Donald Trump’s proposed $5.7bn (£4.5bn) steel wall along the USA’s southern border with Mexico would be more expensive than using concrete, however does have structural advantages, experts have said.
The US president has upped his campaign to construct a 377km wall along the Mexican border. Last week, while talking about the proposed structure, Trump said: “I think we will have to build a steel wall, as opposed to a concrete wall, because we have steel companies again.”
The US steel industry has added roughly 11,700 jobs since Trump took office, after he imposed a 25% tariff on foreign steel in March.
Speaking of the advantages of using steel as opposed to concrete, University of Surrey professor of construction systems Mark Lawson said: “The steel systems are easier to repair and demount, re-use and recycle, as in the case for all steel structures. Aesthetically the steel slat systems can be made more interesting by perhaps varying colours and also the profile of the slats.
“Because the steel systems are less bulky, they are easier to transport and construct on rough terrain. In the same way, the steel systems would be better adapted to uneven ground as they would require less ground preparation apart from drilling of the ground to 2m to 3m plus depth for the posts.
“Being able to modify the wall over time perhaps by removing certain panels would also be an advantage, for example if the politics change.”
Also speaking of the benefits of using steel for such a project instead of concrete, University of Sheffield structural engineering professor Ian Burgess added: “If the wall needs to resist impact or explosion then ductility is useful – it absorbs energy without fracturing. As for heating, steel has a much higher thermal conductivity than concrete, and tends to be much thinner so that it gets hot (or cold) much quicker.”
He added: “With concrete it is relatively easy and cheap to mass-produce precast units which can be simply transported to the site and assembled, probably interlocking and massive enough to be held in place by gravity on simple foundations. A steel ‘wall’ would be much lighter but would need lateral support or more substantial foundations. A conventional steel security fence with surveillance devices seems more effective to me.”
However, financial concerns about the cost of building the structure out of steel have been raised.
Dr Charles Clifton, an associate professor of civil engineering at the University of Auckland, has expressed concern over the financial cost of the wall.
“Most of the boarder is in a low corrosion zone, being inland and with a dry climate, and I would expect a steel wall would work as well as a concrete wall. However, to build a solid barrier wall say 3m high in either material across the whole border will be extremely expensive,” he said.
He added: “This region is also prone to localised high rainfall events so a solid barrier will interfere with the natural drainage and generate hydrological and environmental issues.”
President Trump also last week himself acknowledged that building the wall with steel would cost more than building it with concrete.
“The steel is actually more expensive than the concrete, but I think we are probably talking about steel because I really feel the other side feels better about it and I can understand what they are saying,” he said.
Professor Lawson claimed steel systems could be used in the form of vertical slats attached to horizontal “beams” which are connected to vertical “posts”.
He added: “However, the steel systems would have to be suitably corrosion protected and of course they could be easier to cut through. I would imagine that that the steel slats would be a minimum of 3mm thick to be resistant to impact and they would be galvanised (zinc coated) and painted, but the atmosphere is quite dry, so the design life would be long.”
A photo obtained exlcusively by NBC has revealed that testing of a steel slat prototype for border wall showed it could be cut through with a saw.
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