Project: Niagara Falls, Ontario, potable water facility – repair and waterproofing of tanks, 2012 – 2013
Designer: Cole Engineering Group Ltd., Toronto, Ontario
Owner: Region of Niagara Falls, Ontario
Contractor: Kingdom Construction Limited
Installer: Devonshire Restoration and Building Services Inc., St. Thomas, Ontario
Gemite products: Cem-Kote Flex ST, Reinforcing Fabric HD, Gem-Plast TC, Fibre-Prime
Objective: repair and waterproofing of concrete tanks in an existing water treatment facility. The facility was built in the 1930s and concrete in the tank had deep deterioration, up to 8 mm deep in some areas. These areas were repaired using Gem-Plast TC and some structural new concrete was also cast. The mechanical part of the facility is shown in Figure 1. The waterproofing system consisted of Cem-Kote Flex ST reinforced with Reinforcing Fabric HD over existing cracks. All metal parts (pipes) were cleaned to remove rust and protected with cement based rust-proofing Fibre-Prime. Cem-Kote Flex ST was applied onto the walls and slab in two coats, each coat being sprayed and brushed to achieve membrane continuity for a total of 1.6 mm (63 mils) minimum thickness. The application of Cem-Kote Flex ST on a tank wall is shown in Figure 2. Fibre-Prime and Cem-Kote Flex ST applied to cast iron pipes are shown in Figure 3.
Cem-Kote Flex ST has been used in potable water concrete tanks for over 23 years, with no single bond failure. The key advantages of the Cem-Kote Flex ST system over polymer coatings are as follows:
- Flexibility – with the Reinforcing Fabric NW used over drying shrinkage cracks and its inherent flexibility Cem-Kote Flex ST provides excellent crack bridging, much better than epoxy, vinyl-esters or flexibilized epoxies.
- Moisture – application of Cem-Kote Flex ST does not require drying of the concrete prior to application or low humidity in the tanks. Cem-Kote Flex ST is completely insensitive to moisture in concrete, surface moisture and high humidity environments.
- Water insensitivity – polymer membranes are very sensitive to moisture in concrete, surfacemoisture and high relative humidity. Most of the polymer membranes specifications call for drying the concrete to a depth of 1 inch, or application of an additional low moisture content render, prior to application.. These procedures, drying or application of a render, are very expensive. For example, drying this type of tank would require approximately 1-2 weeks, with the cost of heating fuel up to 1200 $ per day.
- Outside moisture – Cem-Kote Flex ST membrane also resists water penetrating from the outside, from the negative side. It has been extensively used for both positive and negative side waterproofing. Cem-Kote Flex ST membrane is insensitive to any moisture which can be present at the concrete/membrane interface, either due to water vapor condensation or penetration through cracks in the concrete. High capillary pressures which develop at the interface may cause debonding of the polymer membranes but will not de-bond cement based material due to its inherent gel porosity.
- Breathable – Cem-Kote Flex ST is “breathable” and can release the water vapour from the substrate concrete. Polymer membranes act as vapour barriers, resulting in the de-bonding problems associated with this property.
- Ease of Application – Cem-Kote Flex ST is a waterborne material so does not present the application difficulties of “sticky” polymer resin coatings. Tools and equipment are easy to clean with water whilst expensive organic solvents must be used when cleaning polymer coatings. .Cem-Kote Flex ST is easily and quickly applied by spraying, unlike polymer coatings.
- Robust – Cem-Kote Flex ST is a very “robust” product in application allowing large variations in moisture content and relative humidity. Its “application window” is very wide and tolerant to varying conditions compared to the very narrow “window” required for application of polymer coatings. Therefore the application of polymer coatings is more risky than applications of Cem-Kote Flex ST.
- Low cost – Cem-Kote Flex ST is considerably less expensive – only 25% of the average applied cost of polymer coatings, mainly due to the application reasons explained above.