What purpose do epoxy resins fulfil in the construction industry and what should be taken into account in the mixing process?
Content
Areas of application of epoxy resins on buildings
Epoxy resins, or reaction resins, are used in many building trades. They are mostly used wherever the mechanical or chemical resistance of components and surfaces is important. In everyday life, epoxy resin applications are often encountered within surface protection as coatings, e.g. in car parks. EP resins are also frequently used in classic concrete refurbishment, for filling cracks or reprofiling components.In addition, building chemical products such as reaction resin adhesives for tiles or screed products also contain components of epoxy resins in order to achieve greater adhesion or flexibility.
Epoxy resin mortars are favoured in various areas due to their excellent properties. Here are some of the most common applications:
- Industrial floors: Due to their high chemical resistance and mechanical strength, epoxy resin mortars are ideal for industrial floors that are exposed to heavy loads.
Epoxy resin is also an ideal building material for basement floors and cellars due to its resistance to moisture.
- Repair of concrete: Epoxy resin mortars are ideal for repairing and renovating damaged concrete components, as they provide strong adhesion, fast curing and a virtually shrinkage-free result. EP mortar offers high temperature resistance and is frost-proof even in frosty conditions, i.e. up to certain limits. Thanks to its excellent adhesion, the mortar is ideal for exterior renovation work where the floor is exposed to extreme temperature differences.
- Grout: Epoxy resin mortars are used as grout in areas that are exposed to high levels of stress, such as laboratories, commercial kitchens, swimming pools or industrial facilities. In addition to its high resistance to chemicals, temperature fluctuations and moisture, the material is also characterised by high resilience and high impermeability.
- EP coatings: They serve as surface protection, particularly in the case of mechanical and chemical influences such as in car parks, shopping centres, and production or logistics areas. The addition of colour pigments or binding materials also opens up a wide range of design options.
- Adhesives: Due to their strong adhesive properties, they are also used as adhesives in the construction industry.
- Decorative applications: In living areas, they are also used for decorative floor coverings, as they are available in various colours and surface textures. Epoxy resin coatings are also frequently used for garages, as they are easy to clean.
What are epoxy resins made of?
Epoxy resin mortar consists of several components:
- Epoxy resin: This is the binder that holds the other components together. It consists of epoxy resin and a hardener, which together undergo a chemical reaction to harden the material (polymerisation).
- Hardener: The hardener is the necessary component for the epoxy resin to react and cure. The hardener must be added to the resin in a specified weight ratio.
- Fillers: These are added to give the mortar certain mechanical properties, such as construction height or resistance. Frequently used fillers are quartz sand, limestone powder or other mineral substances.
- Additives: These can be added to improve certain properties of the mortar, such as flowability, adhesion or resistance to chemicals.
Mixing 2-component floor coating with double-spindle mixer
Premixing the resin/hardener components in the delivery container
Epoxy resin with gravel aggregate as levelling mortar
Processing epoxy resin and what needs to be considered:
The material costs for epoxy resin-based building materials are not insignificant. For this reason, thorough preparation of the project is essential. Work with reaction resins, especially on a large scale, should generally be carried out by professional applicators.
Preparation of the substrate:
The surface to be treated must be dry and clean. Concrete surfaces, in particular, often have to be mechanically prepared by sandblasting or milling and then cleaned to ensure that they are free of dust. Other factors to consider and check are the room temperature and humidity; discuss these with your material supplier.
Which work equipment is used:
- Electronic scales with digital display - if component A and B need to be weighed; in most cases, the two components are already supplied in the correct ratio in separate containers to avoid dosing errors.
- Several sufficiently large, clean mixing buckets - if the material cannot be mixed in the delivery container
- Electric mixer and the appropriate paddle, automatic mixer for larger quantities if necessary
- Trowel, spatula, roller, brush for applying the material;
- Nail shoes to be able to step into the fresh coating
- Spiked roller for compacting and deaerating coatings
- Protective equipment: Always wear gloves and safety goggles to avoid skin contact with the resin. A respirator mask is also recommended for larger quantities.
- Suitable cleaning agent, brushes and paintbrushes for cleaning the tools
Fundamental points to note:
- Mixing epoxy resin with hardener: Before mixing the epoxy resin and sand mixture, the liquid resin must be correctly combined with the hardener. The correct mixing ratio is specified by the manufacturer (e.g. 2:1 or 3:1). Precise weighing is necessary, as too much hardener accelerates the curing process, while too little can lead to a sticky and unstable surface.
- Combination container: Many manufacturers offer epoxy resin and hardener in pre-packaged containers in order to mix the epoxy resin correctly and avoid dosing errors.
- Pot life and processing: After mixing the epoxy resin, the curing process begins. Pot life describes the period of time during which the mixed material can still be processed before it begins to cure. This varies depending on the temperature - at higher temperatures the processing time is considerably shorter.
Mixing:
As a rule, component A (resin) and component (B) are premixed first. The synthetic resin is usually liquid and sticky in its delivery form. The two components should be thoroughly homogenised by premixing. Stir the liquid resin mixture with a slow-running mixer (~300 revolutions) and a paddle that draws little air into the mixture. After premixing, pour the resin mixture into another container (repotting) and mix again. This prevents unmixed components from remaining at the bottom of the container or in the corners, for example.
Depending on the intended use, add the aggregate to the resin mixture and mix thoroughly again.
Pot life: Pot life, also known as processing time or open time, is the period during which a reactive resin can still be processed after mixing the components before it begins to cure. During this time, the resin remains liquid and can be applied or moulded. Pot life is an important factor in the processing of reaction resins and can vary depending on the type of resin, the ambient temperature and the amount of material mixed.
Processing:
If you are processing a coating, transport the finished mixture using a transport device. This will protect your back. Pour out the material, spread it with the smoothing rake and then compact it with the spiked roller. It is important that the material is always worked in fresh on fresh, otherwise undesirable bumps will occur in the surface.
Mortar is usually applied with a suitable trowel. If necessary, you must first prime the surfaces to be treated with a primer.
Curing:
Allow the epoxy resin to cure completely in accordance with the manufacturer's instructions. Depending on the material and external influences, this can take a different amount of time.
Important: the correct speed of the paddle counteracts air bubbles
The paddle is fully immersed, creating fewer air pockets
Avoid faults in the production of epoxy resin mixtures
Inadequate substrate preparation:
The surface is not clean, free of dust or grease and impairs the adhesion of the material.
Dosing error:
Incorrect mixing ratio of resin and hardener. Too little hardener leads to a sticky surface and does not cure. Too much hardener leads to too fast a reaction and the mixture becomes hard during processing. If you measure the two components yourself, be sure to use a digital precision scale and follow the material manufacturer's instructions exactly.
To prevent these errors, the building chemicals are supplied in the correct ratio of pre-packed components.
Incorrect mixing:
Insufficient mixing or insufficient mixing time results in uneven mixing of the ingredients. As a rule, it must be mixed for 3 minutes at low speed and the correct paddle must be used.
Air bubbles in the mixture:
Particularly unfavourable for coatings. The mixing speed was too high or the wrong paddle was used.
Room temperature too low:
Curing is delayed, the surface remains sticky. Ensure that the room temperature is within the prescribed range before starting. Ideally, the ambient temperature during the application of epoxy resin should be between 16 and 20°C. At temperatures below 15°C, the curing time is extended, while it is significantly reduced at temperatures above 25°C.
Application methods for epoxy resins
The right mixing technology for epoxy resin-bonded material
A decisive factor in the processing of epoxy resin is the correct mixing technology. The choice of the right mixer depends on the total quantity, the size of the delivery container and the consistency of the ready-mixed material.
Recommended mixers for mixing epoxy resin mortar
- Double-spindle mixers: These hand-held forced-action mixers, such as the Xo 33 R duo or Xo 55 R duo, are ideal for mixing an epoxy resin-sand mixture evenly and quickly. They ensure intensive mixing in a short time, so that the aggregate is completely wetted. At the same time, the counter-rotation of the mixing tools prevents the forces from the material from acting on the operator. This makes it easier to mix even heavy mixes.
- Basket paddle and disc paddle: Premixing the thin epoxy resin and its hardener is the first step. Depending on the quantity and delivery container, an electronic mixer, e.g. XQ1 or XQ4, is used. To do this, use a stirring rod that draws as little air as possible into the mixture(type KR or AR). For even smaller containers (up to 5 litres), you can also use a drill or a cordless screwdriver as a drive. Depending on the chemical composition of the resin, it can also be thicker in consistency, or colour pigments can be added for a surface coating, for example. A stirring rod that moves the mixture from top to bottom is also suitable for this. The LX paddle type is ideal for this. It must always be ensured that the paddle is completely immersed in the material during mixing.
Mixing technology for larger projects
Automatic mixers: If mortar or coatings have to be mixed on a large scale, the use of suitable machine technology is advisable, if only in terms of pot life. This ensures that sufficient fresh material can be processed constantly, that the mixing process is carried out according to consistent parameters and that the physical strain on employees is minimised. The processing procedure is also accelerated by the machine technology. There are no waiting times or fewer staff can be deployed.
Factors that influence the choice of machine can be: The composition and aggregate of the material mixture, the resulting toughness of the material and the respective quantity per mixture. How is the material transported to the construction site and how long is the transport route from the mixing site to the processing area? How well can the machine and the tool be cleaned from the material?
Mixing machines with interchangeable plastic buckets have proven their worth when processing reaction resins. As soon as the buckets are no longer usable due to hardened resin and corresponding use, they can simply be replaced. This is cheaper than cleaning metal mixing drums by hand.
For a synthetic resin screed with gravel aggregate, a classic forced-action pan mixer is often sufficient, as only the aggregate needs to be wetted with the resin. Surface coatings, grout mortar or renovation mortar should ideally be mixed using a forced-action mixer with planetary gearbox. These work through the components intensively and quickly, while an additional edge scraper prevents material deposits on the edge. It is also advantageous to monitor the mixing process using a timer.
What matters here is an exact and repeatable mixture.
Pre-mixed epoxy resin is added to the quartz sand to produce a grout mortar for void-free casting under concrete components. The Collomatic XM2-650 forced-action mixer is used for mixing, with two rotating mixing tools and edge scrapers for a residue-free mixing result. A timer-monitored mixing process ensures the repeatability of the mixes and thus a consistent quality of the material.
CONCLUSIONS: Mixing epoxy resin mortar
With the right preparation and the right mixing technology, you can easily produce epoxy resin mortar yourself. Be sure to observe the material manufacturer's instructions regarding the mixing ratio and processing. Whether for concrete repairs, heavy-duty flooring or other applications, a correctly manufactured epoxy resin mortar offers a durable and resistant solution. Before using epoxy resin mortars, make sure that the substrate to be treated meets the specifications (dryness, surface condition, temperature, etc ...).
Products used
Xo 55 R duo
XQ4
XQ1
TMX 1000
Mixing buckets
Bucket Dolly
