Concrete is the material of choice for innumerable bridges, roads, buildings and superstructures. Though it is incredibly versatile and deceivingly simple concrete is susceptible to deterioration and deformation if not designed, mixed, poured, cured, and reinforced properly. In concrete structures, both new and old, scaling, spalling, cracking, low strength, and delamination are just a few of the deterioration artefacts that give owners, project managers and contractors cause for concern.
Concrete petrography is utilized to understand what is occurring within the concrete to account for the type of deterioration observed.
What exactly can concrete petrography do? Petrographers evaluate concrete, in bulk and in thin-section, using reflected light, transmitted light and occasionally x-ray diffractometer and scanning electron microscopes to collect an incredibly large amount of data that includes the following:
classification of coarse and fine aggregate;
identification of portland cement and supplementary cementitious materials (including fly ash, slag, and silica fume);
mix design verification including estimates of the water-cement ratio;
evaluation of consolidation and mixing;
investigate for causes of low strength;
identify causes of surface scaling/spalling (including improper finishing);
determine the depth of carbonation and depth of hydrophobic materials;
classification of secondary deposits/mineralisations;
evaluate cracking and microcracking including thermal shrinkage cracking, early-age shrinkage cracking, and plastic shrinkage cracking;
evaluate concrete for thermal damage from a fire event; and
identification of durability mechanisms including alkali-silica reaction (ASR), delayed ettringite formation (DEF), chemical attack, rebar corrosion, freeze-thaw damage, and more.
Microanalysis Australia offers a range of petrographic services that can be utilized on concrete (cores or fragments) of any age and is not specific to either new or old construction. They are also available for the evaluation other building materials such as mortar/render, stucco, aggregate, flooring, and riprap.
For more information on how we can assist you with your concrete petrography please contact our Specialist Geologist/Petrographer Dan Cukierski or Rick Hughes on +61 8 9472 4880.
The Power of the GC-MS
Microanalysis has recently acquired an Agilent 7890 GC-MS (Gas Chromatogram – Mass Spectrometer) for its new premises at East Perth.
The GC-MS will expand Microanalysis Australia’s capabilities in the areas of material identification and characterisation further into the organic sphere, specifically in the areas environmental analysis, polymer characterisation geochemical and industrial chemistry analysis.
This will complement our existing strengths in the areas of mineral and inorganic identification using scanning electron microscopy, light microscopy and x-ray diffractometry.
A GC-MS is composed of three basics building blocks:
A means of introducing the sample via an injection port.
The separation of mixtures of compounds by partitioning them between a gas phase (typically helium) and an activated solid phase attached to a silica capillary column. The difference in the chemical properties between different molecules in a mixture and their relative affinity for the stationary phase of the column will promote separation of the molecules as the sample travels the length of the column. The molecules are retained by the column and then elute (come off) from the column at different times (called the retention time).
As the helium gas phase containing the molecules passes through the mass spectrometer, they are ionised into fragments and detected based on their mass charge ratio. The fragment pattern can be matched to an internal library to provide the absolute identification of a compound.
The true power of the GC-MS is when the information of the retention time and mass fragment patterns are combined to allow the identification of compounds in extremely complex samples such as crude oils, as well as enabling the detection of pesticides, PCB and PAHs down to ppb or even ppt levels.
The diagram below provides a summary of how a typical sample would be analysed on this system.
MAA is planning to develop its investigative and analytical base over the coming months to provide clients with specialised services in the areas of organic analysis.
Be sure with Asbestos
We often think of asbestos as being something from a bygone era which isn’t compatible with today’s health standards. Sadly, the prevalence of asbestos containing materials (ACMs) worldwide is still stubbornly high¹. As well as the ‘70s buildings needing repair or being demolished, there has been an increase in incidents of new imported products being found to contain asbestos. Importing asbestos at any concentration is illegal in Australia².
Asbestos can be found in a range of building materials such as cement, plasterboard, vinyl, window putty and roof tiles, as well as consumer products like crayons, paint and baby powder.
When to suspect asbestos
Asbestos containing material isn’t always obvious. It is worth checking whether a product contains asbestos if any of the following are true:
The product was manufactured in the 1960s, 1970s or 1980s;
There are visible, very fine white, blue, green or brown fibres protruding from the product surface or from broken edges of the product;
The product is plasterboard, fibreboard, vinyl, rubber, wax, cement sheeting or other building material and was recently imported; or
The product has any evidence of fibrous, non-flammable dust.
What to do if you suspect you have asbestos
If you think you may have an ACM, make sure you keep it moist to prevent the asbestos fibres from becoming airborne. This will prevent the asbestos from entering your lungs.
Put a small section (~ 5 cm x 5 cm) in a plastic, sealable bag such as a zip lock bag. Place this bag inside another plastic bag.
Now you’re ready to take your sample to a lab for analysis!
What testing is available
Currently, polarised light microscopy, or PLM, is the first line analysis for detection of asbestos. Over the years there have been several areas of concern raised about the detection limits and technical limitations of the technique. PLM involves examination of the sample using an optical microscope to identify whether fibrous material is present and it is able to differentiate several different types of asbestos.
Scanning Electron Microscopy, or SEM, is an alternate technique to identify asbestos using newer technology. SEM provides quick, accurate detection in a wide variety of different materials. Using Energy Dispersive X-ray Spectroscopy (EDS) with SEM imaging, the elemental composition can be determined to easily and conclusively differentiate between different types of asbestos and non-asbestos fibres (eg fibreglass). SEM EDS also has a much lower detection limit than PLM, often to better than 0.001 wt %, of detecting fibres as small as 50nm in diameter and detecting in a wider background of materials such as in or on ores, aggregates, fillers and polymers.
A recent bulletin³ by the Department of Mines and Petroleum (DMP) outlines the importance of detecting these very fine fibres as they are more likely to move into the deeper parts of the human respiratory system and lodge in the lungs, causing cell damage. The DMP bulletin explains that asbestos fibres below the resolution limit of PLM are easily detected and identified by SEM EDS.
We have outgrown our much loved space in Victoria Park and have acquired a new property in East Perth. The move is taking place Friday, 22 July 2016.
Our new laboratory is located at: 37 Kensington Street, East Perth
Decommissioning of our instruments will take place on Thursday, 21 July 2016 and recommissioned over the weekend. If you have an urgent job on its way to us please contact Rick Hughes on 0407 771 447.
We will be operating from East Perth as of Monday 25 July 2016, please amend your records to account for our change of address.
Our phone number will remain +61 8 9472 4880 and after hours 0407 771 447
SEM Image Auction
Start your bidding…
Microanalysis have pledged to support the Starlight Children’s Foundation who have been helping children and their families since 1988.
These beautifully unique SEM images are being auctioned off by the team at Microanalysis. Professionally printed (12 inch x 12 inch) and framed they would make a stunning addition to your office or home, and will raise some well needed funds to support the incredible work of the Starlight Children’s Foundation.
