David Jones – Concrete Repair Sydney

David Jones Building Redevelopment

DESCRIPTION

The historic David Jones building, which has been in the hands of the retailer since the 1930s, is being redeveloped in a $300 million plus project by CBUS and Scentre Group.

The project will have world-class retailers and restaurants, as well as boutique office floors, topped by a luxury apartment tower sporting Hyde Park views.

Investigation

AECOM initially specified significant concrete rectification works to allow for the installation of Carbon Fibre; however, pull-off testing conducted on the Concrete revealed there was not sufficient strength in the concrete and Steel Plates replaced the installation of the Carbon Fibre.

There were a number of Key areas that needed to be addressed in the rectification process, including Removal and patch repair of defective concrete, treatment of low cover to reinforcement and local reinforcement corrosion and repair of defective concrete encasement of existing steel work.

Observation

The building was built in 1933, so the concrete is only approx. 21Mpa and nearly 90 years old, meaning after the surveys were completed, there were thousands of repairs that needed to be completed.

Identifying, mapping and tracking the repair work created a challenge that had not been seen on this level previously, and it was critical that the team carefully documented each section of the repair process.

Low cover and poor quality concrete in many areas meant the team was additionally challenged with having to rebuild sections without damaging other areas not requiring repairs.

Solution

The rectification process was completed using shrinkage-compensated, polymer-modified, fibre-reinforced Concrete Repair Mortars that were matched as close as possible to the host substrate but would also provide the structural integrity as required by the Engineers.

A number of repairs, such as those highlighted in the photos, required unique solutions using form and pour repair mortars with customised formwork to allow the products to fully penetrate the voids created in the removal of the spalled concrete.

Adding to the repair process’s complexity was that most of the repairs had to be completed overhead, which in some cases meant multiple layers of repair mortar to complete the required depth and the use of mobile work platforms.