The Client reported significant cracking and concrete spalling on an exposed concrete ceiling of a storage room. It was noticed that the top side of the concrete slab had been cladded over with metal deck roof.

However, multiple penetrations had been made on the roof sheets to make way for pipe and electrical conduit penetrations. A water tank for a centralised air conditioning system was also located on the roof. High humidity and water seepage through the roof slab from roof sheet penetrations expedited the concrete spalling.

 

Dilapidated roof sheets allow water ingress

Dilapidated roof sheets with multiple penetrations and corrosions allow water ingress exacerbating the concrete spalling of the slab soffit beneath.

 

Concrete cores were taken from the concrete slab soffit to assess the extent of carbonation and chloride ingress. High carbonation rate and high chloride content were tested from the concrete samples collected.

Temporary props were installed to prevent catastrophic failure to the roof slab when waterproofing works are conducted on the top side and concrete repairs are conducted to the soffit.

 

Installed props and drummy concrete removed

Props installed, removal of drummy concrete exposes corroded reinforcement bar

 

Waterproofed roof slab

Roof slab was waterproofed to ensure longevity of concrete slab

 

SWConsult calculated the number of galvanic anodes required and instructed the contractor to install the galvanic anodes to the repaired area so that they can act as the sacrificial anodes instead of the newly installed reinforcement bars.

 

Galvanic anodes

Galvanic anodes installed to provide corrosion mitigation to repaired areas

 

Galvanic anodes installed

Galvanic anodes installed to repaired area

 

Repaired concrete repairs to ceiling slab

Completed concrete repairs to ceiling slab