huangyhg

dowel racks in lieu of expansion joints?
my firm has done the site engineering for a manufacturing facility that has a loading dock / truck circulation area with concrete paving. our plans specify 6" thick, 4,000 psi concrete with 6 x 6 / w6.5 x w6.5 wwf for the pavement section. the concrete paved area is 86 feet wide x 169 feet long. the plans show 1/2" expansion joint material at the building walls (along one 86-foot side and one 169-foot side), doweled expansion joints within the slab at ~28' o/c along the 86-foot side and ~42' o/c along the 169-foot side, and saw cut joints midway between the expansion joints in both directions.
the contractor has asked if he can substitute "dowel racks" for the doweled expansion joints. as i understand it, this is a method of 'floating' the dowel bars in during the pour, but no expansion joint material is used. only the dowels and a saw cut joint is provided where the doweled expansion joint is shown. they are also asking if a paper bond breaker material can be substituted for the expansion joint along the building wall. the result would be an 86-foot x 169-foot slab with only saw cut joints. when i asked the contractor how this 'system' would account for the expansion that the slab would experience, he responded that the slab would not expand beyond its size when poured. he says that their in-house structural engineer has been specifying this system sucessfully for slab work both inside and outside buildings for several years, and that they have never had any problems.
i am in north carolina and temperature extremes can range from the mid teens to the low 100's, so expansion and contraction is real. i am not aware of any magic dust or snake oil that is being used these days to prevent concrete from expanding and contracting like it and all other materials have been doing since the beginning of time, however i am willing to keep an open mind. has anyone out there heard of this practice. can anyone give me some insight into this or refer me to a source of information on this? thanks.
nealt
check out our whitepaper library.
the portland cement association (pca) has a number of publications that cover slab-on-grade construction with details on layout of control joints, constrcution joints, expansion joints, reinforcing etc. contact them to get a copy of the appropriate info., they are a great resource!

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