Rigid Concrete Pavement Construction Joint Detail

[theCorkster]

Ladies and Gents,

I'm preparing a rigid concrete pavement design for a small office complex. The pavement sections will be 4.0 and 5.0 inches thick. In reviewing details for the different joint designs, I'm in a quandry regarding the "construction" joint detail.

With construction joints in pavements less than 6 inches, using dowels is typically not recommended. Somewhere in the recesses of my brain, I also recall that using a "key" is also subject to questions, since the pavement section is relatively thin and the key tends to break.

Any thoughts or experience on what such a joint should be so that the slabs across the construction joint are interlocked?

Thanks,

theCorkster

 

[cvg]

I see standard details for 6" thick concrete paving with a key. Why not thicken it at the construction joint and construct the key?

 

[dik]

4" is adequate for only the lightest duty pavement. You have to be careful in thickening the slab edge for dowels; this can restrain the concrete for thermal movement and can cause cracking. Concrete should slope 1:12 min. Because of the flexibility of thin pavements, they are much more susceptible to 'pumping' failure at the joints. This is where moisture gets in and softens the soil in the vicinity of the joint. For any type of light useage, I would not use anything less than 6" thickness.

Dik

 

[GeoPaveTraffic]

Keep in mind that residential driveways are typically 4 to 5 inches thick. Think back to the condition of these driveways... If you still want to recommend/construct a commerical parking lot/drive areas of that thickness; I have the following recommendations

1. Maximum joint spacing should be 8 feet for 4" thick pavement and 10 feet for 5". This is in all directions.
2. Try to minimize the number of construction/cold joints.
3. Where cold joints must be made, thicken the slab to 7" and use 1/2 inch smooth epoxy coated steel bars for load transfer.
4. Do not use deformed bars and keyway. Keyway should only be used for longitudinal joints, such as along the center line of a roadway. When keyway is used, deformed bars must be used to hold the keyway together.

 

[civilperson]

Why build cracks in your slab? If WWF is used to reinforce the slab, then cracks can be kept to a size not visible to normal inspection, (need a microscope). Try WWF of 4"x4", D7xD7 in 12' x 20' sheets. A shrinkage-compensating concrete and a wet cure will allow joint spacing to be at 8 to 10 foot intervals. Place WWF on continuous chairs, (not pulled up by hooks in plastic mix).

 

[theCorkster]

cvg, dik, GeoPaveTraffic & civil person;

Thanks for the great input! This parking lot is small in size, without through access. 4-inch pavement will be in parking stalls for autos/light trucks, and 5-inch pavement will provide parking access, moving, delivery, and garbage truck access. Sections will be supported on 4 to 8 inches of compacted baserock.

I plan on 1) limiting construction joints and 2) using a thickened section with dowels where construction joints must be located.

civilperson: My experience with concrete pavement is to avoid using reinforcement (other than doweled joints), especially wire due to the problems of getting it built properly. Even with diligent inspection during placement, mesh seems to alway get displaced, and resetting it during the pour is a always battle. Some structurals I work with will increase slab thickness by 1 inch to avoid the construction problem.

 

[dik]

Error:
For any type of light useage, I would not use anything less than 6" thickness.

should read...

For anything other than light useage, I would not use anything less than 6" thickness.