Bentonite waterproofing: how granules work and where to use them

Bentonite granules are bought where water has to stay on one side of a barrier: foundations, underground structures, tunnels and soil stabilisation. GEOBENT Sp. z o.o. in Rzeszów supplies GB-Granules for that — granular activated bentonite. This note separates what is on the product card from what the industry does with granules in general. The second part is not a GEOBENT guarantee.

The construction page is bentonite for waterproofing. Order answers are in the FAQ. Samples and trucks go through contact.

How the swelling works

Bentonite seals because montmorillonite increases in volume when it is wetted. In a confined space — under a slab, in a joint, in a soil layer — the swelling grains close filtration paths and tighten the barrier. The GB-Granules page puts it this way: the product swells and forms a dense protective layer, protects structures against water, stabilises soil and limits subsidence and deformation.

Dry granules are not a membrane by themselves. They start to work when water reaches them, and only if they can swell without being washed away. Confinement, the neighbouring soil and whether the water is permanent or occasional all sit with the design. GEOBENT does not publish one barrier layout for every site. Performance in a given soil is judged case by case.

The figures you can quote without guessing are on the GB-Granules table:

Parameter	Unit	Value
Montmorillonite	%	65–85
Moisture	%	10–14
Fraction	mm	0.1–5.0
Free swelling index, min.	mm/2 g	25
Filtrate volume, max	ml	18
pH	—	10
Methylene blue adsorption, min.	mg/g	400
Water absorption, min.	%	600

A free swelling index of at least 25 mm/2 g and water absorption of at least 600% describe water uptake. Maximum filtrate of 18 ml is from the same card: it is the result of that test, not a leakage rate for your structure. pH 10, montmorillonite 65–85% and moisture 10–14% are table values. The published fraction is 0.1–5.0 mm.

Where GEOBENT points GB-Granules

The card points GB-Granules at waterproofing of foundations, underground structures and tunnels, and at soil stabilisation and limiting deformation. Barriers are part of that description. Packs on the page are 25 kg bags or 1 t big-bags. GEOBENT also ships bentonite in bulk; that is a company shipping option, not a second recipe. Delivery covers Europe and export.

On site this is a raw material for a barrier you build to the design, not a finished system with a detail drawing from the granule maker. If you need help choosing an arrangement, write to sales: you get technical contact and a free sample, not a universal wall detail.

Neighbouring products do not replace granules. GB-Form is for moulding sands. GB-Litter is for cat litter. GB-Drill is for drilling fluids in oil, gas and geotechnical work. GB-Soil and GB-Feed Additive are for soil and feed. GB-Sorb is for filtering wine, beer, water, juices and oils. For sealing, use the construction card.

Ponds, landfills and pipe penetrations

Outside the GEOBENT list, the industry also uses bentonite granules in a few other places. Treat this as typical practice, not a guaranteed scope for GB-Granules.

At ponds and reservoirs, dry granules are sometimes worked into the bed and banks, or placed as a mineral layer that tightens the soil once it is wet. At landfills, bentonite shows up in mineral sealing layers. At pipe and cable penetrations through concrete, dry granules are packed into the annulus so that, once damp, they swell and close the gap. In each case the design decides thickness, confinement, soil and whether the water is fresh. GEOBENT does not publish a pipe-penetration detail or a landfill cross-section.

Industry texts often quote roughly 5–15 kg/m² for ground sealing, higher on permeable soils. That is not a GB-Granules dose. Do not turn it into an order without a trial on your own soil and a design. The product card does not contain a kilograms-per-square-metre figure.

The minimum order is one full truck. Lead time is from 2 weeks after the order. Samples are always free: info@geobent.pl, +48 573 588 382. Say whether the job is a foundation, a tunnel, soil stabilisation or another seal, which fraction you want to test, and where to send the sample. A 25 kg bag is enough for a trial strip; a 1 t big-bag, or bulk if you can unload it, is the delivery.

The raw material comes from GEOBENT’s own quarry, 2 km from the Rzeszów plant: 3 bentonite layers and 1 palygorskite layer, processing up to 100,000 tonnes a year. More is in the quarry article. Litter producers should use the separate note on choosing bentonite for cat litter — a different card, even where some table lines look alike.

Before you write, pick the table line that actually decides the purchase (often swell, filtrate or fraction), describe the barrier, and give a sample address. Sales confirms the rest.