Resin Bound Knowledge Base
Resin Bound Knowledge Base
Preparation - Surface Preparation
Whether StarScape ULTRA is to be laid on an existing base or a base installed specifically to accommodate the resin surface, there are several stages of base preparation that must be completed prior to the installation of the bound resin surface.
● Repairs – A resin bound surface must only be installed on a structurally sound base. Any form of surface dressing is only as good as the base on which it is applied. Cracks in the base suggest movement and this can result in reflective cracking of the resin surface. Any damaged areas should be removed by mechanical means to a minimum depth of 300mm. This should then be reinstated with either 150mm of DTp3 / Type 3 MOT with 150mm of concrete or 100mm of tarmacadam. In both cases the DTp3 / Type 3 MOT must be compacted to refusal. Cracks greater than 5mm wide but not exceeding 20mm wide can be filled with either concrete or an elastomeric crack repair product and covered with galvanised brick reinforcing mesh however, it should be noted that the reason for the cracking of the base may still be present (such as tree roots or broken drains) and could result in future problems if not rectified prior to the installation.
● Levelling and Edging – A resin bound surface should always be installed to a solid edge. Feathering or stepping the edge of the resin surface can result in the edge becoming damaged by traffic. The use of kerb or block stones that protrude 5mm higher than the minimum resin application depth is the recommended method of edging however the edging can be laid to protrude at the same minimum resin depth for a completely level finish. If the resin surface is working up to a non-permanent, existing edge such as a fence or raised paving then the edge can be masked using a biodegradable self-adhesive paper tape. This will prevent the resin from adhering to the fixed edge and becoming damaged if the fixed edge is moved or replaced.
● Drainage – If the application area has preinstalled manhole covers these should be replaced with recessed or inset trays. A recessed manhole cover can simply be filled with the resin bound screed to hide it or made into a design feature using a different approved aggregate blend. It is important to remember that utility companies will require access to the drains and failure to allow for this can result in the surface being removed and the installer being billed for this.
If drainage is required then this should be in the form of a high strength polymer, concrete drainage channel. Please consult the SUDS (Sustainable Urban Drainage Systems) section of the StarScape Specification document.
● Primers – As with the StarScape PRO resin bonded system, StarScape ULTRA does not typically require the application base to be primed. If the base is constructed from concrete and has smooth, float finish then it should be checked for dusting.
Older bases (over two years old) are less likely to dust or require a primer however this can be confirmed by simply rubbing your finger over a small area of the surface. If small sand particles are easily removed from the surface then the use of StarScape PRIME is advised. If the base is constructed from asphalt it should only be primed if there is any evidence of oils leeching from the surface. This is unlikely on asphalt surfaces over 12 months old however if the surface has an iridescent (coloured) appearance when wet then the use of StarScape PRIME is advised.
● Cleaning and Drying – Before any StarScape installation, the base must always be fully cleaned and dried. This should be done with a stiff sweeping brush and a high-pressure power wash. Ensure any loose material, organic material such as algae growth and chemicals such as oil and brake fluid are removed. The area should then be given a minimum of 24 hours to fully dry. If a heat gun is being used to speed up the drying time, care should be taken on asphalt surfaces as excessive heating can result in oils leeching from the surface.
A new asphalt (tarmacadam) base should be given a minimum of 7 days before the application of StarScape ULTRA:
It is desirable to keep the time between the tarmacadam/bitmac base being installed and the surface layer (such as resin bound) being applied to it as short as possible however, not allowing a sufficient cure time can result in a reduction in the strength of the resin bound surface or even a system failure. Strictly speaking, a bituminous surface relies on thermal transfer, oxidation and solvent evaporation rather than a specific chemical reaction cure although the time taken for a bituminous surface to become solid is still referred to as the ‘cure time’.
Although uncommon, tarmacadam surfaces can have problems with curing and this can result in the surface remaining soft or tacky for much longer than expected. The keys reasons for this can be the use of an unsuitable PEN value binder, the use of a poor-quality solvent or simply climatic conditions delaying the evaporation of the solvents. If the resin bound surface is applied prior to the base achieving full cure, any problems with the tarmacadam installation may not become apparent for weeks or even months after completion. If solvents within the base course have not sufficiently evaporated this can manifest itself by attacking the resin surface and is often mistaken as water damage due to the whitening effect it has on the bound surface.
Star Uretech recommend that a new tarmacadam/bitmac surface is given ten days (a minimum of seven days) to cure before a resin bound surface is installed. It can take up-to seven days for the majority of the system’s volatiles (solvents) to evaporate and a further four to twelve weeks for full oxidation to occur. After 10 days there will only be trace levels of volatiles remaining and any oils on the surface will have sufficiently oxidized making it suitable for a surface coat.
A resin bound surface laid on to a tarmacadam/bitmac base which has not been given seven days to cure may initially look unaffected however it can result in the underside of the bound surface becoming soft due to solvent egress, delamination due to oil contamination between the surfaces and whitening/breakdown of the resin throughout the matrix.
Any new concrete base must be given a minimum of 7 days before the application of StarScape ULTRA.
As with tarmacadam, it is desirable to keep the time between the concrete base being installed and the surface layer (such as resin bound) being applied to it as short as possible however, not allowing a sufficient cure time can result in system failure. Not unlike the resin used for a bound surface, concrete has different stages of curing. The types of concrete typically used for a domestic driveway will achieve approximately 50% of their strength after 24 hours. Between 80% and 90% of the concrete’s total strength is usually achieved after three days. After seven days the concrete should have cured to over 95% of its total strength with full strength/cure taking up to 12 months.
The reaction process that cures cement is called Hydration and this involves the cement reacting with water to form calcium silicate hydrate compounds. As the cement reaction is taking place the level of water left in the concrete is constantly reducing. If water is still present in the concrete when a resin bound surface is applied to it, the isocyanate (hardener) will begin to draw the remaining moisture out of the cement and use this as part of its own curing reaction. The overall strength of a resin bound surface applied to a three-day old concrete surface can be reduced by 20% when compared to a resin bound surface laid onto a seven-day old concrete surface.