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RE: Slab on grade joint repair

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Joe,

This will be an ongoing problem.  You can apply concrete patches from now on, but the problem will not go away.  On new construction, the edges in the drive aisles should be armored with steel plates with headed studs.  The problem is that the slab edge is unconfined and will spall.  You need to either armor the edge or confine the concrete.

For expansion joints or control joints (if the slab is less than 5 years old), I would armor each edge with a Bar 3" x 1/2" (size depends on wheel loads):
1. Rout the slab on each side of the joint to receive the bar.
2. Drill holes to receive a deformed bar anchor to anchor the bar to the slab.
3. Place a sheet metal plate coated with a bond breaker vertically into the joint
4. Weld deformed bar anchors onto the steel bar
5. Fill the concrete holes with grout and apply a grout bed to the routed concrete slab
6. Insert the deformed bar anchors into the grouted holes and set the bar flush with the slab on grade
7. Remove excess grout
8. After curing, remove the sheet metal plate with bond breaker

For control joints in a slab that is over 5 years old (the slab has contracted all it is going to):
1. Rout the slab on each side to a width and depth of 2"
2. Place a sheet metal plate coated with a bond breaker vertically into the joint.  Top of plate should be flush with the slab on grade.
3. Fill the joint on each side of the metal plate with grout flush with slab on grade.

Reference ACI 302.1 "Guide for Concrete Floor and Slab Construction" for the tire loads, or contact the manufacturer of the lift trucks.

The impact varies as the concrete edge spalls, the impact increases and accelerates the spalling problem.

Regards,
Harold Sprague, PE
Krawinkler, Luth & Assoc.


-----Original Message-----
From:	Joseph Murar [SMTP:murarjm(--nospam--at)wwics.com]
Sent:	Tuesday, September 15, 1998 1:07 PM
To:	seaint(--nospam--at)seaint.org
Subject:	Slab on grade joint repair

I need some information and ideas on repairing spalling at the construction
and control joints in an existing concrete slab on grade.  
The slab is about 7 years old and 6" thick 4000psi concrete with #4s @ 24"
o/c E/W.  The control joints are cut in 15 feet square to a depth of 1 ½"
deep and filled with an elastic joint filler. 
Ever since the client switched from pneumatic tire to hard tire forklifts
there has been noticeably cracking at the joints. The capacity of the old &
new lifts and the loads they carry are identical. 
Has anyone had this experience and what was the method of repair, did it
hold after some months of being exposed to traffic?
Also is there a reference were one can compare impact loading between
pneumatic and solid tire lifts?

Thanks 
Joe Murar

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