A water jetting contractor has devised a method to remove render from concrete surfaces using reduced water pressures to control client costs and ensure project deadlines are met during a major university refurbishment project.
Sabre Jetting Services has been commissioned by construction and civil engineering specialist McLaughlin & Harvey to support the new-build and refurbishment project for Coventry University.
Its water jetting teams are carrying out surface preparation work on the university’s seven-storey Graham Sutherland Tower, part of the university’s faculty of arts and humanities.
A key priority has been the need to preserve the tower’s large aluminum windows. They are being retained, but could have been damaged by the conventional technique to removing render from concrete.
This led Sabre Jetting Services, a member of the Water Jetting Association, the UK trade association for the water jetting industry, to rethink its approach.
Managing Director David Malin explained: “Surface preparation is usually carried out at pressures of at least 2,500 bar, which is 36,000 psi. But at that pressure, the windows were at greater risk of being damaged.
“This meant a team of operatives would have had to put in extensive protection measures, such as boarding and taping, before our teams could start work.
“Instead, I thought perhaps we could try lowering the water pressure and increasing the flow rate. We did a series of trials and found a suitable technique that worked.”
Sabre Jetting found the ideal pressure and flow combination was water pressure at 1,150 bar (17,000 psi) while increasing the water flow rate from 25 to 45 L/min.
At those levels, jetting operatives could remove the cementitious render, which included a grit surface coating, without the windows needing substantial protection.
David Malin said: “It has turned out to be very effective. Technical know-how, a willingness to try something new, and the skill of our operatives has contributed to a good solution. The method of removing the render in this manner has substantially reduced costs for the client.
“It’s an example of how we try to think outside the box on behalf of our clients, whether that’s to improve safety, productivity, sustainability, or protect surfaces and control costs, which was the primary factor in this case.
John Jones, President of the WJA, which is the UK’s main provider of water jetting training, said: “This project is a very good example of the advantages of water jetting, and how WJA members add value in planning and delivering building maintenance and refurbishment work in the most effective and sustainable ways.”
Sabre Jetting has had to overcome other challenges as it has carried out the work over the last nine months. The works required a significant amount of extra-long jetting hoses to be laid around the work area to ensure access around a complex site and to work at height.
Its teams have been able to remove around 50m2 of render a day working on the historic Graham Sutherland Building, which opened in 1967.
Water jetting has been the ideal technique to prepare the concrete surfaces for the paint finish required by the design plan. Using mechanical tools would have damaged the concrete, risked damaging the windows, and taken longer.
Founded in 1984, Sabre Jetting delivers a wide range of water jetting services, including hydrodemolition, surface preparation, pipe cleaning, tank cleaning, pile cropping and heat exchanger cleaning.
It is the winner of the 2021 Construction News Training Excellence Award after developing a custom-built water jetting training facility and an internal training programme that breaks down learning and language barriers, ensuring inclusion for all employees.