Water, salt & corrosion are no match for cementitious waterproofing
Concrete is a durable and strong construction material that is relied upon for buildings, bridges, tanks, dams, pools, pipes, and drains, just to name a few. However, concrete is porous and permeable; water and water vapour can penetrate concrete and cause deterioration and damage, especially in cases where the concrete is reinforced by corrodible materials like steel. Waterproofing concrete structures is essential to ensure a long and effective working life. Cementitious waterproofing is a waterproofing method for concrete that uses cement-based polymer coatings to create a barrier to water and moisture.
In this article we look at the benefits and applications of cementitious waterproofing, as well as the manufacturers and cementitious coating products available in New Zealand.
Why you need cementitious coatings – ‘Concrete cancer’ and spalling
Though concrete may seem indestructible and will likely be left long after all of us are gone, it is not infallible. The porosity of concrete makes it particularly prone to attack from chemicals that it absorbs. Concrete without waterproofing will absorb water, salts (in particular chloride ions), and contaminants, leading to the corrosion of the reinforcing steel encased within. This is what is generally referred to as ‘concrete cancer’, where water, salt, or chemicals deteriorate the concrete to the point that expansion and cracking can lead to failure.
Signs of concrete cancer include spalling (flaking, cracking, peeling, or crumbling of the concrete), corrosion or rust stains, or stains that appear to be seeping from the inside of the concrete. Expansion within the concrete causes cracking and allows more contaminants to infuse it, accelerating the problem. The best way to prevent concrete cancer is to ensure that your concrete is adequately waterproofed.
The benefits of cementitious waterproofing
The waterproofing you choose needs to match the requirements of your project. No one coating will work for every situation, and the wrong one can lead to costly repairs and reworks. Cementitious waterproofing has the benefit of a wide range of suitabilities and strengths, including:
- Monolithic – Cementitious waterproofing provides a seamless coating system
- Abrasion resistant and weather resistant – Important where wear or exposure is an issue
- Chemical resistant – Can be used where chemical spills or storage is necessary
- Excellent bonding capability – Bonds to porous and non-porous surfaces
- Works with both negative and positive side pressure
- Resists carbon dioxide and chloride ion diffusion – Prevents concrete cancer and spalling
The advantage of including a polymer in a cement-based coating is that it gains a degree of flexibility (though not enough to withstand movement), it increases adhesion, makes the coating waterproof and chemical resistant, but it also stays breathable. This means the vapour from the concrete will not get trapped and cause blistering.
Crystalline coating versus flexible cementitious
Broadly speaking, cementitious coating can be divided into two types – crystalline and flexible. Both include proprietary blends of crystalline powder material containing cement and silica their formulations.
- CRYSTALLINE CEMENTITIOUS WATERPROOFING
Crystalline coating is composed of cement, specially treated quarts (or silica), and proprietary chemicals. When combined with water, it undergoes a reaction and forms a crystalline structure that permeates and fills pores, micro cracks, and capillaries in concrete. This effectively blocks off those channels that would otherwise allow the ingress of water and damaging chemicals. Crystalline coatings are resistant to hydrostatic pressure and chemicals, and can be used for both positive and negative sides of water-retaining concrete structures.
Application: Crystalline coating works like a surface treatment, diffusing through the surface of the concrete and bonding with it. It can also be included in the wet concrete before pouring, providing waterproofing in its own matrix, or sprinkled onto the wet slab.
- FLEXIBLE CEMENTITIOUS WATERPROOFING
Also called polymer-modified cementitious waterproofing, this is a breathable, flexible, and versatile option that is can be used for a wide range of applications including foundation walls, water storage tanks, basements, secondary containment bunds, swimming pools, digesters, pumping stations, sewers, and the protection of marine structures. This versatility is down to the ability to include the powder cement admixture in a range of polymer coatings.Flexible cementitious coatings provide waterproofing for positive and negative side installations, can be used for crack bridging, and are breathable.
Application: Flexible cementitious coatings are two component – mix the powder component with the liquid binder component then, when properly combined, apply it by airless spray, brush, trowel, or skid leveller. Can be reinforced.
Cementitious waterproofing manufacturers and suppliers in New Zealand
There are a number of cementitious waterproofing manufacturers and contractors operating in New Zealand. Below are some of the cementitious coating manufacturers who supply cementitious waterproofing to the New Zealand market.
If you would like to know more about cementitious waterproofing, get in touch! Our experts are here to help. Whether you are looking for a contractor to carry out a project, or are a business looking for a cementitious coating supplier, we can connect your with the right company for your needs. Simply click the “Request a Quote” button at the bottom of this article and let us know the details so our experts can get to work.
|Cementitious Coating Company||Product Example||Description|
|Equus||Aquafin IC||Crystalline waterproof slurry for exterior and interior waterproofing including drinking and service water.|
|Mapei||Mapelastic Smart||Two-component, high-flexibility cementitious mortar for waterproofing concrete surfaces such as balconies, terraces, basins and swimming pools.|
|Merz Construction Products||MixGuard AC||A two component acrylic modified cementitious coating for a flexible waterproofing system.|
|Vandex||Concrete Grey||Concrete capillary penetrating, crystal growth sealing, cement based, waterproofing system for positive and negative water pressure applications.|
Flexcrete Cementitious Coating 851 still works 29 years later
In 1988, scientists from the Vinci Construction Technology Centre in Bedfordshire, UK, applied Cementitious Coating 851 in a 2mm thick film to a concrete plate and sealed it into a chloride ion diffusion cell. They were testing for the coating’s ability to act as a barrier to chloride ion diffusion, a key cause of concrete cancer and failure. Nearly three decades later and Flexcrete is now owned by AkzoNobel and is known as Intercrete 4851 in some markets, but that original layer is still going strong. Tests show that the coating shows no signs of deterioration in spite of constant exposure for 29 years. An unparalleled success!