Innovative concrete tunnel waterproofing

Citi-Con devised an innovative solution to waterproof a tunnel where grain is transported via a conveyor belt for storage in concrete silo bins. The silo bins have also undergone extensive concrete repairs by the company to prolong their service life.

Excessive moisture is a high risk in this area as it facilitates mold, fungi and mycotoxin growth, insect infestation and heat build-up. This is in addition to physical degradation, such as caking and clumping, leading to blockages during unloading. It also results in asymmetrical pressure on silo walls potentially causing structural damage or even bin collapse. Water ingress also compromises the reinforced underground structure which provides operational, maintenance and repair teams safe and easy access to the equipment inside.

Where water was leaking through concrete around five hopper chutes, unsound, deteriorated concrete was removed all the way behind the steel reinforcing and base plates. Thereafter, the sound substrate was thoroughly cleaned and saturated with water. The areas were then reinstated with Vandex Super and Plug, as well as Tamms Structural Mortar.

Vandex Super becomes an integral part of concrete through a crystallisation process. Once the cementitious carrier is applied to either the positive or negative side of the substrate, crystal growth occurs, blocking the capillaries and minor shrinkage cracks within the concrete to prevent any further water ingress.

Vandex Plug is a rapid-setting hydraulic cement compound with crystalline properties used to instantly stop running water or seepage in masonry or concrete.

Comprising Portland cement, graded aggregates, unique fibres and polymers, Tamms Structural Mortar’s patented formulation increases adhesion and strength.

Unable to drain away effectively due to ineffective water stops, negative water accumulated in the concrete joints and started leaking below the chutes.

To solve the problem, an effective drainage system was installed to prevent water build-up and resulting hydro-static pressure. A channel was created in the concrete slab under the cold joints and treated with Vandex Super and Plug. The gully body and connecting pipework leading to a sump were installed inside the concrete slab under the cold joint and Vandex Super and Plug applied to the required areas. They were primed, reinstated with Tamms Structural Mortar and then finished and painted.

Thereafter, 50mm-diameter downpipes were connected to the drains, extending from chutes 5, 4, 3, 2 and 1.

The hoppers at surface where grain is offloaded were high-pressure washed to expose cracks in the concrete and repaired. They were opened and then thoroughly cleaned and reinstated with Tamms Structural Mortar. These areas were then treated with Vandex Super and Plug and all joints bandaged and plugged.