What is Portland Cement?

Joseph Aspdin, a bricklayer from England, is credited with inventing portland cement in 1824.  The named comes from its similarity to a common building stone found on the Isle of Portland in Dorset, England.  By conducting experiments in his kitchen stove, Aspdin fired ground limestone and clay together to create the first artificial cement.  This new cement was stronger than what the standard unfired crushed limestone of the day was capable of attaining.

Used throughout the world, portland cement is the most common type of cement and is the key ingredient in concrete, mortar and stucco.  When added to concrete, it is the paste that binds the aggregate (made from sand and gravel) with the water.

According to the Portland Cement Association, “Cement is manufactured through a closely controlled chemical combination of calcium, silicon, aluminum, iron and other ingredients.”  To produce portland cement, raw materials such as limestone, shell, or chalk are combined with clay, silica sand, shale, bauxite, fly ash, slag and iron.  This mixture is heated in huge cement kilns at temperatures as high as 2,700 degrees Fahrenheit.  From the extreme heat a dark grey nodular about the size of a marble is produced called a clinker.  The clinker is ground into a fine powder to make cement.  After it has cooled, it may also have a small amount of gypsum added to control the setting process. 

Wikipedia defines portland cement as "hydraulic cement (cement that not only hardens by reacting with water but also forms a water-resistant product) produced by pulverizing clinkers consisting of essentially hydraulic calcium silicates, usually containing one or more of the forms of calcium sulfate as an inter ground addition.”   The strength of the concrete mix depends on the reaction of these calcium silicates with the water. 

1.    cement.org/cement-concrete-basics/how-cement-is-made

2.    en.wikipedia.org/wiki/Portland_cement

The Conco Companies are one of the leading concrete contractors in the Western United States and offer a wide range of innovative, quality services.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects.  We have regional offices serving Northern California, Southern California, Washington State, Oregon, Colorado and Nevada.

Ways to Improve Concrete’s Durability and Workability

One of the ways for concrete to adapt to situations such as specific pumping requirements or to place concrete in extreme weather conditions is to add chemical admixtures.  A chemical admixture can be either a natural or manufactured chemical and is added to the concrete along with portland cement, aggregate, and water, and generally make up less than 5% of the total concrete mix. 

The Portland Cement Association states that, “There are five distinct classes of chemical admixtures: air-entraining, water-reducing, retarding, accelerating, and plasticizers (superplasticizers).”   Also the National Ready Mix Concrete Association (NRMCA) explains that chemical admixtures are added to concrete to increase “durability, workability or strength characteristics of a given concrete mixture.”  They can be in a liquid or powder form and are added to the concrete immediately before or during the mixing process. 

The most commonly used chemical admixtures are air-entraining agents, water-reducers, water-reducing retarders and accelerators.  Air-entraining is the process where microscopic air bubbles are deliberately added to the concrete mix.  This is done to increase the concrete’s durability when exposed to repeated cycles of freezing and thawing as well as to improve the concrete’s workability.  Another benefit is that segregation and bleeding is diminished or completely eliminated.  The only drawback is that the concrete experiences a 5% reduction in strength for each 1% of air added. 

In situations where a job demands a slower pour or during very hot temperatures, retardants are used to slow down or delay the hardening process.  It gives crews more time to place and finish the concrete.  Common retardants are lignin, sugars, and citric and tartaric acids. 

To protect concrete from extreme cold or for those times when there is a tight project deadline, accelerators are used to increase the early strength of concrete and to get it to harden faster.  Chemical accelerators are chloride based or non-chloride based and calcium chloride is one type commonly used as it is inexpensive. 

1. cement.org/cement-concrete-basics/concrete-materials/admixtures

2. nrmca.org/aboutconcrete/cips/15p.pdf

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.

Conco’s Pumping and Shotcrete Services

As a nationally recognized commercial concrete contractor, The Conco Companies serve the West Coast along with Colorado and Nevada.  Our broad range of services includes reinforcing, concrete design, formwork and concrete finishing as well as owning and operating the Reliable Trucking Company.  In addition we have built a reputation for providing premium concrete pumping and shotcrete services. 

We have operated one of the largest concrete pumping companies in the United States for over 40 years and bring to each project our vast experience in placing concrete.  By combining our expertise and extensive fleet of state-of-the-art concrete pumps, we offer customers a wide range of specialized placement options.  We know how to move materials quickly and efficiently to save both time and labor costs.  For the convenience of our customers, we have equipment based at facilities located in Northern California, Southern California and Washington State. 

Our concrete pumps have been busy at work over the last several years on some very notable projects.  We did the concrete on the San Francisco 49ers new stadium and are busy providing concrete services for the new Salesforce Tower in San Francisco.  In February of 2014, we were thrilled to break the world record for the largest continuous mat pour on the Wilshire Grand Center in Los Angeles.  All of these projects have kept our fleet of concrete pumps extremely busy.

Another area where we excel in is our shotcrete services that are offered in Washington State, Northern California, and Southern California.  We specialize in servicing jobsites with extreme operating environments such as chemical plants, gas-fired electrical generators and hydroelectric plants.  As shotcrete almost eliminates the forming process all together, shotcrete walls can be constructed faster and with less material to save time and money.

Conco is a leading supplier of concrete services serving California, Oregon, Washington, Nevada and Colorado.  We have built our reputation with superior concrete formwork, reinforcing, place and finish, shotcrete and other ancillary services that benefit from our vast experience. 

Conco Reinforcing and Design Services

The Conco Companies are one of the foremost commercial concrete contractors in the Western United States and offer customers a wide range of premium services.  In the industry since 1959, Conco has had the opportunity to experience first-hand many of the innovations and techniques that have evolved over more than half a century. 

One of the advantages of being such a large, established company is that we are able to attract some of the most talented individuals in the field to join our team.  As such Conco’s excellent reputation has offered us the opportunity to be a part of some of the most distinguished projects in the area. 

Furthermore, Conco’s line-up of exceptional resources and facilities has helped to set us apart from the competition.  For example, Conco Reinforcing operates two large rebar fabrication facilities located in California and Washington.  This gives us the capability to quickly and efficiently service customers’ needs as well as to be a single source for rebar fabrication and installation projects regardless of the size.  When you use Conco Reinforcing’s fabrication and installation services along with our concrete formwork and placement crews, you get the benefit of a coordinated one-stop-shop approach.

Another one of Conco’s strength is our reinforced concrete design services.  This group of professional engineers and estimators work meticulously on offering effective, efficient design solutions that can alleviate or prevent problems and delays on your project.  They bring to each job their vast experience and expertise as well as state-of-the-art technology and tools such as BIM, on-screen take-off, and construction management software.  Also they are able to make recommendation on the materials and processes needed to ensure a concrete structure meets all sustainability and LEED goals.

The Conco Companies are a leading commercial concrete contractor for the Western United States.  Our concrete services include commercial, educational, parking and other construction development as well as public works projects.  Conco has four regional offices that serve Northern and Southern California, Oregon, Washington, Nevada and Colorado. 

Considering a Career as a Cement Mason?

Cement masons belong to one of the world’s oldest trades, and experienced cement masons can make the difference between whether a project gets done on time and on budget.  To become a cement mason, a person begins the process as an apprentice.  Apprenticeship programs can be found through unions and contractor associations, and the program encompasses both technical training along with on the job training. 

The goal of an apprentice is to work his/her way up to the rank of journeyman, which then puts you at the top of the pay scale.  Journeymen also have the best opportunity for career advancement.  The technical side of the training in an apprenticeship includes instruction in the basics of concrete, concrete formwork, and concrete finishing as well as construction related math skills and blueprint reading.  The job training portion includes learning about the tools of the trade with practical experience that includes finishing sidewalks, curb and gutter, floor slabs, and architectural concrete.  Generally a cement mason’s apprenticeship is done over a three-year period and consists of 4,200 on-the-job hours and over 430 hours of instructional training.

At The Conco Companies, we currently have postings for cement masons at our Northern California, Southern California, Washington, and Colorado locations. Other than Colorado, these are union positions and offer competitive wages along with medical and retirement benefits.  A Conco cement mason may have the opportunity to be involved in a range of projects that includes: heavy highway and engineering construction, bridges, viaducts, tunnels, airports, water supply and drainage systems and sanitation projects, wharves, docks, breakwaters or rip-rap stone.  See the Conco website for more details and contact information regarding our posting for cement masons. 

Conco is a leading supplier of concrete services for the Western United States. We have built our reputation with superior concrete formwork, reinforcing, place and finish, shotcrete and other ancillary services that benefit from our vast experience.  The Conco Companies have four regional offices to serve California, Oregon, Washington, Nevada and Colorado.