Some owners and tenants of new high-bay warehouses are concerned to find that the pristine appearance of floor surfaces can soon become blemished by vehicles leaving black marks that are resistant to cleaning. Grant Roe, BE(Hons) MEngSc MBA MIEAust CPEng NER, explains this commonly misunderstood problem and prescribes the solution.
There can be misunderstandings among trade services and maintenance providers as to what causes the black marks to accumulate and persist on warehouse flooring, and thus misinformation exists as to the appropriate remedy. The curing compound used for greater efficiency and precision in the concreting process, often blamed for the problem, is just one of several necessarily contributive factors for which there is a simple solution according to Grant Roe, Managing Director, Costin Roe Consulting, one of the world’s leading engineering firms in high-bay warehouse design from both civil and structural engineering perspectives, and winners of the ACSE NSW Award for Excellence in Structural Engineering for work including the high-tech concrete pavement at Veolia complexes in Woodlawn and Banksmeadow.
Spectrographic analysis contradicts the subjective opinion
Contrary to the weight of subjective opinion about the role of curing compound in causing floors to become marked, spectrographic analysis of floor-scrapings confirmed the absence of curing compound in the black substance, which was found to consist of carbon-black (from burning) and rubber. Grant explained, in simple terms, the physical actions at work to produce the empirical evidence.
“New warehouse flooring offers less friction for tyres to get traction. When the reduced friction causes loss of traction, the tyre spins, and the rubber can heat to the point of burning. Whether or not any curing compound or other residue is burned during spinning and heating, the black marks are left on the floor by the black rubber tyres. White tyres have been tested as an alternative but the white rubber was found to be not as durable. Since black tyres last longer, and are better for heat absorption, changing to white tyres just to achieve an aesthetic result would not make sense commercially. For some warehouse operators, the appearance of concrete flooring is immaterial and black marks are accepted as an inherent by-product of vehicles being used for materials handling. At other warehouse sites, however, aesthetics will matter as much as performance, without any compromise to the performance being tolerated for the sake of aesthetics. This is where engineers can identify the cause of problems more accurately and objectively, and prescribe the most practical and efficient means of achieving the desired result,” Grant said.
Floor densification treatment the answer for increasing friction
“I have previously commented on industrial flooring impregnation as unnecessary for most monolithic concrete floors that are properly constructed, citing as examples some of the world’s most efficient automated warehouses with high-performance floors that have not been treated with any impregnation products. However, products that increase floor surface density also have the effect of increasing friction. Increased friction means better traction for tyres, and therefore less wheel-spinning, and ultimately less likelihood of the floor surface being affected by black marks,” said Grant. “The simple application of a floor densification treatment can preserve the aesthetic result, where clean appearance is necessary, without losing the benefits delivered by use of a curing compound.”