Ordinary concrete looks like solid rock, but under a microscope it looks like Swiss cheese. As it cures, evaporating water leaves behind millions of microscopic tubes (capillary pores). Through these pores, groundwater finds its way into our basement.
Instead of fighting to seal those pores after the fact with coatings, engineers use Integral Waterproofing. They add special chemicals (Waterproof Admixtures) straight into the concrete mixer ("the barrel") before the concrete is poured into the formwork.
When the contractor orders the concrete from the batching plant, they request one of the following additives:
These are usually liquid admixtures. Once mixed into the concrete, they "coat" the pore walls with a water-repellent film (as if you waxed them). Water, due to surface tension, slides off and cannot penetrate deep. This is the oldest and most classic method.
Remember the crystalline coating from the previous article? Here we're talking about the same technology, but in powder form mixed into the batch. As the concrete cures, the active chemicals react with moisture and create insoluble crystals throughout the entire wall volume! The concrete seals 100% from inside out and, most importantly, gains self-healing ability. If a micro-crack forms in the future, the concrete itself will grow new crystals and close it!
Why is integral waterproofing so ground-breaking?
No need to wait a month for the concrete to dry and then bring a team to apply bituminous or polyurethane coatings. You save the labour cost of the coating crew entirely.
When the bulldozer dumps the backfill, you don't care if rocks scrape the wall. The waterproofing isn't a "skin" on the outside - it's the entire wall thickness (e.g. 25 cm of watertight rock).
Because water cannot even enter the concrete, the reinforcing steel bars will never corrode.
Many contractors say: "I put waterproofer in the barrel, so I don't need anything else." This is the most dangerous lie! The admixture makes the concrete itself watertight. It does NOT seal the joints (the construction joints) where the floor meets the wall. It also can't bridge large cracks (over 0.4 mm) from settlement. That's why integral waterproofing must always be combined with hydrophilic waterstops at the joints!
We're pouring the basement concrete for our 10×10 building.
We order standard C20/25 concrete. After stripping the formwork, we must hire a team to clean, prime and apply 3 coats of cementitious waterproofing on the outside. If the worker misses a spot or if rocks scrape the coating during backfilling, our basement will leak.
We ask the batching plant to add crystalline integral admixture to the mix (approx. €10-15 extra per m³). We also install the hydrophilic waterstop cord at the joint. We pour. We strip the formwork and… we're done! We apply absolutely nothing. We backfill fearlessly. Our basement is an impenetrable "submarine" that seals its own micro-cracks.
Bottom Line: Waterproof admixtures (especially crystalline) are the epitome of preventive construction. They make the very nature of the concrete hydrophobic, reducing labour costs and ensuring your building ages without ever feeling the dampness of the ground.
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