Coring the Shotcrete Test Panel

It was a lot of work and was completed by 4:00 pm Pacific.  And the shotcrete core samples were delivered to HP Inspections by 5:15 pm.

Concrete Core Samples from the Shotcrete Test Panel

We completed the shotcrete test panel on Wednesday, March 18 so now we had to deliver the three shotcrete core samples to HP Inspections.  Bryan, under Jorge’s instructions, used a concrete drill to obtain the core samples.

Bill Brown provided a Hilti concrete drill with various coring bits (3 inch, 4 inch and 6 inch).  Drilling into the shotcrete test panel, with several layers of reinforcing steel, required anchoring the concrete drill to the test panel and then drilling slowing into the concrete.

Anchoring the Concrete Drill

We used a 5/8 inch bit to dril a hole into the shotcrete test panel.  This hole had to be 11 to 16 inches away from where the special inspector wanted the core samples taken from.  After drilling the hole, we used a Red Head Trubolt anchor bolt in the hole and then attached the concrete drill to that bolt.

Concrete drill with 3 inch coring bit attached to shotcrete test panel.

Concrete drill with 3 inch coring bit attached to shotcrete test panel.

Drilling Core Samples

Bryan used the 3 inch bit to obtain a core sample from the first two test locations that were scribed on the shotcrete test panel.  The drilling worked fine until the 3 inch bit went through the #8 reinforcing steel (rebar).  Unless drilled through the center of the rebar, there is very little concrete attached to the rebar and it breaks up.  This condition is exacerbated with a (relatively) small core size.  Thus, the first two 3 inch cores broke up when going through the large rebar locations.

Completed first 3 inch core sample.

Completed first 3 inch core sample.

First core sample. Note #8 rebar at botttom left of core.

First core sample. Note #8 rebar at botttom left of core.

After setting up the third location, Bill Brown arrived at the project site.  Bryan started coring and then the drill bit broke after drilling in three inches.  Bill examined the core and suggested we use a four inch drill bit.  Bryan replaced the drill bit and obtained the four inch core sample.

Bryan drilling the third core sample (4 inch). Photo credit - Bill Brown.

Bryan drilling the third core sample (4 inch). Photo credit – Bill Brown.

With the larger bit in place, Bryan went back to the first two core locations and drilled again.  This yielded new core samples with thin walls, which broke apart at the same locations.  Consequently, using the 4 inch bit, Bryan drilled two additional core samples in new locations.  They worked perfectly.

New core sample location.

New core sample location.

Inside hole from shotcrete test panel, showing where the 3 inch core sample was taken and then the 4 inch core sample. Note the shotcrete is complete, with no voids.

Inside hole from shotcrete test panel, showing where the 3 inch core sample was taken and then the 4 inch core sample. Note the shotcrete is complete, with no voids.

Inside the 4 inch core sample. Note the shotcrete is complete, with no voids.

Inside the 4 inch core sample. Note the shotcrete is complete, with no voids.

Core samples for HP Inspections to review.

Core samples for HP Inspections to review.

Electric Panels Completed

While the coring was underway, Ron and Mike were busy putting the junction boxes and electric panels in place.

Electrical conduit in East Mechanical room.

Electrical conduit in East Mechanical room.

View of East Mechanical room. Note underground electrical conduit coming from street.

View of East Mechanical room. Note underground electrical conduit coming from street.

New Entrance to Project Site

Since the perimeter wall will be in place, Bill Brown’s team had to construct a temporary entrance.

New entry and fixed ladder in place.

New entry and fixed ladder in place.

Delivering Concrete Core Samples to HP Inspections

Bryan spoke with Scott Pinkham and arranged to deliver the five core samples directly to HP Inspections’ offices in San Jose.

Scott reviewed the coring procedures with Bryan and looked at the samples.  No voids or ‘shadows’ were observed in any of the samples Ithis was good).

After discussing the procedures and results, Scott labeled the core samples so he could complete the test results tomorrow and complete their report.

Scott Pinkham, HP Inspections, labeling the shotcrete core samples.

Scott Pinkham, HP Inspections, labeling the shotcrete core samples.

Shotcrete core samples ready for review.

Shotcrete core samples ready for review.

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