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
0 Comments
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/ The University of Michigan is conducting an interesting study that involves developing a more durable concrete using raw acid mine drainage from abandoned mines in Northeast Pennsylvania. The research is focused on whether the impacted water, taken from boreholes in Solomon Creek, could be used in a “mixture for bendable concrete that can withstand four times the amount of pressure than regular concrete.”
Haoliang Wu, a Ph.D. student at the U of M, contacted the Eastern Pennsylvania Coalition for Abandoned Mine Reclamation (EPCAMR) to get about 180 gallons of the water shipped to the university’s laboratory. The executive director of EPCAMR, Robert Hughes, says the research team wants to use the mind drainage in concrete to build roads, bridges and highways. He explains, “They don’t have any raw mine drainage in Michigan that meets the kind of chemistry and criteria that we have here in the water in Solomon Creek coming from the boreholes.” In addition the concrete will be tested to see if it can better protect against rusting and cracking. The EPCAMR is also excited to learn if the acid mine water is a good fit for the experimental concrete as it could lead to a new partnership with the university and a beneficial way to reuse mine drainage in Pennsylvania. A more durable concrete also means bridges and roads would have a greater lifespan and be more sustainable. Furthermore, Hughes is excited at the prospect that something such as the acid mine drainage that has been a pollutant for the area could be a reusable resource in the future. They have plenty of impacted waterways as over 5,500 miles of streams have had run-off from the mines and the group has been trying to find ways to clean up the polluted streams. 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:thetimes-tribune.com/news/local-acid-mine-drainage-helping-in-concrete-research-1.2182101, wnep.com/2017/04/20/power-to-save-acid-mine-drainage-to-concrete/ The final beam was hoisted into place on April 6, 2017 topping off the new Salesforce Tower in downtown San Francisco, which is the tallest building west of Chicago. While the new Wilshire Grand in Los Angeles has a spire that actually makes it higher in height, the San Francisco tower will hold the honor of having the highest occupied floor. The 61-story skyscraper, located at Mission and 1st Street, and has been under construction for four years.
The Conco Companies provided concrete services on the 1,070 ft. skyscraper. We announced last November that we successfully completed the final core wall pour and that it was now officially the tallest building in San Francisco. One year before that, we completed the 12,000 cubic-yard mat pour for the tower and set a record for the largest pour in San Francisco’s history. Before construction of the Salesforce Tower, the 853 ft. tall Transamerica Pyramid had held the record as the tallest building in the city for 43 years. Another skyscraper, the Millennium, just a block away from the Salesforce Tower is garnering attention for the fact that it has sunk 16 inches from when it first opened its doors in 2009. To further complicate matters, the condominium building is sinking unevenly. While the Millennium’s foundations rest on 950 friction piles, they do not go down to the bedrock as does the Salesforce Tower’s foundation, which is anchored to bedrock. The developer of the Salesforce Tower, Boston Properties reports the opening will be rolled out in phases beginning in July and continue through to 2018. Spokesperson, Michael Cantalupa, said, "The steels been finished, concrete finished, the skin of the building is coming up. In terms of later phases of construction, the building needs to be fit out for its tenants. So, each tenant that comes in, its space is going to be designed and constructed for its particular uses." 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. While we tackle projects both big and small, our experience includes providing the complete concrete package for the Levi’s Stadium along with other notable projects. We serve California, Washington State, Oregon, Colorado and Nevada. Source:abc7news.com/realestate/topping-off-ceremony-for-salesforce-tower-in-sf----watch-live/1841834/http%3A%2F%2Fabc7news.com%2F1841834%2F |
Archives
October 2021
Categories
All
|