PSI - Issue 23

Małgorzata Lenart et al. / Procedia Structural Integrity 23 (2019) 113 – 118 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

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Fig. 4. Shrinkage measurement results in Graff-Kaufmann method for mortars: (a) with 1 day granulate, (b) with 14 day granulate.

Analyzing the results of the Graff-Kaufmann method, it can be noticed that the shrinkage of mortars made with 1 day granulate is higher than that with the 14 day granulate. The difference in the shrinkage is about 0.3 mm/m for mortars with 50% granulate content determined after 28 days of beams hardening which is over 30%. This can be explained by the fact that the 1-day granulate still contains reacting cement. Therefore, the total shrinkage consists of the fresh cement matrix shrinkage as well as the probably ongoing shrinkage of granulate. The shrinkage of mortars with 10% granules (both 1 and 14 days) has little effect on the total shrinkage measured. The shrinkage is about 5% higher for mortars with granulate compared to the control mortar. Figure 5 presents the results of shrinkage measurements carried out in automatic measuring gutters. The shrinkage of mortars with 1-day granulate is greater than for mortars with 14-day granulate which is similarly to the Graff-Kaufmann method. A3 mortar (50% 1 day granulate) showed shrinkage of 1.16 mm/m whereas B3 mortar (50% 14 days granulate) shrinkage of 0.96 mm/m after 40 days of measurement. For comparison, the shrinkage of the control mortar was 0.72 mm/m. These values indicate that the shrinkage of A3 mortar is greater by about 20% than that of B3 mortar. While, the shrinkage for A1 mortar recorded was 0.81 mm/m and for B1 mortar was 0.79 mm/m after 40 days of measurements.

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Fig. 5. The shrinkage results of mortars with 1 day (a) and 14 days (b) granulate determine in the automatic gutter method.

Analyzing the obtained curves, it can be noticed that mortars with 10% and 25% content of 1 day granules (A1 and A2) and control mortar (C) have similar values of shrinkage in the initial period of the test. The differences are visible after about 10 days of measurements. Besides, it can be noticed that the curves of mortars with 14-days granules become more flattened comparing the shape of the shrinkage curves of mortars with 1 and 14 day granules. This means greater stabilization of shrinkage deformations of mortars made with 14 days granules. Analyzing the curves, it is also noticed that mortars with 50% granules (A3 and B3) in the first days of measurements showed a rapid increase in the shrinkage (especially B3 mortar with 14 day granulate). This behavior can probably be explained by the absorption of water by the granules which was reflected in the reduction of the samples dimensions.