Research Evaluation Potential: For Growth Of Mold/Fungi On Concrete Masonry Products

Project No—MR 23 March 2004

Conducted by

Introduction The purpose of this project is to assess the potential for mold growth on concrete masonry products, and to evaluate assertions that concrete masonry products do not provide a food source that would encourage mold growth. The project included a review of available standardized test methods to measure the growth of mold cultures on the surface of a material under ideal conditions and the testing of six different sets of concrete masonry unit specimens using one of these methods: ASTM G 21-02, Standard Practice for Determining Resistance of Synthetic Polymeric Materials to Fungi. The evaluation of test methods and coordination of the testing program was conducted by Amal Tamim, Construction Codes Specialist. Samples for testing were identified by NCMA and sent directly to a third-party testing lab: Micro-Test Laboratories of Agawam, Massachusetts. Review of Available Test Criteria A review of available literature revealed a number of resources on mold types, mold occurrence, construction and maintenance to prevent mold growth, and mold detection and remediation. Very few studies were found on the development and application of standardized mold growth testing methods to common building materials used as structural components or construction materials. However, the following standardized test methods were identified for evaluating fungi resistance: ASTM C 739, Standard Specification for Cellulosic Fiber Loose-Fill Thermal Insulation ASTM C 1338, Standard Test Method for Determining Fungi Resistance of Insulation Materials and

Facings ASTM D 2020, Standard Test Methods for Mildew (Fungus) Resistance of Paper and Paperboard ASTM D 3273, Standard Test Method for Resistance to Growth of Mold on the Surface of Interior

Coatings in an Environmental Chamber ASTM D 3274, Standard Test Method for Evaluating Degree of Surface Disfigurement of Paint

Films by Microbial (Fungal or Algal) Growth or Soil and Dirt Accumulation ASTM D 4300, Standard Test Methods for Ability of Adhesive Films to Support or Resist the Growth

of Fungi. ASTM D 4783, Standard Test Methods for Resistance of Adhesive Preparations in Container to

Attack by Bacteria, Yeast, and Fungi ASTM D 6329, Standard Guide for Developing Methodology for Evaluating the Ability of Indoor

Materials to Support Microbial Growth Using Static Environmental Chambers. ASTM G 21, Standard Practice for Determining Resistance of Synthetic Polymeric Materials to

Fungi US MIL-STD-810E, Environmental Test Methods and Engineering Guidelines, Method 508.4

Fungus, 14 JULY 1989 Most of the above methods were developed for insulation, coatings and cellulosic materials with the exception of the Mil-Std 810 E-508.4, which is applicable to any material used in military equipment. All of these methods subject a set of common samples of mold spores to specimens which are then maintained in a controlled environment (temperature of 28-30 °C and relative humidity of 85-95%)

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that is ideal for mold growth during an incubation period lasting typically 28 days. In some of these test methods a testing or humidity chamber is used. In other test methods, samples are tested in a Petri dish. Any material can act as a substrate on which mold can grow. However, some materials are made from organic nutrients on which mold spores can feed and propagate. The purpose of these methods is to determine if the tested material itself actively supports mold growth after spores are applied to its surface, and if so, to what degree. Selection of Test Procedure None of the test methods identified in the literature review were developed specifically for evaluating concrete products. However, there is precedence for the application of two of these methods, ASTM G 21 and MIL-STD-810-E Method 508.4, in the evaluation for mold growth on cementitious materials. Military test standard MIlL-STD-810-E Method 508.4 was developed for determining fungus resistance of military equipment. This standard was used recently in a series of tests run by Masonry Canada to evaluate concrete masonry units, clay masonry units, and wood and drywall construction products. Method 508.4 of MIL-STD-810-E uses a test chamber and strict control of the test samples’ environment when it is used to evaluate different types of equipment. However, when this method is used for evaluating basic materials, it recommends methods such as plate testing in lieu of an environmental chamber. ASTM G 21 is referenced by the Evaluation Service of the International Conference of Building Officials for cementitious fire resistive materials (ICBOE ES Acceptance criteria AC-23). ASTM G 21 is recommended in AC-23 to screen spray applied fire resistive cementitious materials used in plenums for their potential to support mold growth. In ASTM G 21 test specimens are inoculated with mold spores under conditions favorable to mold growth and subsequently visually examined for mold growth. It appears that either ASTM G 21 or MIL STD-810E would be appropriate to evaluate potential for mold growth on concrete masonry products. ASTM G 21 was used in this project. The full test method includes the measurement of physical properties specific to plastics before and after the incubation. However, inasmuch as these properties are not relevant to concrete masonry products they were not applied here. Description of The Test Procedure Under the provisions of ASTM G 21-96 (Reapproved 2002), samples are inoculated with a suspension of five types of fungus cultures:

• Aspergillus niger • Penicillium pinophilum (also known as Penicillium Funiculosm)

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• Chaetomium globosum • Gliocladium virens • Aureobasiudium pullulans.

These organisms used in the cultures for the spore suspensions represent common types of fungi found in homes and found to affect plastic barrier type materials. Following inoculation, the samples were then placed (incubated) in a Petri dish over a salts agar that provides nutrients suitable for mold growth. The samples were stored in this manner for a period of 28 days in an environment of 28 to 38 °C (82.4 to 86 °F) and a relative humidity that was equal to or greater than 85%. Following the incubation period, each sample was visually examined for traces of mold growth and rated based on the amount of growth observed. If no growth or mere traces of growth were observed, samples were then further examined under a microscope. This series of observations was intended to indicate the relative resistance of the samples to microbial growth under favorable conditions. Resistance to mold growth was rated according to the amount of mold observed according to he following schedule.

Observed Mold Growth Applied Rating None Rating 0 – requires confirmation with microscope Traces Less than 10% Rating 1 – requires confirmation with microscope Light growth 10-30% Rating 2 Medium growth 30-60% Rating 3 Heavy growth more than 60% Rating 4

Test Specimens NCMA selected six different sets of concrete masonry materials for testing under this research program. These sets were selected to represent a range of different unit densities and production materials. Shown below is a description of the properties of the concrete within each of these six sets.

Set Identification

Number

Oven-Dry Density

pcf

Absorption pcf

Compressive Strength, psi Materials Used in Production of Units

03-292-L 101.4 11.7 2400 Type III Cement, Pumice, Sand 03-292-M 110.2 11.1 3360 Type III Cement, Pumice, Sand 03-435-1 141.0 8.4 3240 Type I Cement and Limestone 03-435-2 119.6 10.0 2620 Type I Cement, Limestone, Exp. Shale 03-435-4 95.3 12.6 2470 Type I Cement, Limestone, Exp. Shale 03-440-1 135.7 6.5 4900 Type I Cement, Split Stone, Fine Sand

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One concrete masonry unit was randomly selected from available units from each of the six production runs. Six specimens, each measuring approximately 2 x 2 x ¼ in. (50 x 50 x 6 mm), were saw cut from each unit by the NCMA Research and Development Laboratory. The samples were packed and mailed directly to MicroTest Laboratories in six sealed plastic bags. Testing and Results Testing was done under contract with MicroTest laboratories Quote # 02649, MTL TEST # 5005. Testing was started on 12/15/2003 and completed on 1/12/2004. Three samples from each set were tested (unused samples were returned to NCMA) as described in this report. Photographs were taken by MicroTest Laboratories before and after conducting the test to document the condition of the samples. All three samples from all six sets of specimens evaluated showed NO GROWTH after 28 days incubation. Visual observations were confirmed microscopically at 40X magnification. No changes in the physical appearance of the samples were observed. Some discoloration of the samples was observed and was attributed merely to moisture content change of the specimens as a result of their prolonged exposure to moisture. See Appendices A and B for complete test data and photographs. Conclusion and Recommendations This project confirms that concrete masonry materials do not provide a food source that supports mold growth. While this project did not include evaluation of other building materials, it would be expected that other materials made from organic materials, such as wood and paper, would show some level of mold growth under these same conditions. Such testing has been performed to a limited degree by Masonry Canada. However, additional testing should be considered to better document relative performance of different materials. Further consideration could be given to development of methods specific to the evaluation of mold growth potential on concrete masonry and other similar building materials. Use of construction materials that do not provide a food source for mold will certainly reduce the risk of mold growth within inhabited structures. However, any building material can act as a substrate for mold to grow on, including concrete masonry. Dust or other organic debris that accumulates on the surface of mold-resistive materials can sustain mold growth when the right temperature and humidity conditions prevail. Therefore, it is important that proper design and construction procedures be used for concrete masonry as well as all other types of construction materials, to reduce the potential for moisture intrusion that will encourage mold development.

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References 1. Concrete Masonry Design, Jan. 03 Edition, NCMA. 2. AWCI Mold: Cause, Effect and Response, March 03, FWCI 3. ICBO ES Acceptance Criteria AC-23 for sprayed fire resistive materials 4. ASTM G 21. Practice for Determining Resistance of synthetic polymeric materials to fungi. 5. ASTM C 1338. Test Method for Fungi Resistance of Insulation Materials and Facings. 6. ASTM D 2020. Test Method for Mildew (Fungus) resistance of paper and paperboard. 7. ASTM D 3273. Test Method Resistance to Growth of Mold on the surface of interior

coatings in an environmental chamber/ ASTM D 3274 Test Method for Evaluating Surface Disfigurement of Paint Films by Microbial (Fungal or Algal) Growth or Soil and Dirt Accumulation.

8. 8.ASTM D 6329. Developing methodology for evaluating the ability of indoor materials to support microbial growth using static environmental chambers.

9. ASTM D 4300. Test Methods for Ability of Adhesive Films to Support or Resist the Growth of fungi.

10. ASTM D 4783-01 Standard Test Methods for Resistance of Adhesive Preparations in Container to Attack by Bacteria, Yeast, and Fungi

11. ASTM C 739- Specification for Cellulosic Fiber (Wood-Base) Loose-Fill Thermal Insulation–section 5.4 and 11 –fungi resistance

12. US MIL-STD -810E Method 508.4 – Fungi resistance. 13. Guidelines on Assessment and Remediation of Fungi in Indoor Environments. New York

City Department of Health, Bureau of Environmental & Occupational Disease Epidemiology, 2002.

14. Indoor Air Quality Tools for Schools Program, EPA 402-F-02-022. United States Environmental

15. Protection Agency, 2002. 16. Fungal Contamination in Public Buildings: A Guide to Recognition and Management,

Health Canada, 1995. Website Resources

1. University of MN Dept of H&S, Fungal Glossary, www.dehs.umn.edu/iaq/fungus/glossary.html

2. U.S. Environmental Protection Agency – www.epa.gov/iaq/molds/moldresources.htm 3. American Industrial Hygiene Association, http://www.aiha.org/SplashPages/html/topic-

mold.htm

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APPENDIX A Data

APPENDIX B

Test Photographs

SAMPLE03-435-1

Day 0 Day 21

Day 28

SAMPLE 03-435-2

Day 0 Day 21

Day 28

SAMPLE 03-435-4

Day 21Day 0

Day 28

Day 21Day 0

Day 28SAMPLE 03-440-1

SAMPLE 03-292-L

Day 28

Day 21Day 0

Day 0 Day 21

Day 28

SAMPLE 03-292-N