Micropile installation 4

[dik]

I have a colleague that wants to install a micropile through an existing concrete slab. The slab is adequate for the pile loading. The procedure as follows:

Locate rebar,
Core drill the slab,
Install the micropile,
Mechanically roughen the sides of the core,
Clean the core using water and compressed air,
Install primer to the core sides,
Use Sikatop 123 Plus, with 3/8" aggregate added, to replace the concrete,
Bond strength is greater than or equal to the concrete strength (verify with Sika), and
The core 'plug' will support the reaction from the micropile.

Any comments or suggestions?

 

[jayrod12]

I'd prefer to be ensuring you're getting some direct support of the slab on the pile. I.e. ensure at the top of the micropile it's poured underneath the existing slab.

 

[Ron]

dik....add some interface with the slab...don't depend on the bond interface

 

[dik]

JayRod and Ron:

My suggestion, too. He asked why and my only comment was that 'it was more positive'. Any reason why not? I've used Sikatop and it really 'sticks'. The roughened surface would also help.

Dik

 

[oldestguy]

In my experience getting bond between new concrete and the old leaving the old rough and DRY and then applying a creamy consistency of Portland cement with water just before the concrete gives a better strength than the old concrete alone. The creamy consistency cement tends to enter the pores of the old, so having that old surface wet is a drawback.

 

[WARose]

When I have done something like this with micropiles.....this aspect of the design was part of the contractor's scope (i.e. the piles and their attachment). Pretty much every one of them I've dealt with (Hayward Baker comes to mind) can produce (PE sealed) CAD drawings for the job.

Naturally once the force is developed in the slab, it then becomes part of your responsibility......but I've found that these guys have done this so many times, for QC purposes, it's just best to leave it to them.

 

[dik]

OG: I used to use latex bonding agents, and, another OG taught me the error of my ways... and have used dry for absorption, plus cement past, and this has worked well for decades... thanks. Dik

 

[jayrod12]

My feeling is, ensuring a interface connection takes away the possibility of improper installation of the infill piece.

 

[dik]

Thanks, Jay
I sometimes have difficulty in explaining why something else should be considered, not having a good reason (other than common sense) to abandon it. His explanation was sound... and the guy's a good engineer... and, I really couldn't find fault with what he was proposing... deciding not to do it myself, is, not really a good reason. I've suggested he leave the attachment to the contractor... not knowing what his scope was.

Dik

 

[dik]

The fellow is running with the contractor's engineer providing the means and method.

Thanks, Dik