Pavla Ryparová , Michaela Kostelecká, Jan Tywoniak

1. Department of Building Structures, Faculty of Civil Engineering , Czech Technical University in Prague, pavla.ryparova@fsc.cvut.cz Pavla Ryparová, Michaela Kostelecká, Jan Tywoniak Biodegradation of mineral and silicone plasters and its comparison

2. Introduction • Aging of construction complex process • Degradation – physical, chemical and biological • Biodegradation • First period – aesthetic problem – coloring, pigments • Second period - extracellular polymeric substance – cycle shrinkage and swelling – change of pore distribution - water and vapor transport • Third period – accumulation of pollutant - enriched by organic materials and nutrients - lead to microbial colonization • Microbial colonization – mold (microscopic fungi) • Requirement – water content, pH, T, nutrient • First visible growth - in one or two years • pH - 6 -8; RH – up to 60%; nutrient - C, N 1340

3. Materials • Mixtures of plaster – common and commercial • Silicone and mineral • Silicone Si • Mineral scraped brick-plaster Br • Lime-cement plaster LC • Sample – cylinder – 3 cm Ø, 2 cm ↕ • From off after 48 hour, storage 28 days • Elements analysis • Measurement pH • Degradation Br after 28 days in 100% humidity 1340

4. Methods - degradation • Fresh samples – unsuitable pH, any nutrient • Freeze-thaw (labelled F) • ČSN 72 2452 -10 cycles • Burial in the soil (labelled S) • Standard garden soil, wetted, 25±3°C 28 days • Carbonation (labelled C) • Concentration CO2 around 20% and RH 50% for 5 days • Soak in water (labelled W) • Distilled water for 10 days • Combination 1340

5. Label of samples 1340

6. Methods - microbiology • Based on norm ČSN ISO 846 • Complete nutrient medium (Czapek Dox) and in high humidity • Cladosporiumcladosporioides, Alternariaalternata, Penicilliumbrevicompactum, and Penicilliumpurpurogenum in ratio 1:0.5:1:1. • Concentration 4.2×106 to 5.7×106 CFU/ ml as a spore in saline solution • Inoculation and methodology • 100 µl fungal spores pre-incubated in 25 °C for 3 days (Czapek dox) • Placed sample (Czapek dox and desiccator) and inoculated by spraying • Incubation in 25 °C for 28 days • Evaluation every week 1340

7. Results - pH • Decreasing of pH in 10 days by degradation type 1340

8. Results - pH • Time depending change pH 1340

9. Results – 100% RH • The scale at table Samples after 4 week in 100 % humidity, the label samples are in row: Br-C; BR-S, BR-CW (Mineral scraped brick-plaster ) 1340

10. Results – 100% RH 1340

11. Result – Nutrient agar • Evaluation of sample side and top • Non-degraded samples had coverage of side up to 30% • lime cement > silicone > mineral scraped brick-plaster (the last is worst) 1340

12. Result – Nutrient agar - degraded samples • Degraded samples had significant difference 1340

13. The worst result carbonated and soaking in water 1340

14. Results - nutrient agar • The best results - Silicone 1340

15. attack Results - comparison for carbonization • The main pressure for microbiological attack • Carbonization, water soak, burial 1340

16. Conclusion • Occurring of mold not depend on pH • The main factor – water content and nutrient • Nutrient – base on bacterial debris • The resistance Silicone, Mineral scraped brick-plaster and Lime cement Br CW, LC CS Si-CW, Si-W 1340

17. Clay plaster Clay plaster dried in 65% RH, after 28 days in 100% RH Clay plaster dried below 25% RH, after 14 days in 84% RH 1340

18. Pavla Ryparová pavla.ryparova@fsv.cvut.cz 1340