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Can Mould Grow On Or In Bricks & Concrete

Uncategorized Feb 07, 2020

Hello and welcome. Thanks for joining me on this live broadcast. My name's Dr. Cameron Jones, and today in episode two I'm talking about can mould grow on or in bricks and concrete. Think that mould only grows on bread, on a dampened wallpaper, Or plasterboard? Well, I thought so too, but today we're going to be talking about how bacteria, yeast, and fungi can actually grow and thrive on extreme habitats like stone and mineral building elements. I didn't think that this could happen at all. I thought that the only time moulds attack walls and these stone and inert materials is like in caves or churches and that sort of damage. But this whole field is called biodeterioration and mould can very happily grow on or in bricks. Today I want to share with you some of the extreme places that I have found in the urban environment where moulds and fungi are growing.

I'm just going to go through this slideshow and highlight some facts here. You'll see here with this scalpel that I'm pointing towards some mycelium that was found growing behind plaster when it was taken off the brick render inside a building. This is what happens when I swabbed that area, and plated it out, and incubated it. All these different fungi were found to be growing. Now this is pretty amazing because most of us think that water damage only impacts on the porous materials like wood and timber, and maybe a backpack, or some furniture, or carpet, but mould can thrive pretty much everywhere. I want to go through some of what I think is the really interesting research in the literature that is showing how fungi, predominantly, grow on these materials. So I'm going to just go through my slideshow while I talk to you to give you some visual examples of where I found mould to be growing.

One of the things that people often ask me is, is efflorescence ... they're these fluffy, salty deposits that are often white or yellow colored. What are they? Is this mould? Usually I've said to people, "No, it's not mould. These are salt crystals. It is an example of where these brick or concrete has become damp." So you often get efflorescence showing up in highly humid environments, or where there's a lot of air movement over these stone materials. I originally thought that fungi didn't get much nutrition from these low carbon source materials, but it turns out that as long as there is sufficient moisture, there is going to be the ability of these fungi to live in this extreme ecological niche. I want to highlight some research, and again, the papers are all going to be in the show notes at the end, but the first paper is some really elegant research that was done by some Israeli and German scientists.

They were looking at the phenomena of what happens when terrazzo stone tiles start to fragment up. So they did this really great experiment and they pulverized the terrazzo. They discovered that the dominant fungus that was found growing on these mineral deposits was a fungus called Nigrospora sphaerica. It was 100% percent match with the database, so that was really interesting in itself, that that was the dominant colonizer of this terrazzo in these homes. They found that after 10 days the fungus had degraded 70% of the powdered tile and that causes biodeterioration. So whenever you see efflorescence, I've changed my thinking on this topic as well. This is a definite example of areas of a building, even if it is brick or concrete, that is showing signs of fungal attack. Again, there could be significant health concerns because the reason that these scientists did this first experiment was because the occupants were concerned about breathing in these crystalline salt deposits. I'm not surprised because, as it turns out, fungi grow very well in these extreme types of built environments.

So as you can see as we move through the slide show, you can see some great examples of where mould has been found growing. We also discovered that when bricks were cracked open, that they showed clear signs of moisture damage. When we swabbed what I thought was going to be a sterile environment, lo and behold, we got growth. So I thought, "Maybe there's an error in here." So we also used surface contact press plates onto the internal surface of brickwork and, lo and behold, they were found to be contaminated.

So for all of you that don't have brick veneer buildings, what about those who have maybe a lot of concrete in your home? There is another great piece of Russian research which looked at this question. Again, they looked at what would happen when fungi, typical water damage fungi like Penicillium brevicompactum and Aspergillus, were deliberately colonized or introduced into the concrete. They found three things. Calcium was released from the concrete. This is really important because calcium is a fundamental component of concrete. They found that when the concrete had a high moisture content, you would get acceleration of mould growth on it. Most importantly, after 28 days with Penicillium, the stability of the concrete showed a 1% loss. Now that's just in one month. So that is really, really serious. So what do you think's going to happen to your house? What happens if you have rising damp? What happens if you have garden beds butting up onto your building? What happens if, for example, the weep holes collect a lot of water and it comes straight into your property? Rising damp and efflorescence, these are all signs that your building is under biological attack.

So there are a couple of questions raised by these publications. First one is, is it possible to practically remove these microorganisms from the water-damaged building interior? What about these hidden areas like inside brick walls that we can't see? Is there even a need to remediate or is this just a natural phenomenon of the fact that there is a biological ecological exploitation of pretty much every area of the natural world? But does efflorescence create these mineral respirable crystalline silica dusts? Are they similar problems going on inside homes showing efflorescence to those that we see in construction workers exposed to silica dusts when they're cut, like all sorts of health problems like lung cancer, COPD, chronic renal disease? Is this happening at a low level in homes that are water damaged with high amounts of brick or concrete? Then what about the hidden micro toxins, mycotoxins or microbial VOCs, that are possibly being liberated from within the brickwork and coming into our homes?

These are all important questions and we need answers. However, what can you do in your home? What are you going to do if you have efflorescence growing or seeing that on your property? Well, the answer is to use protective sealers or coating systems. There are a couple of different types. There are penetrating sealers, usually based on silane and siloxane, and they do a couple of things for your damp wall. They can make it more hydrophobic or water-hating, meaning that it is less likely that the moisture will be available for microbial attack, or different ones, which can in a sense even make the concrete more dense. There are other things, epoxy surface sealants that can be used, and even things like bitumen and urethane and to create barrier coatings.

In any case, it was a revelation to me that microbes can live in efflorescence but it's true. A lot of these examples in the slide show demonstrate that fungi was found hiding in the brick wall behind the plaster, and that was really a strange observation. That particular building had suffered a fire and so huge volumes of water we used to put out the fire. But nevertheless, these types of environments happen in the built environment and often require remediation. In any case, next week we're going to be covering another topic. That is, what mould remediation standards are available? Which should you use? Are there some which are better or worse than others? If you do need water damage restoration, what should you be looking at in the fine detail of the scope of works? In any case, my name's Dr. Cameron Jones. Thanks for watching and bye for now.



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