ABSTRACT
Precast columns are the main vertical load carrying members in skeletal frames. They may also be used as the horizontal load carrying members in sway frames, but their capacity to achieve this in buildings of more than three storeys is very limited. Typically, a precast column is manufactured in grey concrete and is square or rectangular in cross-sections. a column is joined on site the connection is called a 'splice'. Columns placed into a foundation pocket have roughened surfaces in the contact region, typically over a distance of 1.5 times the column breadth measured from the foot of the column. Retarding agents, which slow down cement hydration and hardening for the first 24 hours after mixing, are applied to the mould where roughening is carried out by mechanical scabbling. Different techniques are used to expose the coarse aggregate without causing structural damage to the cement matrix.
