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
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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 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 Slump is the measure of the consistency in a specific batch of fresh concrete. A slump test accesses the consistency of the fresh concrete, and to ensure that the correct amount of water has been added to the mix.
To conduct the test, an Abrams slump cone is used, a bottomless, 12” high circular cone with an 8” in diameter base and a 4” in diameter top. The cone is placed on a level, impermeable surface and filled in three stages with equal amounts of concrete. Each layer is tamped down using a special rod to make sure the concrete is compacted and leveled off with the top of the cone. The cone is then carefully removed and the concrete is left to settle or “slump.” The slump cone is placed alongside the pile of concrete in order to measure the height of the concrete in comparison to the top of the cone. Measurements are taken to the nearest 5mm. Wikipedia states, “The slumped concrete takes various shapes, and according to the profile of slumped concrete, the slump is termed as true slump, shear slump or collapse slump.” If the concrete simply subsides but generally maintains its shape, it is considered to be a true slump. In the case of a shear slump, the top portion of the concrete shears off. If the test results in a “collapse slump”, it typically indicates the mix is too wet; or it may be a high workability mix that needs to have a flow test done rather than a slump test. Up until just a few decades ago, concrete was made from portland cement, aggregate and water. In this type of concrete mix, the coarse aggregate dictated the water content, and concrete with a lower slump value contained less water and resulted in a better quality of concrete. Today much of the concrete we produce is a blend of not only cement and aggregate but admixtures, fibers and polymers. This means the aggregate is not the only thing that influences the amount of water added and other factors have to be considered to determine the proper consistency of the 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. Sources: concrete.org.uk/fingertips_nuggets.asp?cmd=display&id=559 en.wikipedia.org/wiki/Concrete_slump_test A recently constructed 20,000 sq. ft. home located on Miami’s Coconut Grove bay is an excellent example of integrating a man-made structure into the natural surroundings. Designed by the filmmaker Alejandro Landes, the massive concrete and glass-walled villa is his first architectural project. Throughout the beautiful home, Landes used a selection of tropical materials such as salvaged teak wood, rattan, bamboo, handmade linen and more.
Situated on a .94 acre lot, the raised structure (to avoid flooding and comply with strict hurricane construction codes and FEMA’s national ordinance) features an exposed concrete frame and columns that add to the 3-story building’s durability as well as to its sleek, modern look. The raised ground level provides a huge, shaded courtyard for lounging. Also shallow reflection pools are located beneath a large concrete plinth that wraps around the house. The white, floating staircase is composed of shell-reef slabs and “gently slopes up to the double-height main living space.” In addition the homes floor-to-ceiling windows are double-paned and hurricane proof. Landes says that the hanging concrete staircase, which lightly hangs as through glass, takes something heavy and makes it seems like it floats, while adding a new fragility to it. The $50 million, seven-bedroom project also consists of a 73-foot-long infinity lap pool, steam room, four kitchens, and a 12-person elevator. Furthermore, the home boasts a climate-controlled wine cellar as well as an eight-car garage, and the neighboring guesthouse offers a large theater. Landes states that the construction of a house as unique as this one was a collaborative art form and very much like a film. 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. Source: builderonline.com/design/projects/modern-miami-villa-is-a-concrete-oasis_o At The Conco Companies, we are proud to have provided concrete services on many mixed-use buildings and “green” projects constructed in urban areas up and down the West Coast. The Municipal Research & Services Center in Seattle, Washington defines mixed-use development “as pedestrian-friendly development that blends two or more residential, commercial, cultural, institutional, and/or industrial uses.” As one of the ten principles of Smart Growth, it includes “a planning strategy that seeks to foster community design and development that serves the economy, community, public health, and the environment.”
Vertical mixed-use development combines various uses in the same building with residential or hotel rooms typically on upper levels, and public use businesses such as restaurants and retail at ground level. Horizontal mixed-use development is made up of single-use buildings within a mixed-use zoning area that offers a variety of complementary and integrated uses. By intentionally integrating business and residential areas rather than the traditional practice of separating the two, mixed-use developments are considered to be more “green” as it eliminates or reduces the need for long commutes. Individuals are able to walk to work or to public transportation as well as live in close proximity to restaurants, grocery stores and entertainment and cultural venues. Another benefit of mixed-use projects is they can help to lessen some of the risks to investors. If a mixed-use high-rise includes not only a hotel but luxury condominiums, the sale of the condominiums can off-set part of the cost of the hotel, and so forth. Conco is currently providing concrete services for the first Class A high-rise in Tukwila, WA. The $120 million Washington Place project will be a mixed-use 19-story building with a business class hotel, residential units and a four-story parking garage. In addition it will include a 90-seat restaurant, meeting space, and rooftop garden. It is also in easy walking distance to The Westfield Southcenter mall, entertainment venues, and a bus transit center. Please visit the Conco website to see our portfolio of other similar type projects. 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: completecommunitiesde.org/planning/landuse/what-is-mixed-use-development/ sajebuild.com/trends-in-hotel-building-mixed-use-plans/ Insulating Concrete Form (ICF) systems are being used in everything from single story buildings to 20+ story high-rises. Common types of projects include single and multifamily residential housing, hotels, offices, educational and healthcare facilities, manufacturing and warehouse buildings and others.
ICF construction offers several benefits including energy efficiency, diaster resiliancy, noise reduction, strength and durability, and sustainability. In addition it is competitively priced in comparison to steel frame, wood frame, and masonry construction. Buildings constructed with ICFs are also very fire resistent, and in multi-family housing, can help to isolate the fire to a single unit and protect both lives and property. The system works a lot like LEGOs as it is comprised of interlocking blocks with mechanisms that connect together. Each block is made out of molded expanded polystyrene (EPS) insulation in a variety of sizes. According to an article from Concrete INFOCUS, “the most common configuration of an ICF unit is made of two layers of 2-1/2 to 2-5/8 inch thick EPS spaced 4, 6, 8, 10, or 12 inches apart for most low to mid-rise buildings.” In the case of taller buildings or when the project consists of high ceilings or large loadings, the structure requires thicker walls. ICF blocks are identifyied by the width of the cavity and wider units include 6-inch, 8-inch and larger. Typically blocks are fully assembled at the manufacturing site although some blocks are folded into a flat configuration and shipped, while other manufacturers produce ICF forms that are assembled at the jobsite. After the ICF blocks are installed, concrete is pumped into the cavity to make a strong, uniformly-thick concrete wall. Concrete INFOCUS says the “recommended maximum aggregate size should be 1/2- inch aggregate for 4- and 6-inch cavity forms and ¾-inch aggregate for 8-inch and larger cavity forms.” 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. Source: nxtbook.com/naylor/NRCQ/NRCQ0117/index.php#/20 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.
In terms of cold temperature, normal concrete mixes will not properly set or harden when the concrete temperature is below approximately 35° F. However by making some changes to the mix such as adding heated water and aggregates or the addition of accelerating admixtures, concrete can be placed at below freezing temperatures but it is more expensive. Since most of the West Coast (Conco’s primary service areas) does not experience more than occasional episodes of below freezing temperatures, it is generally easier to wait for a warmer day. In extreme heat of 90° F and above, concrete not only starts to set and harden faster but it can cause a reduction in the ultimate strength of the concrete. Plastic shrinkage and drying shrinkage can also be a problem in very windy or low humidity conditions. To mitigate these problems, the timing of placement along with the addition of retarding admixtures and proper curing are implemented. On the historic continuous mat pour we did a few years ago for the Wilshire Grand Tower in Los Angeles, we needed to make provisions for the heat generated in mat foundations. In mass concrete structures there are two thermal properties that must be considered: the maximum temperature and the temperature difference between the center of the structure and surface. With help from a team of experts, we developed a thermal control plan specific to the mix design, the geometry of the foundation and the configuration of the rebar. The fix involved mechanically controlling the temperature by post-chilling the concrete with cooling pipes to remove the heat. We successfully kept the maximum temperature below ACI limits and a temperature difference that was well within the ranges required to avoid thermal cracking. 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. The Portland Cement Association states that, “Slightly more than half of all low-rise buildings in the United States are constructed from concrete.” It is also the most common man-made material on the planet as well as the 2nd most consumed substance just behind water. The concrete industry is worth over $37 billion, employs over 2 million people in the U.S., and each year about 10 billion tons of concrete are produced.
Concrete is very strong and averages about 3,000 psi (lbs/square inch) with high-performance concrete reaching strengths of over 20,000 psi. While today’s concrete buildings are both strong and durable, they can also be the most economical to construct. ConcreteHelper.com lists a variety of other concrete facts such as the first person to contract and live in a precast concrete home was Thomas Edison. In addition, they cite the fact that the world’s largest concrete structure is the Three Gorges Dam located on the Yangtze River in China. It was built with approximately 21 million cubic yards (16 million cubic meters) of concrete. Furthermore, due to its color, concrete reflects 30 to 50% more light than asphalt and helps to reduce the temperature in large urban areas by as much as 7%. Also did you know that heavy trucks actually get up to 20% better mileage on concrete roads than those paved with asphalt? Concrete not only gets stronger as it ages, but concrete highways typically offer about twice the useful life as asphalt roads and can serve about 20 to 30 years before they need major repair. Asphalt generally lasts about eight to twelve years before resurfacing or major repairs are needed. Around 60 percent of the interstate system in the United States is concrete. Another interesting fact about concrete is that certain types of the material floats and is used to construct concrete canoes and boat docks. The weight of standard concrete is approximately 4,000 lbs. per cubic yard, while lightweight concrete weighs about 3,000 lbs. per cubic yard. Finally over 70% of the world’s population lives in structures that were built with at least some concrete. The Conco Companies are a leading supplier of concrete services throughout 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 and are now one of the foremost concrete contractors in the region. Our concrete services include commercial, educational, industrial and public works projects as well as parking structures. Sources: cement.org/infrastructure/buildings-structures, concretehelper.com/concrete-facts/ |
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