The Development of Shotcrete

Conventional cast-in-place concrete and shotcrete share many of the same properties but shotcrete provides an advantage in placement.  It bonds with most substrates instantly or very rapidly, which makes it a good choice on complex forms or shapes.  Similarities to conventional concrete include high strength, low permeability and high durability.  It has a wide range of applications that include repair or restoration, ground support, architectural and landscape restoration, new construction and much more. 

Shotcrete, originally known as gunite, was developed by Dr. Carl E. Akely.  In his process, the dry material was blown out of a hose and water injected at the nozzle.  Akeley went on to patent his cement gun and the material he called Gunite.  During that period, he created the Cement Gun Company (now called Allentown Equipment).

In the mid-1950s, a wet mix method was introduced to the construction industry.  The benefits were recognized immediately and it was used on many projects.  Shotcrete became even more popular with the development of a rotary gun that had an open hopper which allowed the material to be continuously fed.   

The American Shotcrete Association credits the technical advancements in materials and equipment made in the 1970’s of providing an enormous improvement in the application of shotcrete.  They state that, “Perhaps the most significant step in this period was the development of efficient concrete pumps that could be used for wet shotcrete application.”

The 1980’s continued with advancements in the mixing and batching of ready mix concrete and the development of admixtures that allowed for consistency, hydration and performance.  Today one of the biggest changes to shotcrete applications is the ability of modern equipment to pump any slump as well as to pump it over long distances and up into high-rise construction projects.  

Sources:en.wikipedia.org/wiki/Shotcrete,shotcrete.us/,shotcrete.org/whyshotcrete/index.htm

The Conco Companies are leading suppliers of concrete services for the Western United States. We got our start in the Bay Area in 1959 by offering clients the best value on a wide range of concrete services and products.  Since that time, we have taken a leading role as one of the top concrete contractors in the region. We have four regional offices serving California, Washington, Oregon, Nevada and Colorado.

The History of Concrete Pumps

As a leading commercial concrete contractor, the Conco Companies have had our share of challenging jobs placing concrete over our more than 50 years in the industry.  Our success can be attributed to not only our seasoned team of professional engineers, managers, and pump operators but also to our impressive inventory of pumps conveniently located in California, Washington, Oregon, Colorado, and Nevada.

Many projects that have been built since the end of World War II would not have been possible without the use of concrete pumps.  Records show that the first patent for a concrete pump was applied for in 1913 by C. A. Cornell and S. A. McKee of the U.S. with little further development done at that time.  In 1927, after unsuccessfully attempting to lift concrete to the top of a war memorial in Germany, engineer Fritz Hell started working on a pump that would do that type of job.  Three years later the Rexnord Company of Milwaukee, Wisconsin introduced the Pumpcrete.  Its inventor was C. W. LeValley. 

Many of the early innovations in pump designs were done by the Germans along with other Europeans as they had the need for such equipment during their reconstruction period following WWII.  Information from Ritchiewiki Everything About Equipment site, says the first hydraulic pump was developed by the Torket Company of Germany in the 1950s using water to operate.  They add that in 1957, “the Schwing Company manufactured a fully hydraulic double-cylinder pump that used an oil-operated ram with a water-flushed cylinder.”

During the 1980s and 90s, many of the largest manufacturers of concrete pumps were located in Germany and Japan.  Today manufacturers are located across the globe with the U.S. having several major manufacturers as most large construction projects rely on pumps to place the concrete such as skyscrapers, bridge pilings, dams, and tunnels.  The ability to pour concrete using modern, state-of-the-art pumps saves projects both time and money.

Sources:

ritchiewiki.com/wiki/index.php/Concrete_Pump

concretepumping.com/dictionary/index.php/The_PumpCrete_by_Rexnord_

or_Chain_Belt_is_believed_to_be_the_worlds_first_Concrete_Pump_1930

For over 50 years, Conco has provided premium concrete services throughout the Western United States and is one of the most trusted concrete contractors in the Seattle area.  We partner with clients on every project from the pre-construction stage right through to final completion to maximize efficiency and ensure goals and budgets are met.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects.

A Short History of Shotcrete

 

Shotcrete is pneumatically placed concrete that is used as an economical alternative to traditional cast-in-place walls.  As it almost eliminates the forming process all together, it greatly reduces labor cost and time.  Shotcrete has the same structural characteristics as traditional cast-in-place walls and a wide range of applications including shear walls, retaining walls, architectural walls, slope pavement, and soil nailing. 

Wikipedia reports that shotcrete, originally known as gunite, was first used to repair the crumbling façade of the Field Columbian Museum in Chicago in 1907 by a well-known naturalist, Dr. Carl E. Akely.  He used a process where dry material was blown out of a hose and water was injected from the nozzle.  Mr. Akeley later went on to patent the equipment, which was called a cement gun, and the material called Gunite.  The Cement Gun Company was soon started (now called Allentown Equipment).

It was not until mid-1950 that a wet mix method was introduced to the construction industry.  Right from the start the benefits were recognized and it was successfully used on many projects.  Shotcrete really took off from there with the development of a rotary gun that had an open hopper, which allowed the material to be continuously fed.    

The American Shotcrete Association credits the technical advancements in materials and equipment made during the 1970’s of providing a huge improvement in the applications of shotcrete.  They report that, “The Engineering Foundation organized the first conference for The Use of Shotcrete for Underground Support.”  Furthermore, they write that, “Perhaps the most significant step in this period was the development of efficient concrete pumps that could be used for wet shotcrete application.”

The 1980’s saw advancements in the mixing and batching of ready mix concrete with developments of admixtures that allowed for consistency, hydration and performance.  One of the biggest changes in the shotcrete that is used today is the ability of equipment to pump any slump and to be able to pump it over long distances and up into high rise construction projects.  

* http://en.wikipedia.org/wiki/Shotcrete

* http://www.shotcrete.us/

* source: American Shotcrete Association

Conco is taking a more active role in the Portland area with our expansion of high-quality commercial concrete services.  We bring our years of experience delivering dependable services since 1959, and a vast portfolio of noteworthy and large-scale projects from throughout the Western U.S.  Our work includes commercial, industrial, educational and multi-residential construction as well as public works projects. 

Cast-in-place Concrete

By Conco  

Cast-in-place concrete is a commonly used building material for commercial and residential structures and accounts for 75% of all concrete used.  The process starts with a temporary form in which reinforcement such as steel bars (rebar) may be added.  The next step is to pour the liquid, ready mix concrete that has been transported to the jobsite (it may in some cases be mixed on site) into the removable forms.

Using cast-in-place offers the same benefits as other types of concrete such as durability, and strength and can use some recycled material.  It is resilient when faced with severe weather conditions such as tornados as well as resistant to mold, rot, bugs, and fire.  The thermal mass of the concrete helps to reduce a building’s energy costs and has the added benefit of acting as a sound insulator.  Moreover the concrete is ready to use once the forms are stripped and does not require any further treatment.

Originally this method was only used for sub-grade walls but the renowned inventor, Thomas Edison, experimented with using cast-in-place concrete on above-grade projects.  He demonstrated the success of his work by constructing several homes that were made entirely out of cast-in-place concrete.  With many improvements and new developments since then, cast-in-place is now used for constructing slabs, walls, beams columns floors, and roofs as well as for forming special architectural features.

The forms need to remain in place until the concrete is self-supporting.  Since one of the primary costs of cast-in-place is the forming process, using prefabricated formwork can help speed up a job and save money.  They are assembled on site and can be reused over and over again.

Conco is a leading supplier of concrete services for the Western United States. We got our start in the Bay Area in 1959 by offering clients the best value on a wide range of concrete services and products.  Since that time, we have steadily taken a leading role as one of the Bay Area’s top concrete contractors. 

Retrofitting Historic Buildings Against Earthquakes

New construction is being built better than ever to withstand the threat of earthquakes.  Moreover since earthquake activity is not limited to the West Coast, local building codes throughout the country mandate that new construction be resistant to the strongest earthquake activity that is believed possible in an area.  This task has become easier with new high-tech materials that are available such as fiber-reinforced polymers, fiber reinforced concrete and high strength steel.  

One of the on-going phases in creating safer buildings is the seismic retrofitting of older structures to be more resistant to seismic activity and ground motion.  Among these projects include significant historical buildings that have the additional task of ensuring the structure is stronger while still preserving the distinctive characteristics that make the buildings special.  

Obviously first and foremost human safety is addressed and then the focus switches to work on retaining the distinct architectural features of the building. Common weaknesses in historic buildings when faced with earthquake activity include unreinforced masonry and structural connections between walls, floors, and foundations.  Older construction used unreinforced bearing walls that offer inadequate lateral resistance and ductility or flexibility when subjected to seismic activity.     

According to the NPS Department of Interior’s Preservation Briefs, it is imperative to put together a team of experienced engineers, architects, and building code officials as well as consulting with their agency’s administrative staff.  They state that, “Historic materials should be preserved and retained to the greatest extent possible.”  Also that, “New seismic retrofit systems, whether hidden or exposed, should respect the character and integrity of the historic building and be visually compatible with it in design; and that, seismic work should be ‘reversible’ to the greatest extent possible to allow removal for future use of improved systems and traditional repair of remaining historic materials.” 



 

Conco is a leading supplier of concrete services for the Western United States. We have built our reputation in the Los Angeles area with superior concrete formwork, reinforcing, place and finish, shotcrete and other ancillary services that benefit from our vast experience.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects.

 

Some of the Largest Concrete Pours

Conco’s regional office in Washington completed a 2,880 cubic yard mat pour using 275 tons of rebar for The Martin, a 24-story luxury apartment tower for general contractor Exxel Pacific.  The Martin is located in Seattle’s downtown area known as Belltown, adjacent to the Monorail, which made access and time constraints a concern.  

A total of three pumps were used - a 36 meter, 47 meter & 58 meter to complete the mat pour pumping 450 cubic yards per hour at peak times. Cadman, Inc. delivered the ready-mix with trucks arriving approximately every 80 seconds to fill the mat which measures 7′-6″ at the deepest point.

While we are proud of our accomplishment at The Martin, we are in awe of some of the world records set for concrete pours.  According to the International Union of Bricklayers and Allied Craftworkers (BAC), the largest mat pour in the U.S. was for the Venetian Hotel in Las Vegas.  It was a 22,000 cubic yard pour. 

BAC states the second largest pour in the U.S. was for the luxurious Trump Royale condominium, a 22-story, 386-unit building in Southern Florida that was done in 2007.  At the end of a very busy 24 hours, utilizing 190 trucks in constant rotation, and a 1500 man crew, 13,500 cubic yards of concrete were poured and 1,600 tons of rebar used. 

The world record for the largest concrete pour on a single project took a period of 17 years to complete.  The Three Gorges Dam in Hubei Province, China used an estimated 21 million cubic yards of concrete. 

There even stands a record for the largest continuous underwater concrete pour that was done in New Orleans in 2010.  It was for 10,251 cubic yards of concrete pumped over a period of 58 hours.   

As one of the leading commercial concrete contractors in the San Jose area, Conco has been involved with large-scale projects in the area including the Mineta Airport.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects and highways.

Why Concrete Makes Such a Good Building Material

Why Concrete Makes Such a Good Building Material

Concrete is an enormously important resource to the construction industry and the infrastructure of our country.  There are many reasons why building with concrete is such a great idea.  It is one of the most durable materials available and will last for decades, especially when you compared it to wood, asphalt or other materials.  Since concrete is extremely fire resistant, it is also a much safer material to use.

Another factor to consider of why concrete is such an excellence building material is that it is produced locally here in the U.S.  It is estimated that the concrete industry provides over two million jobs to Americans.  Furthermore, the concrete used for a project is generally produced somewhere near to the construction project, which cuts down on transportation and energy cost.  The Portland Cement Association (PCA) sites the regional nature of the cement industry and that nearly 98% of U.S. cement is shipped to customers by truck with the rest by barge or train.

Even after several decades of use, concrete can be recycled into an aggregate that has a hundred or more different uses.  The National Ready Mixed Concrete Association (NRMCA) points out the fact that concrete is “green” as it does not have any toxic runoff as asphalt does and is produced locally from abundant local sources.  Thus the mere sustainability of concrete makes it a good choice both environmentally and economically.

The newer high-strength concrete can save a project time and labor cost with earlier form stripping times and less post-tensioning required in floors.  This also results in columns with less rebar congestions.   

To fully appreciate the significance of concrete, you need to know that concrete is the single most widely used man-made material in the world.  It is used to construct the skyline in cities and to build highways, schools, hospitals, factories, entertainment venues and public work projects.  

One of the properties of concrete is that of a natural insulator.  The thermal mass of a concrete wall acts as an efficient insulator in commercial and residential structures that helps to save on heating and cooling expenses.  The concrete forms an integral wall that is exceedingly airtight and solid without allowing any cracks that cause air leaks.  The largest percent of energy lost in a wood structure comes from air leaks.

Concrete buildings offer year-round benefits by allowing the concrete to absorb energy slowly and hold on to it for a much longer period of time than less massive building material.  This both delays and reduces heat transfers, which slows down the temperature fluctuations in a thermal mass building.  Today, modern concrete walls utilize both external insulation and thermal mass to form an energy-efficient structure with fewer spikes in heating and cooling demands.

Some construction is done using Insulated Concrete Forms (ICF) that are hollow forms or molds with built-in insulation made of foam or rastra filled with reinforced concrete.  Studies have shown that residential buildings constructed with ICF can provide energy savings of over 20% when compared to the same size wood-framed home in a cold climate.  Structures build using ICF are very quiet, safe buildings that can be outfitted with smaller heating and cooling units, which again saves money.

Conco is a leading supplier of concrete services for the Western United States.  As one of the leading commercial concrete contractors in the San Jose area, we have been involved with large-scale projects in the area including the Mineta Airport.  We have built our reputation in the Los Angeles area with superior concrete formwork, reinforcing, place and finish, shotcrete and other ancillary services that benefit from our vast experience.   Our concrete services include commercial, educational, parking and other construction development as well as public works projects and highways.

The Early History of Concrete

The earliest evidence of concrete is from a naturally occurring event caused by a spontaneous combustion between limestone and oil shale in Israel more than 12 million years ago.  These deposits still exist today.  More recently and manmade, concrete was first used by the Egyptians around 3,000 BC.  They mixed mud with straw to bind dried bricks and later used lime and gypsum mortar for the binding agent when building the Pyramids. 

Through time, concrete was used to build many of the ancient structures of which some still exist today.  The Greeks first used lime mortars around 800 BC, which were much harder than what the Romans would later use.  There is even evidence that the Assyrians used a fully waterproof concrete to construct the Jerwan Aqueduct around 700 BC. 

Modern concrete is derived from the developments made during the Roman Empire.  The Romans widely used concrete from 300 BC - 476 AD, which made possible their revolutionary architectural designs that were structurally very complex and dimensional.  Some of the cement used was from a slaked lime found in volcanic ash called pozzuolana.

The Romans used the concrete to create buildings with arches, vaults and domes.  The most famous examples of building projects include the Roman baths, the Coliseum, the Pantheon in Rome, and the Pont du Gard aqueduct in southern France.  After the fall of the Roman Empire, the art of concrete was lost for many hundreds of years. 

An interesting fact is that modern tests have proven that Roman cement (opus caementicium) had as much compressive strength as modern Portland-cement concrete.  Of course, its tensile strength was much lower without the reinforcement of today’s concrete.

Conco is a leading supplier of concrete services for the Western United States. We got our start in the Bay Area  in 1959 by offering clients the best value on a wide range of concrete services and products.  Since that time, we have steadily taken a leading role as one of the Bay Area’s top concrete contractors. Our concrete services include commercial, educational, parking and other construction development as well as public works projects and highways.