 11 presents the response surface of the influence of X1, X2, and X3 factors on the subjective rating by a specialist (Y3). The fit factor of the *R*<sup>2</sup> model in this case was 0.749. Statistically, as can be seen from Equations (8)–(10), the most important factor was the amount of cellulose ether (X2 factor). Adding as little as 1.82% cellulose ether led to favorable application properties (Figure 11).

$$\mathbf{Y}\_3 = 0.685 - 0.11\mathbf{X}\_1 - 0.0018\mathbf{X}\_1^2 + 13.932\mathbf{X}\_2 - 4.29\mathbf{X}\_2^2,\tag{8}$$

$$\mathbf{Y}\_3 = 0.685 - 0.11\mathbf{X}\_1 - 0.0018\mathbf{X}\_1^2 + 0.0003\mathbf{X}\_3.\tag{9}$$

$$\mathbf{Y}\_3 = 0.685 + 13.932\mathbf{X}\_2 - 4.29\mathbf{X}\_2^2 + 0.0003\mathbf{X}\_3. \tag{10}$$

**Figure 11.** Utility function for subjective rating of mortars by a specialist: (**a**) correlation between cellulose ether amount and hydrated lime amount; (**b**) correlation between cellulose ether viscosity and hydrated lime amount; (**c**) correlation between cellulose ether viscosity and cellulose ether amount.
