Hygiene & Anti-Contamination in Concrete Floor Slabs
To talk about contamination and hygiene, we really need to look at contamination in concrete in all aspects, and understand how contamination enters into concrete in the first place.
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THIS IS APPLICABLE to a concrete slab or a hygiene situation, a bridge or a wharf or whatever it may be contamination can get into concrete.
This is because concrete is porous by nature. The reason is because when concrete is cured, or when it’s first poured, it’s obviously in a softer or plastic state, and excess water – bleed water from the mix – comes back out of the concrete, and leaves behind capillaries.
In this picture here, it’s shown as a blue path making its way through the Calcium Silicate Hydrate in the sand, shown in the grey, and the aggregates around that.
THE IMPORTANT THING to remember is that these capillaries left by the moisture become a permanent part of the concrete. They are in there for the life of the concrete. These don’t close up over time, or get smaller, or disappear; they’re there.
We’ve got to remember that once moisture has gone out, it can also get back into the concrete at any stage of the concrete’s life. So moisture coming back in, brings back contaminants, whatever these contaminants might be. That starts wearing or breaking down the concrete.
Why is this a problem?
BACK TO THE HYGIENIC situation – the reason this is a problem is because, say we’re in an aged care situation and contaminants such as biofluids or food spills have got into the floor, you get more moisture under there, then you start getting bacterial and fungal growth inside the concrete.
You could imagine deep down inside the concrete, it’s very dark, and there’s moisture there, so it’s damp. It’s a perfect growing platform for this to happen. One of the ways we can tell this is happening is because of the odours in the room. No doubt you’ve have been in these sorts of situations and you can smell it, and it’s not pleasant.
This odour can’t be cleaned away easily; the bacterial contamination won’t budge with a surface clean, where you just give it a good scrub and you’ve got rid of it. It is deep inside the concrete. The MARKHAM team are involved in some aged care refurbishment projects where even a good grind doesn’t get rid of the bacteria that’s grown into the capillaries.
THE OTHER ISSUE asset owners find is that the actual concrete itself starts to prematurely age – the contamination begins to break down the matrix of the concrete itself. In the early stages, you find that your steel is starting to rust out. It starts to crack open the slab, and you end up with concrete cancer. This is quite often discovered in refurbs, where they’ve pulled up the floor coverings and found concrete cancer underneath – it must be dealt with before they can go on with the refurbishment, but it’s a large sum of money to get it sorted.
Urines and biofluids, things like that do get into the concrete very easily, through the carpet. You might even have carpets that are vinyl-backed etc.; over time, they’ll break down with the wear on the concrete, and moisture does get through and into the concrete slab.
What sort of slabs are at risk?
As mentioned above, aged care facilities are a common case for biofluid contamination.
Other sites include:
- Hospitals and other hygiene-sensitive projects (e.g. dental clinics)
- Public facilities (e.g. Stadiums, rest-rooms).
- Universities and schools
- Animal housing (e.g. Kennels)
What’s the long-term cost?
First, let’s look at the cost of doing nothing.
Obviously, straight up you’re saving money on your structure, designing or building it without the cost of protecting the slab.
But over time, that degradation of concrete is huge, that cost of maintenance is huge. And the cost of hygiene, the cost to keep clean, is huge.
Then for the tenants themselves, who are using the facility – What do they get and how do they react to what the concrete is giving them? Do they have to put up with a smell that’s accumulated over time?
Often, in a high-care dependency unit and an aged care facility, they’ll almost renovate a room every time they get a new tenant, and that often involves pulling up the flooring. If it hasn’t been treated, it requires grinding back the concrete to get back to something nice and clean to start again.
THESE SORTS OF THINGS are huge dollars and time over the life of a structure, if it’s not done right at the start. So this is the sort of thing we need to start thinking about, getting it into design, getting it into the project, and thinking of the long-term effects, and what’s actually needed for this job.
How to protect the concrete long-term?
The capillaries formed by bleed where are what needs blocking and densifying – increase concrete’s impermeability.
So we do that through treatment, where we bring a colloidal silica treatment into the concrete, and the formation of a hydrogel. Have you ever seen the gel test before? That gel is forming in all these little pores. Now, we have to remember, this is at microscopic level. A typical concrete pore or capillary is around 50 nanometres, and colloidal silica is in the range of 5-20 nanometres in size. For scale, a human hair is 100,000 nanometres.
MARKHAM does this through a spray-applied treatment or admixture. Spray-applied is best for the aged care sector that we’re talking about, because it achieves curing as well; we’ll explain that in one minute’s time. But the hydrogel doesn’t introduce anything foreign to the concrete, it just transforms moisture and creates more of the good stuff, more of the Calcium Silicate Hydrate that has been destroyed by the bleed water– it really densifies all that area.
Then, it prevents moisture moving up or down or in, it prevents moisture moving through the concrete, and obviously, it prevents contaminants growing and moving into the concrete. The fungal growth that needs moisture to grow – if you take away moisture migration, you’re effectively stopping growth and increasing hygiene in those sectors.
This also prevents any corrosion of the rebar as well – by removing moisture from the corrosion equation. This treatment really extends the service life of the concrete.
Multiple benefits in one system
Now, what the treatment is doing, is retaining that moisture in there to keep the concrete curing, so it gives you a good quality slab. Turning the moisture into a gel at the cure stage reduces the evaporation rate, and allows the concrete to gain strength earlier. It is not critical to be applied at curing stage – any aged concrete slab will take the treatment, as long as it is absorbent.
It’s compatible with any flooring adhesive that is compatible with untreated concrete, as it doesn’t introduce anything foreign to the concrete.
As for downtime, you’ll find that this treatment, incorporated in the FLOOR-TECT system, actually reduces the wait time for new concrete. Where concrete takes 1 month per 25mm thickness to dry, for a 150mm slab colloidal silica hydrogels will reduce the wait time from 6 months down to 28 days.
Speeding up aged care construction by meeting multiple specifications is a strong point for the builder.
Have a look at choosing the system for your own project!