The Mat Foundation: The Concrete Pours By Section-First the Elevator Pits

On Thursday, February 16, 2017, the first concrete foundation pour took place in the southwest corner elevator pit. This foundation pour, which began at 7:30 am and ended around 2:00 pm, took approximately 500 cubic feet (50 truck loads) of concrete.

As I stood on the edge of the northeast shoring wall, I could observe a beehive of activity in the southwest corner of the pit. Above the shoring wall were two cement trucks, a pumping machine and an articulating boom dangling over the side of the wall. The first of what would eventually be seven foundation pours (four elevator pits and three expansive floors) had begun.

The articulating boom reaches high over the west shoring wall to deliver concrete to the job site below.

At the end of the articulating boom is a discharge hose, which is controlled by a discharge operator.  From the southwest shoring wall, I was able to get a bird’s eye view of the worksite. Each of the concrete tradesmen on this job has a specific task to perform: there are sweepers, boom watchers, safety engineers, at least one hopper watcher, a pump operator, a discharge hose operator (in the white), a remote control operator, pneumatic vibrator operators, tampers, screed operators, power trowel operators, and concrete finishers. Safety is the watchword!

No easy task being perched on the rebar while guiding the discharge hose along the delivery path. This pour or any concrete pour is no easy task and is very dangerous. For safety reasons, all movements are carefully choreographed.

Even the local Ravens made several passes overhead to observe the work in the pit.

The remote control operator (center) operates the articulating boom and the flow of concrete from the hopper to the job site below.

A truck mounted concrete pump hopper churns the concrete as the operator waits for the next concrete truck to back in place. The grate keeps the large rocks out of the hopper to prevent them from clogging the hose. Once in the hopper, the concrete is sucked into a valve system, which pushes the mix through and out the hose.

After the concrete truck backs up to the hopper, the concrete is pushed from the drum and oozes down the chute–slowly at first–and into the hopper. The project foremen visually check the first batch as it falls through the grate and into the hopper.

In the shade of the Children’s Hospital, engineers tamp down concrete samples into cylinder molds for testing purposes. Mandatory tests are performed on site and at a laboratory to ensure the strength and integrity of the concrete foundation.

After over six hours of grueling work, the smiling discharge hose operator (in the white) gives a thumbs up as the team moves closer to the end of the section.

An overhead view of the concrete pour. The section that has been leveled is approximately four feet thick.

A view of the pour from the pit. As the concrete is still being pumped, the first section that was poured is being finished at the opposite end.

Following the concrete pour, the whole section was covered in plastic to aid in retaining moisture, which in the end will help the concrete to cure harder.

Cleanup of the southwest elevator pit after curing for approximately eight days.

MARCH 1, 2017, THE CENTER ELEVATOR PIT IS POURED

(THE POUR BEGINS AT 5:00 am)

A 4:30 AM smartphone photo (by Liz) of the construction site as the concrete crew
prepares for pouring the center elevator pit. One boom pump stationed above the south
shoring wall will deliver the concrete to the site while the other boom will pump the
concrete from the rat slab.

On March 1, 2017, the foundation for the center elevator pit was poured. To complete the job it was estimated that  920 cubic yards of concrete would be pumped.

03.01.17

%MCEPASTEBIN%https://www.youtube.com/watch?v=w9sV1HF4-1Y

Approximately 92 concrete trucks will be used to complete the center elevator pit pour. Of the 92 trucks, four are in line with two (2) concrete trucks at the pump.

One of the concrete trucks is delivering concrete from the chute into the pumps hopper.

A view of the pour from the south shoring wall.

A view of the pit from above the southeast shoring wall. The complex has four (4) elevator pits. The southwest pit foundation has been poured, the center pit was being poured when this photo was taken, and rebar is still being laid in the east elevator pit. The northeast elevator pit will be dug after the dirt ramp is removed.

The proceeding photo and the photo above puts the project in context as of March 1, 2017. The east elevator pit is the second largest pit on the site and is being prepared for the foundation pour. After the dirt ramp is removed, the remaining dirt pad will be graded, the northeast elevator pit will be dug, the last section of the rat slab will be poured, and then the rodbusters will begin laying rebar. Once the dirt ramp is removed all heavy equipment and material will be lowered into and raised out of the pit by crane.

The pour as seen from the second tier z-bar rising above the center pits foundation floor. Concrete inspector Dominic is eating a salad since the pour will continue well after lunch. Rudy (right) continues to guide the hose, which discharges the concrete under pressure.

The pumping nears the end at the south section of the center elevator pit. The plywood platform is stationed on the second rebar tier, which allows for the workers to get up and over the z-bar. When taking the previous photo, the chronicler set on the edge of the plywood overlooking the pit. The unfinished concrete to the right (under the rebar) will be covered when the foundation is poured. The main foundation will rise approximately four-feet above the elevator pad.

The concrete elevator pit foundation floor flows under the forms to the sloping edge of the rat slab, which allows for added strength to the four-foot foundation wall as it surrounds the elevator pit.

No room for error! Rudy crouches as he carefully maneuvers a single strand of rebar between the first and second tiers on the east side of the elevator pit. After the concrete is poured, the rodbusters will add additional rebar to the area to give additional strength to the foundation.

Inspectors are checking the east elevator pit, which is scheduled for a concrete pour tomorrow March 30, 2017.

MARCH 30, 2017, THE EAST ELEVATOR PIT IS POURED

(THE POUR BEGINS AT 7:30 am)

The foundation pour on the last of the three elevator pits has begun. Looking south is the Patient Parking structure 4, which is under construction.

A little later in the pour, a closeup of the pit reveals that the concrete in the northwest section of the pit tops the rebar.

Two concrete trucks are at the pump are with three in line and another truck just passed through the Barton Road gate.

A view from the platform looking north into elevator pit 3.

A view of elevator pit 3 a seen from grade on the south shoring wall.

A study in perspective. It appears that the boom of the crane is touching the boom of the concrete truck but in reality, the booms are yards apart.

Running out of real estate: From the vantage point of the south wall, one can see that the moat around elevator pit 3 is now filled with concrete and
the concrete laborers are moving closer to the south side of the pit. It is getting crowded down in the pit as the laid rebar and the yet-to-be laid
rebar moves closer to the east shoring wall. Once the rebar covers the whole rat slab it will not be possible for a civilian like me to get down in
the pit. It takes great skill to walk the rebar and, I admire the rodbusters who have the skill and can spend eight hours a day walking the rebar.

03.30.17 – Video

A GoPro video of the eastern elevator pit (depression) pour. The medical center and children’s hospitals loom large in the background. The first section (western third) of the main foundation was poured five days earlier. The section is still covered with a tarp to aid in the curing process.

03.30.17 – Video

Another view and a closer view of the third and last elevator concrete pour.

As the real estate gets smaller down in the pit, safety signs are posted to caution everyone down in the pit to take
notice of their surroundings. The “We Are Safety” sign looms large over the pit from the south shoring wall railing.

PPE stands for “Personal Protection Equipment, which is required: Hard Hat, Goggles, A Vest, gloves, and Steel Toed Shoes. Other additional safety measures must be taken as required by specific tasks. Safety managers are on site to monitor and enforce all safety requirements.