Monolthic Pour at Concrete elevation Change?? 1

[x5bulldog]

I want to avoid having a construction joint at the interface of a 4'x10'x3'deep concrete pedestal / pads on a mat foundation. Vibratory equipment is going to bear on the concrete pedestals. Can the field / construction guys easily form and pour concrete in this area to get a monolithic pour (then finish the concrete) or will I need to call-out a joint for two different pours?

I do not like the idea of creating a weaken shear plane at the joint (even though I can add reinf.for shear friction and properly embed the reinforcement into the pedestal and down into the mat). I dislike that forces from the vibratory machinery come in from all different directions / angles and having a joint at the pedestal and mat interface.

 

[hokie66]

The pedestal can be built monolithically if you insist, but in my opinion, your concerns are ill founded. A clean and roughened joint, together with adequate reinforcement across the joint, are all that is necessary.

 

[jayrod12]

You could also consider leaving a 4'x10'x8"deep void in the mat foundation(depending on mat thickness) for the pedestal to key into. That way you've got solid concrete on concrete shear resistance plus the reinforcement across the joint.

But as hokie said, I believe your concern is ill founded as well. Whether you pour it monolithically or in two separate pours you still end up relying mostly on the reinforcement for any shear resistance.