Monday, March 16, 2015

Concrete Industry and Boom Pumping Trucks

Concrete is made by mixing cement with water and aggregate (sand and gravel). Fly ash from coal fired power plants is also used for aggregate. We have already seen that it used to create pre-stressed structural members.

Copyleft: 2005 photo by David Benbennick
As a kid, we moved into a new subdivision so I was able to watch ready-mix trucks pour the foundation for a house several times. Back then (1960s), they were all rear discharge and they did not have the extra set of wheels on the back to carry the discharge shoot when travelling on public highways. The mixing drum was mounted close to the cabin to distribute some of the weight to the front wheels.
Public Domain: 2004 photo by Scott Seitz
A newer design puts in the engine in the back so the drum can discharge in front. This makes it easier to steer the discharge chute to the correct location.

There is an auger (spiral blade) the full length of the drum. When the concrete is being transported, the drum is rotated in the direction that well push the material to the back of the drum. This mixes the materials and keeps the concrete liquid. At the site, the drum is rotated in the other direction to push the concrete out of the drum and down the discharge chute.

Public Domain: Jacks Rache
As a kid, I also helped shovel gravel into a portable mixer on my Grandfather's dairy farm. Especially when they paved their barnyard. Using a shovel is one of the few things I learned to do left-handed. That was because my uncle would be on the side used for right-handed shoveling. As an adult, I again had the joy of shoveling gravel when we poured 3.5-foot deep footings for our deck.

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While checking out the railroad in Macomb, IL, I came across a plant that charges the ready-mix trucks with the needed materials. (Note the covered hopper on the right side of the photo that is still in Burlington Northern green even though it has been almost ten years since it merged with Santa Fe to form BNSF.)
John W. Coke posted
German 30T capacity, 50T Gross Cement mixer
[I've noticed in general that Europe seems to allow a lot bigger trucks on their roads than the USA does.]

The photos of mixing the concrete on site in the 1920s have been moved to their own notes.

(Update: the world's largest concrete pump truck has its own notes.)

The ready-mix trucks during my youth would struggle to drive across the property so that the chute would discharge where it was needed. Even then, they may have to use wheel borrows and shovels to move the concrete to where it was needed. Now they build trucks with a boom that folds and that carries pipes and hoses so that the concrete can be discharged directly where needed while the truck remains off to the side.
Folded photo from KCP Pumps

Unfolded photo from CIFA

Schwing America posted
No doubt this fine looking Schwing 58SX will star in a future publication of the GRAY MATTERS Newsletter! Special thanks to Wayne and Lori Bylsma of Cherokee Pumping Inc (Hampton GA)!

Photo from Loop Belt Industries
When they poured the foundation for a house across the street from me, they used a technology I had not seen before --- a telescopic conveyor boom. They parked the truck at the curb and used the boom to deliver the concrete. They would have had a hard time doing it the old fashioned way of backing a truck onto the property close to where it was needed because the houses on the adjacent lots are rather close.
Photo from Loop Belt Industries

They used a smaller version than this truck. These big outriggers would have interfered with the second lane of traffic on Main Street. Just as a photo is sometimes worth a thousand words, a video can be worth a thousand photos. I learned from the video that an advantage of the conveyor belt is that it can deliver gravel for the substrate as well as the concrete. Skip to timestamp 8:00 to see the concrete being poured. The truck used for the house in our neighborhood was also controlled by a man carrying a remote control box. The beginning of the wind energy video is interesting to see how wide the support foundation is to resist the force exerted by the turbine tower.

I notice that the development of concrete pumps and conveyor trucks has reduced the need for front-discharge trucks.

In addition to advances in technologies to deliver the concrete to the forms and slabs at the construction site, advances have been made in how to mix the concrete. After concrete is poured, the cement reacts with the water to form the strong "glue" that hold the aggregates together. This hydration of cementitious materials is an exothermic reaction. In large monoliths such as dams or the 10-foot deep "mats" for skyscrapers and smokestacks, the reaction can raise the temperature of the interior high enough that it would cause cracking. To control the temperatures for the Hoover Dam, they installed pipe in the structure to pump cooling water through the dam. For modern construction they add a few ounces of several ingredients to control the temperature. For example, for Trump's Big Pour, standard concrete would reach temperatures of around 200 degrees at the center. The mix developed for that pour was specified to have a placement temperature of less than 80 degrees (F) and a maximum of 170 degrees (F). The supplier, Prairie Materials, developed a special mix that exceeded the specifications.

Using a Self-Consolidating Concrete mix design that featured super plasticizers, low water and special cement, the concrete temperature never rose above 77 degrees during placement and the concrete in place reached a maximum of 155 degrees. The compressive strength reached 9,950 psi at 7 days and over 12,000 psi at 28 days - well within the specifications. (PRWEB)
Update:

World's Largest Concrete Pump Truck

Ahmad Akhras posted
Screenshot
Steve Hampton posted four photos with the comment: "Little deck pour 360+."
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Two pump trucks, each with room for two concrete trucks so that both pumps can continuously pour concrete.
Photo from Gallery from DeBruler
They quit adding to the video gallery in 2016 even though construction is not supposed to be complete until 2018.
 
Schwing America posted
Thanks to Michel and everyone at TPG for investing in another 8-Axle Quebec Legal Schwing 61SX. Our paint department loves this eye catching paint scheme!
Westly Walker: I ran a 61m for Brundage & Bone and ACI Concrete Placement and that set up with the boom so far back really sucks! Not sure why anyone would want that.
[There are some comments about the dead space behind the cab costing boom length.]

Chance Mckibbin posted six photos with the comment: "Emergency recovery of a pump truck that went over on Friday. Went pretty smooth and amazingly there was not apparent damage to the pump truck boom. They folded her up and drive her away." (An advantage of a crane is that it can easily lift bigger mats off a support truck and place them on the ground and then extend the outriggers over the bigger mats. The cost of renting a crane to place bigger mats for this pump would be less than renting a crane to bail it out. That is, mats would need a lot smaller crane.)
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A video of a gal pushing the hose around and operating it with a remote strapped to her waist   I wonder why the concrete doesn't flow more consistently.
Gary Ferguson Very rare that the pump operator would ever also handle the hose. It is not only wrong but very unsafe in my opinion.
Ken Degman That girl is badass!! Usually pump operators just stand there.[Normally I see the operator on the side with the remote and the crew handles the hose.]
Terry Sumner Barely a trickle there.
[There are other comments about the operator should not be on the placing hose.]
Jim Holland Looks like wet ass concrete, no consolidation being done... how much did the client pay for those shrinkage cracks he will absolutely have?
[I've seen unions use the argument for safety to justify featherbedding. But in this case, I think operating the boom and handling the hose is two jobs.]
أبو يوسف المنشاوي commented on a video



The 92-story Trump Tower in Chicago was the world's tallest concrete-reinforced building when it was completed. Its construction used concrete pumps including "A custom-built pump imported from Germany was used to handle the uppermost stories because so much force was needed to push the concrete that high."

Six concrete-pump trucks to pour a pad with 1,700 truckloads in 20 hours.



See Buckingham Fountain for an example of how they delivered concrete on site long before the concrete pump was developed.

Screenshot (source)
The technology for transferring concrete from a ready-mix truck to the forms built on the site before the pump was developed was a bucket. I'll add a closeup of a bucket when I come across one in the construction photos I took this summer. Sometimes a bucket is still used with a crane. Although I have never seen it moved as fast around here as it is in this video. Evidently the crane operator is paid by the bucket-load.

For smaller jobs, such as our driveway, gas powered wheelbarrows are used.
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Pyramids in Bosnia were made with concrete blocks long before Roman times with concrete that is better than what we can make today.

The first concrete street in America

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