Grouting issues cause of embarrassing crumbling in CBUS's Pantscraper construction project

Grouting issues cause of embarrassing crumbling in CBUS's Pantscraper construction project
Grouting issues cause of embarrassing crumbling in CBUS's Pantscraper construction project

Multiplex has pinpointed incomplete grouting as having caused crumbling of precast concrete columns at its $1.2 billion Collins Arch project.

The issue halted work at the Collins Street, Melbourne CBD work site of the CBUS project, nicknamed the Pantscaper.

The builder would not say how many columns had been affected or what levels of the 44-level twin-tower project had been affected.

The embarrassed super fund, which provides superannuation and income stream accounts to more than 790,000 members, prides itself as being a leading commercial and residential property developer across the country.

The concerns triggered an investigation by structural engineers.

"In limited locations the liquid grouting solution between the column and the floor slab has been found not to have fully penetrated, leading to minor spalling of the precast column edges," Multiplex said on Wednesday.

"The columns in question have since been remediated in accordance with the engineers’ recommendation and a full audit of all precast structural columns is expected to be complete later today."

The builder said there were no structural problems with the building, the design or the precast columns separating floors.

But is acknowledged that "spalling", or crumbling, of the pillars had occurred where pressure built up because the grouting was not evenly spreading the load of the column above.

RCP was appointed by Cbus Property in 2015 to project manage the redevelopment of 447 Collins Street, Melbourne. The quantity surveyor is Rider Levett Bucknall.

It is understood Cbus Property board members were briefed on the issue after the stopwork gained national attention on the Nine Entertainment website.

Mark Ford has been the Cbus Property chair since 2006. Ford is a professional director with extensive property industry experience, including previously being managing director, head of DB Real Estate Australia.

The Cbus Property board includes trade union construction boss Dave Noonan who worked as a builder’s labourer, and managed major union sites at several iconic Melbourne landmarks.

Noonan’s qualifications now comprise the RG146 for Superannuation.

Chris Kakoufas is the Cbus Property general manager of development.
 
A CBUS presentation indicated there were unique design considerations for 447 Collins Street due to its complex form, and focuses on the linking of East and West Towers via the skybridge.
 
"Each tower experiences permanent lateral deflections in different directions due its unique geometry," Rob DiBlasi, Director, 4D Workshop said in 2017 at the Council on Tall Buildings and Urban Habitat.
 
"This is all about construction...by tieing them together it's an extremely stiff building" said DiBlasi.
 
"The architectural aspiration was to maintain an uninterrupted façade across connecting towers," he advised.
 
"The skybridge structure has been utilized to link the towers and avoid expansion joints.
 
"Design considerations include individual tower movement during construction and construction tolerance, skybridge and link structure design and detailing, consequential design effects on stability elements, and skybridge construction methodology.
 
"The linking of towers can be carried out successfully to create a unique continuous and homogenous architectural form," 
 
The presentation advised internal linking forces can be significant and may affect design, detailing and construction.

Poor grouting was part of the problem at Sydney's troubled Opal Tower, from which residents were evacuated on Christmas Eve.

Along with the poor assembly of beams, there was also insufficient grout – concrete glue made up of water, cement, and sand – at the joints between the hob beams and panels, causing stress in the panels, the Opal investigation found.

Opal Tower also had unique construction challenges.

 

Jonathan Chancellor

Jonathan Chancellor

Jonathan Chancellor is one of our authors. Jonathan has been writing about property since the early 1980s and is editor-at-large of Property Observer.

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Cbus 447 Collins

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