PSI - Issue 74

Małgorzata Lenart et al. / Procedia Structural Integrity 74 (2025) 44 – 49 Małgorzata Lenart / Structural Integrity Procedia 00 (2025) 000–000

47

4

Carboxylated stearin-butadiene latex in the form of a polymer-water emulsion was used as a polymer additive. The additive was in the form of a white liquid with a density of about 1.03 kg/dm 3 . The additive was added to the mixing water using a simple substitution i.e. replacing the appropriate amount of water by the polymer emulsion. The additive was dosed at two levels using water to polymer emulsion mixing ratios of 1:3 and 1:1. Three types of mortars were made during the study: M1 – a reference one, M2 – a mortar made with a mixing liquid containing 30% of polymer emulsion and M3 – a mortar containing 50% of polymer emulsion in the mixing liquid. All mortars had a constant mixing liquid to cement ratio of 0.5 and their composition was a modification of the standard mortar in accordance with EN 196-1. Immediately after mixing the ingredients, the particular mortars were placed in gutters to measure shrinkage. The volumetric changes of the mortars placed in the gutters were recorded and saved automatically for a period of 90 days. In order to determine the effect of care on the size of measured volumetric changes, each of the tested mortars was placed in three different measuring gutters which were secured in different ways. The first was left uncovered (no additional protection against drying), the second was covered with a care preparation and the third was protected with a foil. The ambient temperature and humidity were monitored during the study, the temperature was practically constant at 20÷21 o C and the relative humidity of the environment fluctuated between 50÷60% throughout the study period. Fig. 1 shows a view of the test stand.

Fig. 1. View of the test site.

5.2. Results and analysis of the obtained research results Analyzing the graphs presented in Fig . 2, it can be seen that an increase in dimensions was observed in each of the tested mortars during the initial period of the study. The largest of these changes were observed for mortars cured under the foil and they were: +0.12 mm/m for the reference mortar, +0.18 mm/m for the mortar with 50% polymer suspension content and +0.30 mm/m for the mortar with 30% polymer suspension content. After 90 days of testing, it can be seen that the results obtained grouped into three areas. The first one (the lowest graphs on the 90th day of the test in Fig. 2) includes the shrinkage course for the reference mortars without care (- 0.89 mm/m) and the reference mortar coated with the care preparation (-0.88 mm/m). As can be seen, the influence of care with a care preparation is not as significant as the influence of care under a foil. Nevertheless, its influence is noticeable and significant especially in the first period after laying fresh mortar in the gutters. The second area of results (the middle graphs at the 90th day of the test shown in Fig. 2) included all the other samples modified with polymer and cured with the preparation or not protected against evaporation. Their shrinkage ranged from -0.57 mm/m for the mortar modified with 50% polymer suspension content and cured with the curing preparation to -0.62 mm/m for the mortar with 30% polymer suspension content and not subjected to any curing. The reference mortar cured under foil was also included in this area. Analysing the course of volumetric changes for this case, it is worth noting that after forming, this mortar did not show negative changes (shrinkage) for a long period of time, i.e. for 15 days, i.e. protection against water evaporation with foil met expectations. Nevertheless, the course of the graph for this sample has a rather sharp decrease, which allows us to estimate that in the long term (beyond the duration of the test) the shrinkage for this case will be significantly higher than for the polymer-modified samples.