Because it is durable, attractive, and requires little maintenance, architectural aluminium is widely used for window and door frames. However, unprotected aluminium reacts with cement-based materials, sometimes causing severe frame damage. This article explains how to construct safety walls using aluminum frames.
Aluminium primarily reacts with alkali hydroxides from cement in fresh concrete. The pH of fresh mortar ranges between 12 and 13. Significantly, aluminium can rust when it comes into contact with plain concrete. The situation is exacerbated if the concrete contains calcium chloride as an admixture.
Proper material selection and construction practices are essential for ensuring a high-quality installation of aluminium-framed windows and doors.
1. Materials
The American Architectural Manufacturers Association recommends only coated windows for installations involving any cement-based materials, including masonry. Coating materials can be organic (such as paint) or inorganic (such as anodized aluminium). However, organic-type coatings are currently the most popular architectural aluminium finishes. Additionally, the AAMA recommends high-performance coatings for aluminium framing that can withstand outdoor exposure for at least 20 years.
Some coatings, however, can only protect against a pH of about 11. Fresh mortar can stain these materials-coated frames, causing corrosion or other surface damage if left on the frame. Removing fresh mortar droppings from aluminium frames as soon as possible is advisable to avoid this.
Anodized finishes, for example, convert the outer layer of aluminium to aluminium oxide, resulting in a highly durable surface. A clear (organic) coating can help to protect the anodized surface even more. However, to avoid staining, you should remove alkaline building materials such as wet mortar, plaster, or concrete from anodized surfaces as soon as possible.
2. Construction
To protect aluminium, you should build masonry walls before inserting frames into the wall. This gives the mortar time to cure and dry, which reduces alkali movement. The frame is then screwed at the bottom, top, and sides.
Around the frame, it’s best to leave a 1/2-inch gap. This gap, when filled with caulk, separates the inside of the building from the outside. It also reduces wall stresses acting on the frame and creates a barrier between the mortar and the window/door frame material.
It would be best if you adequately protected aluminium from chemical attack with suitable coatings. In severe applications, two coats of bituminous paint or zinc chromate primer are frequently used to separate aluminium from cement-based products. Also another method for providing temporary protection to the finish during construction is to paint a light coating of petroleum jelly onto the surface of the frame.
Significantly, alkali exposure is reduced by anything that directs moisture away from the frame. As a result, separating the structure from direct contact with the mortar with a sheet material (flashing) can also help reduce corrosion.
Additionally, if the masonry wall is to be cleaned after construction, the aluminium should not be exposed to harsh chemicals and should be thoroughly rinsed. Clear water should remove any cleaning products used on the wall and any alkalies washed off the building’s face.
3. Protecting Aluminum Frames in Masonry Walls
- Thicker coatings are generally better.
- Choose coatings for resistance to high pH.
- Create a caulk gap between the frame and the masonry.
- Temporary coatings (paper, cloth, plastic film, or petroleum jelly) can protect construction.
- Organics are usually more resistant than non-organics.
- Place aluminium frames into walls after the mortar has cured.
- Remove fresh mortar from aluminium frames as soon as possible.
- With drips and flashings, direct water away from the wall.
4. Why Aluminium is Perfect for Doors and Windows
- Decorative: Aluminium can be decoratively anodized or powder coated to give it a smooth or textured finish. As a result, aluminium windows, doors, and curtain walling not only perform well but also look great. The aluminium is anodized by immersing it in an acid electrolyte bath and passing an electric current through it. This results in a decorative, long-lasting, corrosion-resistant aluminium oxide finish on the metal surface.
- Lightweight: Aluminium is a very light metal, weighing only 2.7 g/cm3, or roughly one-third the weight of steel or copper.
- Resistant to corrosion: When aluminium comes into contact with air, a protective layer of aluminium oxide forms on the surface almost immediately. This layer is resistant to corrosion from the elements, including acid rain, and will not be harmed by cleaning products.
- 100% Recyclable: When it comes to metal recycling, aluminium is unique. It is entirely recyclable, and the quality of recycled aluminium is identical to that of virgin aluminium.
- Easy to make into frames: Aluminium window frames are created through an extrusion process, forcing a pre-heated aluminium alloy through a die to form an aluminium profile. The frame is then constructed by joining these profiles together. The design of these profiles gives the window frames a distinct appearance.
- Won’t break: Aluminium is malleable as well as ductile. It can be bent, pressed, or drawn into a thin wire without losing its toughness, breaking, or cracking.
- Readily forms alloys: Aluminum is usually alloyed with other elements to improve its physical properties. For example, by adding manganese, pure commercial aluminium’s strength can be increased by 20%. Aluminium alloys easily with silicon, copper, zinc, iron, and magnesium. This means you can create various alloys with properties tailored to specific applications.
Bottomline
Assembling structures for the specific needs of an application is simplified with the correct aluminium framing system. You name it: interior design, wall and ceiling structures, houses, retail displays, assembly lines, workstations.
