PSI - Issue 64

Irene Palomar et al. / Procedia Structural Integrity 64 (2024) 1435–1443 Irene Palomar et al. / Structural Integrity Procedia 00 (2024) 000 – 000

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3.2. Hardened microstructure and mechanical characterization Microstructural changes of mortars with SAP and PCM were assessed considering density, water absorption coefficient and microporosity measured by mercury intrusion coefficient (Fig. 4). It was observed that SAP did not modify significantly reference density (1844 kg/m 3 ), ranging 1750 to 1940 kg/m 3 , while PCM reduced density, as expected due to the low density of PCM, ranging 1580 to 1660 kg/m 3 . On the other hand, both SAP and PCM slightly reduced water absorption coefficient, from the reference average value of 11.91 %, to 10.78-10.98 % in the case of mortars with SAP and 10.94-11.17 % when PCM was incorporated. However, when microporosity was measured, it was observed that SAP reduced from 17 % to 13-18 %, while PCM remarkably increased microporosity up to 20-27 %. Mechanical performance results of hardened mortars are summarized in Figure 4. SAP slightly increased compressive strength rising from 4 to 3-5 MPa, flexural strength from 1.5 to 1.2-2 MPa and ultrasonic modulus from 12 to 9-14 GPa. The incorporation of microencapsulated PCM acted as microdefects, weakening mortar microstructure and reducing compressive strength to 2 MPa and ultrasonic modulus to 4 GPa.

Fig. 4. Hardened microstructure and mechanical experimental results of bio-based self-modulating mortars with SAP and PCM..

3.3. Long Term Carbonation Carbonation of cement-lime mortars was also affected by the incorporation of Sap and PCM, as presented in Figure 5. SAP increased carbonated area, reaching up to 70 % at 28 days. The incorporation of PCM reduced maximum carbonated area (55-65 %). In the long term, reference and SAP mortars showed similar carbonated area values, while PCM mortars were fully carbonated at 180 days. This fact can be related to the pore microstructure, as PCM showed larger microporosity but lower water absorption coefficient (Figure 4). In the short term, the presence of water inside the microporosity delayed carbonation, whereas on the long term microporosity facilitated carbonation.

Fig. 5. Long term carbonation experimental results of bio-based self-modulating mortars with SAP and PCM..