A Study on Sensitivity of Soil-Based Building Mixtures to Biodeterioration by Fungi: Towards Sustainable Earth Structures
Since earthen building materials are one of the green solutions for contemporary constructions, and fungal growth can lead to health risks for occupants, questions are raised about the optimized soil mixture to be used in hot–arid regions that reduces fungal development. This study investigates susceptibility to fungal growth on the surface of earth constructions. Additionally, it aims to explore the impact of adding cement, limestone, and a fast acrylic-based bond to a mixture for moisture resistance. Laboratory tests were conducted on mixtures under conditions found in inhabited buildings in hot–arid regions, where fungal growth is expected. The study’s findings will highlight the optimized mixture of a stabilized earth material that prevents fungal growth and maintains acceptable indoor air quality. The selected mixture was used to construct a prototype rammed earth building in the study area to examine the efficiency of such material in preventing mold growth.
2. Materials and Methods
The procedure, explained in the subsequent paragraphs, is focused on thoroughly examining the laboratory tests employed to observe fungal growth.
2.1. Preparation of Samples and Decontamination
All samples underwent decontamination, exposing them to exceptionally elevated temperatures in an oven that reached up to a scorching 150 °C for 24 h. The fundamental aim of this process was to successfully eliminate any probable existence of mold, thereby ensuring the integrity and purity of the samples under investigation.
Label (1A): 80% soil, 5% acrylic-based additive, and 15% quicklime.
Label (2B): 65% soil, 15% acrylic-based additive, and 15% cement.
Label (3C): 50% soil, 15% acrylic-based additive, 15% quicklime, and 20% cement.
Label (4D): 100% soil (control sample).
Label (5E): 100% concrete mixture.
Label (6F): 100% concrete mixture, painted with emulsion.
To execute the procedure, it was necessary to implement a consistent and unvarying relative humidity factor, which was maintained at approximately 45%. This value was carefully chosen to ensure that it simulated the indoor environmental conditions of typical buildings in the study area.
Standardization of Humidity Level
Samples were incubated for seven weeks, from the 7th of June to the 25th of July. Throughout this time, meticulous measures were implemented to maintain optimal conditions for the experiment, specifically by regulating the room temperature to fall within the range of 18 °C and 19 °C. Furthermore, humidity levels were carefully controlled to fluctuate between 45% and 50%. These specific parameters were selected due to their suitability in fostering the growth of fungi within the study area and to ensure the simulation of indoor environmental conditions of typical buildings in Jordan.
2.4. Macroscopic and Microscopic Examination
The samples were examined macroscopically during the 7th week for visual signs of mycelial growth or spores. After a long examination period, substantial results were recorded to facilitate comparison.
2.5. Microscopic Observation
Samples were swabbed properly from all sides of the specimen with a wet swab, and the swab was then mixed in a drop of the lacto phenol blue stain and placed on a clean and dry microscopic slide. The smear was then covered with a cover slip and observed under a bright field microscope at 400× magnification.
2.6. Environmental Post-Occupancy Evaluation for the Experimental Rammed Earth Building
The experiment mentioned above was conducted to ascertain if specific combinations of construction materials are susceptible to fungus development. After infecting the samples with fungi, the results obtained are as follows.
After that, fungi were inoculated and added to the samples, then placed under a consistent relative humidity factor (45%) achieved using wet cotton wool. The incubation of samples lasted seven weeks by regulating the room temperature to fall between 18 °C and 19 °C and maintaining a controlled humidity level between 45% and 50%. These specific parameters were selected due to their suitability in fostering the growth of fungi within the study area and to ensure similar indoor environmental conditions in typical buildings in Jordan.
This study investigated mold growth on the surface of earth constructions in the hot–arid region of Jordan. In addition, it explored the impact of adding cement, limestone, and a fast acrylic-based bond to the mixture on fungal growth resistance. Observations after seven weeks, under a regulated room temperature ranging between 18 °C and 19 °C, and a controlled humidity level between 45% and 50%, which covers the environmental conditions of residential buildings in the study area, showed that the growth of fungi was exhibited on mixtures that included higher percentages of soil and lower percentages of additives. Mixtures stabilized with quicklime, ordinary Portland cement, and acrylic-based additives were revealed as the best soil mixtures, which showed no fungal growth. The sample composed of 50% soil, 15% acrylic-based additive, 15% quicklime, and 20% Portland cement was put to the test in a rammed earth construction project and proved to be suitable for use as a green, sustainable, and efficient replacement after post-occupancy evaluation.
Disasters Expo USA, is proud to be supported by Inergency for their next upcoming edition on March 6th & 7th 2024!
The leading event mitigating the world’s most costly disasters is returning to the Miami Beach
And in case you missed it, here is our ultimate road trip playlist is the perfect mix of podcasts, and hidden gems that will keep you energized for the entire journey-