Stone testing + bluestone characteristics
Bamstone connected with Stone Initiative’s Principal and chief consultant, James (Jim) Mann to discuss the importance of stone testing and the unique characteristics of Australian bluestone.
Why is stone testing important?
The purpose of stone testing is to determine the properties of the material – by testing your product you’re able to build confidence in the product and its fitness for use. Testing your product can also save you money – for example, you might initially plan to use your product at 30mm thick, but by having good confidence in its strength properties, determined through appropriate testing, you can make the decision to use it at say 20mm, meaning you can produce it at a cheaper cost and be more competitive.
On the other side of things, testing is vitally important in avoiding product failures. Stone is a natural product, and you really need to understand its strengths, weaknesses and any variability. Even if only a small percentage of your material has a weakness in it, it can be a problem. When it goes to site, if one out of every fifty pavers starts to break because it’s not strong enough, and you multiply that one in fifty by a whole project, you’ve got dozens or hundreds of pavers that have the potential to fail in service. Understanding the variability and properties of the product can help you avoid situations like this.
What testing processes for natural stone are involved at Stone Initiatives?
Once we are engaged by a client, we like to spend time upfront learning about the project and product – particularly the ‘what, where, why.’ What they want to test, at what thickness and size, what it will be used for, where it’s going to be used, and why they want to use this particular type of material; is there a set aesthetic they’re after? Once we get that type of understanding we can develop a testing protocol around that. We spend a lot of time making sure we understand the scope of the job. We then choose relevant tests from the range of Australian and International Standards that are most appropriate to determine the properties required by the client, taking into account specific project specifications.
We’ve also developed a range of in-house testing methods, for example stain resistance testing to help determine fitness for use in particular areas. We perform a lot of fitness for use evaluations for Tier 1 builders who are using natural stone as floor finishes in high-end projects, including various tests for strength, water absorption, slip resistance, abrasion resistance, stain resistance, durability, and petrographic examination, which for example can be used to determine if there are any minerals in the stone that might be unstable.
When clients supply us with samples for testing in our laboratories, we remind them that representative sampling is very important – if you’re testing for a particular project, it’s best to test from a batch that is going to be used. It’s also important for us to test at a thickness and finish that is relevant to the project.
Once testing has been completed, we work with the client to ensure they understand what the results mean – it’s about more than just numbers. We can also help them to work with the strengths and minimise the weaknesses of their product.
Why is it valuable for industry professionals such as architects, engineers and local shires to consider stone products that have undergone extensive testing with a qualified, experienced laboratory?
It’s important to make sure all the surprises are uncovered upfront. If a stone product has undergone a thorough evaluation to understand the variability of the material and its various properties, this will help the engineers to design with confidence. When you know what the weaknesses are within the material, you can work with or around those and concentrate on the strengths. For example, a project might want to use 600 x 400 x 30mm pavers in a particular area, but the stone isn’t strong enough for that – if it has already undergone evaluation you can know that it works at 400 x 400 x 30mm or 600 x 400 x 40mm. It’s a lot better to understand that upfront, rather than further down the track when the impact of changing the paving size, for example, would be greater. Historic test results may be used for evaluation at design stage, if they’re relatively recent, and then when you get to acceptance stage you may say, okay we’ll choose this stone given that the properties are the same, and choose key performance indicator tests that are relevant to the project, for example strength. Then you might do even more limited spot tests throughout project completion.
What should the common customer and/or designer know about Australian bluestone?
Australian bluestone is a rock type known as basalt. As a natural stone, it is formed by nature and not in a factory. It can vary in appearance and physical properties throughout the quarry, just like other natural stones. Regular testing is required to ensure you have confidence in the supply. But while it’s important to ensure thorough evaluation of the stone’s variability has been completed, this same variability also makes every piece unique, meaning every project that uses natural stone can be distinctive. One of the things I appreciate most about natural stone is that every piece has a story to tell.
What characteristics should people look for when buying Australian bluestone?
Dimensional stability is important. There are some types of bluestone that aren’t dimensionally stable and can warp at some paver formats and thicknesses – this is not usually a problem with Australian bluestone, but there are some imported products that have been known to warp when exposed to moisture. Another element to consider is that the visual characteristics of the stone meet your requirements. Imported bluestone products can be very different to the distinctive Australian bluestone.
What are the unique characteristics of Australian bluestone?
The vesicular ‘cats paw’ nature is the principal difference that made Australian bluestone an iconic feature of Melbourne and surrounds. These ‘cat paws’ are recognised as a heritage feature of Melbourne buildings and walkways.
Australian bluestone is ideal for external paving projects because it is highly durable, it is resistant to staining, and it is very effective at maintaining its slip resistance under wear from high traffic activity. It’s also the type of stone whose appearance improves with age. As you walk down the streets of Melbourne you can see the patina that has built up on the stone over time, giving it a great look while not significantly affecting the slip resistance of the paving.
Interview conducted with James (Jim) Mann.
– Principal and chief consultant, Stone Initiatives.
– Director, Australian Stone Advisory Association.
Dedicated to the testing and analysis of dimensional stone, Stone Initiatives is recognised as one of the predominant materials testing facilities in the Australasian region. The highly qualified and experienced team are committed to providing an end-to-end consulting service that is an asset for the architectural, conservation and building industries from “the ground up”.