Лако-красочные материалы — производство

Some of the earliest major applications of adhesives in civil engineering involved the use of resins for abrasion resistant and non-slip surfaces to heavy duty floors and roads. This was achieved by the use of synthetic anti-skid grits, such as calcined bauxite, set in a resin base. Both epoxy and polyester resins have been used, applied either by trowel or in slurry form by squeegee. Trowelled systems are usually heavily filled mortars with an aggregate:resin ratio of the order of 6 : 1 and as such usually require a priming

coat on both steel and concrete surfaces. In contrast resin-rich slurry systems are self-wetting on steel surfaces but may require a primer when applied to concrete. Like mortars they can be gritted after application but the grit must only partially sink into the slurry to give an appropriate degree of embedment for both adhesion and skid resistance.

The initial interest in improving skid resistance stems from the fact that a high proportion of road accidents involving casualties occur within a short distance of road junctions and pedestrian crossings(2). Many of the road surfaces at such locations have poor skid resistance and this led the Transport and Road Research Laboratory to conduct trials into methods of resurfacing which did not eventually polish under traffic(3). Small-scale trials were initiated in London in 1966 using epoxy based adhesives and these were so promising that the then Greater London Council gave the go ahead for full-scale trials at seven major road junctions the following year. The success of these trials has since led to the development of proprietary systems for treating asphaltic road surfaces which are accompanied by automated metering, mixing and application systems capable of applying the epoxy at a rate of up to 80 m2 per minute(4).

Resin-based surfacings have also played a part in temporary structures and some interesting trials were carried out in 1970 on a flyover in East London(l). The structure had a precast concrete deck and a number of steel removable panels in the approach ramp carriageways. About twenty different surfacing systems were applied to the panels, including polymer cement, polyurethane, polyester and epoxy resins. Ten years later three of the epoxy systems and one polymer cement material were still found to be in good condition. However, the repair of failed panels in the intervening period created problems due to weather conditions and short overnight closure periods. This precluded epoxy systems and a polyester resin mortar was used. In service the polyester was found to be less wear resistant than the more successful epoxy compounds and after 12 months trafficking it would lose grit and polish.

On steel surfaces solvent degreasing and gritblasting is rec­ommended as the surface preparation method, although where this has to be done in the factory prior to delivery, application of an anti-corrosion priming layer is often specified. A primer which is compatible with the surfacing formulation must be used but, even when applied correctly, there is usually some reduction in bond strength. If a primer is used it is recommended that all solvents be allowed to evaporate prior to application of the resin itself. On concrete surfaces, where all laitance must be removed and the surface be sound, dry and free from oil, grease and dust, a wetting coat of unfilled binder may be necessary immediately prior to final surfacing. Such principles are no different from those described in earlier chapters for efficient bonding to steel and concrete substrates in other applications.

Nowadays resin bonded anti-slip surfaces are a common feature of many pedestrian walkways including footbridges. Given appropriate substrate preparation and careful selection of the adhesive they can prove to be a lightweight, durable and effective surfacing method.