Article written by Nelson Birch
Laying Resin Bound Aggregate in High Temperatures: Top Tips
Resin bound aggregate cures through a combination of heat and moisture. The polyurethane binder needs warmth and a small amount of moisture to start the cross-linking process, turning the resin from a liquid into a solid.
This is why resin cures much faster during the summer than in winter.
In colder weather, the curing process can be accelerated by adding a catalyst. In fact, most manufacturers already include a set amount of catalyst in the resin’s base component, with some adjusting the dosage depending on the season. This is why you may see summer-grade and winter-grade resin kits.
While adding catalyst to speed up curing in winter is common practice, slowing the cure during extremely hot weather is much more difficult. At present, there are no commercially available retarders for resin bound systems, so successful installation relies on good planning, experience, and efficiency.
Tip 1 – Start Early
Starting work early in the morning is one of the best ways to avoid problems.
By laying the material before the hottest part of the day, you can work using your normal routines and minimise mistakes caused by the resin curing too quickly.
Tip 2 – Measure the Slab Temperature, Not the Air Temperature
Never rely solely on the weather forecast.
The temperature of the base you’re laying onto can be significantly higher than the surrounding air temperature. Depending on the material, the slab can be 15°C or more hotter, dramatically reducing pot life and working time.
Open-graded asphalt usually reaches the highest temperatures because its dark colour absorbs and radiates heat far more than lighter coloured bases such as permeable concrete.
Every contractor should carry an infrared temperature gun and regularly check the base throughout the installation so the laying method can be adjusted if necessary.
Tip 3 – Shade is Your Friend
Shade can make a huge difference.
Keep the mixing station under a canopy whenever possible.
Cover pallets of aggregate to keep them cool.
Store resin kits out of direct sunlight.
Cooler materials provide longer pot life and more working time.
If natural shade moves across the site during the day, plan the installation to take advantage of it. Some contractors also cover the base with a light-coloured tarpaulin or membrane and gradually remove it as they progress, helping prevent the surface from overheating.
Tip 4 – All Hands on Deck
Having enough people on site is a major advantage during hot weather.
More installers mean:
Faster laying.
Less fatigue.
Fewer mistakes.
Time for staff to take short hydration breaks while work continues safely.
Resin bound installations are continuous pours, so maintaining momentum is essential.
Tip 5 – Keep the Wet Edge Short
The wet edge is the active edge where the next mix joins the previous one.
If this edge begins to cure before the next batch is laid, blending becomes difficult and can spoil the finished appearance.
Plan the installation route carefully to keep the wet edge as short as possible.
On larger projects, incorporating borders, patterns or separate zones can divide the work into smaller, more manageable sections.
Tip 6 – Be Realistic
If extreme temperatures are forecast, postponing the installation may be the best decision.
Smaller projects of around 60m² can often still be completed successfully by experienced installers. However, large areas of 200m² or more require careful consideration of both working conditions and the capability of the installation team.
Never compromise health, safety or quality simply to stay on schedule.
Tip 7 – Follow the Manufacturer’s Guidelines
Always follow the installation instructions supplied with your chosen resin system.
These will specify the minimum and maximum installation temperatures. Working outside these limits will usually invalidate any warranty, leaving the contractor responsible for any failures.
High temperatures affect more than curing speed—they also reduce the resin’s viscosity.
As the resin gets hotter it becomes thinner, increasing the risk of resin run-through, where resin drains away from the surface and pools at the bottom of the layer.
This creates two serious problems:
The surface is left with insufficient resin to fully bind the aggregate, increasing the risk of ravelling.
The pooled resin can seal the base beneath the surface, reducing permeability.
Advanced Tip
Many experienced contractors use uncatalysed resin and add catalyst on site.
This allows the catalyst level to be adjusted throughout the day to maintain a consistent working time.
For example, 2ml of catalyst at 9:00am may need to be reduced to 1ml by 11:00am as the base temperature increases.
This method requires constant temperature monitoring and careful control of every batch.
However, it carries significant risk. If the catalyst is accidentally omitted from a mix, that batch will not cure. The laying crew may not notice until the following day, by which time the surrounding area has already hardened.
This mistake has ruined many installations and resulted in substantial costs, so it is not recommended for inexperienced contractors.
In Summary
When installing resin bound aggregate in hot weather:
- Start early.
- Work efficiently.
- Use shade wherever possible.
- Ensure you have enough staff.
- Use the correct seasonal grade of resin.
Be realistic about what can be achieved safely.
Good planning and preparation are the keys to producing a successful, high-quality resin bound installation.
