The reasons why more and more people are choosing StoneSet Permeable Paving are well known:
- StoneSet is FLEXIBLE and therefore resists crack formation (even when laid over concrete)
- StoneSet is POROUS, allowing rain water to be collected or passed into the ground where it is needed, not down the drains
- StoneSet is ATTRACTIVE and is available in many natural colours that reflect the beautiful natural rocks available in Australia
- StoneSet is VERSATILE and can be laid in unlimited shapes, infinite shades and colours and in many applications
But for many applications StoneSet has another BIG advantage as it is very SLIP RESISTANT
It is worth taking a look at the factors that affect slipping and how StoneSet can satisfy our needs. The fact that paving needs to be long lasting, weather tolerant and attractive has resulted in a wide range of options including asphalt, concrete, loose rock or pebbles, cobblestone, concrete or clay bricks and pavers, natural stone pavers and even timber.
Many of these are prone to slipping, especially when wet. Some also polish as a result of the wearing action of foot traffic over a period of years as a walk through many towns and cities worldwide will demonstrate, especially if it has been raining. Clearly all parties want to avoid injury to people but options are limited.
Other factors that may influence a slip fall incident include type of footwear, speed and type of gait, use of walking aids, and lighting. (http://www.sliptesting.com.au)
It is a difficult area for council and public engineers as budgets are tight and yet in the claim culture world we live in there is the ever present threat of legal action if someone falls and breaks a bone, or worse. One thing we do know is that we cannot rely on the public (i.e. ourselves!) to wear good sensible shoes with grippy soles before venturing outdoors in inclement conditions.
Surfaces can be treated with anti-slip products which can be very effective but sometimes it is helpful to specify the paving product with a good eye on slip resistance as well as decorative effect, cost or availability.
So, what makes some paving systems more slippery than others?
A roughened surface will offer far more grip than if it is smooth.
Glazed tiles or bricks are likely to be very slippery compared with unglazed.
Choice of aggregates in asphalt, concrete, StoneSet etc will influence the end result
Cleanliness – a good clean surface will help in many situations especially where moss, lichen or other organic matter is prevalent.
Slip Resistance can be measured to help us select the most suitable type of surface. There are a number of tests that have been developed over the years but the most relevant and frequently used are the Ramp Test and the Pendulum Test.
The ramp test is just what it says and takes into account the slip characteristics of the surface product at different angles. It is a very good tool for ranking paving systems and researching alternatives but has the limitation of being a laboratory based test so it is not possible to test suspect surfaces in situ.
The Pendulum concept came originally from the USA and was further developed at the Road Research Laboratory in England in the 1960’s. The method was developed by Roger Hoskin who I worked with in the aggregates section of the lab at the time the specification for the test method was perfected.
The Pendulum has the big advantage that it can be used on laboratory samples for evaluating surfaces AND it can be used on site to check whether the standard predicted in the Laboratory has been achieved on site, useful when things “get legal”!
pastedGraphic_1.pngIt might be useful to look at a few examples of how different types of paving fare when subjected to this kind of rigorous testing and first some guidance on what standards are needed.
The wet pendulum slip resistance test (AS/NZS 4586 Appendix A) is conducted using a Wessex or Munro – Stanley London Pendulum Friction Tester. This pendulum device is portable and consists of a weighted foot with a test slider that swings down and slides across the surface wetted with water. The weighted foot comprises a spring loaded rubber test slider that exerts a prescribed force over the specimen as it slides across the surface. The results of expressed as a British Pendulum Number (BPN) and classified according to AS/NZS 4586
Wet pendulum slip resistance testing is recommended where there is a likelihood of the surface being contaminated with any liquid by rain, accidental spillage or ingress. A wet pendulum test offers the advantage of slip resistance determination in situ, which can be used to quantify slip resistance under a wide range of environmental conditions. Because the wet pendulum test can be applied to installed surfaces, it can also provide a measure of the inevitable change in slip resistance over time, enabling the risk of slipping to be monitored.
Ref: ATTAR website www.attar.com.au
DIFFERENT PAVING SURFACES
Ratings using the Pendulum tester suggest poor slip resistance for materials such as slate (R9), Cobblestone (R10), good for Exposed aggregate and Wood float (R13) with other concrete variants falling between these groups.
Asphalt is generally good for pedestrian use depending on the texture and type of aggregate used. A dense 6mm asphaltic concrete will not produce such a good slip resistance as a 10mm AC or a more open 6mm AC. Choice of aggregate will affect the result as a rounded beach pebble will polish the more it is used and become gradually more slippery. The choice of a crushed rock will give a much better performance especially if a gritstone is used which has a very high resistance to polishing.
It is a similar process when looking at a StoneSet resin bound paving option. The permeable nature of StoneSet goes hand in hand with having a rugous texture and if this is backed up by selecting aggregate types with polish resistance in mind, some excellent standards of slip resistance can be achieved. Virtually all StoneSet resin bound paving will be at worst Class x (Pendulum value in low 40’s which is only a moderate risk of contribution to risk) most will be Class W (Pendulum mid 40s to mid 50s – very low risk contribution). It is easy to achieve Class V with StoneSet with pendulum results of over 55, well over in fact.
It is therefore no surprise that StoneSet is being considered as a solution to slipping risks regardless of whether other issues such as permeability, long life or decorative capacity are uppermost in mind.
The sample below shows the texture a typical StoneSet offering fantastic grip. This is enhanced by the careful application of fine sand or recycled glass.
TREATMENT OF EXISTING SURFACES
The methods of increasing the slip resistance of floors include acid etching, blasting, grinding, paint with sand, grooves, floor sanding, proprietary treatments and adhesive strips. More information is outlined within is AS/NZS 3661.2:1994 Slip resistance of pedestrian surfaces – Guide to the reduction of slip hazards.
It is recommended that when modifying the surface, samples of treatments be evaluated in terms of the increase in slip resistance and any other characteristic deemed to be important to the form and function of the floor surface. This may include but is not limited to; cost, cleanability, mechanical properties, chemical properties adhesion to surface and aesthetics.
A trial of suitable options will provide the required information to conduct a cost-benefit analysis of the identified treatments. A range of specialist slip resistance treatment companies offer these services. When considering the selected treatment the long term sustainable slip resistance should also be assessed.
An overlay using StoneSet offers a superb treatment for worn and slippery paved areas and can be laid is thinly as 12mm (using 3mm aggregate) re-shaping and re-juvenating the area at the same time.
6th February 2014