Bentonite-Based Under-Foundation Waterproofing

Bentonite-Based Under-Foundation Waterproofing

Bentonite-based waterproofing is a long-lasting, environmentally friendly solution produced from 100% natural sodium bentonite mineral. Held between two geotextile layers, the sodium bentonite expands in volume on contact with water to form an impermeable layer, protecting your structures from the harmful effects of water.

Bentonite waterproofing material can be laid horizontally or vertically directly onto the soil surface, with no need for blinding concrete. This makes it easy to install and saves time. Its long-lasting structure provides effective protection even in difficult ground conditions.

Advantages of Bentonite-Based Waterproofing:

• Natural and Environmentally Friendly: Produced from 100% natural sodium bentonite material.
• High Performance: Forms an impermeable layer on contact with water, providing effective protection against water.
• Easy Installation: Can be laid directly onto the soil surface without the need for blinding concrete.
• Flexible Use: Designed for both horizontal and vertical applications.
• Long-Lasting Protection: Provides a durable structure even in difficult ground conditions.

At Likit İzolasyon we provide long-lasting protection for your structures with our innovative bentonite-based sub-foundation waterproofing applications. Contact us for professional service and natural solutions.

Application Areas of Bentonite-Based Sub-Foundation Waterproofing

• Beneath raft foundations — on the blinding concrete before the pour
• Bored pile and diaphragm wall faces — areas that cannot be reached later
• In deep basements, against a high groundwater table
• Narrow working areas remaining between the shoring wall and the retaining wall
• Surfaces in contact with soil in tunnel and underpass structures

The Working Principle of Bentonite Systems

The Self-Healing Swelling Mechanism

On contact with water, sodium bentonite increases its volume many times over and reaches a gel consistency. When it swells within a confined volume it forms an impermeable barrier. In small punctures and tears the bentonite fills the gap and heals itself; this is a decisive advantage in areas that cannot be reached later.

Bentonite Panels and Membranes

Bentonite granules are compressed between geotextile or cardboard carriers to form panels. They are laid on the blinding concrete, and reinforcement can be tied and concrete poured directly on top. A tight bond forms between the fresh concrete and the bentonite.

Waterstops and Sealant Pastes

Swelling waterstops and sealant pastes are used at discontinuities such as construction joints, pile heads and pipe penetrations. These details are the areas where leaks are most frequently seen in foundation waterproofing.

The Application Process

• 1. Preparing the blinding concrete surface: The surface must be even, sound and free of sharp protrusions. Standing water and loose material are removed.
• 2. Laying the panels: The panels are laid with the bentonite face towards the concrete. Overlaps are left in accordance with the manufacturer's data and fixed with nails or tape.
• 3. Detail solutions: Swelling waterstops and sealant paste are applied around pile heads, column starters and pipe penetrations. Corners are reinforced with additional pieces.
• 4. Protection: If necessary, a protective layer is laid so that the panels are not damaged during reinforcement fixing; precautions are taken against premature wetting.
• 5. Concrete pour: The concrete is poured directly onto the panels. Care is taken not to puncture the panels while using the vibrator.

Technical Notes and Standards

• Because bentonite systems bond mechanically with the concrete, the interlayer void and water migration problem seen in membrane systems does not occur.
• The system only works correctly within a confined volume; in areas where free expansion is possible, swelling does not form a barrier.
• Premature wetting of the panels by rain before the concrete pour can cause a loss of performance; weather conditions must be planned for.
• In saline groundwater and groundwater containing chemicals, the swelling capacity of standard sodium bentonite falls; specially modified products must be used in these conditions.

Frequently Asked Questions

Why is bentonite waterproofing preferred over a membrane?

The area beneath the foundation cannot be reached later, and repairing a leak that develops there is very costly. The self-healing property of bentonite reduces this risk. In addition, being able to pour concrete directly onto it removes the need for a protective screed and shortens the programme.

Can reinforcement be tied directly onto the panels?

Yes, and this is one of the main advantages of the system. However, care must be taken that sharp-ended bars do not tear the panels and that cover spacers do not damage them. Damaged areas are repaired before the concrete pour.

Is the application damaged if it rains?

Short-term wetting is generally tolerated, but prolonged contact with water can cause the bentonite to swell in an unconfined state and lose its properties. For this reason the period between laying and the concrete pour is kept short and the area is covered if necessary.

Can it be used in an existing building?

Bentonite systems are essentially applied in new structures, before the concrete pour. As there is no access beneath the foundation in existing buildings, negative-side cementitious systems or injection methods are preferred.