At The Conco Companies, we have experience placing any type of concrete for a broad range of projects and in a variety of weather conditions. Our crews use several different methods for curing concrete as it is determined by the type of construction and the concrete mix as well as outside temperatures and humidity. Other considerations include project specifications and/or parameters of the jobsite. However regardless of the technique used for curing, it is important to keep the concrete moist and prevent further loss of moisture.
The Portland Cement Association explains that the purpose of curing is to provide the “adequate amount of moisture for continued hydration and development of strength, volume stability, resistance to freezing and thawing, and abrasion and scaling resistance.” When we control the rate and amount of moisture the concrete loses during cement hydration, it is allowed to achieve its optimal strength and durability. Curing is done at the jobsite once the concrete is placed and finished, or during the manufacturing of concrete products. While curing may only take a few days, the concrete requires a number of days or in some cases weeks or months to attain its full strength and durability. Preventing the loss of moisture during curing is done in a number of ways. One method leaves the formwork in place and/or covers the concrete with an impervious paper, plastic sheeting or a membrane-forming compound. Another includes spraying (or fogging), ponding or using wet coverings to cool the concrete as the water evaporates. The American Concrete Institute (ACI) recommends a curing period of a minimum of 7 days or until 70% of the specified compressive strength is achieved for most concrete structures in temperatures 40º F and above. If desired an accelerant can be used to speed up the hardening process and reduce the curing period to only 3 days if temperatures are above 50º F. Other variables are determined by the size and shape of the structure and strength requirements as well as the type of weather conditions the concrete will be exposed to during its life-cycle. The Conco Companies are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. We serve California, Washington State, Oregon, Colorado and Nevada. Source: cement.org/for-concrete-books-learning/concrete-technology/concrete-construction/curing-in-construction, concrete.org/TopicsinConcrete/TopicDetail.aspx?id=25&Search=Curing
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Concrete spalling and cracking, sometime referred to as concrete cancer, is caused by rebar corrosion and can affect buildings and other concrete structures. Once the steel reinforcing in a concrete slab begins to rust, the steel rust can expand up to 7 times its original size and results in concrete being displaced and getting flakey. As the steel pushes the concrete away, it allows more water to come into contact with the steel and compounds the problem.
Visible rust stains on the outside of the concrete or leaking, bubbling up stains from within the concrete are probably all signs of concrete spalling and can be a dangerous. The spalling can cause chucks of concrete to separate from a building or bridge and becomes a real hazard to any pedestrians or traffic passing by below. The good news is that a group of researchers at the University of British Columbia in Canada may have found a cure for concrete cancer. According to their study, they have gotten good results with producing concrete using discarded glass. The researchers report that “by partially replacing cement with polymer, fly ash and glass powder, we were able to produce concrete that was more than 60% stronger than what was previously believed possible.” They are looking to further test their products but hope to eventually replace up to 25% of traditional cement materials, mined from the earth with recycled glass. One of the authors of the report, Shahria Alam, an associate professor of engineering at the University, explains that millions of tons of glass bypass recycling centers and end up in North American landfills. Their goal was to make smarter and “greener” building materials without having to take new resources out of the ground. At The Conco Companies, we are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. We serve California, Washington State, Oregon, Colorado and Nevada. Source: remedial.com.au/structural-repairs/concrete-cancer Reactive Powder Concrete (RPC), which is also known as Ultra-High Performance Concrete (UHPC), is a combination of portland cement, silica fume, quartz flour, fine silica sand, high-range water reducer, water, and optional additives. The Portland Cement Association explains that reactive powder concrete is “extremely workable, durable and yields ultra-high strengths without using coarse aggregates. Reaching compressive strengths of 30,000 pounds per square inch (psi), this new-age concrete also has tensile strength with the inclusion of steel and synthetic fibers.” The micro structure of RPC is optimized by precise graduation of all particles in the mix to give it maximum density.
An article on the Concrete Portal website explains that Reactive Powder Concrete (RPC) is “a developing composite material that will allow the concrete industry to optimize material use, generate economic benefits, and build structures that are strong, durable, and sensitive to environment.” When researchers compare the physical, mechanical, and durability properties of RPC to HPC (High Performance Concrete), studies show RPC offering “better strength (both compressive and flexural) and lower permeability compared to HPC.” HPC is designed to be more durable and sometimes stronger than conventional concrete and is a mixture of cement, water, and aggregate as well as mineral components and chemical admixtures with specific characteristics. Achieving its maximum compressive strength, the coarse aggregate in the HPC prevents it from going further. In the case of RPC, the coarse aggregate is removed to provide the concrete with an even better compressive strength. Along with very fine powders of cement, sand, quartz powder and silica fume, a RPC mix may contain steel fibers and a superplasticizer. RPC was developed by P. Richard and M. Cheyrezy and first produced in the early 1990s in France at the Bouygues’ Laboratory. The first project to use RPC was the Sherbrooke Bridge, a pedestrian bridge in Canada. At The Conco Companies, we are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. We serve California, Washington State, Oregon, Colorado and Nevada. Sources:cement.org/designaids/emerging-trends, theconcreteportal.com/reac_pow.html Fiber reinforced concrete (FRC), a type of reinforced concrete that uses a fibrous substance to increase structural strength, durability and ductility, is a subject of new research and developments. In FRC, short, discrete fibers are uniformly distributed and randomly oriented to provide a kind of three-dimensional stability and include fibers made of steel, glass and synthetic or natural material. Depending on which material is used, they offer varying properties and characteristics.
For example steel fibers can increase the structural strength of concrete and reduce the steel reinforcement requirements as well as crack widths for better durability. Also the addition of steel fibers to a concrete mix can improve impact along with abrasion-resistance and freeze-thaw resistance. Using polypropylene or nylon fibers in concrete can improve the mix cohesion and freeze/ thaw resistance and make concrete easier to pump long distances. Furthermore, the fibers provide an increased resistance to plastic shrinkage during curing and improve the structural strength and ductility. As with steel fibers, polypropylene and nylon fibers reduce the steel reinforcement requirements. Sometimes a construction project will use both steel and polymeric fibers to get the benefit of structural strength provided by steel fibers and the “resistance to explosive spalling and plastic shrinkage improvements provided by polymeric fibers.” After testing to ensure minimum requirements are met, some precast applications and industrial flooring use steel or synthetic fibers in place of rebar in reinforced concrete. While fiber reinforced concrete has been around for centuries such as horsehair in mortar, straw in mudbricks, and the use of asbestos fibers during the 1900s, there are new developments and innovations in FRC. One example is High-performance Fiber Reinforced Concrete (HPFRC), which researchers claim to be 500 times more resistance to cracking and 40 percent lighter than traditional concrete. More research is being done to validate the claims. Another recent study used carpet waste fibers in concrete as a way to environmentally recycle carpet. Also a new trend that completely changes our view of concrete as an opaque mass is to add optical fibers to the mix to create a translucent concrete. At The Conco Companies, we are one of the leading concrete contractors in the Western U.S. and offer a wide range of quality services and products. Our experience includes providing services for commercial, educational, parking and other construction development as well as public works projects. We serve California, Washington State, Oregon, Colorado and Nevada. Source: en.wikipedia.org/wiki/Fiber-reinforced_concrete At The Conco Companies, we make it a point to stay up-to-date on the latest concrete news and innovations, and implement new ideas and technologies designed to save our customers time and money as well as to create a better finished product. Some emerging trends in concrete that are changing concrete design and construction include high strength / high performance concrete (HSC/HPC); self-consolidating concrete (SCC); fiber reinforced concrete (FRC) polymer modified concrete (PMC); high volume flyash concrete (HVFC); reactive powder concrete (RPC); and self-healing concrete / bacterial concrete.
Innovations in precast concrete, which is produced by casting concrete in a reusable mold or "form" and cured in a controlled environment before being transported to the jobsite include the manufacturing of ultralite panels using Carbon Cast. This precast concrete technology uses carbon-fiber grid reinforcing to create panels that weigh less and result in reduced shipping, erection and substructure costs. The Portland Cement Association cites the new P.O.S.T. (Prestressed Open Space Truss) as providing a “solution for long-spans, while maintaining the shallow floor depth of a flat plate system.” They say the system works well for hotel and condominium applications, especially for those constructed with lower level parking. The National Ready Mix Concrete Association states that self-consolidating concrete is another time and labor saver as it “pumps easier, fills complex shapes, produces pristine finishes and encapsulates congested reinforcement.” They explain that the two important properties specific to SCC in its plastic state are its flowability and stability. This is typically accomplished by using high-range water-reducing admixtures, not by adding more water. Insulated Concrete Form (ICF) walls are also increasingly becoming a popular option in residential and commercial markets and offer the advantage of fast construction, energy savings and increased durability. The walls provide occupants not only a quieter environment but a safer one as studies show improved “results for resistance to catastrophic loadings, including fire, wind, and tornados.” Conco’s mission is to be the best supplier of concrete services in the Western United States and to bring expertise, experience and quality to each project. We continue to upgrade and expand facilities to better serve the growing market for public works projects, commercial, parking structures, educational, and other construction development. We serve California, Washington State, Oregon, Colorado and Nevada. Sources: slideshare.net/sabnisajit/an-overview-of-emerging-trends-in-construction-technologies cement.org/designaids/emerging-trends The Conco Companies have owned and operated one of the largest concrete pumping companies in the United States for over 40 years. To remain a leader, we continue to invest in new concrete pumps to provide customers one of the most modern, state-of-the-art operations on the West Coast.
To serve our customers, we have a large fleet of concrete pumps that are located in Northern California, Southern California and Washington. Our pumps are manufactured by two of the top names in the industry. Putzmeister America, Inc. is the North American division of one of the most recognized and respected manufacturers of concrete and material placing equipment. Schwing America is a member of the SCHWING Group, a worldwide designer, manufacturer and distributor of premium concrete production and handling equipment that is headquartered in Herne, Germany. All three of our pump locations have a Schwing 58SX long boom concrete pump that meets the latest emissions standards and is helping to reduce emissions at our jobsites. With a 4-Section Overhead Roll and Fold, the innovative boom design works well on bridges, commercial and industrial work and has a reach of 175 feet. The versatile boom has a main section that articulates 180-degrees, which allows it to be angled away from the pour and then guided horizontally into enclosed areas, positioned vertically for elevated work, and stretched out over the cab for flatwork. Another impressive pump we have available in all locations is the Putzmeister 36Z. With its detachable Putzmeister Z-Fold boom, the 36Z has great reach. It is the only four-section, 116-foot 10-inch boom on the market using X-style outriggers. The powerful pumping performance with a small footprint makes it perfect for restrictive job sites. Please see our website, iPhone App or Android App for access to a complete list of our concrete pumps along with descriptions, diagrams, specifications and instructions for ordering. Conco’s mission is to be the best supplier of concrete services in the Western United States and to bring expertise, experience and quality to each project. We continue to upgrade and expand facilities to better serve the growing market for public works projects, commercial, parking structures, educational, and other construction development. We serve California, Washington State, Oregon, Colorado and Nevada. Tilt-up construction, also known as tilt-slab or tilt-wall, is a construction technique in which concrete wall panels are cast-on-site and tilted into place. It was first used in America around 1905, and patented in 1908 by Robert Akin during the concrete construction of the Schindler House in West Hollywood, CA.
In the last fifty years a large number of buildings throughout North America have been designed and constructed using the tilt-up building method. The Structure Magazine website references the ACI Tilt-Up Construction Guide (ACI 551) with the following quote, “Tilt-up panels are generally handled only once. They are lifted or tilted from the casting slab and erected in their final position in one, continuous operation. Tilt-up panels are generally of such large size and weight that they can only be constructed on site and in close proximity to their final location in the structure.” The document further states that tilt-up concrete construction “is a unique form of site-cast precast construction and, as such, has its own specialized set of design parameters and construction techniques.” Tilt-up construction offers the advantage of fast construction, low-cost, and advanced architectural treatments. To ensure success, the project requires careful preparation from beginning to end including a thorough evaluation of the: site; the size and height of the building; its intended purpose; and how easy will it be to get materials to the jobsite. After the site preparation work is complete and the floor slab or casting surface has cured, the forms are built on top typically using a plywood or fiber board, or in some cases steel or aluminum forms. The forms include all door and window openings as well as other architecture features, and are anchored to the pad. When the rest of the prep work is completed including the construction of a rebar grid inside the form, the concrete is poured. After the concrete is cured the forms are removed and a crane lift tilts the panel (in some cases lifts) into place, which is secured with braces while the roof is being completed. A couple of years ago, Conco provided services on a concrete parking garage and a concrete tilt-up structural frame building, the 100 Grand, in downtown Oakland, CA. The structure is now a contemporary apartment building that offers spectacular views of the city and includes lofts and 1 and 2-bedroom units as well as spacious 3-bedrooms. The Conco Companies are a leading supplier of concrete services for the Western U.S. 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, Nevada, Washington, Oregon and Colorado. Sources: en.wikipedia.org/wiki/Tilt_up structuremag.org/wp-content/uploads/2014/08/C-GuestColumn-Smith-Apr091.pdf The Conco Companies have expanded our operations over the last several years, and as a result, we are always looking for talented individuals to join our team. One of our current postings is for several qualified, full-time Project Managers for our Southern California locations.
We are one of the nation’s leading commercial concrete contractors and offer talented individuals the opportunity to be a part of our dynamic operation. As a Project Manager for one of our Southern California locations, you will be working with an exceptional team of professionals on some of the top projects in the area. Applicants must have strong leadership skills and the know-how to safely complete projects on time and on budget while maintaining Conco’s high standards. Project Managers work together with Project Superintendents to accomplish these goals. In addition all applicants are required to have a four-year Management or Engineering Degree, or the equivalent combination of technical training and related experience. Conco’s Project Managers develop and maintain a project schedule as well as coordinate and communicate various aspects of the job with the owner and general contractor. Responsibilities include submitting and coordinating all project schedules, change orders, pay applications, submittals and approvals, and RFIs. As a Project Manager, you will direct and coordinate activities so that the project stays on schedule and on budget. The position also entails developing and maintaining customer relationships that enhances Conco’s ability to procure projects, reduce risk, and ensure operation efficiency. Applicants should have an in-depth understanding of concrete formwork systems and equipment utilization as well as concrete-construction documents, concrete materials, and characteristics. Since duties include scheduling and managing sub-contractors and interacting with many different groups, Project Managers need good verbal and written communication skills and should be able to work well in a team. Please see Conco’s website for the full job description and contact information. The Conco Companies are 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. |
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