Nov 27

Concrete Homes – Built to last!

Concrete Homes

Courtesy of Buildipedia.com

With an ever growing population in a constant need for new housing options, a planet that seems to want to shake us of her back with record floods, earthquakes, hurricanes, tornadoes and wild fires, building stronger home as well as conserving non-renewable resources is becoming an absolute imperative. As a result, old and new ideas emerge, and in the field of construction, concrete homes is making a headway.

WHAT ARE CONCRETE HOMES

In addition to pouring the usual concrete slab as the foundation and a driveway, concrete homes replace stick framing with concrete walls that are made with forms. The idea to replace wood structures is by no mean new, adobe homes are some of the oldest dwellings still standing that used rammed earth in lieu of wood. But they require substantial man power and time. Concrete homes on the other hand can be built in very little time with a small crew for about the same price as regular stick framed homes.

NEW DISCOVERY?

Not really! In 1908, while looking for an affordable and durable housing solution, Thomas Edison invented a concrete forming system for homes and patented it! The whole process would take 4 days to erect the mold structure, then pouring the concrete in 6-hour increments, completing the entire project in less than 2 weeks!  In 1937, Frank Lloyd Wright built its famous Fallingwater home in concrete showcasing its strength and ability to create unique shapes that beautiful blend with the surrounding natural setting.

concrete home using insulated concrete forms, ICFs

Setting up insulated concrete forms. Courtesy of saipreethiprecastbuilder.com

HOW CONCRETE HOMES ARE BUILT

To replace the wood structure, insulated concrete forms (ICF) are used. Once the forms are stacked up to form the wall, they are braced on the outside, a moving scaffolding is used to pour the concrete poured into the walls. Some insulated concrete forms incorporate expanded polistyrene (EPS) for greater insulation (R-60). The next day, the walls are set and framing of the interior walls can start and the scaffolding can be moved to the next house. This process could save up to 2 days of work per house!
Watch how a 250 square foot studio home is built in less that 3 hours in this short video.

WHY BUILD A CONCRETE HOME

Concrete homes are tornado and hurricane proof

Concrete home left standing after Katrina.      Courtesy of Conradscastles.com

Ask any long-time home owner what features would an ideal house have and the following is mentioned:
– Moisture, mildew and mold protection
– Termite resistant
– Provide better insulation at the same price
– Eliminate cold spots
– Provide even temperature through day and night.
– Protection against wild fires in drought prone regions (concrete is naturally fireproof)
– Withstand high winds (in hurricane prone regions)
– Meet seismic building code requirements (up to zone 4)
– Better sound proofing
Unbelievable but true, concrete homes address every feature in this list without adding extra cost for each problem.

GREEN BUILDING

Concrete homes are considered green because they recycle cementitious materials like fly ash, slag cement, silica fume that would otherwise be dumped into landfills.

For builders and home owners looking to green their homes, concrete homes completely eliminate the need for volatile preservatives found in the various glues that make up particle wood panels.

With over 9 states in the US experiencing exceptional to abnormally dry weather in 2015, the need for better insulated homes is paramount. When cooling and heating bills in Southern California can be as high as $600-800 a month for a 2,800-square-foot home, the possibility of saving up to 50% of your energy is a huge plus.

DESIGN BENEFITS

Left in its original grey color , concrete can be experienced as masculine, a bit cold and dull, but the use of concrete finishes can transform this material into warm and stunning surfaces that can be combined with wood, glass and other materials.
Concrete homes also offer a greater flexibility in terms of design. Curved walls can easily be incorporated and cheaper to build. They can be very simple and have been transformed into magnificent designs by architects around the world leveraging the surrounding landscape and terrain. Concrete can accommodate very unique modern futuristic designs and angles and can even be used to build monolythic domes.

ISSUES WITH CONCRETE HOMES

Placing concrete in the walls can be challenging and blow-outs can occur. But a experienced operator can take all the necessary precautions to avoid them.

Concrete homes used to cost 3-5% more than standard stick-framed buildings but with a 30-45% energy savings and up to 20% insurance discounts, the monthly operating costs of a concrete homeowner is equal and often even less than regular homes. So cost is no longer an issue when building a concrete home!

MARKET ADOPTION

In a market that constantly sees ups and downs, concrete homes represents a real business opportunity for concrete operators and pumping companies to stand out. Accurate placement of walls requires expertise and know-how. As in all well-established industries, new ideas can be threatening but the benefits of concrete homes so far outweighs the small learning curve builders have to go through to familiarize themselves with ICFs, pouring techniques etc.

More and more environmentally conscious consumers are doing their research and asking for concrete homes that offer energy-efficient solutions, that are much more durable and less toxic. They will only hire contractors that have experience and can do the work. So while most builders may shy away from new techniques and rather do what they know best, there is a growing new market that is waiting to be grabbed.

What size market are we talking? About 14% of the single family homes built in 2002, that’s about 171,000 homes were concrete homes, according to Jim Nicholl, PCA residential promotion manager. So with increasing unpredictable harsh weather patterns we are seeing all over the world and certainly in the US, the need and future for safer and more sustainable concrete homes is real and promising.

If you are looking for great deals on used concrete pumps or aerial lifts,
call United Equipment Sales at: (503)283-2105.

REFERENCE MATERIAL

http://concretehomesmagazine.com/

http://www.cement.org/think-harder-concrete-/homes/building-systems

S.M.L.

Share
Nov 05

Panama’s New Canal Expansion opening in 2016!

Concrete pumping

Courtesy of Canal de Panama

Originally built in 1914, the Panama Canal has been working at full capacity for years and was plagued by congestion due to an ever growing international trade. The size of ships having also increased over decades (from Panamax to Post-Panamax ships), the creation of a larger third set of locks was the agreed long-term solution. The idea isn’t new since the US started the construction in 1939 but came to a grinding stop in 1942 when it joined the allied forces in WWII. It is now almost completed, but it wasn’t done overnight!

PROJECT GOALS

  • Create 2 new lanes and increase by 1 ½ the maximum width and length of the channels to accommodate Post-Panamax ships. These lanes will be able to carry twice as much cargo and a result double the current canal’s capacity by 2016. In addition to increasing capacity, the third set of locks will also improve productivity, efficiency and safety. It will eliminate the congestion that occurs every year during the high season between December and March that can cause up to a week in delay.
  • Raising 1.5 feet the maximum operational level of the Gatun lake and widening the navigational channel will also increase the water reserve capacity, the quantity of water used by the locks without impacting the supply of water for human consumption.

A GREENER DESIGN

The new channels will each have three chambers and water saving basins. The third lock in each channel will be re-utilizing 60% of the water thus using 70% less water per transit/lock cycles compared to existing locks. The basins will be filled by gravity (without water pumps) like their older counterparts.

IMPORTANT PROJECT MILESTONES: 

Sept 2007 – The project breaks ground.

July 2009 – Contract is signed with Consortium Grupo Unidos por el Canal (GUPA) to undertake the project.

Sept 2009 – Dredging of Canal’s Atlantic entrance starts (removal of approx. 14.8 million cubic meters of material!)

2010 – Dredging of Pacific section completed (4.6 million cubic meters of material).

July 2011 – Start of pouring structural concrete in the third set of the locks project.

Oct 2011 – 1.4 million cubic of water are used to partially flood the channel (1,300 acres area).

Sept 2012 – Extension of the 14 existing gates allowing a 1 1/2-foot increase the Gatun spillway’s maximum operational level.

June 2013 – Both Pacific and Atlantic maritime entrances are now wider and deeper.

2014-2015 – Installation of 16 new gates.

June 2015 – Both Pacific and Atlantic locks are filled and gates are tested.

April 2016 – Official completion of the project.

ELEMENTS OF THE PROJECT:

Panama Canal concrete placing

Panama Canal Expansion Project – Courtesy of Canal de Panama

To create a larger lock, two 1,400-foot long by 180-foot wide by 60-foot deep lock facilities were built. One to access the Pacific side and the other for the Atlantic side. View complete drawings of the Canal new lock system.

SOME CHALLENGES :

Being prone to landslides, unstable banks and flooding, the job site required a mobile and flexible system for placing material. Concrete and gravel was first placed to lay the foundation. Six Telebelts TB 130 telescopic belt conveyors were chosen because they allow the placement of different types of material with one piece of equipment. Also, if changes in terrain conditions were suddenly to occur, the equipment could quickly be teared down, moved and setup again elsewhere.

EQUIPMENT USED: 

Used Putzmeister Katt-kretter pump

Putzmeister Katt-kretter pump

In addition to the 6 Telebelt TB 130 telescopic belt conveyors, Putzmeister America and its Special Applications Business group (SAB) supplied Thom-Katt trailer pumps and boom pumps for a complete pumping solution-based approach.

SOME NUMBERS:

To complete the third Set of locks:
– 39,238 cubic yards were excavated.
– 4,486 cubic yards of reinforced concrete were poured.
– 260 tons of reinforced bars were used.
– 1,060 ton on cement was placed.

With over 47 years of experience in the construction industry, United Equipment Sales has advised on several international large projects similar to the Panama Canal and is always available to help you find the best deal on pumping equipment (pumps, hose and accessories) and aerial lifts. Give us a call!

S.M.L.

 

Jun 04

Wireless Remote Controls For Concrete Pumping

When thinking about the evolution of concrete pumping, from carrying concrete buckets, to the invention of pump trucks, boom pumps, line pumps and more, one can’t help to marvel at man’s ingenuity when it comes to increasing performance, production and safety! As buildings get taller and more complex, equipment becomes more sophisticated to meet the ever growing demand.

Remote controls are one of these practical devices that can assist concrete operators achieve better concrete placing in a safer way. These handheld device transmitters are now standard on job sites for large equipment like loader cranes, tower cranes, overhead cranes, concrete pumps and other mobile equipment.

Below are some examples where using remote controls will make the whole difference:

Pump Trucks
Pump trucks often come equipped with both wired and fixed frequency wireless setups.  One of the problems with fixed frequency wireless controls is communication interruptions and even drop off when operating in heavy radio traffic areas as it is often the case in large cities. Remote controls powered by cables can also be dangerous and must be handled safely. Cables can get entangled in other cables laying around putting the workers at risk on the job site. Wireless controls can solve both problems.

Placing boom truck:
Operators usually hire a spotter equipped with a two-way radio or hand signals to help them maneuver the boom if they cannot leave the pump.

When operators can’t leave the pump truck and have to place the boom, they are faced with the challenge of properly gaging the depth between the boom and the wires. By using a radio remote control, they can stand perpendicular to the boom and know exactly where to place the boom.

A radio remote offers greater control over the flow of concrete, it provides the ability to turn on/off the pump at any time, and usually comes with an emergency stop too.

What to look for when buying remote controls
Some nice features to have are: weatherproof, impact resistant plastic exterior, antenna for extended wireless range, several configuration modes, good charging time, additional outputs etc.
One thing to keep in mind is that some of the best models support Frequency Hopping Spread Spectrum (FHSS) radio technology for the broadest wireless range like the OMNEX products.

Brands of remote controls
There are many models on the market, below are just a few good examples:

concrete pump remote controls

Courtesy of Hetronic – leader in remote controls

Hetronics offers the following models of controls for boom trucks and concrete pumps: With the GL series, GL-3Nova-SNova-L Nova-XL, operators can easily operate booms up to 65 meters (213 feet). All models come equipped with a battery charger and 2 rechargeable batteries.

 

 

 

 

 

 

Putzmeister Ergonic Remote Controls:

Concrete pumping

Putzmeister Ergonic Remote Control

Comes with two joysticks and rotary push buttons.
Provides direct system feedback to operator

 

 

 

Used Concrete pumps

Courtesy of Cooper Industries

OMNEX Trusted Wireless™ remote control
From Cooper Industries

Some models can even regulate the engine speed to minimize fuel consumption and wear.

 

Depending on the job, you many only need a simple remote control, so don’t over kill it. More complex remotes require more time to learn all their features, practice


Troubleshooting the remote
:
The good news is that only a few things can go wrong with a remote control:

– Most often the battery needs to be recharged and after prolonged use and replaced if the charge is holding less and less over time.

– The antenna may not be functioning. Check the antenna and its connection. It could have come loose or been damaged during a project.

So why not incorporate a remote control in your next job? Are you looking for a good concrete line pump, as plaster pump, a gunite pump? Don’t know which one comes with a remote control? Call us (503/283-2105) and we will tell you all about it so that you get in the power seat.

SML

Apr 09

Repairing Our Aging Bridges, a Concrete Dilemma!

Aging bridges

Aging bridges

In 2013, our nation’s bridges were rated and we got a C+ on our scorecard!  With the majority of our bridges approaching the ripe age of 42 years, United States is officially dealing with issues caused by an aging road infrastructure. We have over 607,380 bridges spread across the nation’s 102 largest metropolitan areas (where most of the traffic takes place with commuters and freight vehicles) and one out of nine bridges has been declared structurally deficient. The Federal Highway Administration has its work cut out for itself! The current annual budget of $12.8 billion won’t address the existing backlog by 2028! An additional $8 billion a year is needed to repair them appropriately, an additional budget that states and counties need to find to speed this process.

So what are the main issues with our aging bridges? They are either deficient, structurally deficient and/or functionally obsolete. So what’s does this mean? Well, a bridge that is considered structurally deficient will require significant maintenance, repair or even replacement and annual inspections. A deficient bridge is both structurally deficient and functionally obsolete.
A functionally obsolete bridge does not meet the current standards like load carrying capacity and width of lanes.

States that top the list of structural deficient bridges (with over 20%) are Pennsylvania followed by Iowa and Oklahoma. However, when you combined the number of bridges that have structural deficiency and are functionally obsolete, the District of Columbia leads all 50 states with 77%!

Concrete repair

Highway repair ahead!

The first signs of aging bridges are potholes, cracks, missing concrete chunks, posted signs with load restrictions and can extend in extreme cases to the closure of the bridge. The right bridge lane usually shows signs of damage faster that the left lane used for accelerating and decelerating, the shoulder lanes. To the naked eye, spalls or chips of concrete appear, they are usually caused by thermal strain due to rapid freeze thaw weathering. Dangerous explosive spalling can occur of refractory concrete and render the structure not usable as a result. Delamination or blisters is another common problem. When excess water and air in the mix are trapped under the surface mortar, voids are created along with weakened areas just below the surface that will come apart in the future. This problem stems from starting the finishing phase before the bleeding process is complete or when concrete is placed on cold substrates when ground temperatures are below 40F.

PROBLEMS:

Corrosion of steel reinforcements in concrete
This occurs when chloride ion that is found in sea water, ice melt water and deicer salts (made of sodium chloride and calcium chloride) starts corroding the concrete-steel contact surface. This can happen through drying shrinkage, cracking or the concrete’s pore water. The higher the temperature, the faster the corrosion! So regions like the Florida coast encounter constant and rapid degradation due to its warm temperatures and exposure to sea water. The corrosion produces rust which causes internal pressure and creates cracks, potholes…

Rust must be removed from the exposed reinforcing steel before repairing or the corrosion will continue under repaired patches. A layer of corrosion inhibitor must also be applied for the repair to last.

Unprotected concrete elements

Some bridges were built using bare concrete elements with black steel. Others used reinforced steel without epoxy or galvanized coating or a polymer concrete overlay. Others were made with a low slump dense concrete that results in low permeability concrete and allows chloride ions to do corrode the structure.

REPAIRS

Deck patching: for temporary partial depth repairs, bitumous concrete, quick-set hydraulic concrete, polymer mortar can be used. For full-depth patch repairs, Portland cement is the choice material.

Deck overlays:
In this method, repairs are done without removal of the chloride contaminated concrete.
Material used for these temporary repair methods are: latex-modified concrete (LMC), low slump dense concrete (LSDC) and hot mix asphaltic concrete with a preformed membrane.

Patching with Cast-in-Place PCC for Superstructure and Substructure:
This method requires the removal of loose concrete identified by sounding with a hammer. Formwork may be needed, which excludes the application of bonding agents but requires keeping forms cool by providing a cover during the curing phase.

shotcrete pump

Reed B50 Shotcrete pump

SchwingBPA500

Schwing BPA 500 Shotcrete Pump

Patching with shotcrete:
Removal of lose concrete is required. Repairs on superstructure and substructures tend to use dry-mix mortar. No bonding agent should be used. A single layer of shotcrete should be applied to avoid cold layers. A bottom up application technique should be followed to fill vertical cavities. Overhead surface may require multiple layers, 1 to 2 in. thick so that sagging doesn’t occur. Moist curing for 7 days should be provided using a cover or sprinkling system.

Encasement and Jacketing:
When column and piers have greatly deteriorated over time, concrete can be place to fill cavities, providing a new encasement for the element. In worse cases, a concrete jacket can be added after the damaged concrete has been removed.

EXPERIMENTAL  METHODS
For deck, some of the techniques involve Microsilica concrete overlays, corrosion inhibitor overlays, polymer impregnation and more.

For Superstructure and substructure elements, patching with Corrosion inhibitors is mostly used.

PREVENTION

Anything that will prevent chloride ions from entering and diffusing into concrete will work. It needs to be breathable so that water vapor can pass but not liquid water.

Deck sealers are a good option, they are either solvent or water based. Penetrating sealers are the only via options for the job (a combination of silanes and siloxanes). However, they should not be used on structure with active corrosion or high chloride contaminated concrete.

In general, large scale bridges in urban areas should be repaired first since the demand on them is higher than in rural areas. So if you are looking for a good shotcrete machine at a competitive price, give us a call at: 503-283-2105.

Further Reading:

Infrastructure Report Card (2013)

Concrete Bridge Protection Repair & Rehabilitation Plan from the Strategic Highway Research Program

 

 

 

 

Mar 24

Translucent Concrete

Light-transmitting concrete

Litracon Wall

Innovators in the concrete industry never cease to surprise us. When we first heard of “translucent concrete” we weren’t quite sure how these two words could go together! After all, concrete conjures images of heavy, solid, rough material that blocks just about everything and especially light. What if concrete could let light through? What if a wall could also turn into a window to the outside?

So what is this light-transmitting concrete?

As in all new concrete products, they use variations from the traditional ingredients. One of the main differences is the use of translucent alternatives, like glass or plastic fragments to replace conventional aggregates and let light through with the use of resins or clear glue as binding agents. Another formula involves mixing white Portland cement with white silica sand and fiber glass or plastic rods as reinforcement. Various methods have been developed and patented as a result. In most cases, a thin layer of concrete is poured manually in a mold, then fiber glass is placed on top and another concrete layer covers it. This method allows light to travel from one side of the block to the other.

Another benefit of this promising material is its ability to greatly increase insulation for buildings in harsh regions. This means that privacy is retained while allowing daylight in.That’s pretty cool for Northern regions of the world that suffer from lack of lighting for half the year!

Who are some of the pioneers?

Dr. Price from the University of Houston is not only looking into making translucent concrete, he wants to make transparent concrete made from recyclable materials that can be poured on site (currently it is only available in pre-cast bricks or panels). His vision is that in the future, cities could glow from within from translucent (and eventually transparent) zones within curving walls. A tall order that would undoubtedly revolutionize the building industry.

Other players that are selling blocks and panels include Impact Lighting Inc, Lucem (in Germany), Litracon (in Hungry), just to mention a few.

Usages for translucent concrete. Imagine the possibilities…

Translucent concrete lamp

Litracube

 

What started as a cool medium mostly used in art exhibits, in museums, was then introduced into furniture items like desks, lamps, park benches, counters and now found its way into building walls and floors.

At the Shanghai World Expo in 2010, the Italian Pavilion featured its first application in buildings. When blocks of translucent concrete were inserted into a wall in various geometric positions, soft natural light was let in during the day and a gentle glow appeared at night. The building was transformed into a soothing living structure where the separation between the inside and the outside had been greatly reduced.

Translucent wall

Lucem LED concrete wall

In 2013, the German company Lucem erected the first led infused concrete wall, with 136 color-changing led panels controlled with DMX technology via internet! With one click, these same color panels can be turned into one large display wall that can be used for communication and advertising. The age of giant billboards make soon be over!

What if sidewalks could be lit at night? This is what they did in Stockholm and pedestrians can see their path by simply looking down.

It could be use to bring natural light in underground buildings like train or subway stations. Think about safety uses, anything that could be lit from below, like speed bumps, emergency signs in case of power outage etc.

What if concrete could conduct electricity? It can and as a result airport runways and drives could automatically eliminate snow and ice as it builds up. That’s just one practical application that would save billions of dollars in cold regions of the world!

Some challenges and much promises

Being such a novelty material, translucent concrete is only available in prefabricated blocks and panels. It may take a few more years for it to be poured on site. This makes its price 4-5 times that of its conventional counterpart. However, translucent blocks can be inserted in wall and still obtain the natural lighting effect.

One experimental case had structural strength issues and with the help of chemical additives the problem was corrected. Most formulas (like the Lozoncze’s concrete block from Hungry) have shown impressive compressive and tensile strength without steel reinforcement. Translucent concrete can in fact be used a structural support!

If you are a hands-on person and want to play with the idea of translucent concrete, check out this diy article on the subject.

Getting major concrete manufacturers, engineers and architects to experiment with translucent concrete will lead to its broader adoption and more amazing applications. The future of concrete is bright and truly promising!

United Equipment Sales

 

If you have any questions about concrete equipment, give us a call.

References:

http://www.impactlab.net/2009/03/07/litracon-see-through-light-transmitting/

http://www.lucem.de/index.php?id=219&L=1

http://www.economist.com/node/779421

Mar 15

The Art of Vertical Concrete Pumping

Vertical concrete pumping

High rise construction

With the world tallest building (160 floors) completed in 2008 in Dubai (the Burj Dubai Tower)
reaching 1988.19 Ft (606 meters), the high-rise building industry has come a long way. From its humble beginning hand carrying small concrete buckets, to large buckets being lifted by cranes, the ever growing needs of long distance line pumping has pushed concrete pumps manufacturers to reinvent its technology to respond the ever growing new demands.

Some of the challenges:

When the city of Taipei decided to build in 1998 its Taipei 101 Tower/Financial Center (1,667 feet), the project was even more challenging than Dubai because of the known risks of typhoons, high winds and earthquakes. As a result, the building is able to withstand winds up to 133 miles per hour and 7-point earthquakes! This required concrete filled steel mega columns, mega-truss, a truss structure at the core, a Tuned Mass Dumper System and a 800-ton spherical steel ball suspended like a pendulum! Not your average hi-rise engineering design!

The challenge in long-distance pumping isn’t only the pumping but it is the logistics. How much pipe, hose, elbows, thrusts blocks, anchors ? How many guys you need on-site? Who will set up what by when?

When building structures reach over 1900 feet, concrete has to flow and remain longer in the delivery line (anywhere around 35 minutes). This means that the entire content of the pump chamber has to move through with each motion (piston or peristaltic) otherwise any concrete residue can harden, wear out moving parts and cause serious damage.

Projects placing higher concrete volumes require additional planning and design for pump lines. You will need 1.1 pounds of pressure, when using a standard 5-inch standpipe to move concrete one vertical foot. So, if you need to pump 1000 vertical feet, you will need at least 1.1 pounds of pressure. There is nothing better to understand the complexity involved in vertical pumping the projects than see it. So we have compiled a short series of videos showing long-distance concrete pumping on various projects around the world.

Vertical pumping also requires thorough testing of concrete performance at the batching plant, measuring concrete obtain with various pump types, output and the inner pressure of the pipe. In addition core tests and porosity tests were conducted. In the case of the Taipei financial center, a Schwing BP 8000 HDR pump was selected for consistent output and quality of concrete pumped. For the Burj Dubai Tower, 3 Putzmeister 14000 SHP D super high pressure pumps pumped a total of 165,000 m3 of high-strength concrete over a period of 32 months! Now, that’s durability! The frame, hopper, S-transfer tube and bearings have been enhanced to handle the tremendous force.

Tips From the Pros:

As a rule of thumb, the pipe’s diameter should be minimum 3-4 times the size of the largest aggregate size. When pumping concrete against gravity (vertically), a diameter smaller than the usual 125 mm pipeline should be used. It is absolutely necessary to anchor riser pipelines to the structure for the duration of the project. Pipe bends can be secured by casting them through concrete “thrust blocks”.

Be careful and always top the feeder hopper. NEVER let air into the line, especially at the beginning of the pouring job. Hose whipping is the number one cause of injuries and death on the job. When pumping at great heights, this danger is multiplied. To find out how to avoid hose whipping on the job, you can read this article.

Slump loss isn’t usually a common problem when pumping long-distance especially when the aggregate absorption is low. The key is to keep the aggregate wet during the project. This can easily be accomplished in hot regions with sprinklers watering aggregate piles.

New technologies

The country of Saudi Arabia is developing various hi-strength high-rise concrete mixes (Saudi Readymix Concrete) to be used in conjunction with advanced pumping techniques for the exploding construction market in this region of the world. Their high alumina cement content is heat resistant (up to 1500 C), ideal for building in the Middle East.

Schwing-SP1000X

Schwing-SP1000X

At United Equipment Sales, we carry all major pump brands like Schwing, Putzmeister, Reed, Mayco, Olin and more that can handle just about any job size. Below are some examples. Give us a call at (503)283-2105 if you have any questions on pumps, hose and accessories.

See our latest inventory here.

Vertical concrete pumping

Putzmeister TK30

 

 

 

Reed concrete line pump

Reed 4050

concrete line pump

Olin 565 Concrete line pump

Feb 28

Self-Consolidating Concrete

self-consolidating concrete

scc concrete

WHAT IS IT?
Self-consolidating concrete was first developed in Japan in the early 1980’s in an attempt to address the problem of lower quality construction due to a shrinking skilled labor pool that is required to create compaction and produce durable concrete structures. Also called flowing or self-compacting concrete, self-consolidating concrete (SCC) doesn’t bleed or segregate. It self-levels and can easily fill form work and confined zones of reinforcing bars due to its high flowability. Its slump is usually greater than 71/2 in (190mm) while maintaining its cohesiveness. In order to obtain a highly viscous paste with high deformability the addition of a superplasticizer is required to keep the water-powder ratio very low. ACI 237R-07 refers to it as “highly flowable, non-segregating concrete that can spread into place, fill the formwork, and encapsulate the reinforcement without any mechanical consolidation.”1

WHAT IS IT MADE OF?
Usually 50% of the solid volume is made of coarse aggregate. Fine aggregate make up 40% of the mortar volume. The water-powder ratio can be set between 0.9-1.0 with the addition of superplasticizer to achieve self-compactibility.

IT IS BEST USED…
To easily fill any form work with heavy reinforcement or in confined zones where vibrating compaction is a challenge. In precast concrete manufacturing facilities and concrete products plants. The smoothness it produces makes it an ideal candidate for architectural concrete. It is most often used for form work, reinforcement, structural design, in columns, beams, wherever lateral pressures need to be predicted and consolidation is obtained by self-weight instead of vibration. In precast concrete manufacturing facilities, the use of self-consolidating concrete is known to improve production rates and lower labor.

HOW TO TEST IT
A traditional flow test won’t work due to SCC’s high flowability. A slump flow test is better suited and can easily be conducted on construction sites. A baseline sample should be taken when placement begins, then left undisturbed, then taken again at regular intervals afterwards. What is being measured is the slump flow and the stiffening behavior of the concrete which can be altered by types of admixture, water content, dosages and temperature. Portable rheometers can be used and installed in forms for added on-site measurements. Concrete conditioning (agitated or not agitated) will impact the test results. New lateral pressures prediction models are being developed (see 2 under references for details ). Over vibrating will not cause segregation with self-consolidating concrete, however, segregation could occur if concrete is pumped over long distances.

Want to find out more about this promising product? Why not attend the 6th North American Conference on Design and Use of Self-Consolidating Concrete on May 15-18, 2016, in Washington D.C.?

Do you have any questions about concrete equipment? Call Dick at: (503)283-2105 United Equipment Sales

REFERENCES
1.  ACI Committee 237, “Self-Consolidating Concrete (ACI 237R-07),” American Concrete Institute, Farmington Hills, MI, 2007, 30 pp
2. Field investigation of self-consolidating concrete in formwork
Self-consolidating concrete: Proceedings from the first International RILEM Conference (The International Union of Testing and Research Laboratories for Materials and Structures)
Concrete flow behavior testing for self-consolidated concrete

Concrete International magazine articles:
Flowing or Self-Consolidating Concrete
Field Investigation of Formwork Pressures Using Self-Consolidating Concrete
Comparison of Three Methods to Measure Formwork Pressure When Using SCC
Pressure of Self-Consolidating Concrete on Formwork
From Rheology of Fresh Concrete to Casting Processes

 

Feb 18

Hempcrete – the Wonder of the Concrete World

Hemp productionWith 10 states having passed laws allowing hemp to be grown in the past year (*1)  for research purposes and 11 more states that introduced hemp bills this year (*2), hemp seems to be making a major coming back from its glory days. And glory days they were.

 

 

 

Some interesting facts about hemp!
Did you now that

– Hemp farming dates as far back as 5000 years in China.
– For thousands of year over 90% of all ships’ sails and ropes were made out of hemp.
– Prior to 1820s, 80% of all textiles, clothes, drapes, fabrics and most paper for schoolbooks were made of hemp.
– During the 17th and 18th century, you could be put in jail if you had land and refused to grow hemp.
– Henry Ford’s first Model-T was designed to run on hemp gasoline and that the car’s body was made of hemp plastic (which was 10 times stronger than steel!).
– It was in fact America’s first cash crop that yielded over a billion dollar, until the 19th century. Hemp rope
– In 1916, the US Government anticipated that by 1940s, all paper would be made out of hemp, ending once and for all the need to cut trees.

So how did this wonder plant manage to disappear but be banned altogether?

It all started under Hoover’s presidency, when Dupont, the chemical tycoon realized that he could not build his chemical empire and grow his powerful financial and business interests as long as this plant continued to be the main cash crop in America. After all, it required no chemical in order to grow and thrive. So financial interests combined with buying political favors resulted in a massive disinformation campaign, associating hemp with marijuana (a Mexican import) and the creation of the Federal Bureau of Narcotics in 1930, followed by the Marijuana Tax Act in 1937 making hemp the “evil weed”!

SO HOW IS HEMPCRETE MADE?
Simply by taking the inside stem of the hemp plant and mix it with a heated lime base binder to create the building material. Sand and pozzolans or cement can also be added. In terms of finishing, all that is needed for hempcrete walls, is either lime or clay plaster for internal surfaces and lime render for external walls. Stone, timber or brick can also be used as finishing. Lime-based paint should also be used.

WHAT IS HEMPCRETE USED FOR?
Uses include drywall, exterior walls, flooring, roofing and more.
– six-inch layer of Hempcrete can be sprayed on external walls and between the ceiling rafters to make the house more energy efficient.
– Hemp is used for wall insulation. But even better, building hempcrete walls do not require any insulation as they form the wall and insulation in one layer.
– It is an ideal material for restoration of old buildings, to repair infill panels and add insulation to uneven aging walls.
– To build hemp drywalls.
–   Hemp bricks are sold under names such as: Hemcrete, Canobiote, Canosmose, and Isochanvre.

WHAT ARE SOME OF BENEFITS OF HEMPCRETE?

It is flame resistant, water-proof, mildew resistant and rot-proof as long as it’s above ground.

Its thermal qualities are amazing, keeping buildings cooler in the summer and warmer in the colder month. And as a result, could reduce our energy bills in homes by half. Think of the possibilities and the impact when buildings are known to be one of the largest source of greenhouse gases in the US!

Hempcrete has great acoustic properties and is known to absorb noise, making quieter homes on busy streets.

Hempcrete is a hygroscopic material. In other words, when used to builld exterior walls, hempcrete will absorb moisture without rotting or damaging the material. It will then naturally release it during warmer and dryer temperatures. This is ideal for hot, cold and humid regions of the world that struggle with mold damage. Hemp puts an end to this problem.

Hempcrete is one of the best material for people suffering from allergies as it contains no formaldehyde, latex, urethanes or VOCs and is known to clean the air and remove toxins.

Do you live in an earthquake prone region? Foundations made with hempcrete provides 3 times more resistance to earthquake than regular concrete! Unlike cement, known for its brittleness, hempcrete combines strength and flexibility.

Hempcrete is extremely strong. When the lime hardens, it eventually turns into rock and petrifies. This means that hempcrete walls will last thousands of years, instead of 40-100 years for regular concrete. They can also be completely recycled in the ground.

MOST ECO-FRIENDLY ALTERNATIVE:   Hempcrete is Carbon negative

As a tall and super fast growing plant (new plants grow in just a few months), the cultivation of hemp removes more carbon dioxide from the atmosphere (due to its very high cellulose content) than the production and application of hempcrete combined! It is estimated that during its growing phase, it can remove over 15 tons of carbon from the atmosphere. A 1,250 sq. ft hemp house could save about 20,000lbs of carbon and only require 2.5 acres of hemp to be cultivated!

Hempcrete uses the woody stem that was previously thought as waste! Being naturally pest resistant and weed suppressant, its cultivation requires no chemical fertilizers and insecticides. Even better, the simple fact of growing hemp will help deterring insects from the area. Because of its deep root system, hemp cultivation is known to break down pour soil.

Since lime doesn’t need to be heated as much as with regular concrete when it is mixed with hemp, the process uses a lot less energy. Made too much hempcrete? Just use as fertilizer.

ARE THERE ANY ISSUES WITH HEMPCRETE?

Learning curve: As with all new technologies, there is a certain learning curve for using hempcrete and hemp building products. The good news is that there is plenty of information online and case studies available. Time will say how building using hempcrete will live up to their promises in different climates over time.

Pricing: Hemp products may be more expensive at the moment but the advantages outweigh the costs in most cases. With a broader adoption, prices will go down and make it the products of choice for all new construction.

Maintenance: Because of its high breathability, hempcrete requires the use of lime based paint which is more expensive (3 coats are required to achieve the right finish).

As our ancestors discovered, hemp offers one of the most renewable resource for construction, it answers every builder and home owner’s needs. It is in fact nature’s gift to humanity and it is time we give it its proper place in our world.

FURTHER READING

  1. Building with hempcrete
  2. Watch a hemp house being built in this video: Bringing it Home  
  3. Hempcrete Could Change The Way We Build Everything

(*1)States that have passed hemp law: California, Colorado, Kentucky, Maine, Montana, North Dakota, Oregon, Vermont, Washington, and West Virginia
(*2)States that introduced hemp law this year: Hawaii, Indiana, Nebraska, New Jersey, New York, Oklahoma, South Carolina, Tennessee.

Jan 28

Polyaspartic Coating for Concrete

What if in the sea of concrete sealants available on the market today, there was a new type of product that answered just about every operator’s wish list for achieving stunning looking concrete surfaces time after time? Too good to be true? What’s the catch? Let’s see what some of the claims that have been made about polyaspartic sealers:

What are the main Benefits of polyaspartics?

– Can be applied at any temperature (-30°F to 140°F).
– Bond to any concrete surface as long as it is prepped properly.
– Very low viscosity material can even seal small cracks due to its high flexibility.
– Produce a high film build with a single coat reaching 8 mils.
– Rapid curing to full strength  (from 5 to 120 minutes depending on the formula used).
– No or Low VOCs (volatile organic compounds) because made with high solids content.
– Superior stain and corrosion resistance.
– Greater impact resistance than epoxy or urethane coating.
– UV stable means it will never turn yellow and is a UV protected layer to the underlying coats.

That’s a pretty impressive list by any account!

So what are polyaspartic sealers made with?

Basically a two-part a polymer coating material where a resin is mixed to a catalyst to create the curing reaction that hardens the material. It has been compared to epoxy and was first invented in the mid 1980’s by Texaco Chemical Company. The original formula has since been experimented and vastly improved with a myriad of variables.

What are they best used for?
Residential and commercial applications.

Indoor:
Garage floors, auto showrooms, warehouses because of their high resistance to stain, heavy traffic, abrasion and chemical corrosion. The fact that an entire garage floor can be completed in 5 hours (instead of 5 days for an epoxy floor) when using polyaspartic coating, makes it stand out from the competition. Quartz sands or vinyl flecks can even be added to the formula for a more decorative finish look. While the cost of material may be a little higher than epoxy, the time saving makes it a superior alternative.

Great for sealing concrete counter tops due to their ability to resist acidic materials like lemon, wine etc. (link to other article)

polyaspartic coatingOutdoor:
Bridges – when embedded reinforced steel in bridges are sealed with polyaspartic coating, the structure is protected from the corrosion caused by fresh or sea water. All concrete piles of the 7-mile San Mateo/Hayward bridge in California received a 3-coat application of polyaspartic polymer during its construction, providing UV protection and deterring barnacles from clinging to the structure.

Limitations & risks

– Insufficient surface preparation can lead to disastrous results.
– Polyaspartics are impermeable so new floors should be cured for 28 days or more before applying sealer. If the substrate is contaminated or moisture is found on the surface, the coating will stick to it rather than the surface!
– Surfaces that have been cleaned with acid etching will not work because it lowers the pH and can cause delaminations problems.
– Potlife of some products can be less than 20 and as a result not adequate for large jobs.
– Product’s low tolerance for mis-application and poor installation practices.
– Not appropriate for floors with high moisture vapor emission rates.
– Fail to properly prepare will yield costly failures and rework.

CONCLUSION:
As for all new technologies, there is a phase of trial and error and a definite learning curve that are required. The most important thing to remember is that polyaspartic sealers are not for all jobs. The appeal in finishing a flooring surface in a day shouldn’t outweigh the other factors to consider. The two main causes of adhesion failure are the underlying surface has not been adequately prepared and when moisture is found on the surface. As long as you follow the manufacturer’s instructions, you should end up with a stunning results.

Examples of polyaspartic products:
InstaDrive from Kamcrete
Rapid 1000 from Rapid Coating Systems
Roll On Rock from Versatile Building Products

Have questions about concrete finishing, concrete pumps or accessories, give us a call at: (503)283-2105.United Equipment Sales

 

 

Additional reading
Different types of polyurea
Polyaspartic floor coating uses
Buyer’s Guide to polyaspartics

 

 

Jan 09

Tips for Cold Weather Concreting

Record low temperatures

Record low temperatures

With news of polar arctic weather sweeping through the Midwest and Eastern part of the country, one can’t help thinking about the movie The Day After and wondering if this is just a passing thing or something more serious! With record low temperatures (-20!) bringing many cities to a grinding halt, we thought it would be interesting to find out what are some of the challenges of pouring concrete in cold weather and recommended mitigation methods.

So how cold is cold? According to the American Concrete Institute (ACI) the definition of cold-weather concreting, as stated in ACI 306 is, “a period when for more than three successive days the average daily air temperature drops below 40 degrees Fahrenheit and stays below 50 degrees Fahrenheit for more than one-half of any 24 hour period.”  Based on this information and this week’s nationwide temperatures, no construction is happening in most of the country! Or is it?

SPECIAL PLANNING FOR LOW TEMPERATURES

To ensure that concrete placed in cold weather will last a long time, proper planning is required. This includes: selection of cement mix, proper mixing, placing, curing time, finishing techniques and overall protection of the site and concrete. In cold weather, the curing period takes longer because the lower rate of strength gain. Make sure to take into account the transportation time from the plant to the point of placement as it can have a major impact on the temperature of the mix.

If at the time of pouring, temperatures drop below 40-50°F, you can heat the water or the aggregates to reach the desired temperature. Heating cement is not an option!

Concrete operators can also use a low slump concrete for flatwork and lower water/cement ratio mixes because it will reduce the setting time and bleeding water. Selecting a concrete mix that contains admixtures that accelerate or a Type III Portland cement, Hi-Early cement that will greatly help reducing the protection time from freezing. It is especially important to increase the quantity of accelerated admixtures (PolarSet®, DCI®, Daraccel®, Gilco® or Lubricon®) towards the end of the pour to produce a more consistent set and avoid the results of cooler mixing water. It will also speed up the setting time of the last concrete batches so that the entire concrete area can set at the same time.

THE MAIN RISK: PREVENT THERMAL CRACKING

Freezing

Freezing

It is essential that every surface that will enter in contact with the concrete is free of frost, ice and snow. Whether it is reinforcement, embeds, forms, fillers, or ground

The first 24 hours after the concrete is poured is the most critical period because it is the usual amount of time that is required to reach its minimal strength of 500 pounds per square inch. If freezing occurs while the concrete is fresh or has not reached this minimal strength, ice will form in the frozen water altering the cement mix which in turn will damage its overall strength. So at 500 psi, the cement is able to resist the expansion caused by freezing water and be safely removed from the forms. As a rule of thumb, an 18°F (10°C) drop in concrete temperature will double the setting time and make it more vulnerable to freezing. Use the maturity method to verify that the concrete has reached the proper strengthening level.

PROTECTIONS TO KEEP TEMPERATURES ABOVE 50F

Insulated blanket

Insulated blanket

Some of the most commonly used methods to keep temperatures above 50° Fahrenheit are: evaporation reducers, curing compounds, polyethylene sheeting and insulating blankets. Cover protruding rebars and make sure that they don’t blow away at night when the temperatures are even lower. If the temperatures are very low, you can use a combination of electric heated blankets and insulated blankets. If the site is subject to cold winds, a 6-foot wind breakers is recommended to reduce evaporation and drop in temperature. A more costly method involves heated enclosures that can be made of wood, canvas tarpaulins, or polyethylene. Heaters can be direct-fire, indirect-fire or hydronic systems (use glycol/water solution to produce heat in a closed system of pipes). Adequate venting to the outside must be included to protect workers from inhaling carbon monoxide gas. Operators should make sure that the heaters are properly fueled to last through the night.

Two elements will affect the quality of curing: moisture and temperature. In cold weather, little to no moisture is required for curing in cold weather conditions. It is recommended to keep the concrete temperature above 40° degrees Fahrenheit for three to seven days.

WHAT IF TEMPERATURES DROP BELOW 50F?
If during the three to seven days that followed the pouring, the temperatures drop below 50 degrees Fahrenheit or are near freezing, then the time has come for a good curing compound to create a  protective liquid membrane (usually made of a water based hydrocarbon resin).

MAINTENANCE DO’s AND DON’Ts

Do make sure that no extra water or bleed water is on the surface of the concrete.
Do prevent ice from forming at all costs (this will cause an immediate drop in hydration and strength).
Do watch for hardened concrete area and make sure that they don’t occur.
Do leave forms in place as long as possible because they distribute heat more evenly during the setting phase.

Don’t overworked areas that seem to be setting more slowing.
Don’t seal freshly placed concrete or if bleed water is visible.
Don’t turn off heat too quickly as the difference of temperature between the enclosed area and the outside could cause thermal cracking (days and weeks may be required in case of large structures)

Have more questions about cold weather concrete or concrete pumping? Call Dick at (503)283-2105.

United Equipment Sales

 

Further reading:

Additional information can be found in ACI 306.1, Standard Specification for Cold Weather Concreting, ACI 306R, Cold Weather Concreting

Technical Bulletin
Role of Concrete Pouring