Resin Bonded Driveways

This type of application refers to process of scattering loose dried aggregates onto a coating of resin after the resin has been applied to the surface. It is often referred to as a scatter coat, broad cast or coat system. This method involves applying the resin over a suitable base using a squeegee, and then 'scattering' the chosen gravel or aggregate over the tacky resin before it sets. Some systems use pre-coated aggregates, while others rely on applying a resin over the scattered stone to seal the system.

Often referred to as hand trowelled this system sees the aggregate blended within the resin prior to application and is trowelled to a smooth level finish. Design elements such as logos or numbers can be incorporated into the finished area by using contrasting stone colours to create the desired finish. This method relies on the aggregate and the resin being agitated together in mixer, and then spread over the prepared base with hand floats, screeding bars and trowels. This type of application generally ensures an adequate thickness is applied to the entire area and is a fairly common method of application.

The above systems ensure that the resin sets relatively quickly in most cases within 60 minutes. This means that the resin and aggregate need to be applied correctly with smoothing out and levelling carried out prior to the resin setting and becoming too stiff to manipulate. Given the makeup of resin and the dried aggregates used manufactures guides to moisture and temperature must be adhered to or the product could be damaged and discoloured during the laying process.

What are Permeable Systems?

Various Resin Bonded systems are designed and manufactured to allow them to be permeable. This allows the system to be used in applications such as tree pits and permits the system to be used in accordance with the SUDS building regulations. For more information about SUDS go to www.environment-agency.co.uk and click on Business Sectors / Construction

Can the system be laid in any weather?

If there is a possibility of rain or damp the products should not be laid. Variations in temperature and humidity can affect the application process. Most manufactures give guidelines as to what conditions their products can be layed. If there is a possibility of rain with 24 hours of the systems application it would be advisable to protect the resin by covering it up to prevent water reacting with the uncured resin. Differences in temperature and humidity will affect the amount of time taken for the resin to cure.

Who can apply the systems?

Although not beyond the skilled DIY’er this type of surface should be laid by experienced specialist contractors. All tools and mixers should be cleaned with a solvent type cleaner in line with the manufactures instructions. Full safety clothing and equipment should be used at all times during the manufacturing process and this should include masks or respirators when working with solvents or epoxy based products.

How much Aggregate will I need?

This depends on the type of system used and the level that it is laid.
In a resin bonded system laid at approximately 15mm around 25kg of aggregate per square meter is required. This would increase if the resin was laid at a thicker level.
On a Resin Bonded application a typical scheme would use between 8 and 10kg per square meter.

How is the resin laid?

The resins usually consist of two parts with the resin that requires mixing with an activator fluid on site using a mixer. The two parts should be mixed together thoroughly for around 2-3 minutes until the resin becomes homogenous, usually using a drill and paddle mix attachment. In the case of resin bonded the mixture should be poured in a series of lines and the 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.

Resin bonded aggregates are usually mixed in a rotary paddle type mixer with the two part resin mixed with measured amounts of aggregates to ensure each mix is identical. Manufactures usually pack their products so that a certain square meterage is achieved when mixed with a measured weight of aggregate. Once mixed the blend can be poured onto the pre-prepared base and is trowelled out to form a smooth even surface. The surface should not be walked on until the resin has set and care should be taken to ensure that no contaminates can adhere to the newly laid surface.

Can the surface be cleaned?

One of the beauties of resin based surfaces is the extremely low maintenance properties. Always follow the instructions given by the resin manufacturer. A gentle power wash is usually all that is required to clean the surface.

What colours are available?

With over 50 different aggregates available virtually any colour scheme can be catered for. Careful on site blending of different colours can create a unique range of colours. A number of aggregates can also be coloured to allow customers or clients to select standard finishes any colour that they wish. It should be remembered that aggregates that are resin bonded will change the appearance of the aggregate creating a darker ‘wet’ look for the stone.

How do I deal with items such as manhole covers?

Manhole or access covers such as stop tap boxes or cable ducting will need to be left 'proud' of the base course layer. Where a new base layer has been laid, this is easily done as part of those works. When an existing surface is to be overlaid, it will be necessary to 'lift' the covers, by breaking them out and re-seating them to an elevated level roughly 10mm or so above the base layer. On schemes were this is necessary this should be done at least 24 hours before the resin-bonded surfacing is laid to make sure adequate time is allowed for any bedding mortars or patch repairs to cure/harden.

How thick is the resin bonded surface required to be?

This will vary depending on how smooth and level the original base is that the products are to be applied to. On average the thickness is 15mm and should not be less than 12mm and could go up to 30mm or more if the base is uneven. Remember the thicker the laying thickness the more resin and aggregate required and this will increase the cost of the application.

How much does it cost?

The price per square metre will vary depending on the system and areas to be covered. Many contractors have a minimum rate or size so this is worth checking out. If you are obtaining a price for this type of surfacing, make sure the contractor stipulates what is and what isn't included in the price. The resin based surfacing itself can costs on average, between £60 and £80 per square metre. This figure will be based on the size of the area to be covered and the type of aggregate chosen along with the thickness of application. Construction of a suitable base is not included, nor is preparation of an existing base. The type of resin used will affect the cost with the better systems using better quality resin that is UV stable and will resist the changes in resin colour that can occur when subjected to sunlight.

What sort of base should I be putting the resin system onto?

Resin Bonded systems both require an existing or new sub base to which the resin system is to be applied. A typical existing or newly laid base or substrate can be an existing surface of tarmac, asphalt, concrete or other monolithic material that has been cleaned and prepared. The existing surface should be in good condition as any system applied is dependent on the soundness of the area that it is applied to.

It is important that the surface is cleaned properly with all loose materials and dust removed and sealed if necessary. Any contaminates such as oil or traffic film will require removal with a suitable de-greaser to ensure the resin can bond fully to the base. Fully remove any Algae or fungal that may be present. Any damaged areas or cracks will require treatment and repair prior to the application of the resin. Attention to how level the surface is that the resin will applied is important. If the level varies then more resin and aggregate will be required to create a level surface. This can raise the cost of the scheme given that more materials are required and care will be needed at the estimation stage.

The base should be suitable for the loads it’s expected to carry once the resin system is applied. There is no preferred base as this can vary depending on the system used and advice from the resin supplier should be sought prior to application. Surfaces that have fewer joints and are predominately large slab areas such as Tarmac or concrete should provide the best finish.

Bases that are made up of paving type products such as block paving, sets or flags ect. are NOT suitable for use as the base for a resin-based system. The amount of cracks or lines below the surface of any resin applied to a paved surface would ultimately lead to cracks in the resin and failure of the system due to the extreme pressure loaded onto the resin during day to day usage. Any new surface should be allowed to cure properly prior to the application of resin systems.

In the case of bitumen surfaces a minimum of 28 days should be given to allow it to weather and oxidize. For concrete at least 7 days should be given to allow it to cure properly. With any base it is important that the moisture levels surface meets an acceptable level as recommended by the resin manufacturer. In all cases, the manufacturer's advice and recommendations should be followed regarding preparation, pre-cleaning, etching or whatever is required. A primer should be used on surfaces that may be absorbent. Any areas that are close by or edges should be masked off with a suitable tape. This tape should be removed before the resin is fully set as if left too late a clean straight edge would be difficult to achieve. Ensure there is sufficient fall on the area to allow drainage.

Tree Pits

Despite claims by some manufactures that wood decking, paving flags or block paving may be suitable general opinion within the trade suggests this is not the case. Whilst decking could possibly be coated on an internal application but the poor stability of timber will ultimately lead to cracking in the resin. If a wooden base is to be used, only a proper exterior grade wooden deck surface should ever be considered.

With the exception of applications such as tree pits resin-based surfacing cannot usually be laid on a granular sub-base, such as a layer of Type 1, gravel or sand, no matter how well compacted. Damp striking up through the base could affect the resin and if there is high moisture content in the base it can seep into the resin with adverse affects such as clouding of the resin.

What can go wrong?

When applied correctly aggregate bonded paving systems give a long lasting attractive finish that requires little to no maintenance. It cannot be stressed enough that the bond between the resin and the base it is applied to is critical. The need to select a reputable approved contractor can eliminate most of the issues associated with this type of finish. Problems such as the top surface detaching itself from the sub base are usually caused by frost or moisture as the surface has not been sealed correctly and the base it was applied to was unsuitable. Repairs to this type of system as with tarmac or concrete cannot be done invisibly and would require a patch cutting out and resurfacing that given ageing of the original product and colour variations of stone would be impossible to hide.

It is important to ensure that all of the mixes used on site are equal. All products should be weighed on site using scales to ensure the same mix is used at all times. As with all natural products the stone should be blended through and mixed to provide a consistent colour as this can vary from batch to batch due to aggregate being naturally coloured.

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