New High-rise Project in San Jose

The Conco Companies are providing concrete services for One South Market, a new high-rise residential tower that is being constructed in downtown San Jose at the corner of Market and Santa Clara streets.  The project broke ground in June, 2013 and is scheduled to be completed next year.  The developer on the $135 million project is Essex Property Trust and the contractor is Balfour Beatty Construction. 

The 23-story mixed use redevelopment project will consist of 312 multi-family attached units and 6,000 square feet of commercial space on almost an acre of property.  The project is part of the Downtown Growth Area that is identified in the Envision San Jose 2040 General Plan.  Since San Jose has experienced a faster job growth than the national average in large part due to Silicon Valley, the city hopes that the new high-rise will attract more people to the downtown area.   

For Conco’s part, we once again had to come up with a creative way to fulfill one of our responsibilities on the project.  The task was to backfill 2,900 tons of crushed rock in a period of three 8-hour days and any delay in completing the job would impact the timeliness of future jobs on the project.

A jobsite is already a busy place so in order not to congest the site any further, Conco brought in its 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.  This allowed us to feed material from the hopper onto one of Conco’s Telebelts.  From there, the Telebelt placed the material directly to the point of placement.

Using this system, we eliminated the need to stockpile material on the jobsite and did not have to handle it twice via a loader or bobcat.  The job was quicker and less labor intensive than using a loader since the material was discharged directly from the back of a truck.  Reliable Trucking provided the Super Dumps for the project and the job was completed well within the required timeframe.

Sources:

nbcbayarea.com/news/local/One-South-Market-High-Rise-Building-to-Change-San-Jose-Skyline-213004711.html

 

conco is a leading supplier of concrete services for the Western United States.  As one of the leading commercial concrete contractors in the Bay Area, we have 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.

 

 

Reinforced Concrete

 

The Conco Companies reinforcing division was established in 1989, and since then, we have grown to become one of the leading reinforcing steel and post-tension cable subcontractors in the Western U.S.  We own and operate two large, state-of-the-art rebar fabrication facilities in Benicia, CA and Rochester, WA.   Utilizing our extensive in-house services and resources, we offer the most advanced technologies including building informational modeling (BIM) to meet fabrication specifications and requirements.

Our plants are outfitted with modern shear lines, benders and post-tension cable manufacturing equipment to increase accuracy and productivity and meet the most exacting standards.  Furthermore since the fabrication process requires highly skilled workers, we train our employees on up-to-date technologies that make use of BIM and our advanced field fabrication tools such as a Bartec coupler system.

So why does a project require reinforced concrete?  Without reinforce concrete, many buildings and structures that are built today would not be possible.  The natural tendency of concrete is to be brittle and it can crack or break under high pressure or when faced with strong winds, earthquakes, and other forces.  When steel reinforced bars (rebar) are embedded into the concrete before it sets, it gives the concrete a higher tensile strength and ductility. 

Reinforced concrete is used in precast or cast-in-place concrete to construct slabs, walls, foundations, beams, and columns as well as other projects.  In most cases to achieve the maximum performance required for a specific construction project, concrete only requires a relatively low percentage of rebar.  A typical equation for a concrete beam is to add 1% rebar while a column may use up to 6% of embedded rebar.  By adding the rebar, it gives concrete the required strength, ductility and durability needed for the structure and is an economical way of doing it.  

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.

 

High-Performance Concrete

 

The Conco Companies have extensive experience using different types of concrete to meet the demands of a project.  One form of concrete we use is high-performance concrete (HPC).  It is specifically designed to be more durable and/or stronger than standard concrete.  The American Concrete Institute (ACI) defines high-performance concrete as “meeting special combinations of performance and uniformity requirements that cannot always be achieved routinely using conventional constituents and normal mixing, placing, and curing practices.” 

 

While a mixture for HPC basically contains the same materials as conventional concrete, the difference is in the proportion of the materials added to give the concrete the required strength and durability.  HPC mixtures must meet structure demands as well as the environmental conditions of the project and typically use materials other than just cement to achieve the desired results.  The materials used for the mixtures are flyash, ground blast furnace slag, or microsilica fume.

 

Not all high-strength concrete is high performance.  Since HPC is used in the construction of bridge decks and highways it must contain properties such as high density, low permeability and resistance to environmental conditions.  The Federal Highway Administration says that the performance benefits of HPC are ease of placement and consolidation without affecting strength, long-term mechanical properties, early high strength, volume stability, and longer life in severe environments.  They add that the cost benefits are less material and fewer beams reduced maintenance, and an extended life cycle.   

The ACI states that HPC has a specified compressive strength of 8000 psi (55 MPa) or greater.  They add that, “The value of 8000 psi (55 MPa) was selected because it represented a strength level at which special care is required for production and testing of the concrete and at which special structural design requirements may be needed.”

Sources:

concrete.org/topicsinconcrete/topicdetail/high%20performance%20concrete

cement.org/for-concrete-books-learning/concrete-technology/concrete-design-production/ultra-high-performance-concrete

fhwa.dot.gov/research/resources/uhpc/index.cfm

Conco is one of the leading commercial concrete contractors in the Western United States.  We have four regional offices serving California, Washington, Oregon, Nevada and Colorado.  We are experts at creating cost-effective solutions that take advantage of the most up-to-date techniques.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects.

Since Conco is hard at work on the Wilshire Grand Center in L.A., which will be the tallest skyscraper in the U.S. west of the Mississippi, we thought it only fitting to do a blog series on “super tall buildings.”  Keep in mind that skyscrapers are ranked by the Council on Tall Buildings and Urban Habitat (CTBUH) and they use set criteria to designate the official height for each building.  According to the Council, “measurements are from the level of the lowest, significant, open-air, pedestrian entrance to the architectural top of the building.  This includes spires, but does not include antennae, signage, flagpoles or other functional-technical equipment.”  

For the new blog post in our series on tallest buildings in the world, we come to the fourth one, which is right here in the U.S.  The ultra-modern One World Trade Center in downtown Manhattan was designed by the renowned architect David Childs, of Skidmore, Owings and Merrill, LLP.  The building has received the designation as the tallest building in the U.S. and the fourth tallest in the world after some controversy regarding its height.  Recently the CTBUH declared that the mast on top of the building is a spire since it is a permanent part of the skyscraper’s architecture, which means the One World Trade Center is officially 1,776 ft. tall. 

The skyscraper is built with safety in mind as well as sustainability and has received LEEDS Gold certification.  According to the Port Authority of New York and New Jersey who own the building, “Its structure is designed around a strong, redundant steel frame, consisting of beams and columns. Paired with a concrete-core shear wall the redundant steel frame lends substantial rigidity and redundancy to the overall building structure while providing column-free interior spans for maximum flexibility.”  The One World Trade Center is expected to open later this year.  

Conco is a leading supplier of concrete services for the Western United States and is once again involved in doing concrete work for a major landmark project. The new Wilshire Grand Center will reshape the Los Angeles skyline as the tallest building west of the Mississippi.  As a part of the project, Conco successfully poured the largest continuous mat foundation ever done in the U.S. on February 15, 2014.

 

Concrete Work for the New San Francisco 49ers Stadium

One of Conco’s latest projects is concrete services for the new San Francisco 49ers, Levi Stadium in Santa Clara, CA.  The project began in April 2012 and has a completion date of August 2014, which is ambitious given the size and complexity of the project.  In addition, the 49ers were recently awarded the Super Bowl game of 2016.  According to NFL rules, a stadium must be completed and operational for at least two years before the game.  

The Levi is being built differently to accommodate the aggressive schedule.  Generally a stadium has one tier layered on top of the next one, around the whole arena.  In order to maximize both time and cost efficiencies, the stadium was separated into four individual projects consisting of both end zones and the two midfield sections. 

Conco’s role in the project is equally ambitious.  Project manager, Dave Fink, explains, “We had to excavate 60,000 yards of dirt, reinforce and pump 18,000 cubic yards of concrete, backfill and build a half-mile of perimeter wall in 40 calendar days.”  To get an idea of just how large the project is, twenty-three semi truckloads of anchor bolts were used on the foundations.  The concrete pumping was constant and skillfully accomplished with Conco’s newly acquired, state-of-the-art Schwing S 58 SX boom trucks with their 188-foot reach and easy set-up.  The Schwing KVM 52 and S 47 SX were also utilized.

The Levi Stadium is being billed as one of the most advanced sustainable designs, and is one of the largest buildings to be registered with the US Green Building Council.  It will have a green roof as well as solar panels, water-conserving plumbing, and state-of-the-art building controls to name just a few of the features.  The stadium should be an extremely interesting building to visit once it is completed.

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.

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.

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.