Jun 20

HOW TO TEST FRESH CONCRETE – Part 1

Fresh Concrete Testing

Considering the many factors that can affect the quality of fresh concrete, it is understandable that dozens of tests methods are available and being used today. However, we will focus today on one of the most prevalent test method called Slump test.

What are the main properties of fresh concrete that should be measured?
Primarily its strength and durability. Both factors are highly dependable on the degree of compaction and affected by transportation, placement and curing. So creating and maintaining the consistency of the mix are essential to a successful job and regular testing will help achieve the desired results.

There are 4 main areas that need to be tested:
1. Consistency
2. Workability (compacting factor test, WeBe Time test)
3. Segregation
4. Bleeding water test

Consistency or fluidity of concrete:
Think of it as the degree of wetness but beware, the wetter the mix doesn’t equate to greater workability.  Too much water can lead to segregation, too much bleeding, sand streaking on the surface. Too dry of a mix and holes and cracks (another form of segregation) will form as a sign of low plasticity.

What kinds of Test should be done
:
The most commonly used method is called Slump test. It can easily be performed and doesn’t require complicated equipment. It measures the behavior of an inverted cone of concrete (focusing on workability, consistency & wetness).

What does the process entail: Use a lightly moisten slump cone (metallic mould open at both ends with a handle). Fill it in three successive layers that have been each temped +20 times. It is recommended to hold the mold with feet to make sure that it doesn’t move during the pouring of the concrete. Quickly lift the mold right after it has been filled to the top, place the mold next to it. You can now measure the decrease in height (usually in increments of ¼ in).

Main Slump test results

Types of Slump
Collapse Slump
: it indicates a mix that is too wet or that the high workability mix you need shouldn’t be tested with this method.

Shear Slump: either the top or half of the cone tapers off. You should repeat the test. If the same result keeps happening, your mix needs more cohesion.

True Slump: most of the original shape remains, indicating a dry mix with stiff consistency.
Note: Slump test is not reliable for lean mixes (lower cement content to liquid ratio used for base layers).

Action to take:
Any variation in slump results is a signal to the mixer operator that he needs to make a change. If you experience an increase in slump, your moisture level could have suddenly increased or you may not be adding enough sand to your mix without you realizing it.

WORKABILITY
Level

SLUMP (mm)

COMPACTING
Factor

SUITABLE USES

Very low

0-25

0.78

Super dry mixes for making road with power operated vibrated machines

Low

25-50

0.85

For foundations with reinforcement and road with hand operated machines

Medium

50-100

0.92

Manually compacted flat slabs and reinforced concrete

High

100-175

0.95

great for void filling, underwater applications, pumping over long distances, large flat areas, not appropriate for vibration

When to perform a Slump Test?
On site on a day-to-day or even hour-to-hour basis when material is being brought into the mixer.

Is there an easier way to conduct the test?
You can use a K-Slump tester (best for in-situ measurement and in form testing). It looks like a syringe.

There are digital Slump Meters that use sensors and controls. They will save operators time to clean, pour, temper and measure the slump throughout the job.

There are other more sophisticated systems that combine devices and software to monitor the consistent quality of concrete from the plant and during transportation in the ready mix truck (concrete process control)

Are there any limitations to the slump test?
This test is best for testing medium to high workability (between 5-260 mm). It should only be performed on concrete using 1.5 inch aggregates or less and not be used for stiff mixes with zero slump or for wet mixes which resulted with a collapsed slump.

If the on-site slump test fails, should engineers allow the contractor continue the concreting work?
In some cases, they can order to stop the job. Depending on which school of thought they follow, some engineers may trust compression tests more than slump tests. If this is the case, they will let the contractor continue their work but demand that the finished work complies with the agreed upon compression strength. However, if the compression test fail, the work will have to be entirely demolished and redone. This approach is both costly in terms of time, resources and will break the budget. So why risk it when you can do it right from the beginning?

Using the right concrete pump for the job is also essential. With over 40 years in the concrete pumping industry, United Equipment Sales stand by its products, can help you solve challenges on the job and give you great deals on your next machine. Call Dick at (503)283-2105

Suggested Further Reading:
Fresh Concrete Properties and Its Standard Tests
The Importance of Testing Concrete
Slump Test  

 

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Jun 08

AVOID CONCRETE HOSE WHIPPING – Tips from the Pros

Hose Whipping

Hose whipping is one of the most common accident that occurs when operating a concrete pump. If you have never seen it happen on the job, check Youtube and you will see that this is no joke. The good news is that it can easily be prevented if you understand what can cause it and what simple measures to take.

So, what is hose whipping? Simply put, it is the uncontrolled and rapid motion of a flexible rubber hose on the end of a concrete placement boom or other type of concrete delivery line.

 

What causes it?
Most of the time, it happens, when air enters the line and finds a blockage in the line. The pressure increases and whatever blocked the line shoots out violently. It can also be caused by the ready mix driver that lets the hopper go dry, or the pump operator who doesn’t realize the hopper has gone dry or has a plug in the line.

However, the risk can occur way before the concrete comes out of the system. If, when the system starts up, the air comes into the line and the operator pushes a concrete mix that contains too much rocks, the pipe and hose will be dry and not yet primed. Some loose components are separated from the rest of the mix by air, creating pressure and a block. When the boom is connected to one or more lay-down rubber hoses, the danger is even greater.

Another common situation that has most operators tend to ignore is whenever you stop pumping and restart. It accounts for about 50% of these accidents because the reality on the job is that pumps stops dozens of times a day.  If after stopping, a small amount of concrete come out, it means that the line is lubricated.  However, since it is rare that the air in the line can trigger a hose whip, workers tend to downplay the risk and not stay away from the end of the hose when restarting pumping. Big mistake and again so easily preventable!

When does hose whipping happen?
Either during priming, pumping operation or when cleaning out the system. In other words, anytime the pump is on!

Dangers for the crew
Workers can either be directly hit by the hose, knocked over by it or injured by material that is ejected. It all happens really quickly and violently.

What Should Be Done to ensure that hose whipping never happens?
Here are some practical tips from the pros that have seen just about everything on the job site:

 

Always Wear Safety Gear on the Job!

ALWAYS…

  • Use properly trained professional pump operators.
  • Keep workers away from the hose at least in the first one-half yard of pumping.
  • Use quality air clamp on hose end.
  • Limit reductions as much as possible. Use a steel reducer, if you have to.
  • Have a person monitor the hopper and shut the pump in the event air is sucked into the line (it isn’t the delivery truck driver’s responsibility!)
  • Pump a little slower so that you can catch when your turn your strokes down or put it in reverse to expel the air out.
  • Use smaller rocks on smaller hoses to reduce block and releases in reducer.
  • Use safety gear: glasses, helmet, gloves etc.

NEVER…

  • Stand near the hose until the concrete is flowing freely.
  • Stand within 20 feet of the hose when starting, priming and restarting.
  • Use a metal fittings on end of delivery hoses
  • Stretch the delivery hose if it doesn’t quite reach the pouring area. Instead, move the concrete pump closer or use a larger boom.
  • Allow concrete to flow out of the hose after stopping, this can let air into it. Instead fold the hose.
  • Allow concrete to harden in the line, this will result in blockages and damage to your equipment.
  • Allow an untrained worker near the hose on the job site.

AVOID…

  • Reducers, reduction hoses, always use a steel reducer, if you have to reduce.
  • Keep the work area clean to avoid falls and tripping.

With over 40 years in the industry,  we know the importance of safety, understanding technology, proper planning and execution. We also know that using the right pump for the job means greater safety, better results, more savings in the long run. So give us a call at (503)283-2105 if you are looking for a great deal on concrete or plaster pumps or visit our website.

Additional Recommended Reading:

How to Avoid Blockages
Hose Whip Safety Alert
Examples of unsafe practices

May 27

Underwater Concrete Pumping

While most concrete jobs are done on dry land, there are many uses for concrete underwater, like building dams, bridges, sea walls, underwater foundations, repairing coral reefs and more. The first successful attempt to build under water is credited to the Greeks and dates as far back as 600 BC with the discovery of pozzualana, a
special calcined lime found on the island of Santorini.

Coral Reef in Florida

One interesting case was the underwater project that repaired the Molasses Reed, the third largest barrier reef in the world,  that was damaged by a shipwreck 6 miles Southeast of Key Largo, Florida. This accident caused the destruction of a major habitat for fish, marine and coral life. The solution was to create modules by combining small lime stone boulders, fiberglass reinforcement bars, concrete and sand. Then to lower the modules underwater and pour concrete in these modules with a hydraulic concrete pump to tie them to the damaged reef. A Putzmeister Katt-Kreter pump was used to complete this project along with a 4-yard mixer truck on the barge. Its ability to reverse the concrete back to the hopper was essential to the success of the operation.

Putzmeister Katt Kreter Pump (Side-view)

 

 

 

 

 

 

THE PROCESS

Usual settings include a boom pump or placing boom either land based or large barge mounted. In addition, there are a few challenges operators must keep in mind:

1) Placing the line below water surface requires the line to be grouted or “primed” in a way so that no water is in contact with the priming material before the prime reaches the discharge end of the pumping system. If this doesn’t happen, the grout can become too diluted and no longer properly lubricates the system, which will cause plugs. This will cause costly delays and extra steps to clear them.

2) To grout a water filled line, we recommend using 2 sponges suited for the size of the pipe line placed above the water level. Concrete must be pumped slowly so that it never passes the sponges and the water is displaced by the concrete without ever contaminating one another. Another way to achieve this is to place the concrete line inside existing concrete. Even though concrete is poured in water, the line must be kept out of the  This is essential to the integrity and strength of the resulting poured concrete.

3) In terms of cement material content, operators must include a high volume of fly ash and silica fume and chemical admixtures.

4) One of the biggest risk is overloading the pumping boom.This requires close collaboration between the pump and crane operators. Both should check to see a droop in the hose between the placing boom and the additional system to make sure it doesn’t happen.

If you are looking for a great deal on concrete pumps for a job on dry land or underwater, don’t hesitate to call Dick at (503)283-2105.

Recommended further reading:

http://www.concretepumping.com/dictionary/index.php?title=Under_Water_Concrete_Pumping

http://www.ce.berkeley.edu/~paulmont/165/tremie.pdf

ftp://dfi.org/OneMine/Marine%20Foundations%20Book%20-%20individual%20papers/29-5.4%20Underwater%20Concrete%20-%20Mix%20Design%20and%20Construction%20Practices.pdf

May 09

Milestones in Concrete Construction

We thought we would take a trip into the past to find out some of the major milestones in the history of concrete construction. After all, how can we appreciate the technologies we have today, without knowing the work that countless individuals have contributed to this industry by giving their lives, passion and vision to better our world. The timeline below is by no mean everything but covers some of the most important milestones.

12,000,000 BC – It turns out that cement compounds can be found as a result of a natural process where limestone came in contact with oil shale in a process of spontaneous combustion. It was discovered in Israel.

5600 BC – First form of concrete discovered in Europe in the region of the Danube River in Yugoslavia. It was used to make floors in stone age huts providing a major upgrade in the quality of life for hunters and gatherers.

3000 BC – First known use of concrete-like material in China with the building of the Great Wall. Made from a mix of sand, pottery shards, bones and water, this cement was greenish-black.

Egyptian pyramid

2500 BC – The practice of binding bricks using mud mixed with straw appears. The addition of lime and gypsum mortar to the process can be seen in the Pyramids in Egypt.

800 BC – The first use of bitumen (a.k.a. asphalt), a semi-solid form of petroleum that can bind stones with bricks is credited to the Babylonians and Assyrians.

600 BC – Use of the first concrete that can harden under water and in the air was made by the Greeks, thanks to the discovery of pozzuolana (a.k.a. pozzolan or calcined lime) on the Island of Santorini.

Roman Colosseum

82 AD – The Colosseum in Rome is completed using tons of Roman concrete which bears no resemblance whatsoever to Portland cement, since it is never in a plastic state and is more like cemented rubble made by manually packing mortar around stones of various sizes.

AFTER 400 AD – With the fall of the Roman Empire, the art of concrete is lost for almost 1300 years, reverting to lime based mortars and concrete.

1756-1796 – Multiple patents are filed in England for hydraulic cement (stucco), hydraulic lime etc.

1825 – Creation of the Erie Canal launching the need for cement in the United States using hydraulic lime.

1828 – First application of Portland cement used to seal breaches in the Thames Tunnel.

1850s – Building of the first concrete roads in Austria, England, other European countries and the US.

1850-1880 – French builder, Francois Coignet popularizes the use of concrete in construction.

1856 – First patent filed for the use of reinforcement in concrete using iron bars and wire mesh in small rowboats by French gentleman farmer named Jean-Louis Lambot.

1891 – First concrete streets built in the US, in Ohio.

1904 – First concrete skyscraper is built in Cincinnati, Ohio.

1905 – The National Association of Cement users is created, which will later become the American Concrete Institute.

1911 – Shotcrete is invented, allowing for the first time placement of concrete on vertical or horizontal planes.

1913 – The first concrete pump patent is filed.

1936 –  The Hoover Dam and the Grand Coulee Dam, are the first concrete dams built.

1970s – The first fiber reinforced concrete appears on the market.

1983 –  Invention of Syndecrete™, a light weight concrete that combined cement with recycled materials such as coal fly ash (a byproduct of coal plants) with polypropolene fiber to provide reinforcement (from carpet manufacturers). The finished product is used in kitchen countertops, tile flooring and more.

1985 – Introduction of silica fumes or micro silica into cement to produce the strongest concrete with very low permeability.

1995 –  Insulated Concrete Forms (ICF) are being introduced to build homes and to hold concrete, providing greater insulation (temperature and sound) than common stud walls.

Concrete pumping has grown to become a vast industry that keeps expanding its boundaries, and possibilities. Looking back over the timeline, it is interesting to see that French and British have contributed a great deal to the progress of concrete in construction and Ohio leads the way in the US! So, it isn’t surprising that the American Concrete Pumping Association is based in Ohio!

Stay tuned for a future article on newer developments in the world of concrete and what the future of concrete holds. Until then, if you are looking for a great deal on a concrete pump for your next job, why don’t you give us a call at (503)283-2105. With over 40 years of experience in the industry, we can help you solve challenges and work within your budget. We always love to hear from you.

Suggested further reading:
http://excavatorheavyequipment.com/blog/2013/06/03/plaster-used-by-ancient-builders-still-used-today/

https://fp.auburn.edu/heinmic/ConcreteHistory/Pages/timeline.htm

Apr 28

Friedrich Schwing Sr. – Visionary, Pioneer and Hall of Fame Inductee

Friedrich Schwing Sr.

Photo Courtesy of Schwing America, Inc.

It is rare that an entire industry can emerge from one man’s life work and dedication. When it comes to concrete production and handling equipment, the name and reputation of SCHWING is not only a household name but it is mostly stands out for its innovation and superior quality.

It all started in 1934, when Friedrich Schwing Sr. (1909-1992) started SCHWING GmbH, a manufacturing firm in West Germany. With over 1200 patents to his name, it was time to start building! It is hard to imagine that most buildings and high-rises that were constructed before the 1950’s were built hauling buckets of concrete! The amount of labor and inefficiencies that resulted from it, inspired Friedrich Schwing Sr. to come up with the first modern concrete pump! He chose an all-hydraulic, twin-cylinder pump that not only delivered amazing speed of placement but also allowed pumping at record heights (over 1665 ft at the One World Trade Center, for instance). Two words can describe what he achieved: faster and higher concrete pumping!

Knowing that technology alone won’t guaranty a company’s success, he made sure that his sons (Friedrich and Gerhard) received a proper education in management so that they could take care of the daily operations which happened in 1982. This also means that he could now spend more time focusing on what he did best, designing more engineering solutions.

Safety On the Job

In 1974, SCHWING America, Inc. and its 400,000 square foot manufacturing plan were created in Minnesota bringing not only German innovation and performance to America but also greater safety for all concrete operators. This was done thru the creation of safety guidelines and numerous seminars and participation in committees and boards.

In 2012, Schwing’s reputation and success lead to a merger with XCMG, China’s largest manufacturer of construction equipment. An alliance that benefited both parties as they continue to grow.

As a result, in November 2013, Friedrich Schwing Sr. was inducted into the Association of Equipment Manufacturers (AEM) Hall of Fame. In the words of the president of the American Concrete Pumping Association: “He will be remembered a pioneer and a Thomas Edison of the modern concrete machinery business” .

Dick Hibbard, a.k.a Mr. Concrete Pump!

With over 40 years in the industry, United Equipment Sales has seen and refurbished its share of worn out concrete pumps, so we can tell you from experience, that Schwing pumps are truly some of the best built concrete pumps on the market. Watch a short video hosted by Dick Hibbard as he explains why Schwing pumps are so amazing and worth the investment.

Give us a call at: (503)281-2106 if you have any questions on Schwing equipment or are looking for a great deals on used Schwing pumps.

Apr 09

Advances in Spray Concrete Lining in Tunnels

Tunnel building

For the longest times, tunnels were built using Sprayed Concrete Lining (a.k.a SCL). This technique involved an application of several layers starting with a primary lining of sprayed concrete over a membrane and was topped with a permanent layer of concrete lining over reinforced steel bars. This worked particularly well for soft ground.  Because of its layered approach, this process can be costly in terms of time, material and money. It also generates a lot of waste material adding to the cost.

To address these challenges, new designs have been tested. They range from using a permanent sprayed concrete on various types of waterproofing membranes to using permanent waterproof concrete, to applying two coats of sprayed concrete on projects where water seepage could be an issue.

Reinforced Steel Bars in Tunnel

Design options have also expanded to work with these new techniques and accommodate different geological and hydrological situations.  There are three main designs: Double Shell Lining (DSL), Single Shell Lining (SSL) and Composite Shell Lining (CSL).

Double Shell Lining process as its name implies includes a primary and a secondary linings that handle both temporary and permanent loads. Most primary linings usually contains structural fiber to reinforce them against post-crack resistance and increase the concrete ductability. This is considered a heavy duty design that will do well with ground loads and hydrostatic.

With the Single Shell linings a portion of the permanent load is handled through action with the secondary lining sometimes accomplished with multiple passes and with the use of a waterproof membrane. This technique is ideal for dry or mostly dry ground. The use of a single layer makes the construction process one of the fastest one.  Many examples of Single Shell Lining can be seen in Norway, in areas with little or no hydrostatic  load, with a watertight concrete design that accommodates for local seepage.

Composite Shell Linings consists of 3 steps, a sprayed permanent first lining, a sprayed waterproof membrane and a secondary sprayed lining. The first lining is sprayed directly on the ground and is not included in the long-term load capacity calculations. The secondary lining will handle the long-term water pressure, internal loads, shrinkage due to temperature variations etc. There are several  advantages to this technique, one of them is not having to use lattice girders. They are known for being hard to spray, for leaking and causing corrosion over time.

Safety on the Job

Another advantage is making the site safer, since placement of lattice girders can be dangerous to the crew, as it takes place at the face of the tunnel when it isn’t yet supported.

In terms of equipment to do the job, we recommend Schwing and Mayco machines.

 

We carry most Schwing models and the Schwing SP1000X, the most powerful of all. We also sell the whole line of Mayco pumps that ranges from LS30’s to LS80’s (30 to 80 yard/hour).


Call Dick Hibbard at (503)283-2105 to find out the best deals for your next job or visit us at: Unitedequipmentsales.com

 

More information can be found on this topic at: www.tunnellingjournal.com

Mar 31

Maintenance Tips for Gunite/Dry-mix Equipment

A little planning and precaution always goes a long way in the success of a project and the life of your equipment.

For any given job, a gunite contractor and its crew will have, as a very minimum, to operate and maintain a gunite machine, a material nozzle and hose, water hose, air compressor and an air hose.

Lubrication is an essential part of maintenance

A good part of maintenance on new and used machines will involve regularly oiling various part of your equipment and replacing certain parts over time. That’s just the reality of operating heavy equipment! Another good thing to remember is that every part of the machine that touches material flowing through it will wear out the fastest. So let’s see what some of these are.

If you have a bowl-type gunite machine, you will eventually have to replace the wear plate, the wear pad and material outlet. But before you get to that point, you will need to oil the pockets of the bowl after having cleaned it first after each job so that you don’t get material accumulation. If you have a steel bowl, you will need to use a hammer and something like a chisel to dislodge dried leftover material. If you have a steel/poly bowl, flip it on its belly and pound it  all over using a rubber mallet then chip any small pieces left, after every job.

Over time, the wear plate will also start to degrade. How can you tell?  Grooves will be showing up on the plate and/or in the pocket surfaces which can affect the rotation of the plate. When this happens, you should have a company resurface the plate.

Another part that will also show sign of deterioration is the wear pad due to its contact with the material. Don’t wait to replace it because it will cause faster wearing out of the wear plate if left damaged. It will also affect the quality of the air flow into the system.

DON’T: Tighten the hold clamp to try to extend the life of the wear!
DO:  Replace the wear pad as soon as it shows signs of slight deterioration.

There is also a piece of felt that protects the wear plate from the bottom of the hopper that should be lubricated until it becomes flexible and seal. No need to take anything apart to reach the felt, just use the holes in the hopper to do the lubricating. Having well oiled seals will prevent dust from escaping and create a safer work environment for your crew.

DON’T: Ignore an accumulation of dust next to your gunite machine. This is a sign that something is not working properly and needs to be checked.
DO: Replace the felt piece with a new one.

What about the air motor? The air lines comes with a filter and lubricator. Without the filter, the air that goes into the motor wouldn’t be clean and the lubricator puts a small amount of oil into the air. Both are required for the motor to function properly. As with all filters, you will need to check it to see whether or not they need to be replaced. Make sure to regularly inspect and adjust the oil level of the air lubricator.

Most gunite machines are connected to a gear box which will also need to be oiled. Some models come with an exhaust chamber that needs to be emptied out on a daily basis. The idea is to remove anything that could end up in the hopper base and could prevent rotation in the feed bowl.

DON’T: ever reach inside the hopper with your hands or arms while the air line is connected because the agitator could be moving.

DO: Connect an extra exhaust hose to the machine to bring down even more the level of dust on the job site.

Nozzles

What about hose accessories and nozzle maintenance?
The one more important piece to take care of in a nozzle is the water ring, usually made of brass or aluminum. You must inspect the tiny holes in the ring before starting any job and make sure there is nothing clogging them from a previous job. When cleaning the holes is no longer possible it is time to replace the ring.

DO: coat the water ring with some oil for extra protection
DON’T: ever drill holes in the water ring if the original holes are no longer working.

To eliminate any potential defects which cannot be seen by visual examination or in order to determine certain characteristics of the hose while it is under internal pressure, we suggest you conduct non-Destructive Hose Pressure Tests

Airplaco PG25 Gunite Machine

If you are looking for a  great gunite machine for your next job, give us a call at 503-281-2105 and we can help you find a perfect fit.

Mar 07

Best Concrete Pumps for Building a Gunite Pool

Luxury pools

Since we are experiencing one of the worse winter in decades in most of the US, we thought we would talk about swimming pools! Native Americans do rain dances during droughts, we will invoke milder weather through visions of gorgeous swimming pools!

In terms of types of swimming pools, gunite pools are, by far, one of the most popular types of pools built in the US. One of the reasons is that they are super durable and can be built in any shape or size. To build a gunite pool there are basically 9 steps you must follow, they are:

  1. Obtain permits
  2. Design layout
  3. Excavate
  4. Put plumbing in place
  5. Assemble & lay the steel framework
  6. Spray the concrete shell
  7. Apply finish coat
  8. Lay Tile/coping stone
  9. Place decking and pool finish

Since they are many other good articles that cover steps 1 through 4 and 8-9, we will focus on the gunite process itself. Once the framework grid has been assembled and laid (using 3/8 inch steel rebars), you are now ready to spray a thick coating of gunite (a mixture of cement, sand and water), around the reinforcing rods that are usually spaced 10 inches apart and secured by wire. The concrete sprayer machine combines the dry mix with water just before spraying.

After the shell is applied, a crew will smooth out the surface using trowels and let it sit for about a week before adding a finish coat because the surface will be rough and uncomfortable to the touch. At this point, some companies wet down the shell once or twice a day for a week to help the curing process. There are many types of finish like tile, fiberglass but plaster is one of the most popular ones (a mixture of marble sand and cement), and concrete paint is another good option.

Now that we are a little clearer on the overall process what are some of the best concrete pumps for the job? We recommend the following:

The Mayco LS-400 Concrete Pump

Mayco LS400

 

 

 

 

 

The Olin 545-65 

Olin 565 Concrete Pump

 

 

 

 

 

 

The Reed B50 HP 

A Reed B50 ready to ship

 

 

 

 

 

 

 

The Schwing BPA 450-500

Schwing BPA-500 concrete pump

 

 

 

 

 

 

 

The Putzmeister TK40-50

Putzmeister TK40

 

 

 

 

 

 

 

So, why these pumps?
First, they are all medium size pumps, so they can easily being towed behind a pickup truck carrying all the needed hoses and accessories.

Second, these models are not only easy and quick to setup, they also have a low hose pulsation, meaning the hose doesn’t vibrate or shake very much and greater safety for the crew.

In terms of power, they can output 7-15 yards per hour, so you will have more than you need.  Another important advantage these four models offer is the ability to pump long distances, no matter how far your ready mix truck happens to be parked on the street. You get perfect mobility which is always a plus for this type of job.

Still have questions? Don’t be shy! Just call Dick Hibbard at United Equipment Sales at (503)283-2105. He can help you solve problems,  find the perfect machine for your next job! Or visit: www.Unitedequipmentsales.com for more details.

Feb 16

Recycled Glass Use in Concrete

 The concrete industry is constantly looking for innovations, better performance and ways to lower its carbon footprint. Surprisingly, cement production accounts for about 5% of the total CO2 emitted in the atmosphere around the world.

CO2 Emissions

Another way to look at it is that each ton of cement produced outputs a ton of CO2. Much of it comes from the high melting temperature (2500°F) and from the process of decarbonation of limestone. So to lower the carbon footprint, the industry would have to either change the cement production process or to use less cement in concrete mixtures. Much research has been done around the world in finding ways to dispose of industrial byproducts like fly ash or silica fume and use them in making concrete. So much that these are now commonly found in most concrete mixtures.  What other material can be recycled into cement?

Recycled glass

Meet recycled glass
In the US, only 33% of the glass products is being recycled and only 40% of the glass that is collected is actually recycled. Part of the reason may be that glass recycling is still costly due to transportation and color sorting.  Crushed glass in large particles (larger than 75µm) produces an expansive gel that results in concrete cracking, so the particle size must be finer than 75µm to not create an alkali silicate reaction.  When this happens, mortar durability is increased. The only exception to this is the use of large glass particles in making concrete kitchen counter tops. These are becoming very popular as they combine cost saving, green practices, beautiful and unique results.

A better solution is glass powder as it has been found to improve concrete’s compressive strength and durability. Another great discovery was the water reducing effect of glass powder, leaving more water to improve the cement’s workability.

Michigan State University has been conducting extensive research in their labs on the use of glass in concrete on their campus.  They have managed to replace about 20 percent of the cement used to produce concrete by milled, or finely ground glass. The resulting concrete becomes lighter but has the same appearance with regular concrete, maybe a little lighter in color. More research is underway to test all variables needed to make this new element a standard in the industry.  To read more on this, two papers were published on the durability of the mixture, one in the Journal of Solid Waste Technology and Management, and the other in the Journal of Construction and Building Materials of Michigan State University.

The American Journal of Engineering Research (AJER) conducted workability test, density test and compressive strength test on waste glass powder in concrete. They also found that glass powder does increase the workability, density and compressive strength of concrete.  Read the complete report here.

Europe and India have also successfully spearheaded research in this emerging field. The study conducted by Dr. G.Vijayakumar, Ms H. Vishaliny and Dr. D. Govindarajulu at  Pondicherry Engineering College, in Pondicherry India, had the following very positive conclusions:

“Replacement of glass powder in cement by 20%, 30% and 40% increases:

  1.  the flexural strength by 83.07%, 99.07% and 100% respectively.
  2. the compressive strength by 19.6%, 25.3% and 33.7% respectively.
    Glass powder concrete increases the compressive, tensile and flexural strength effectively, when compared with conventional concrete. Very finely ground glass has been shown to be excellent filler.”  The complete report can be read here*

The Centre of Sustainable Development in Quebec, Canada was an early adopter of powder glass in concrete, which allowed them to reach a LEED Platinum certification. They simultaneously managed to reduce the amount of concrete used and the amount of glass dumped in landfills.

It is still too early to know whether or not glass can be used for shotcrete applications. Not enough testing and research has been done on wet or dry mix shotcrete. However, promising results were discovered in early findings for dry mix on rebound and reinforcement of bar encapsulation in the placement phase.

Stay abreast on new technologies and the latest research with United Equipment Sales. With over 40 years in the industry and all things concrete, we can help you on your next concrete job, solve challenges and find you a great deal on concrete pumps.

ADDITIONAL READING

Recipe for success: Recycled glass and cement 
Glass Powder Utilization in Concrete Production from the European Journal of Applied Sciences
Studies on Glass Powder as Partial Replacement of Cement in Concrete Production
Performance of Using Waste Glass Powder In Concrete As Replacement Of Cement from the American Journal of Engineering Research

 

Jan 30

United Equipment Sales Expands Its Operations!

Moving into a new home is considered to be a life event, but when you move 40 years of business, a warehouse and its entire inventory, it takes a move to an entire new level! So when we decided to move to a new and larger facility, we knew that it would temporarily disrupt our business so we chose a quieter period. We ended up not only expanding our working space, but also upgrading some of our office equipment, software that was in serious need of upgrade. More space means more machines, more business, more custom repair which have kept us busy, busy, busy!  And that’s a good thing!

So, we have put together a short video tour of our new 13,000 sq ft facility. You’ll get to meet Dick Hibbard, a.k.a. Mr. Concrete Pump! See our certified mechanics take concrete pumps in dire need of TLC and bring them back to life!

Our PARTS SHOP has everything you need!

Parts Shop

Clamps, couplings, reducers, gaskets, nozzles, elbows, adapters, welded groove ends, hoses of all sizes and much more…

 

Rich runs the repair Shop

 

 

 

 

 

Talk to Rich in our Repair Services if your pumps or hoses need to be repaired or have some custom work done.

Our staff is here to serve you and your business.

Meet The Team!

Our company mascot and official greeter couldn’t make it for the group photo, so here she is in her command post:

Snowbella

 If you are in the area, come by and visit us, we would love to see you!
Or call us at: (503)283-2105