Reflecting an international trend, polyurea is coming to the fore in South Africa as an innovative solution for repairing concrete buildings and structures and Concor Civils’ recently established concrete repair division is using this high performance plural component elastomer in an increasing number of applications with beyond-expectation success.

“Polyurea has an extremely long service life, with high puncture and impact resistance and a completely seamless water proofing barrier,” Hein Pretorius, contracts manager at Murray & Roberts Concrete Repair, says. “Originally designed as a waterproofing product, it can also withstand harsh industrial chemicals including acids, is fully UV-resistant and is available in a large range of different colours, opening up a spectrum of potential applications.

“Although its use is relatively new to South Africa, it has been tried and tested in USA for more than a decade. Its heat and impact resistant properties add up to a long lifespan and, depending on the application, the product can be guaranteed for up to 15 years.

“Polyurea can be applied to any type of substrate and it’s also extremely flexible up to 400 times its nominal thickness. This characteristic lends itself to the sealing of construction joints as an alternative to the traditionally used hypalon bandages.”

Polyurea can be applied over torched-on waterproofing products, eliminating the costly exercise of removing a previous product before the treatment can be applied. As an industrial coating, it demonstrates excellent chemical resistance to hydrocarbons and hydrogen sulphide gas, as well as properties that enable its use in submerged sewage applications. It is also ideal for sealing potable water retaining structures, waterproofing applications, restraints, as steel corrosion protection and the internal lining of steel chutes.

“Since polyurea is a spray-on application, it’s possible to cover up to 800 square metres of surface area in one day,” Pretorius says. “Only two people are needed to operate the application equipment, so it’s also not a labour intensive process, and the area becomes fully trafficable only two minutes after application.”

Murray & Roberts Concrete Repair team used polyurea for repair work on the ABSA Towers in central Pretoria, where the scope of work called for the application of 32 000 square metres of 1.5 mm thick polyurea to the external facade of the 34-storey building. Existing mosaic tiles had begun peeling and would have impacted the aesthetics of the building and possibly the safety of pedestrians in the area. Applying the polyurea to the outside face of the existing cladding effectively restrained the mosaics and allowed the building renovators to install a new façade, secure in the knowledge that the substrate will not peel or come away in time.

“This is an historic building and it was important that the repair work did not damage the building façade in any way,” Pretorius explains. “Using polyurea technology, we were able to give the client a guarantee in this regard. It was also a highly cost effective option, because the mosaic tiling did not have to be removed to allow for repairs.”

Polyurea was also used at Standard Bank’s Johannesburg headquarters to restrain marble tiles applied to marble clad arches. The marble slabs were pulling away from the cladding structure and needed to be reattached, as this also posed a safety issue to the local pedestrian traffic. In this instance, the cladding comprised large marble slabs 50 mm thick and 1.6 metres by 0.9 metres and, by the end of the project, a total area of 1 800 square metres had been restrained.

“What made this project unique was that the polyurea was applied to the internal face, between the tile back and the structure itself,” he adds. “This in itself presented challenges, as access to the back of the façades was limited and restricted. Where access was severely limited, we re-engineered the stringer attachment system to ensure the structural integrity of this façade.”

At Middelburg Ferrochrome, Murray & Roberts Concrete Repair used polyurea as water-proofing, applying it to numerous concrete roof slabs to make them water tight. Its benefit in this type of application is that the water-proofing can be guaranteed for ten years with no maintenance agreement – successfully delivering a labour free solution for the next 10 years to the customer.

Murray & Roberts Concrete Repair’s standalone concrete repair division was established earlier this year and is equipped to carry out the repair and rehabilitation of concrete chimney stacks, bridges and cooling towers, and to provide fast track floor coatings. The new division offers a high level of skills, complemented by a depth of technical and application knowledge and is underpinned by access to the Murray & Roberts Concrete Centre of Excellence.

POLYUREA IN CONCRETE REPAIR PIC 01 : View of ABSA Towers during the application of polyurea and drilling and dowelling for anchoring new facades.

POLYUREA IN CONCRETE REPAIR PIC 02 : External view of marble arches at Standard Bank sprayed with polyurea on inside.