Construction adhesives used for structural and non-structural bonding are growing in importance in keeping with new developments in the construction industry.
From bonding insulation boards, wooden laths and plaster to structural reinforcement and bonding façade items, construction adhesives are suitable for a wide range of applications
A huge advantage of construction adhesives over traditional methods of bonding using nails or screws is uniform stress distribution over a larger bonding area and a more aesthetic look.
Structural and Non-Structural Bonding
Before examining the right procedure to apply construction adhesives it is important to understand the different types of bonding using construction adhesives. The two types of bonding are structural and non-structural bonding.
Structural bonding mainly involves structural reinforcement such as the strengthening of pillars and concrete beams, rebar bonding and facade panel bonding.
Adhesive applications usually require engineered bonding solutions involving design calculations, testing and accurate application procedures.
Non-structural bonding on the other hand, involves a more generic application of adhesives.
Aside from some general guidance on procedures to be followed, there are no restrictive measures in the application of adhesives.
Examples of non-structural bonding applications are:
- Bonding gypsum boards to timber battens,
- Waterproofing involving bonding of membranes to concrete,
- Insulation, for example, bonding EPS boards in position
- Installations such as tiling, floor finishes and electrical fittings including switches and lamps
- Decorative fixtures, fittings and finishes
Rigid versus Elastic Bonding
There are generally two types of bonding – rigid and elastic bonding.
Rigid bonding is a traditional method where the adhesive is applied on both surfaces to be bonded.
The surfaces are then pressed together and are strongly bonded after some time. Rigid bonding is most appropriate for bonding similar materials. The adhesives can be solvent, water based or epoxy adhesives.
A more advanced method is elastic bonding where the adhesive is applied in dots or beads on the surfaces. These surfaces are gently pressed together to leave a thick layer of adhesive between objects. The adhesive acts as an intermediate material between the two surfaces to accommodate movement and stress.
After several hours to a few days, the thick layers get cured causing the objects to join elastically.
Application of Construction Adhesives
The best method of applying adhesives is dependent on the type of adhesive used.
Water-borne adhesives harden upon loss of water. To accommodate this, apply dots evenly on one of the surfaces and firmly press both surfaces together to form a uniform film spread over the entire surface. The layer of adhesive should be thin because water loss causes the adhesive to shrink and therefore applying a thick film will not work.
Solvent borne adhesives tend to harden due to solvent loss. Unlike water-borne adhesives that require at least one of the surfaces to take up water, solvent-borne adhesives are suitable for use on non-porous surfaces.
To allow the solvent to evaporate, the surfaces should be taken apart for a short time after they have been initially joined and then re-joined. Just like water-borne adhesives, solvent-borne adhesives can work only with thin films.
Reactive adhesives are cured by the process of polymerisation. Polymerisation is driven by moisture from the air and surfaces being bound and reactive adhesives should be applied as dots or vertical stripes.
Full surface coverage should be avoided in order to allow the adhesive to be completely moisturised. Good quality reactive adhesives don’t shrink and can be pressed to films with a thickness of 1-3 mm.
It is recommended to apply dots or vertical stripes, especially in outdoor applications to avoid accumulation of water between the adhesive layer’s bond interfaces. Water accumulation can have a detrimental effect on adhesion.
Once the surfaces have been joined together, there is still a small window of time room for them to be slightly repositioned.
During the curing or hardening of traditional adhesives the surfaces often need to be temporarily fixed mechanically. Modern construction adhesives can overcome this requirement as they are able to hold the object which is being bonded in place, even when it is in the uncured state.
If you are unsure about the correct procedure for applying adhesives for your construction project or which adhesive you should choose, we have the expertise and range of products to help.
Call us on 07 3266 8699 or CLICK HERE to contact for more help or guidance.