Concrete being a heterogeneous material is susceptible to damage due to water infiltration, moisture presence, chloride diffusion and acid. The water and moisture penetrates through concrete pores, capillaries and micro-cracks in the concrete. This can cause rapid structure deterioration that will lead to expensive repairs. Crystalline waterproofing prevents the ingress of water, blocks the pore and micro-cracks by making the entire concrete structure water-resistant from the inside.
Crystalline waterproofing is a process where the active ingredients in a crystalline product that comes in a dry, powdered form react with calcium hydroxide, free lime and moisture in the concrete that causes a catalytic reaction that generates crystals. These crystals fill the pores and minor shrinkage cracks in the concrete to prevent any further water ingress. If a crack forms, any water influx causes more crystals to grow, re-blocking and sealing the passage against water and waterborne contaminants. Whenever new water enters the concrete through changing water levels or new cracks, crystals continue to grow and seal the concrete.
The crystals formed inside the concrete capillaries are resistant to deterioration and physical damage. With crystalline waterproofing, concrete is also protected from water-borne chemicals, even if your concrete is exposed to high hydrostatic pressure. As any form of water attempts to penetrate your concrete, the self-sealing new crystals form to grow and seal it off.
The diagram above shows that upon the application of crystalline waterproofing product chemicals starts to migrate inside the concrete, Crystalline chemicals migrate into the pores and start reacting with calcium hydroxide forming crystals. The formed crystals waterproof the pores.
Crystalline waterproofing application methods
There are three different application methods:
- As Surface applied coating
- As an admixture
- As Dry shake
Surface Applied Coating Application Method
- Crystalline waterproofing as a coating system can be brushed or sprayed
- Concrete surfaces should have an open pore texture to allow the transfer of the crystalline additives from the surface coating into the concrete.
- The surface also needs to be clean and free of dirt that can clog the pores and prevent the effective diffusion of the additives into the concrete.
- Surface preparation may be carried out by water jetting, or acid etching
Wetting the Surface
- The concrete surface to saturated in saturated damp condition to facilitate the diffusion of the chemicals from the coating into the concrete pores
- To make sure that concrete on vertical surfaces is saturated, wet the walls with clean water and allow the moisture to be drawn into the substrate
- In hot weather, when evaporation rates are high, it may be necessary to soak the concrete overnight
- The crystalline waterproofing coating materials are mixed with water by volume and are applied with a brush at a coverage area
- Coatings can be applied by brush, hopper gun or specialised spray equipments
- Curing should begin as soon as the coating has hardened sufficiently
- Under normal conditions, curing can begin two to three hours after coating
- Curing has to be carried out by spraying water
Crystalline Waterproofing Admixture Application Method
- The crystalline powder is added to the concrete as it is being mixed, before the pour
- Once the concrete hardens, and the initial waterproofing has occurred, the active ingredients in these admixtures remain dormant inside the concrete and will reactivate to block future microcracks and voids
Dry Shake Application Method
In this method, the crystalline powder is sprinkled onto the surface using a mechanical spreader and worked into the slab during the normal finishing process with a power trowel.
Advantages of crystalline waterproofing
- Can be applied to new and old concrete
- Effective against high hydrostatic pressure
- Increases concrete’s compressive strength
- Does not require protection during backfilling, placement of steel or wire mesh, and other common procedures.
- Seals hairline and shrinkage cracks
- Protection from freeze/thaw cycles
- Blocks concrete capillaries stop passage of water.
- Chloride Protection
- Carbonation Protection
- Sulphate Protection
- Reduces Chloride Diffusion
- Penetrates deep into concrete
- Abrasion Resistance
- Protects concrete against alkali aggregate reactions
- Reduces the amount and diameter of the capillary pores
- Self healing properties of treated concrete of hairline cracks up to 0.5 mm.
Applications of crystalline waterproofing
- Basement retaining walls
- Parking structures
- Concrete slabs (floor/roof/balcony, etc.)
- Tunnels and subway systems
- Construction joints
- Water retaining structures
- Underground vaults
- Swimming pools
- Sewage and water treatment plants
- Marine structures
Crystalline waterproofing is a self-sealing, highly-durable waterproofing solution that improves the efficiency of construction and the durability of structures. Crystalline waterproofing ensures denser concrete and chemical resistance by becoming a part of concrete.