Resin-bonded Information – How to mix resins & apply

Types of resin

There are two principal types of resin for bonding and bound these are Aromatic Resin and Aliphatic Resin with differing properties and uses.

• Aromatic resin is a non UV stable polyurethane resin used in both resin bound and bonded applications and will be affected by sunlight in that it will     change colour to a darker shade and is generally used for darker aggregates or non decorative applications. This resin is less expensive than the Aliphatic uv stable resin.
• Aliphatic resin is a UV stable clear polyurethane resin for all applications and is not affected by the sunlight keeping its appearance and showing the     aggregates to their best effect. Although more expensive it will not fade and can be refreshed with a clear coat of resin at any time.

Mixing of resins

The resin and hardner are mixed using a drill paddle mixer for several minuites to ensure everything is combined, if an accelerator is required in colder temperatures below 15 degrees and if there is a chance of dew or light rain overnight its added now. The mixed resin is poured into the mixer containing the aggregates, this should also be mixed for about 5 minuites to ensure products are fully coated but also that the dispersion of resin is even as poor mixes will leave areas weak or resin rich where the resin is too heavy filling all the voids between the stones creating a shiny patch.

Resin-bound application

With resin bound the mixed resin and hardner are added to the aggregate in a mixer and mixed for 5 minutes until the resin and aggregate are fully blended. This is then transferred to wheelbarrow to where it is needed, at this point it is very important to trowel out evenly and consistently going from mix to mixbefore it sets. Setting in hot weather can be a matter of minutes and any moisture or rainfall must be avoided until the resin has fully cured, moisture will lead to foaming or cracking of the bound layer.

Resin quantities to aggregate vary but as a general rule 7-15% resin by weight depending on the stone size, depth of layer and strength required. A blend of stone sizes 2-5mm and 1-3mm will give a terrific increase in strength or allow a lower resin ratio but is not as open as just using a 2-5mm stone and customers often prefer a more gravel like appearance. However a through blended mix filling the cavities will produce a longer lasting stronger surface and cheaper than increasing the resin content to get the same effect.

For a non slip surface two things can be done, introduce a small bag of C52 sand into the mix to give a gritty finish to the resin or broadcast some C52 sand onto the surface before it sets completely.

Thickness of resin aggregate systems vary depending on strength of resin mix and levels of traffic but as a rough guide 3mm stone-12-20mm thick, 2-5mm stone 16-26mm thick and 10mm stone 22-24mm. Tree pit applications are generally 40- 50mm thick with a loose collar of 50mm around the tree trunk.

Resin-bonded application

With resin bonded, the mixed resin and hardner should be poured in a series of lines and then spread and regulated over the area using a serrated squeegee. After leaving around 10 minutes to allow the resin to self-level the aggregate should be broadcasted onto the surface ensuring that the resin is completely covered.

Do not walk on the aggregate or resin whilst broadcasting. Any masking tape should be removed after the aggregate has been broadcast. The aggregate will settle on the surface but keep an eye out for any resin rich areas and ensure sufficient aggregate is applied to them to keep the surface appearance consistent. If adjoining areas are to be treated leave a wet edge (sometimes referred to as a hot line) and start the application for this area as the previously laid area is setting trying to keep the run going until the full area is completed. If large areas are to be covered careful planning is required to ensure a suitable finishing or day joint can be formed. A suitable point might be a drainage grid line or kerb.

It is important to keep the trowelling out process going without stoppages toeffect a uniform finish up to the stop joint. In very hot conditions you may onlyhave 8-10 minutes and if too hot can crack and expand so retarders are used. In very cold conditions accelerators are used to prevent overnight dew affecting the finish.

NEXT PAGE >