Many types of surface treatment systems are available for the treatment of horizontal surface such as roofs and vertical surfaces for instance wall buildings constructed from various construction materials such brick, stone, concrete, tarmac and slate.
Penetrating sealers, surface-applied corrosion inhibitors, surface sealers, high coating, membranes, and overlays are the major types of surface treatment type. The surface treatments must be applied to a clean, dry, and sound substrate at moderate temperature and humidity conditions in a well-ventilated space.
A relatively smooth surface is needed for liquid-applied membranes. All concrete repairs should be completed and allowed to cure before applying most of the surface treatments.
The curing time is usually 28 days but varies with the repair material. Details of expansion and control joints, door and window openings, drains, and curbs must be reviewed and installed properly.
Purpose of Surface Treatment
The purpose of surface treatment application is to improve surface aesthetics, repair, protect, and consequently increase service/ wear life of various surfaces.
This can be done by restricting corrosion which can be achieved through reducing the existing moisture level in the concrete and preventing further ingress of moisture and chlorides.
Types of Surface Treatment Systems
1. Penetrating sealers
Penetrating sealers are materials that are generally absorbed within the repaired concrete. The depth of penetration varies by the product, the size of the sealer molecule, and the size of the pore structure in the concrete. Deep penetration of sealers is usually not an important factor, but it is desirable for abrasion resistance of surfaces.
Penetrants do not have crack-bridging capabilities, but the hydrophobic properties imparted by some of these products may reduce the intrusion of moisture into narrow cracks.
The appearance of concrete surface is usually not affected by applying these sealers, only slight change in color may take place. The sealants do not usually hide the surface flaws.
1.1 Functions of Penetrating Sealer
Penetrating sealers are effective for protection in two ways:
- Water repellents
- Surface hardeners; ultra-violate, wear, and abrasion resistance are generally good when compared with coatings or membrane systems.
1.2 Types of Penetrating Sealers
Different types of penetrating sealers are presented below. Some of these products are solvent-based (that can cause air-pollution) and others are water-based:
- Boiled linseed oil, silanes
- Certain epoxies
- Magnesium and zinc fluorosilicates
- High molecular-weight methacrylates.
1.3 Tools for Applications
Different equipment can be used apply penetrating sealer to the concrete substrate and proper surface preparation is important for successful application:
2. Surface-applied Corrosion Inhibitors
Surface-applied corrosion inhibitors are designed to reduce the rate of corrosion. The effectiveness and life expectancy of these materials varies with the properties of the concrete, site conditions and type of inhibitor material.
3. Surface Sealers
Sealers and paints are applied on the surface of concrete where it adheres. The finished thickness may be 0.03 to 0.25 mm. Pigmented or naturally colored paints are used according to the requirements, while transparent paints result in a wet or glossy appearance.
Surface sealers do not have significant crack-bridging capabilities. The hydrophobic nature of some of these products may reduce the movement of moisture into narrow cracks and some of these products may fill dormant cracks, and are effective in filling (not bridging) small, nonmoving cracks.
3.1 Function of Surface Sealers
- Reduce the intrusion of water, chlorides, and mild chemicals.
- Decrease skid resistance
- They also may or may not permit the transmission of water vapor.
3.2 Types of Surface Sealers
Some of these products depend on solvents to work and may have problems with environmental quality. These products are affected by UV exposure and wear under surface abrasion:
- High molecular weight methacrylate(HMWM)
- Moisture-cured urethanes
- Acrylic resins
- Certain paints, whether oil-based or latex-based (such as styrenebutadiene, polyvinyl acetate, acrylic or blends of these with other polymers dispersed in water), can also be included if the resulting thickness of layer is less than 0.25 mm.
3.3 Tools for Applications
4. High-build Coatings
High-build coatings are materials with a dry thickness between 0.25 mm and 0.75 mm applied to the surface of the concrete. Breathability is often an important factor when selecting a protection material on exterior walls and slabs-on-ground. For exterior environments, the coating must be resistant to oxidation and UV and infrared radiation exposure.
On floors, resistance to abrasion and punctures and resistance to mild chemicals (salts, grease and oil, and detergents) are also important. The coating material must be durable and the bond between the coating and concrete substrate must be strong.
4.1 Functions of High-build Coating
- High-build coating is used for decorative or protective barrier systems.
- Improve abrasion and skid resistance.
- Reduce reinforcement corrosion in repair work.
- Suitable for use against rain, salts, and mild chemicals.
- High-build coatings alter the appearance of the surface and may be pigmented.
- Some high-build coatings result in a very slippery surface when wet and may not be suitable for pedestrian or vehicular traffic.
4.2 Types of High-build Coating
Epoxy resins are commonly used repair materials that generally have good bonding and durability characteristics and can be mixed with fine aggregates to improve abrasion and skid resistance.
Non-elastomeric high-build coatings generally do not bridge moving cracks, but are usually effective in filling small, nonmoving cracks. These products have better wear characteristics than thinner systems.
The base polymers of such products include acrylics, alkyds, styrene butadiene copolymers, vinyl esters, chlorinated rubbers, urethanes, silicones, polyesters, polyurethanes, polyurea, and epoxies. Some of these products are solvent-based and can have pollution problems.
4.3 Tools for Applications
Membrane systems are treatments with thicknesses between 0.7 mm and 6 mm applied to the surface of the concrete, significantly changing the appearance of the concrete surface.
They may be bonded, partially bonded, or unbonded to the concrete surface. Some systems require that cracks wider than 0.25 to 0.375 mm should be located and sealed before application of the membrane.
Preformed sheets are sealed at the edges to form a continuous waterproofing membrane. Most of these membranes are resistant to water absorption and bridge small (less than 0.25 mm) moving or nonmoving cracks.
Standardized tests must be conducted for permeability, elongation, tensile strength, tear strength, adhesion, modulus of elasticity, abrasion resistance, low temperature flexibility, and water vapor transmission.
5.1 Functions of Membranes
- Membranes are used as protective layer
- Bridge narrow, nonmoving cracks of various widths.
- Wearing course for traffic
- Damp-proofing systems
5.2 Composition of Membranes
Elastomeric membranes are usually gray or black, but some manufacturers offer several other colors.
Chemically these materials consist of urethanes, acrylics, epoxies, neoprene, cement, polymer concrete, and asphaltic products.
Membranes with a rigid urethane mortar or epoxy-mortar top coat offer reasonable skid and abrasion resistance under traffic.
5.3 Tools for Applications
Overlays are depositions of 6 mm or greater in thickness that can be bonded, partially bonded, or unbonded to the surface of the concrete. The details of the overlay materials and the placing methods are given earlier. The materials for the overlays may be Portland cement concrete, latex modified concrete, polymer concrete and silica-fume concrete, as described earlier.