Steps to Prevent Concrete from Shrinking

We know that all concrete shrinks and that it is caused by a loss of volume that occurs in different stages of the process.  Shrinkage can affect the long-term strength and durability of the concrete as well as lead to cracking.  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).”  

Even though we understand what causes shrinkage, it is still a challenge to prevent or alleviate it.  It is especially important to control it in concrete floors as the subsequent cracking will affect the performance of the floor.  This is why when Conco broke the world record for the largest continuous mat pour on the Wilshire Grand in L.A., we worked to carefully monitor the thermal characteristics of the pour to prevent cracking. 

One of the first things we addressed was to increase the proportion of fly-ash in the concrete mix design, which normally results in reduced maximum temperatures.  The next step was to mechanically control the temperatures, and for a project of that size, pre-chilling was not an option.  What we did was to post-chill the concrete by means of cooling pipes that mechanically removed the heat.

For this undertaking, we teamed up with several companies that helped to design and implement a thermal control plan specific to the mix design, the geometry of the foundation, and the configuration of the rebar.  In the end, the system we installed to post-chill the concrete was composed of 18 miles of cooling pipes, over 660 tons of chiller capacity, 40,000 gallons of chilled water, multiple pumps, 3 x 500kva of generators, and over 2,200 valves.  By keeping temperatures well below the ACI limits, we were able to avoid thermal cracking.

Sources:

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

Our mission is to be the best supplier of concrete services in the Western U.S. and to bring experience, expertise and quality to each project. We continue to upgrade and expand facilities to better serve the growing market for a wide range of construction development.  The Conco Companies have regional offices serving Northern California, Southern California, Washington State, Oregon, Colorado and Nevada.

Blended Cements Extend the Life Span of Concrete

Concrete mixes made of portland cement are porous and are susceptible to cracking especially during freeze/thaw cycles.  They can even be the cause of deterioration of rebar as moisture may seep in over time.  To reduce concrete’s permeability to water and prolong its life span, blended cements are used and offer an advantage of reducing the water-cement ratio (w/c), which one method of producing high-strength concrete. 

Blended cement as defined by the American Concrete Institute’s (ACI) Cement and Concrete Terminology is “hydraulic cement that is produced by intergrinding portland cement clinker with the other materials or by blending portland cement with the other materials or a combination of intergrinding and blending.”  Changes were made to blended cements in 2012 for special applications as well as for general use that have the approval of the ASTM.  

The ASTM’s C595 abstract on hydraulic blended cements describes “Type IS” as Portland Blast-furnace Slag cement and “Type IP” as Portland-pozzolan cement.  The C595 abstract states that, “They can also be described according to air-entraining, moderate sulfate resistance, moderate heat of hydration, high sulfate resistance, or low heat of hydration properties.”  Type I (SM) Slag-modified Portland cement has a standard that contains less than 25% slag by mass of the cement.  With the ASTM’s C595 change, it now permits Type IS Portland Blast-furnace Slag cement to contain between 25 and 70% by mass of the finished cement. 

 

By varying the proportions of the mix, blended cements are customized and produced to meet the demands of specific projects.  Furthermore, the ASTM goes on to say that, “cement shall undergo different tests to determine the following properties: chemical analysis, fineness by sieving, fineness by air-permeability, autoclave expansion, time of setting, air content of mortar, compressive strength, heat of hydration, normal consistency, specific gravity, water requirement, mortar expansions of blended cement and pozzolan, drying shrinkage, activity index with Portland cement, and sulfate resistance.”

At The Conco Companies, our mission is to be the best supplier of concrete services in the Western U.S. and to bring experience, expertise and quality to each project. We continue to upgrade and expand facilities to better serve the growing market for a wide range of construction development.

Conco’s Founder, Matt Gonsalves

The Conco Companies were founded in 1959 by Matt Gonsalves, Gerald Santucci, Ray Santucci, Will Gonsalves, and Mel Gonsalves.  Matt Gonsalves has held the position of President and is still active in the company serving as the Chairman of the Board.

The business got its start by pouring patios and driveways in Contra Costa and Alameda Counties.  Today Conco is one of the largest commercial concrete construction companies in the Western U.S. operating in California, Oregon, Washington, Nevada, and Colorado. 

The highlights of Conco’s longevity in the industry include providing premium concrete services for many of the most distinguished projects on the West Coast throughout the decades.  Some of the more prominent projects include the Pacific Bell Park, San Francisco Giants Stadium, the retrofit of Los Angles City Hall, Nokia Theater L.A. LIVE and Parking Structure, UCSF Neurosciences Lab and Research Center, Seattle Seahawk Parking Garage, Millbrae and Concord/Martinez BART Stations, and the Marriott Hotel in San Francisco. Recently we have been involved in the San Francisco 49ers Levi’s Stadium, the Bay Bridge Repair, the Wilshire Grand in L.A., and currently the Salesforce Tower in S.F.

As an innovator and inventor, Matt Gonsalves is credited with pioneering the use of 10” to 12” MAT slabs to create slab foundations that are not as prone to cracking or bending with earth movements.  He also invented the Waffle-Mat System, which is the process of pouring concrete over plastic molds to create a waffle-type mat effective on expansive soils. 

He also initiated the formation of the Concrete Contractors Association and has served as the President of the Building Industry of America (BIA).  Furthermore Mr. Gonsalves assisted the California Contractors State Licensing Board in developing test questions for its contractor license exam and working with political representatives to make changes to the cash retention policies in the construction industry.  Many of his ideas on various concrete methodologies have become today’s standards and practices.  In 2000, he was inducted into the CBIF Hall of Fame.   

Conco’s mission is to be the best supplier of concrete services in the Western U.S. and to bring experience, expertise and quality to each project. We continue to upgrade and expand facilities to better serve the growing market for a wide range of construction development.

Conco’s Reliable Trucking Company

 

In the Conco Companies’ quest to offer customers the best value in concrete construction services, we also own and operate the Reliable Trucking Company.  Just as the name suggests, the trucking company is known for safe, dependable construction hauling. 

Our fleet is fully CARB compliant (the legislation that mandates reductions in diesel emissions for all trucks in CA.) and we bring the same professionalism to our trucking services as to the rest of our Conco services.  Our modern fleet consists of pneumatic tankers, bottom dumps, semi-end dumps, ten wheelers, transfers and flat beds capable of hauling cement, aggregates and construction materials.

 

Reliable drivers are chosen carefully as with any of our Conco employees and commercial vehicle drivers must possess a Commercial Driver’s License (CDL).  In addition fleet operations must be performed in accordance with all state and federal regulations including but not limited to the Department of Transportation (DOT) and the Department of Motor Vehicles (DMV).  Our company’s Fleet Safety Program focuses on driver courtesy, regulatory compliance and accident prevention thru weekly training, quarterly safety meetings and management compliance audits. 

Currently Reliable is looking for truck drivers across their California locations for local deliveries only.  For Bulk Pneumatic Drivers, we have openings in Redwood City, Martinez, Stockton, and Woodland.  Applicants must possess a Class A license with doubles/triples and tank endorsements.  Experience with pneumatic trailers is preferred but not necessary. 

For Bottom Dump Drivers, openings are in Redwood City and Martinez.  Candidates must possess a Class A license with doubles/triples endorsement.  Experience with bottom dump trailers is preferred but not necessary.  Both of these jobs offer competitive wages along with medical and retirement benefits.  A clean DMV and no failed drug tests are also a must.  Please see our website for all of the details and contact info. 

As one of the top commercial concrete contractors in the Western U.S. since 1959, we understand the importance of building materials to be delivered safely and in a timely manner.  We work hard to provide our customers, employees, and the general public with the safest, most efficient trucking services in the industry. 

 

Conco is an leading supplier of commercial concrete services for the Western United States.  Our extensive services include commercial, educational, parking and other construction development as well as public works projects and highways.  We have four regional offices serving California, Oregon, Washington, Nevada and Colorado. 

 

Another Way to Make Concrete Stronger

Mineral admixtures are an economical way to create even stronger concrete and provide an environmentally responsible way to recycle industrial and other waste by-products.  In addition while chemical admixtures only make up about 5% of the concrete mass, mineral admixtures can be used in large amounts to replace portland cement and/or fine aggregates. 

So what are mineral admixtures?   Wikipedia states that mineral admixtures are “inorganic materials that also have pozzolanic or latent hydraulic properties. These very fine-grained materials are added to the concrete mix to improve the properties of concrete, or as a replacement for portland cement (blended cements).”  They are defined by the American Concrete Institute as “a siliceous or siliceous and aluminous material that in itself possesses little or no cementitious value but will, in finely divided form and in the presence of moisture, chemically reacts with calcium hydroxide at ordinary temperatures to form compounds having cementitious properties.” 

The most common mineral admixtures are fly ash, silica fume, blast furnace slag, and metakaolin.  Fly ash is a by-product from coal plants and is used to replace up to 60% of portland cement.  Silica fume is a by-product of silicon and ferrosilicon alloys and has particle size 100 times smaller than fly ash.  Blast furnace slag is a by-product of steel production and can replace portland cement by up to 80% of the mass. 

So what are the advantages of using mineral admixtures?  According to the U.S. Department of Transportation, when mineral admixtures are added to concrete in larger amounts, “it enhances the workability of fresh concrete.”  DOT also states that it improves the resistance of concrete to thermal cracking, alkali-aggregate expansion, and sulfate attack as well as enables a reduction in cement content.

1.en.wikipedia.org/wiki/Concrete

2. concrete.org/TopicsinConcrete/TopicDetail.aspx?id=71&Search=Pozzolans

3. fhwa.dot.gov/infrastructure/materialsgrp/admixture.html

 

The Conco Companies mission is to be the best supplier of concrete services in the Western U.S. and to bring experience, expertise and quality to each project. We continue to upgrade and expand facilities to better serve the growing market for a wide range of construction development.

The Production of Cement in the US

 

According to the Portland Cement Association, “Nearly two-thirds of U.S. cement consumption occurs in the six months between May and October.”  They also say that around 70 percent of cement shipments are sent to ready-mix concrete operators.   The remaining cement is shipped to manufacturers, government entities, contractors and to oil well, mining, and drilling companies.  

The fine gray powder that is known as portland cement is the key component in concrete mixtures.  With more than 100 cement plants in the United States, our country has the capacity to produce over 100 million tons of cement a year, and we are one of the largest manufacturers in the world just behind China and India. 

The U.S. cement manufacturing plants are located in 36 states; however California, Texas, Pennsylvania, Florida, and Alabama produce about 48% of the cement manufactured in the U.S.  Many of the U.S. plants are owned by or are subsidiaries of foreign companies and almost 80% of our cement production comes from these companies.  

Most cement is transported by trucks as it is generally manufactured close to the site where it will be used as well as close to limestone quarries where the raw material comes from.  Furthermore, cement consumption is dependent upon favorable weather conditions, so in many places, it is a seasonal business.   

The production of cement reflects the state of the construction industry.  At those times when construction slows down, so does the demand for cement.  With the recent recovery in the economy and the subsequent uptick of many construction projects around the country, the cement industry is currently doing quite well.   

Source:

cement.org/for-concrete-books-learning/cement-manufacturing

The Conco Companies are a leading supplier of commercial concrete services for the Western United States.  Our extensive services include commercial, educational, parking and other construction development as well as public works projects and highways.  We have four regional offices serving California, Oregon, Washington, Nevada and Colorado. 

Intern Opportunities for Project Engineers

The Conco Companies are presently seeking interns and/or graduates for positions of Project Engineer.  We offer qualified candidates a chance to work with top professionals in the industry as well as with a company that has been or is involved in many of the most architecturally distinguished projects throughout the Western U.S.

Recently we have had the privilege to supply concrete services on projects such as the San Francisco 49ers Levi Stadium, the new Salesforce Tower in San Francisco and the Wilshire Grand in Los Angeles.  Our current posting for Project Engineers is from our Concord office and we will train the right candidates. 

The job responsibilities will include but are not limited to the following:

·         Handle required daily jobsite paperwork such as: Inspection requests, Safety reports, Pre-task paperwork, and Tailgate meetings. 

·         Manage Requests for Information (RFI’s) and handle “field condition” issues as they arise. Will need to learn the requirements for processing RFIs: Work with field personnel/General Contractor to identify best solutions to issues; Provide pictures/sketches/explanations to detailer; and Oversee field fix. 

·         Scheduling of Deliveries and Manpower: Attend jobsite scheduling meetings with Project Manager; Work with Project Manager adjusting delivery/crane/manpower schedules based on scheduling meetings; and Maintain and distribute schedules. 

·         Monitor and order/stock/track field/office use items: Gloves, glasses and vests, Harnesses, Oxy/Acet bottles, and Water 

·         Field support: Understand General Contractor’s schedule and how to achieve their goals; Work with and support our field personnel to achieve these goals; Quality control assistance; and Do a once per day safety walk.

Desired skills and experience include a strong familiarity with industry standards and knowledge of Microsoft Excel, Microsoft Word, PowerPoint and Adobe Acrobat Professional.  Please refer to our website for complete requirements and contact information. 

 

Conco is a leading supplier of commercial concrete services for the Western United States.  Our extensive services include commercial, educational, parking and other construction development as well as public works projects and highways.  We have four regional offices serving California, Oregon, Washington, Nevada and Colorado.