concrete cover below ground
 

concrete cover below ground
when designing rc columns that start at foundation level, do you increase the cover for the reinforcing below ground? and then change it higer up only? is it an option to investigate the the cost effectivenes of using some specialist cover enhancer to the sections of reinf below ground and in this way keep the cover consistant?
forget the 'cover enhancer'.
decrease the cover above the floor, if it is critical, or increase the column size below the floor (thereby increasing the cover).
aci requires 1.5" clear if exposed and not greater than #5 and 2" for larger han #5. since ties are at least #3 you are ok below grade and 1.5" cover plus #3 is almost 2". i would say ok. it would be within tolerance. if you wanted to meet the letter of the code you could use #4 ties. i wouldn't change sizes since the contractor would have to rebuild forms and that is too expensive.
i believe if the concrete is permanently exposed to the ground the cover should be 3".
that is for concrete cast against the ground and is due to soil mixing with the concrete.