Column concrete spalling.
Rebar embedded in chloride contaminated concrete gives intense pitting rapid corrosion (black areas of bar) in anodic conditions. Adjacent steel acts as cathode
Toggle fit of GF & FF column on an external corner with tongues of FF ring beams sandwich between. Fractured concrete of columns, beams & panels with corrosion of rebar beyond render removal area means it is extremely difficult to obtain a longterm repair
Extensive break down of the concrete structure is exposed
The risk of column failure through buckling is high as concrete cover to the rebar is lost. The bolted reinforced concrete panels become distressed through corroding rebars & high floor & roof loads get transfered via failing FF ring beams, held together through insecure lap or toggle joints
Their Construction
They consist of over 400 reinforced concrete members with storey height columns toggle fit into lengths of ring beams that support the first floor & roof .
The aerated concrete generally contains chlorides from the sea sand used & the added calcium chloride used at time of casting. The porous nature of the concrete allows moisture movement when the hard render cracks due to thermal movement & ease of concrete carbonation. This combination of circumstances creates a concrete structure that deteriorates rapidly
