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Firstly, silicosis is a severe and incurable lung disease which can lead to disability and death. Typically it builds up slowly over time, but under certain conditions, for example when crystalline silica is in the air in large amounts, the disease can be induced very quickly.
Secondly, concrete dust contains crystalline silica. The sand that goes into the mix contains silica, although of course it’s not floating in the air at that point.
“Crystalline silica (quartz) is a common mineral found in:
Dust containing respirable crystalline silica (RCS) is generated by high-energy processes such as cutting, sawing, grinding, drilling, polishing, scabbling and crushing of silica-containing materials. RCS particles are so small they cannot be seen under ordinary lighting, and stay airborne long after larger particles have settled to the ground – the small particle size means it is easily inhaled deep into the lungs.
RCS is a hazardous chemical. Inhaling RCS can lead to silicosis, an incurable lung disease that can lead to disability and death. RCS can also contribute to lung cancer, renal cancer and chronic obstructive pulmonary disease (COPD).” — Queensland WorkCover
In the context of concrete, the most common risk arises during construction, while concrete is being cut or ground; and of course, the relevant PPE is essential. However, dust may still be produced by wear or abrasion under traffic, and the risk is not as obvious.
It is less commonly realised that exposed concrete can continue to produce dust long after the completion of the project, usually by carbonation or similar ageing processes, and also by wear and abrasion. Concrete ceilings can drop dust as they age, which may not be significant enough to attract attention, but is still breathable by persons living or working underneath. Carpark floors may shed dust under the abrasion of vehicle traffic.
Exposure to the hazard of silica dust is coming increasingly under focus. Yes, there is a requirement to protect workers from the hazard, and to monitor their health if they are exposed regularly to situations where silica dust is generated.
(Guidelines from Worksafe NZ and SafeWork Australia)
Is there a solution which will reduce the risk both at the construction stage and for the long term?
Application of a spray-applied colloidal silica treatment will induce the formation of a hydrogel within the concrete, resulting in free moisture, calcium and silica being immobilised. This has the result of hardening the concrete – to a depth of about 150mm – and binding up the elements which would otherwise form concrete dust through wear or degeneration.