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.

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. (more…)