Placing Concrete in Extreme Temperatures

At The Conco Companies we have years of experience placing concrete in all kinds of weather conditions.   We are often asked if it is ever too cold or too hot to safely place concrete.   The answer is not necessarily a “yes” or “no” but rather other factors are taken into consideration. 

“Topping Off” Ceremony for the Salesforce Tower

The final beam was hoisted into place on April 6, 2017 topping off the new Salesforce Tower in downtown San Francisco, which is the tallest building west of Chicago. While the new Wilshire Grand in Los Angeles has a spire that actually makes it higher in height, the San Francisco tower will hold the honor of having the highest occupied floor.  The 61-story skyscraper, located at Mission and 1^st Street, and has been under construction for four years.    

About the Exciting Career Opportunities for Shotcrete Professionals

Shotcrete professionals are highly valued members of the team at The Conco Companies. Shotcrete is the term used to define the entire act of spraying concrete or mortar instead of pouring by hand.

What is a Shotcrete Nozzleman?

A nozzleman is a person who understands the process of making and placing wet-mix shotcrete via a nozzle. Different kinds of shotcrete methods require different kinds of skills. For example, a nozzleman working with wet-mix shotcrete will be spraying a pre-mixed solution onto the surface. Gunite, on the other hand, is a dry-mix process in which the dry mix and the water are mixed on-demand from the nozzle. This process requires a highly skilled shotcrete professional with experience with this process.

The Conco Companies Are Always Hiring Shotcrete Professionals

Conco is one of leading commercial concrete contractors in the Western US. As Conco expands in the region, we need qualified, hardworking professionals to join our growing team. We are seeking qualified shotcrete professionals at all of our locations in Northern California, Southern California, Washington, and Colorado. A qualified candidate must have requisite shotcrete experience. In addition to shotcrete work, Conco has job openings for qualified cement masons, ironworkers, laborers, engineers, and more.  With the exception of Colorado, these are all union positions offering competitive wages, medical, and retirement benefits. Please visit our website for further details on open positions and appropriate contact information.

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

Understanding the LEED’s Rating System

The Conco Companies offer our concrete services to projects throughout the Western U.S. and many of the prominent buildings we help to construct have received high LEED certifications.  The following is a short description of some of the criteria that is used in the rating system to determine LEED certification for buildings.  

LEED is an acronym for Leadership in Energy and Environmental Design and was started in 1998 by the U.S. Green Building Council (USGBC).  According to the USGBC, the green building certification program recognizes best-in-class building strategies and practice that have a positive impact on the health of occupants, while promoting renewable, clean energy.   

LEED offers third-party guidelines for the building industry to strive to design, construct, and operate buildings that provide the most optimal environments as possible while at the same time save money and resources.  With a membership of almost 20,000, the USGBC reviews and publically updates the standards every few years.  The key issue they promote is energy efficiency and protecting or using renewable resources. Today LEED certification is sought after and a higher endorsement can increase a building’s market value.

Buildings receive LEED certification based on specific guidelines and the higher the points for achieving those goals, the higher the certification.  Levels of endorsement include Certified, Silver, or Gold – right through to Platinum, the highest award.  The five basic categories of how points are earned are:  Sustainable Sites, Water Efficiency, Energy and Atmosphere, Materials and Resources, and Indoor Environmental Quality. 

Energy-efficient appliances and heating and cooling systems increase LEED certification as does using recycled materials.  Extra points can be achieved through special recognition of Innovation in Design and Regional Priorities.  Regional points are earned when a builder has taken care to lessen or eliminate the harmful impacts on a sensitive, local environment.     Endorsements are offered on residential homes, commercial and industrial buildings and entire neighborhood projects.

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 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.

Today’s Modern Equipment Saves Time on a Jobsite

The Conco Companies are one of the top commercial concrete contractors and independent reinforcing steel and post-tension cable suppliers in the Western United States, and as such, we recognize the need to finish projects on time and on budget.  This is why we continue to purchase and utilize the most up-to-date equipment to help us successfully fulfill our commitments.  

As one of our lesser known pieces of timesaving equipment, Telebelts are designed to move heavy materials on or off a jobsite quickly and easily.  Telebelts are a mobile telescopic belt conveyor that is very versatile and comes in a variety of sizes.  This type of equipment is used to place high volumes of concrete, gravel, rock, and backfill fast and efficiently to save time and labor.  The set-up on a Telebelt is easy to do, and since it is mobile, offers the option to move around a jobsite as needed and is ideal for jobs that would otherwise have few options but to wheelbarrow material by hand.

Telebelts are fast and efficient with outputs up to 5 cubic yards per minute.  They are perfect for use in low clearance areas or under bridges and can go into limited access structures.  One example is a Putzmeister TB 130 that has a horizontal reach of 126’ 6” and a maximum rated capacity of 360 cubic yards an hour.  The unit has a 360 degree hydraulic rotation and a variety of hopper options.   

To demonstrate how we utilize Telebelts in a project, Conco recently had to backfill 2,900 tons of crushed rock in just three 8-hour days.  There was no room for error as any delay in placing the material would impact other jobs on the project.  To finish on time, we brought in our Direct Feed trailer which allows a Superdump, Transfer, End Dump or 10-Wheeler to unload its contents directly into the hopper attached to the trailer.  The material was then fed from the hopper onto one of our Telebelts.  The Telebelt placed the material directly at the point of placement, which all helped in our efforts to meet a tight deadline.

When your project demands exceptional services and the best value, Conco can deliver.  We have been offering premium concrete services throughout the Western U.S. since 1959, and have four regional offices serving California, Washington, Oregon, Nevada and Colorado. With state-of-the-art equipment and modern facilities, we work diligently to meet goals and stay within budget.

How to Control Shrinkage and Cracking in Concrete

All concrete experiences some degree of shrinkage that can affect its long-term strength and durability as well as result in cracks.  Since shrinkage is an inherent property of concrete, it is impossible to totally eliminate cracking but it can be controlled.  Concrete engineers such as those at The Conco Companies work diligently to understand and address the issues associated with shrinkage.  

We know that shrinkage is caused by a loss of volume that occurs in different stages of the process but it is still a challenge to prevent or alleviate shrinkage, and thereby the cracking.  It is an especially important consideration on projects that involve large mat pours such as the ones that Conco is doing on the Salesforce Tower in San Francisco and recently completed on the Wilshire Grand in Los Angeles. 

According to the Portland Cement Association, “The shortening of concrete slabs can be caused by temperature decreases or moisture loss. These two causes are also related to curling and warping of slabs, respectively. Curling is the deformation of the slab due to a difference in temperature between the surface and the bottom of the slab (temperature gradient).  Slab “warping” is the deformation of the slab surface profile due to a difference in moisture between the surface and bottom of the slab (moisture gradient).”* 

To ensure the placement of concrete moves quickly, it is mixed with more water than what is necessary to hydrate the cement materials.  Once the concrete is placed, the excess water separates from the hardening concrete, which results in a loss of volume that causes the concrete to shrink.  The concrete’s reinforcement or base friction works to restrain it, which in turn can create tensile stresses in the slab causing cracks. 

In an effort to prevent the shrinkage, one of the things we do at Conco is to watch out for fluctuating temperatures during the first 24 hours after placement.  We also take considerable care to use the correct concrete mixture design so that the least amount of extra water is added and the largest size of aggregate is used.  All of this can work to help reduce shrinkage.

Source:cement.org/for-concrete-books-learning/concrete-technology/focus-on-floors/concrete-shrinkage

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 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 Importance of Concrete to the World Economy

Right behind water, concrete is the second most widely used substance in the world, and as such, it is an enormous industry with billions of tons produced annually.  In the United States alone, it is a $200 billion industry and more than 500,000 people are employed in some form of career that involves concrete.

The size of the industry reflects the versatility of concrete and its many applications.  It is used in the construction of roads, bridges, dams and public works as well as most office buildings, retail stores and parking structures throughout the world.  Concrete is also used in the construction of some of the safest, most energy-efficient homes.  In addition it is pumped up to extreme heights to build today’s skyscrapers and other building projects. 

Compared to wood, asphalt and most other construction materials, concrete is very durable and will last for decades.  And unlike other materials, it gets stronger as it ages.   Also it is extremely good at standing up to natural disasters such as earthquakes, hurricanes and floods.  Add to that the fact that it is fire resistant to make it one of the safest construction materials available.   

Even after several decades of use, concrete can be recycled into an aggregate that has a variety of different uses.  It is commonly used as backfill or as gravel in new construction projects.  The National Ready Mixed Concrete Association (NRMCA) points out that concrete is “green” as it does not contain 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.

Sources:concretehelper.com/concrete-facts/,en.wikipedia.org/wiki/Concrete_Industry_Management

When your project demands exceptional services and the best value, The Conco Companies can deliver.  We have been offering premium concrete services throughout the Western U.S. since 1959, and have four regional offices serving California, Washington, Oregon, Nevada and Colorado. With state-of-the-art equipment and modern facilities, we work diligently to meet goals and stay within budget.

Construction is Underway on the Salesforce Tower

Another of The Conco Companies’ projects, the Transbay Tower was recently renamed the Salesforce Tower after the company leased a large portion of the building to become the biggest commercial real estate deal in San Francisco's history.  The new Salesforce Tower is designed by Cesar Pelli of the Pelli Clarke Pelli Architect firm and will transform the city’s skyline to become the tallest building in San Francisco and the second tallest skyscraper west of the Mississippi.

Here are some interesting facts on the new Salesforce Tower:

·        Once completed, the tower will have 1.4 million sq. ft. of office space and Salesforce will occupy 714,000 sq. ft. of it.

·         Building will be 61 floors, and have a height of 1070 feet (326 meters).

·         Salesforce will occupy the floors 1-30 as well as the whole top floor.

·         A new Transbay Transit Center will be located at the base of the tower.

·        According to the architect, the design of the skyscraper has the simple, timeless form of the obelisk, giving the 60-​story tower a slender, tapering silhouette.

·         The walls are composed of clear glass with pearlescent metal accents. 

·         High performance, low-​emission glass as well as the integrated sun shades on each floor will help to reduce the building’s cooling load.

·         Both the tower and transit center will include water recycling systems.

·         The tower is expected to receive LEED Gold certification.

 

Conco is busy laying the groundwork to accomplish another historic feat this coming fall by undertaking the largest continuous mat pour in San Francisco that will be nearly 14,000 cubic yards.  Like the Wilshire Grand Tower in L.A., both skyscrapers will have a concrete core with a structural steel frame requiring lightweight concrete to be pumped at heights that had not previously been attempted on the West coast.

Sources:

 

http://sf.curbed.com/places/transbay-tower

http://pcparch.com/project/transbay-tower

 

Conco is one of the leading concrete contractors in San Francisco offering a range of innovative, quality services.  We have been honored to work on many high-profile projects and recently completed the extensive concrete work for the San Francisco 49ers Stadium.  We have been offering premium concrete services throughout the Western U.S. since 1959, and have four regional offices serving California, Washington, Oregon, Nevada and Colorado.

 

 

Post Tension Cable

Conco is now one of the largest reinforcing steel and post tension cable suppliers in the Western U.S.  Our high-quality post tension (PT) cable meets precise engineering specifications and provides a great value to customers throughout Northern California, Southern California, Washington, Oregon and Colorado.  So what is post tensioning and how is it used in concrete construction?  

Post tensioning is the process of using high-strength, prestressed steel cables or tendons to actively reinforce concrete and apply compression after concrete is poured.  Once the concrete has hardened, the cables are tensioned, or pulled tight with hydraulic jacks and anchored to the outside edges of the concrete.  Pre-tensioned concrete, according to Wikipedia, “is cast around steel tendons—cables or bars—while they are under tension. The concrete bond to the tendons as it cures, and when the tension is released it is transferred to the concrete as compression by static friction.” 

The job of fabricating, assembling, and installing PT cable requires highly skilled workers and specialized tools.  Post tensioned concrete has all the same attributes of reinforced concrete but is used in projects that call for thinner slabs or when a greater span length is called for between support columns.  Many projects could not be done without the use of post tensioning, and it is often the choice for parking structures as it allows flexibility in the design of ramps and span lengths.  The system is also commonly used in stadiums, bridges, and office and apartment buildings.  

Additionally post tensioning reduces the amount of beams needed and allows beams to be placed the full length of a structure rather than from column to column.  Since slabs and other structural members can be constructed thinner, they require less concrete, and thereby, reduce the overall weight of a structure.  It also reduces or eliminates shrinkage cracking and is considered to be active reinforcement.    

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

*http://www.dsicanada.ca/uploads/media/DSI-USA_What_is_Post-Tensioning_us_02.pdf

For over 50 years, Conco has been providing premium concrete services and is one of the most trusted concrete contractors in Seattle.  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.

Great Progress Achieved Thus Far on the 49ers Levi Stadium

The new San Francisco 49ers Levi Stadium construction project is progressing at the fast pace needed in order to meet the approaching August 2014 opening date.  When the Levi was awarded the 2016 NFL Super Bowl game, it required the stadium to be operational for at least two years before the big game.  Hosting the Super Bowl is an honor for the stadium and will be the celebration of the 50th anniversary of the championship game.

Conco was awarded the concrete package for the $1.2 billion project that broke ground in April of 2012.  The new stadium is being built by the construction/design team of Turner Construction and Devon Construction.  Due to the aggressive timeline, construction is being handled differently.  In most cases, stadiums are built like a wedding cake with one tier on top of another.  For the new Levi, the stadium was divided into four sections and each section is concurrently being constructed as separate projects. 

Conco had to jump right into the project with the enormous task of excavating 60,000 yards of dirt, reinforce and pump 18,000 cubic yards of concrete, backfill and build a half-mile of perimeter wall – all in 40 calendar days.  According to an article in the Concrete Pumping, Fall 2013 publication, the design specifications “made the level of difficulty extremely high for what is the largest structural steel building under construction in the U.S.”  To demonstrate how large the project is, the foundation took twenty-three semi truckloads of anchor bolts to complete.  Crews worked basically day and night starting at 5 a.m. and finished up at 1 a.m. 

Concrete pumping was constant throughout the construction of the foundation and was skillfully accomplished with the help of Conco’s recently acquired, Schwing S 58 SX boom trucks, equipped with a 188-foot reach and easy set-up.  The Schwing KVM 52 and S 47 SX were also utilized.  The foundation portion was done as a series of smaller pours rather than a large slab pour.  On a typically day, 500 yards of concrete were pumped with most of the concrete a standard 4,000 psi mix, and 8,000 psi at shear lugs.  

The Schwing 58 meter boom trucks were a valuable asset on the project.   Pumps were located both inside and outside the structure and the narrow-front spread and curved outriggers provided the crew the ability to shoot around any obstacles that were in the way.  There were times that a pump ran almost 24 hours a day with one operator quickly replacing the prior operator to start pumping again.  Conco successfully met the Phase 1 foundation deadline in July 2012.  The whole team pulled together for the difficult project and has done an excellent job!       

Conco is a leading supplier of concrete services for the Western United States. We got our start in the San Francisco 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.

Why Concrete Cracks

It is a fact that concrete is the best and most widely used building material.  It is far more durable that wood or asphalt and generally requires a lot less maintenance during its lifespan than other types of material.  While we understand the hardness and durability of concrete, we are also aware that it has the tendency to crack. 

Concrete contractors know this and work to mitigate many of the controllable conditions that create the cracks.  They use preventative methods when laying the concrete that can reduce and control the amount and type of cracks.  According to the Portland Cement Association, the most common type of cracks is caused by tensile stresses that develop with the slight change of volume as concrete dries.  This is the reasons that joints are placed in concrete pavement which allows for the shrinkage in a controlled manner, thus reducing cracking.

In most cases, cracks are not structurally damaging and are to be expected in foundations and slabs.  The three basic reasons for cracking are thermal temperatures difference, plastic cracking, and shrinkage cracking.

When cracks occur before the hardening is complete, it is most likely a result of settling or shrinkage in the volume.  The Concrete Foundation Association says that shrinkage of the surface (plastic-shrinkage cracks) is caused by loss of water while the concrete is still plastic.   The types of cracks that occur after the hardening process is completed are generally the result of drying shrinkage, thermal contraction, or subgrade settlement. 

Experienced concrete contractors know all of this and much more.  They understand the proper mix and type of concrete to help eliminate cracking and to prepare the concrete to withstand all the weather conditions it will face over the years.  

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.

How Concrete Pumps Works

Concrete pumping is a very efficient and reliable means of placing concrete.  One of their advantages is that they provide the ability to access places that other methods would be unable to reach.  A concrete pump can be used for small or large jobs and provides a smooth and even distribution. 

Concrete pumps are the only placement option in very tight, confined spaces or on tall high-rises.  Pumps are the favored method for large volume mat pours and handle these jobs efficiently.  Additionally, concrete pumps can accomplish most placement jobs more economically.  Today’s concrete pumps can place concrete so precisely, there is less need for shoveling and moving it around.  This greatly reduces labor and time.

There are two types of concrete pumps.  One of them is attached to a truck and is known as a boom concrete pump.  It is used on big construction projects to quickly move large volumes of concrete into place.  The pump is operated with a robotic arm that is controlled by a pump operator and is extremely accurate in its placement.  The other type of concrete pump is called a line pump and is mounted on a trailer or truck.  It is operated manually and used on smaller projects such as residential driveways or pools. 

Concrete pump operators are certified by the American Concrete Pumping Association (ACPA), which is the only recognized certification program in the industry.  In order to get certified, an applicant must do the required prerequisite safety training and pass a test before they are given the ACPA endorsement. 

Conco is one of the leading concrete contractors in San Francisco offering a range of innovative, quality services.  We have been honored to work on many high-profile projects and were recently awarded the concrete package for the San Francisco 49ers Stadium.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects.