Astra Tower

Astra Tower is a 450 foot tall residential building made of reinforced concrete. It will surpass the Wells Fargo Center as the tallest building in Utah. Jacobsen Construction should have the building complete by the end of 2024.

This post is my best photos up until now. I'll make more posts as the building progresses.

Astra tower as of June 20, 2023. The tower consists of a reinforced concrete core, concrete columns and shear walls, and post-tensioned concrete floor slabs. The large shear wall on the left is the north wall. It is full of steel embeds - steel plates embedded in the concrete to which future facade panels will be welded. I kinda like the exposed concrete, though.

The site on August 6, 2021. A Carl's Jr. restaurant was demolished to make way for the building. On the left you can see some preliminary excavations to expose the footings of the adjacent building to the north. That is an old brick pawn shop which will soon be dwarfed by Astra.
I'm very lucky there is a large parking structure right next to the site. It's a great vantage point.

Foundation work begins! This is my favorite part of a construction project. I don't know what it is about reinforced concrete, but it just fascinates me.
The blue machine with the large black boom is a rig for drilling the deep foundation piles. Rebar cages are lined up along the bottom of the photo (West end of site), along with ~100-foot-long hollow threaded pipes which will also go into the piles. Along the North perimeter (left), a short shoring wall has gone up to protect the pawn shop. 4-5 feet of soil has been excavated along the North side to flatten the site for drilling.

Pile installation continues. This photo gives a better look at the 130-foot-tall drill rig. It's basically a large hollow auger. After drilling to depth, as the drill is retracted, a cement slurry is pumped down through the hollow auger into the hole. Once the drill is removed and hole is full of slurry, one of the thick (3" diameter I would guess) threaded steel pipes is inserted in the hole. Then, a cylindrical rebar cage is inserted. Once the cement cures, the pile is complete.
At the center of this photo, you can see excavation around some of the completed piles. These will tie into the foundation.

Bad day. Here is the large drilling rig on its side. It tipped late the night before while they were moving it to drill another pile. The two cars visible were severely damaged. The owner of the silver car came out of a show at a nearby theater to see their car destroyed. The only injury was the drill operator who fell 12 feet or so, fracturing his back. All things considered, it's amazing more damage wasn't done. If it fell a bit more to the North, those old brick businesses could be leveled.

Surveillance video taken from the rear of the pawn show shows the rig fall.
Rig Collapse Video
The report of the accident reveals several equipment procedures were not being followed when the collapse occurred. Work at the site is paused for a number of days.
Visiting the site after the rig was removed, I noticed it had smashed a large electrical transformer box as flat as a pancake.
A replacement drill rig showed up a week or so after the accident to finish pile work.

At the Northeast corner of the site, the tops of the piles are exposed. There are no below ground levels in this building. 6 levels of above-ground parking structure will be topped with residences.
Rebar for the foundation will be tied into the pile reinforcement, and one massive foundation will result.
The thickness of the footing here is 7 or 8 feet. Further South (upper left) where the core of the building will rest, the foundation grows to a thickness of about 20 feet.

Lots going on in this photo. Pile installation is complete.
The pile tops from the previous photo are at the far left. A pad of concrete has been placed to facilitate level rebar placement. Just to the right of those piles is 8-4" power conduits. These will be encased in the concrete foundation.
The upper center of the photo shows footing rebar assembly has started. An amazing jungle of rebar ties into the piles. Dead center in the photo (just up and left of the yellow mini excavator) is where the base for the tower crane will be incorporated into the footing.
Excavation for spot footings is complete at bottom left. Each spot footing rests on several deep piles. Excavation continues along the West side (bottom of photo).
At the top of the photo on the sidewalk is a group of finely-dressed business people. Not sure who they were, but they were very interested in the site as one man pointed things out to them. Perhaps they are stakeholders in the building.

Another view of the Northeast corner. The concrete slab has been placed and reinforcement for the foundation is starting to go down. Formwork is going up at the right side of the photo. The adjacent worker helps show the scale of the thickness of this foundation. The power conduits are seen running along the center of the photo.

Tons and tons of rebar get placed and tied. Waterproofing membrane (white) begins to line the walls of the excavation.
A large white drain line has shown up near the Southeast corner. This may be the main sewer line for the entire building, but I'm not sure.

Spot footings are formed and rebar installed. More drain lines snake through the foundation. The final shape of the main foundation is becoming more clear.

Long reach!

Green collars are added to each of the central threaded bars in each pile. I assume these are to act against uplift of the foundation, but I could be wrong.

Nearly ready for concrete. The base for the tower crane is in place (red truss structure at the center). Column reinforcement sticks up from the foundation rebar. 

Two pumps ran all day to place all the concrete in the main foundation. Smaller spot footings were poured earlier. I made sure to write my initials on some pennies and toss them in there a few days before this, now they'll be buried in concrete forever.

Core rebar. I guess there is a little bit of room left for concrete.
The parking garage in the background is where I get my aerial shots. Security doesn't like me loitering there.

Columns begin to rise. A bit to the right of center is a large footing for one of the shear walls which will rise the entire height of the building.
The tower crane is now assembled and in use.

Steady progress.
The first deck forms are going up along the North end. These first 6 floors will be mainly parking garage. I believe part of the Southeast corner will be residences starting at level 2.

First post-tensioned decks are poured. The parking garage ramp slopes down to the South.

The tower crane. I think this is a called luffing boom crane. The counterweight assembly is coupled to the boom and dynamically moves in and out to balance the load. One crane is all that will fit on this small site.

Another setback: Formwork collapsed during a concrete pour for the first parking garage slab. After this happened, much more diagonal bracing was added to these tall red formwork posts.

An aerial view of the formwork failure (just above the center of the photo). The red strands crisscrossing the deck are post-tensioning cables. Some of these cables are seen hanging where the formwork failed beneath. No injuries resulted to my knowledge.
All the concrete seen in this photo had to be saw cut and removed before trying again.

After the concrete mishap, vertical progress accelerates and hasn't stopped. During the day, the site is buzzing, but all is quiet in the evenings when I visit.
The concrete core keeps ahead of the decks by only 2 or 3 floors. At 95 State, one block North of Astra, the core was nearly at its full height when steel began to rise.
I have a lot of respect for those organizing projects like these. It can't be easy.

A side view of the deck slabs and formwork. Small black dots along the slab's sides mark each post-tension cable. After each cable is tensioned, the excess is cut off, and the hole filled with grout.
Similar concrete structures often use deep concrete beams to support the decks, but this building has no such beams. Keeping the decks so thin means more floors and higher profitability for the owner.

Dozens of tension cables run along the slabs and through columns.

The top of the parking structure makes a great spot for material staging and rebar cage assembly. Precast concrete cladding is hung from the floor slabs, and windows follow.