Concrete Q & A: Construction Loads and Cracking

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Title: Concrete Q & A: Construction Loads and Cracking

Author(s): S.K. Ghosh

Publication: Concrete International

Volume: 32

Issue: 1

Appears on pages(s): 75-76

Keywords:

Date: 1/1/2010

Abstract:
We’re constructing a parking garage and want to place concrete in some interior columns by using a forklift to carry a concrete bucket. We will be running the forklift and loaded bucket on the newly completed elevated slab. The Engineer of Record (EOR) has indicated that the slab is designed for a live load of 50 psf (3 kPa) uniform load or 3000 lb (1350 kg) concentrated wheel load over a 20 in.2 (13,000 mm2) area. Also, the EOR will allow us to match, but not exceed, the controlling live load as a construction load. We can do this with a forklift that will raise the bucket to the desired height above the column by controlling the volume of concrete in the bucket so as not to exceed the live load. The Construction Manager (CM) disapproves of this placing method and says we’ll be responsible for slab cracking due to construction loads that include the use of the forklift and loaded concrete bucket. We’re worried that the CM will hold us responsible for any flexural cracking if we put a forklift and loaded bucket on the slab. Are the responses by the EOR and CM compatible? Also, cracking caused by drying shrinkage, thermal contraction, or both is common but we fear this cracking too will be attributed to our use of the forklift for placing concrete. How can we protect ourselves against claims by the CM that we are responsible for repairing all cracks in the elevated slab?