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101-604: The North Pine Dam is a mass concrete gravity dam with earth-fill embankments on abutments with a gated spillway across the North Pine River that is located in the South East region of Queensland , Australia . The main purpose of the dam is for supply of potable water for the Moreton Bay region and Brisbane 's northern suburbs. The impounded reservoir is called Lake Samsonvale . The dam

202-411: A calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone ). Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces , and polymer concretes that use polymers as a binder. Concrete

303-553: A common-pool resource which is rivalrous in nature but non-excludable. Thus, on public grounds, all can enjoy the benefits of fishing so long as fish continue to be stocked. Fish stocking is a practice that dates back hundreds of years. According to biologist Edwin Pister, widespread trout stocking in the United States dates back to the 1800s. For the first hundred years of stocking, the location and number of fish introduced

404-635: A water security project in the South East Queensland region, known as the South East Queensland Water Grid . The accompanying water treatment plant is also managed by SEQ Water. Prior to the initial flooding of the valley, many of the surrounding grazing and dairy farms were compulsorily acquired, and the only evidence of these farms is now the names of roads leading to the lake's shoreline, such as Winn Road and Golds Scrub Lane. Golds Scrub Lane now leads only to

505-482: A 255-page report on United States fish resources. Congress granted the team $ 15,000 to develop food fish stocks, and non-native fish such as rainbow trout , salmon , striped bass and carp were subsequently introduced successfully into United States lakes and rivers. In the early years, fish were stocked by sports clubs and private citizens. Today, state fish and wildlife agencies along with hatcheries are responsible for distributing fish. And until recently, their goal

606-433: A French structural and civil engineer . Concrete components or structures are compressed by tendon cables during, or after, their fabrication in order to strengthen them against tensile forces developing when put in service. Freyssinet patented the technique on 2 October 1928. Concrete is an artificial composite material , comprising a matrix of cementitious binder (typically Portland cement paste or asphalt ) and

707-404: A balanced ecosystem with biological diversity is also extremely important. Many scientists have claimed that because fish that are stocked tend to be apex predators , native species may become prey and have to compete with the oftentimes larger introduced fish for food and habitats. Additionally, the use of aircraft to stock fish in the second half of the 20th century meant pilots often stocked

808-443: A better job of recording exactly what species of fish are stocked at any given location. This began in the 1960s when research suggested the negative impacts of fish stocking on the ecological complexity of other life forms. The Wilderness Act of 1964 also opened the public's eyes to the impact stocking has on other organisms. Thus, fish stocking is now the subject of much debate as there are various costs and benefits associated with

909-452: A cementitious material forms a cement paste by the process of hydration. The cement paste glues the aggregate together, fills voids within it, and makes it flow more freely. As stated by Abrams' law , a lower water-to-cement ratio yields a stronger, more durable concrete, whereas more water gives a freer-flowing concrete with a higher slump . The hydration of cement involves many concurrent reactions. The process involves polymerization ,

1010-400: A concrete component—and become a part of the binder for the aggregate. Fly ash and slag can enhance some properties of concrete such as fresh properties and durability. Alternatively, other materials can also be used as a concrete binder: the most prevalent substitute is asphalt , which is used as the binder in asphalt concrete . Admixtures are added to modify the cure rate or properties of

1111-434: A dispersed phase or "filler" of aggregate (typically a rocky material, loose stones, and sand). The binder "glues" the filler together to form a synthetic conglomerate . Many types of concrete are available, determined by the formulations of binders and the types of aggregate used to suit the application of the engineered material. These variables determine strength and density, as well as chemical and thermal resistance of

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1212-437: A fluid cement that cures to a solid over time. Concrete is the second-most-used substance in the world after water , and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined. When aggregate is mixed with dry Portland cement and water , the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts with

1313-452: A greater degree of fracture resistance even in seismically active environments. Roman concrete is significantly more resistant to erosion by seawater than modern concrete; it used pyroclastic materials which react with seawater to form Al- tobermorite crystals over time. The use of hot mixing and the presence of lime clasts are thought to give the concrete a self-healing ability, where cracks that form become filled with calcite that prevents

1414-415: A large aggregate that is too large for the size of the formwork, or which has too few smaller aggregate grades to serve to fill the gaps between the larger grades, or using too little or too much sand for the same reason, or using too little water, or too much cement, or even using jagged crushed stone instead of smoother round aggregate such as pebbles. Any combination of these factors and others may result in

1515-461: A large type of industrial facility called a concrete plant , or often a batch plant. The usual method of placement is casting in formwork , which holds the mix in shape until it has set enough to hold its shape unaided. Concrete plants come in two main types, ready-mix plants and central mix plants. A ready-mix plant blends all of the solid ingredients, while a central mix does the same but adds water. A central-mix plant offers more precise control of

1616-464: A mix which is too harsh, i.e., which does not flow or spread out smoothly, is difficult to get into the formwork, and which is difficult to surface finish. Fish stocking Fish stocking may be conducted by governmental fisheries management agencies, non-profit organizations, and voluntary associations in public waters, or by for-profit NGOs, clubs and commercial enterprises in privately owned waters. When in public waters, fish stocking creates

1717-469: A mixture of calcium silicates ( alite , belite ), aluminates and ferrites —compounds, which will react with water. Portland cement and similar materials are made by heating limestone (a source of calcium) with clay or shale (a source of silicon, aluminium and iron) and grinding this product (called clinker ) with a source of sulfate (most commonly gypsum ). Cement kilns are extremely large, complex, and inherently dusty industrial installations. Of

1818-518: A more "natural" level where herring populations are reduced and zooplankton flourish, thus benefiting the ecosystem as a whole. There are additional benefits to fish stocking. Anglers across the country spend millions of dollars through license fees (which benefit state governments) and fishing equipment such as rods, reels, and lures. Members of fishing societies such as the International Game Fish Association and

1919-497: A now-threatened species, has been linked to stocking of non-native species. As a matter of fact, 35 species of fish and amphibians have been negatively affected by stocking practices in California. Scientists have established a direct link between non-native fish stocking and decline of these species: golden trout, Lahontan cutthroat trout , mountain yellow-legged frog , Yosemite toad and Cascades frog are all threatened by

2020-405: A number of manufactured aggregates, including air-cooled blast furnace slag and bottom ash are also permitted. The size distribution of the aggregate determines how much binder is required. Aggregate with a very even size distribution has the biggest gaps whereas adding aggregate with smaller particles tends to fill these gaps. The binder must fill the gaps between the aggregate as well as paste

2121-479: A policy, for example, that states "where a body of scientific evidence shows that stocking in historically non-salmonid waters adversely affects native biodiversity, such stocking should cease." While many organizations remain focused solely on providing quality fishing opportunities, policies and attitudes are shifting toward resource integrity and protection. In Pennsylvania alone, the PA Fish & Boat Commission

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2222-412: A private pond, it is important to introduce three prey fish for every predator fish. This ensures that predatory fish have enough nutrition to survive and that prey fish can still reproduce. It is also recommended to stock fathead minnows so that both predator and prey fish have enough to feed on. Introducing fish of similar sizes is another important step to ensure that the population grows together. At

2323-424: A semi-liquid slurry (paste) that can be shaped, typically by pouring it into a form. The concrete solidifies and hardens through a chemical process called hydration . The water reacts with the cement, which bonds the other components together, creating a robust, stone-like material. Other cementitious materials, such as fly ash and slag cement , are sometimes added—either pre-blended with the cement or directly as

2424-493: A simple, fast way of getting a basic idea of the properties of the finished concrete without having to perform testing in advance. Various governing bodies (such as British Standards ) define nominal mix ratios into a number of grades, usually ranging from lower compressive strength to higher compressive strength. The grades usually indicate the 28-day cure strength. Thorough mixing is essential to produce uniform, high-quality concrete. Separate paste mixing has shown that

2525-526: A stocked impoundment permit is required to fish in North Pine Dam. All boating on the lake is prohibited except through two groups. The Lake Samsonvale Water Sports Association and the stocking group Pine Rivers Fish Stocking Association have 300 permits to release each year for non petrol powered craft to members of the public for a small licence fee Concrete Concrete is a composite material composed of aggregate bonded together with

2626-614: A variety of water activities. Studies have also examined the economic viability of fish stocking. Hansson, Arrheniusm, and Nellbring of Stockholm University find that simple economic analysis suggests Volga pikeperch stocking can be profitable; based on the capital invested in the stock, the economic yield results in an annual interest rate of 43% (from the viewpoint of anglers). These authors also find that increased populations of stocked fish decreases manpower and equipment costs associated with each catch. They also find that specifically for pikeperch, stocking can restore food web interactions to

2727-427: Is 45 metres (148 ft) high and 1,375 metres (4,511 ft) long. The 450-thousand-cubic-metre (16 × 10 ^  cu ft) dam wall holds back the 215,000-megalitre (47 × 10 ^  imp gal; 57 × 10 ^  US gal) reservoir when at full capacity. From a catchment area of 347 square kilometres (134 sq mi) that includes much of the south–eastern slopes of the D'Aguilar National Park ,

2828-442: Is a government office or private individual conducting the stocking. In the past century, many areas have banned fish stocking for a variety of reasons. In 1959, for example, Yellowstone National Park fish stocking was banned due to cross-breeding between native and nonnative species that was harming the genetic uniqueness of existing populations. This makes fish populations more susceptible to disease. Today, Yellowstone has adopted

2929-682: Is a popular pastime, with 101.6 million Americans over 16 years old participating in wildlife-related activities such as fishing and hunting. Additionally, a report by the U.S. Department of the Interior recorded an 8% increase in angling participation between 2011 and 2016. In 2017, just over 49 million Americans participated in some form of fishing, of which 11.9 million were youth. Most anglers even fish between four and eleven times per year, with some reporting over 100 trips. Adding fish to public lakes and streams makes fishing more fun, especially for young anglers. Fishing also provides Americans

3030-430: Is also home to the noxious species tilapia which is a fine eating sportfish in its larger sizes but tends to overpopulate and stunt if uncontrolled, as well as a population of Australian red claw crayfish , usually native only to Northern Queensland. Both the tilapia and red claw species are the target of considerable local effort for their capture and complete removal. Like various other Queensland freshwater fisheries,

3131-511: Is distinct from mortar . Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks , tiles and other masonry units together. Grout is another material associated with concrete and cement. It does not contain coarse aggregates and is usually either pourable or thixotropic , and is used to fill gaps between masonry components or coarse aggregate which has already been put in place. Some methods of concrete manufacture and repair involve pumping grout into

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3232-454: Is important to make sure that no pond or body of water is overstocked. Each has a carrying capacity , meaning that any given body of water can only sustain a certain amount of fish. If this carrying capacity is exceeded, fish will have to compete for food and cover, resulting in damage to all organisms in the water. Different countries and states have their own regulations regarding fish stocking. These regulations also differ depending on if it

3333-449: Is in the spring or fall due to mild temperatures and higher levels of oxygen in the water. To acclimate the fish, place the transportation bag in a shaded part of the water and leave it floating for 15–20 minutes. Before releasing the fish, make sure that larger fish and smaller fish are released at different ends of the pond, giving the prey an opportunity to find shelter. Studies show that releasing small numbers of fish at regular intervals

3434-735: Is located north-west of Brisbane, within the Moreton Bay region, at Joyner, near the settlements of Whiteside, and Petrie. The North Pine Dam was designed by the Department of Local Government, with the Co-ordinator General's Department supervising construction contracts headed by Transfield . The cost of the dam was A$ 20 million, and the dam was opened on 12 August 1976 by the Lord Mayor of Brisbane City Council , Alderman Frank Sleeman . The concrete dam structure

3535-412: Is more effective than releasing all at once, so if possible, plan to release them over a few weeks. It is also important to stock the correct species of fish. For warm water ponds, it is recommended to stock largemouth bass , bluegill , crappie , channel catfish , and bullheads . For larger and deeper lakes, stocking cool water game fish such as walleye and trout species is recommended. Lastly, it

3636-465: Is not entirely monitored by the Federal government; most current federal regulations hand authority for fish stocking to the states, except on federal lands or when "direct involvement of federal wilderness" managers is necessary for decision making. Historically, there has been a jurisdictional debate between state and federal agencies, with states arguing that fish stocking is a prerogative supported by

3737-480: Is running low in a given body of water, fish are transported from hatcheries in a large water tank or airplane to their respective locations. The costs associated with stocking are typically covered by angler associations, commercial fishermen, state fish and game agencies, and at times government subsidies; today, most stocking is conducted by state fish and game departments. Radinger et al., 2023 conducted large-scale experiments across 20 lakes, to systematically test

3838-456: Is scheduled to stock 4,398,227 trout (brook, brown, and rainbows) into its streams and lakes in 2019. Also in 2019, Lake Ontario , one of the five Great Lakes , is projected to receive 2,767,660 stocked salmon and trout. According to data by state agencies, in 2004 roughly 1.7 billion fish were stocked across the United States. With 104 different species of fish stocked, a total of 43.65 million pounds of fish were released, primarily in

3939-559: Is then blended with aggregates and any remaining batch water and final mixing is completed in conventional concrete mixing equipment. Workability is the ability of a fresh (plastic) concrete mix to fill the form/mold properly with the desired work (pouring, pumping, spreading, tamping, vibration) and without reducing the concrete's quality. Workability depends on water content, aggregate (shape and size distribution), cementitious content and age (level of hydration ) and can be modified by adding chemical admixtures, like superplasticizer. Raising

4040-453: Is used to restore native species to waters where they have been overfished or can no longer breed. "Give and take" stocking practices are those where fish are stocked only to be fished and then restocked. In response, most states have adopted regulations that prohibit fish stocking in areas that may damage aquatic life or ecosystem diversity, and encourage stocking in bodies of water where no harm will result from doing so. Trout Unlimited has

4141-399: Is usually reinforced with materials that are strong in tension, typically steel rebar . The mix design depends on the type of structure being built, how the concrete is mixed and delivered, and how it is placed to form the structure. Portland cement is the most common type of cement in general usage. It is a basic ingredient of concrete, mortar , and many plasters . It consists of

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4242-590: The Bass Anglers Sportsman Society also enjoy fishing in more robust bodies of water. Despite the findings mentioned above, Virginia researchers have found that even with stockings of rainbow trout, 80% of fish in its stocked streams are still natives. The Department of Natural Resources in Minnesota also found that stocked muskie can coexist because biologically-based guidelines are used when choosing what and where to stock. Until recently,

4343-853: The Ecological Society of America , when gulls in the Great Lakes area were examined after fish stocking, they consumed more garbage, presumably due to the decrease in native prey fish by the predatory stocked fish. Another study found that stocked fish in the Pacific Northwest spread a disease that caused a 15% increase in amphibian embryo mortality. In 2005, the Center for Biological Diversity studied bodies of water across California and found that non-native trout had been stocked in at least 47 areas where rare species were present, damaging 39 imperiled fish and amphibians. Members of

4444-480: The construction industry , whose demand is ever growing with greater impacts on raw material extraction, waste generation and landfill practices. Concrete production is the process of mixing together the various ingredients—water, aggregate, cement, and any additives—to produce concrete. Concrete production is time-sensitive. Once the ingredients are mixed, workers must put the concrete in place before it hardens. In modern usage, most concrete production takes place in

4545-444: The "catch-and-release method" to ensure that fishermen release fish back into the water after catching them. There are also restrictions on what types of lures can be used; for example, some sections of the park are open to fly fishing only, a much safer form of fishing that does not damage aquatic life. There is a Native Trout Conservation Area where regulations are structured so that fishermen can selectively remove nonnative fish from

4646-583: The 10th Amendment to the Constitution. Interestingly, the roots of wildlife ownership are grounded in feudal Europe where fish were considered to be common property to all citizens, subject to government control. However, this control over wildlife was transferred to the states with the separation of the Colonies from Britain. Despite the federal government's right to exercise wildlife authority, current regulation states that "Congress has, in fact, reaffirmed

4747-523: The California Department of Fish and Game agreed to eliminate the environmental harm of its stocking practices, but when it filed its impact report in 2011, protection of native fish and amphibians was clearly not a priority. The agency was brought to court again but was promptly denied. With the state Commission denying the Department of Fish and Game's proposed changes for fish stocking, private hatcheries continue to stock state waters under

4848-529: The North Pine River. The North Pine Dam was designed with little flood mitigation capacity in mind, being designed only for water storage. As such, during flood seasons the location of the dam spillway causes the flooding and closure of Youngs Crossing Road. Flood conditions last affected the dam catchment in October 2010, and prior to that 1991, 1989 and 2000 & 2009. The dam wall is also one of

4949-478: The Samsonvale Cemetery; prior to the flooding of the dam, the site was also home to a church and a post office. To allow for the dam's flooding, 27 kilometres (17 mi) of road had to be relocated and rebuilt. In May 2007, the dam, which was providing approximately 100 megalitres (22,000 × 10 ^  imp gal; 26,000 × 10 ^  US gal) per day or 20% of the region's water supply,

5050-489: The US, grossing $ 720 million that year. Many species of fish including grass carp and the suckermouth catfish help clean bodies of water by eating algae and other green organisms. Algae can take over stagnant ponds, attracting insects and making lakes, rivers, and ponds unpleasant to look at. To treat them, many individuals will choose to stock certain species of fish. This creates a positive externality for those who enjoy

5151-460: The Western states. In the US, common species that are currently stocked for sport include trout , bass , salmon , muskellunge , walleye , and several species of panfish . Before being released into rivers, lakes, ponds, and occasionally oceans across the country, fish are raised in a fish hatchery . Just like humans have a demand for groceries, anglers have a demand for fish. When the supply

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5252-607: The Wilderness Research Institute claim that fish stocking compromises the "naturalness" of aquatic ecosystems and that protecting water quality is more important than recreational opportunities. Although stocking programs were designed to boost conservation, in some cases they have harmed them. The increased boat traffic associated with better fishing opportunities creates negative externalities. These include water contamination, congestion, noise pollution, and disruption of wilderness experiences. When stocking

5353-643: The absence of reinforcement, its tensile strength was far lower than modern reinforced concrete , and its mode of application also differed: Modern structural concrete differs from Roman concrete in two important details. First, its mix consistency is fluid and homogeneous, allowing it to be poured into forms rather than requiring hand-layering together with the placement of aggregate, which, in Roman practice, often consisted of rubble . Second, integral reinforcing steel gives modern concrete assemblies great strength in tension, whereas Roman concrete could depend only upon

5454-589: The basic responsibility and authority of the States to manage fish and resident wildlife." In the future, if more differences in opinion between state and federal managers arise, there may be a need for increased cooperation and coordination between state and federal wilderness managers. Colorado, for example, has regulations to control the stocking of nonnative fish, but only below 6,500 feet. To find out more about each state's fish stocking regulations, visit their respective Department of Fish and Wildlife websites. Today,

5555-630: The cisterns secret as these enabled the Nabataeans to thrive in the desert. Some of these structures survive to this day. In the Ancient Egyptian and later Roman eras, builders discovered that adding volcanic ash to lime allowed the mix to set underwater. They discovered the pozzolanic reaction . The Romans used concrete extensively from 300 BC to AD 476. During the Roman Empire, Roman concrete (or opus caementicium )

5656-526: The concrete at the time of batching/mixing. (See § Production below.) The common types of admixtures are as follows: Inorganic materials that have pozzolanic or latent hydraulic properties, these very fine-grained materials are added to the concrete mix to improve the properties of concrete (mineral admixtures), or as a replacement for Portland cement (blended cements). Products which incorporate limestone , fly ash , blast furnace slag , and other useful materials with pozzolanic properties into

5757-399: The concrete can cause the initially placed material to begin to set before the next batch is added on top. This creates a horizontal plane of weakness called a cold joint between the two batches. Once the mix is where it should be, the curing process must be controlled to ensure that the concrete attains the desired attributes. During concrete preparation, various technical details may affect

5858-461: The concrete quality. Central mix plants must be close to the work site where the concrete will be used, since hydration begins at the plant. A concrete plant consists of large hoppers for storage of various ingredients like cement, storage for bulk ingredients like aggregate and water, mechanisms for the addition of various additives and amendments, machinery to accurately weigh, move, and mix some or all of those ingredients, and facilities to dispense

5959-528: The crack from spreading. The widespread use of concrete in many Roman structures ensured that many survive to the present day. The Baths of Caracalla in Rome are just one example. Many Roman aqueducts and bridges, such as the magnificent Pont du Gard in southern France, have masonry cladding on a concrete core, as does the dome of the Pantheon . After the Roman Empire, the use of burned lime and pozzolana

6060-550: The dam creates Lake Samsonvale at an elevation of 39.63 m (130.0 ft) above sea level , with a surface area of 2,180 hectares (5,400 acres). The gated spillway, with five steel gates, has a discharge capacity of 3,700 cubic metres per second (130,000 cu ft/s). Initially managed by the Brisbane City Council and then SunWater , management of the dam was transferred to SEQ Water in July 2008 as part of

6161-404: The dam, with access prohibited outside of daylight hours. For many years fishing was banned in the dam. Lake Samsonvale has been stocked by Pine Rivers Fish Stocking Association www.prfma.com.au with fresh water fish, including spangled perch , snub-nosed garfish , golden perch , silver perch , eastern freshwater cod , saratoga and Australian bass , with varying levels of success. The dam

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6262-560: The ecology of lakes and rivers was not well understood. To maximize the benefits of stocking and control the costs, fish must be stocked strategically in places where they can be enjoyed but do not pose a threat to native species. Although there are many benefits of stocking, some groups, including the Pacific Rivers Council , believe that it diverts money away from more effective conservation and protection efforts. In addition, declining populations of native golden trout ,

6363-469: The effects of stocking fish compared to habitat-based interventions (i.e. creating shallow zones and adding coarse woody habitats). Over a period of six years, they closely monitored the fish population response in each lake. The study revealed that species-focused fish stocking was completely unsuccessful and demonstrated the potential for ecosystem-based management to better meet conservation goals. Stocking fish provides various benefits to society. Fishing

6464-588: The few in Queensland to be located upstream of a large urban area, and in the event of overtopping or dam failure, Geoscience Australia suggests that the downstream urban population would be flooded within three hours. Recreational use of the lake and its surrounding bushland reserve is severely limited, with prohibited recreational activities including swimming, water skiing, diving, mountain biking, horse riding, canoeing and kayaking, camping, and bushwalking. Picnic facilities are available at four locations around

6565-431: The finished product. Construction aggregates consist of large chunks of material in a concrete mix, generally a coarse gravel or crushed rocks such as limestone , or granite , along with finer materials such as sand . Cement paste, most commonly made of Portland cement , is the most prevalent kind of concrete binder. For cementitious binders, water is mixed with the dry cement powder and aggregate, which produces

6666-681: The gaps to make up a solid mass in situ . The word concrete comes from the Latin word " concretus " (meaning compact or condensed), the perfect passive participle of " concrescere ", from " con -" (together) and " crescere " (to grow). Concrete floors were found in the royal palace of Tiryns , Greece, which dates roughly to 1400 to 1200 BC. Lime mortars were used in Greece, such as in Crete and Cyprus, in 800 BC. The Assyrian Jerwan Aqueduct (688 BC) made use of waterproof concrete . Concrete

6767-554: The interlinking of the silicates and aluminate components as well as their bonding to sand and gravel particles to form a solid mass. One illustrative conversion is the hydration of tricalcium silicate: The hydration (curing) of cement is irreversible. Fine and coarse aggregates make up the bulk of a concrete mixture. Sand , natural gravel, and crushed stone are used mainly for this purpose. Recycled aggregates (from construction, demolition, and excavation waste) are increasingly used as partial replacements for natural aggregates, while

6868-406: The making of mortar. In an English translation from 1397, it reads "lyme ... is a stone brent; by medlynge thereof with sonde and water sement is made". From the 14th century, the quality of mortar was again excellent, but only from the 17th century was pozzolana commonly added. The Canal du Midi was built using concrete in 1670. Perhaps the greatest step forward in the modern use of concrete

6969-531: The material. Mineral admixtures use recycled materials as concrete ingredients. Conspicuous materials include fly ash , a by-product of coal-fired power plants ; ground granulated blast furnace slag , a by-product of steelmaking ; and silica fume , a by-product of industrial electric arc furnaces . Structures employing Portland cement concrete usually include steel reinforcement because this type of concrete can be formulated with high compressive strength , but always has lower tensile strength . Therefore, it

7070-419: The mix, are being tested and used. These developments are ever growing in relevance to minimize the impacts caused by cement use, notorious for being one of the largest producers (at about 5 to 10%) of global greenhouse gas emissions . The use of alternative materials also is capable of lowering costs, improving concrete properties, and recycling wastes, the latest being relevant for circular economy aspects of

7171-478: The mixed concrete, often to a concrete mixer truck. Modern concrete is usually prepared as a viscous fluid, so that it may be poured into forms. The forms are containers that define the desired shape. Concrete formwork can be prepared in several ways, such as slip forming and steel plate construction . Alternatively, concrete can be mixed into dryer, non-fluid forms and used in factory settings to manufacture precast concrete products. Interruption in pouring

7272-441: The mixing of cement and water into a paste before combining these materials with aggregates can increase the compressive strength of the resulting concrete. The paste is generally mixed in a high-speed , shear-type mixer at a w/c (water to cement ratio) of 0.30 to 0.45 by mass. The cement paste premix may include admixtures such as accelerators or retarders, superplasticizers , pigments , or silica fume . The premixed paste

7373-441: The mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. Most concrete is poured with reinforcing materials (such as steel rebar ) embedded to provide tensile strength , yielding reinforced concrete . In the past, lime -based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements , (water resistant) such as

7474-482: The number of endangered or extirpated species. Many of the fish commonly used for stocking also have low reproductive rates and tend to be overfished if not stocked annually. Moreover, as stocked fish tend to contain larger trophy fish, many anglers are more willing to pay for a fishing license , meaning state fishing departments have more revenue to spend on natural resource management and conservation efforts. In 2018, there were roughly 30 million paid license holders in

7575-504: The opportunity to enjoy nature in solitude and escape from their busy lives. It is a form of exercise and a great way to bond with friends and family; fishing has also been linked to increased patience among children. According to a survey by the Outdoor Foundation, 60.3% of fishermen report fishing as a means of getting exercise, 59.1% report fishing to bond with family, and 51.2% report fishing to be close to nature and observe

7676-442: The opportunity to fish in stocked lakes and ponds in the future. Each state has its own regulations regarding fish stocking. Though some state stocking programs restore native populations, others compromise the ecological values of the wilderness areas. The Bureau of Land Management regulates that fishless waters may only be stocked after considering the scientific value of the waters on a case-by-case basis. Fish stocking, however,

7777-670: The practice. In the United States, stocking non-native fish for sport and food was just beginning in 1871 when the US Fish Commission was established. The head of the new agency, Spencer Fullerton Baird , was tasked to research "the decrease of the food fishes of the seacoasts and the lakes of the United States and to suggest remedial measures". Baird made his headquarters at Woods Hole on Cape Cod , Massachusetts . There, his team of scientists and researchers conducted studies on striped bass , blue fish and many other commercial and sport fish. They compiled their research into

7878-506: The properties or increase the performance envelope of the mix. Design-mix concrete can have very broad specifications that cannot be met with more basic nominal mixes, but the involvement of the engineer often increases the cost of the concrete mix. Concrete mixes are primarily divided into nominal mix, standard mix and design mix. Nominal mix ratios are given in volume of Cement : Sand : Aggregate {\displaystyle {\text{Cement : Sand : Aggregate}}} . Nominal mixes are

7979-468: The quality and nature of the product. Design mix ratios are decided by an engineer after analyzing the properties of the specific ingredients being used. Instead of using a 'nominal mix' of 1 part cement, 2 parts sand, and 4 parts aggregate (the second example from above), a civil engineer will custom-design a concrete mix to exactly meet the requirements of the site and conditions, setting material ratios and often designing an admixture package to fine-tune

8080-691: The same permit regulations. The Department aimed to require that all hatcheries and fisheries pay for biological assessment before stocking, thus preventing many of its negative consequences. However, the state of California made it clear that it will not make fisheries go through the stringent permitting process. In February of 2015, the California Third District of Appeals struck down the Department of Fish and Wildlife's permitting requirement on recreational fishing, which would have essentially driven fish farms and hatcheries out of business. This ruling ensures fishermen in California will have

8181-470: The same time, make sure that the existing fish in the pond are not significantly larger than the ones being added. For a standard one-quarter acre pond, it is recommended to stock 120 sunfish, 60 yellow perch, 15 largemouth bass, and 8 pounds of fathead minnows. One way to determine what kinds of fish are already living in a given body of water is to monitor local streams, rivers, and lakes and record what species of fish are being caught. The best time to stock

8282-523: The scenery. Some of the fish caught are also large, providing a source of nutrition to successful fishermen. Roughly 40% of fishermen eat the fish they catch, according to a survey by the Outdoor Foundation. Stocking can also restore threatened, endangered, or native fish species. The Union for Conservation of Nature's red list of endangered species has 1,414 species of fish that are at risk of extinction. Stocking them into lakes, rivers, and streams can support existing populations that are threatened and reduce

8383-470: The stocking practice. Mating between native and introduced fish species can lower the fitness of natural populations, thereby introducing diseases that affect fish and other wildlife. In fact, a study conducted in Virginian streams found that an infectious virus was found only in brook trout populations that had a history of stocking. These diseases may affect humans who consume them as well. Maintaining

8484-411: The strength of the concrete bonding to resist tension. The long-term durability of Roman concrete structures has been found to be due to its use of pyroclastic (volcanic) rock and ash, whereby the crystallization of strätlingite (a specific and complex calcium aluminosilicate hydrate) and the coalescence of this and similar calcium–aluminium-silicate–hydrate cementing binders helped give the concrete

8585-497: The surface of concrete for a decorative "exposed aggregate" finish, popular among landscape designers. Admixtures are materials in the form of powder or fluids that are added to the concrete to give it certain characteristics not obtainable with plain concrete mixes. Admixtures are defined as additions "made as the concrete mix is being prepared". The most common admixtures are retarders and accelerators. In normal use, admixture dosages are less than 5% by mass of cement and are added to

8686-535: The surfaces of the aggregate together, and is typically the most expensive component. Thus, variation in sizes of the aggregate reduces the cost of concrete. The aggregate is nearly always stronger than the binder, so its use does not negatively affect the strength of the concrete. Redistribution of aggregates after compaction often creates non-homogeneity due to the influence of vibration. This can lead to strength gradients. Decorative stones such as quartzite , small river stones or crushed glass are sometimes added to

8787-655: The various ingredients used to produce a given quantity of concrete, the cement is the most energetically expensive. Even complex and efficient kilns require 3.3 to 3.6 gigajoules of energy to produce a ton of clinker and then grind it into cement . Many kilns can be fueled with difficult-to-dispose-of wastes, the most common being used tires. The extremely high temperatures and long periods of time at those temperatures allows cement kilns to efficiently and completely burn even difficult-to-use fuels. The five major compounds of calcium silicates and aluminates comprising Portland cement range from 5 to 50% in weight. Combining water with

8888-439: The water content or adding chemical admixtures increases concrete workability. Excessive water leads to increased bleeding or segregation of aggregates (when the cement and aggregates start to separate), with the resulting concrete having reduced quality. Changes in gradation can also affect workability of the concrete, although a wide range of gradation can be used for various applications. An undesirable gradation can mean using

8989-527: The water through a process called concrete hydration that hardens it over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. This time allows concrete to not only be cast in forms, but also to have a variety of tooled processes performed. The hydration process is exothermic , which means ambient temperature plays a significant role in how long it takes concrete to set. Often, additives (such as pozzolans or superplasticizers ) are included in

9090-593: The water without damaging native fishery. In 2005, California's Center for Biological Diversity submitted a petition to the Department of Fish and Game requesting that the state initiate a review of its fish stocking practices. The reform campaign aimed to protect existing habitats and native populations of fish and amphibians. Finally, in 2008, the Sacramento Superior Court ordered the state to consult with various groups in finding ways to protect native species from fish stocking practices. Initially,

9191-501: The wrong lakes or rivers. In many cases, this had disastrous consequences. When fish, specifically trout , are stocked into ecologically sensitive bodies of water, invertebrate populations and amphibians are threatened, altering the natural selection pressures within the ecosystem. Stocked rainbow trout have been outcompeting native brook trout in many southeastern United States bodies of water, for example. Even bird populations such as cormorants are affected. According to findings by

9292-524: Was Smeaton's Tower , built by British engineer John Smeaton in Devon , England, between 1756 and 1759. This third Eddystone Lighthouse pioneered the use of hydraulic lime in concrete, using pebbles and powdered brick as aggregate. A method for producing Portland cement was developed in England and patented by Joseph Aspdin in 1824. Aspdin chose the name for its similarity to Portland stone , which

9393-626: Was built largely of concrete, and the Pantheon has the world's largest unreinforced concrete dome. Concrete, as the Romans knew it, was a new and revolutionary material. Laid in the shape of arches , vaults and domes , it quickly hardened into a rigid mass, free from many of the internal thrusts and strains that troubled the builders of similar structures in stone or brick. Modern tests show that opus caementicium had as much compressive strength as modern Portland-cement concrete (c. 200 kg/cm  [20 MPa; 2,800 psi]). However, due to

9494-602: Was greatly reduced. Low kiln temperatures in the burning of lime, lack of pozzolana, and poor mixing all contributed to a decline in the quality of concrete and mortar. From the 11th century, the increased use of stone in church and castle construction led to an increased demand for mortar. Quality began to improve in the 12th century through better grinding and sieving. Medieval lime mortars and concretes were non-hydraulic and were used for binding masonry, "hearting" (binding rubble masonry cores) and foundations. Bartholomaeus Anglicus in his De proprietatibus rerum (1240) describes

9595-452: Was made from quicklime , pozzolana and an aggregate of pumice . Its widespread use in many Roman structures , a key event in the history of architecture termed the Roman architectural revolution , freed Roman construction from the restrictions of stone and brick materials. It enabled revolutionary new designs in terms of both structural complexity and dimension. The Colosseum in Rome

9696-468: Was not well recorded; the singular goal of stocking was to enhance sport fishing regardless of ecological ramifications such as erosion of biodiversity . As Pister states, "When trout planting was first implemented, the nation was gripped with a highly utilitarian resource management ethic that placed short-term human interests above virtually any other consideration". Recently, the U.S. Fish and Wildlife Service along with state fishery branches have done

9797-498: Was pioneered by the Nabatean traders who occupied and controlled a series of oases and developed a small empire in the regions of southern Syria and northern Jordan from the 4th century BC. They discovered the advantages of hydraulic lime , with some self-cementing properties, by 700 BC. They built kilns to supply mortar for the construction of rubble masonry houses, concrete floors, and underground waterproof cisterns . They kept

9898-622: Was quarried on the Isle of Portland in Dorset , England. His son William continued developments into the 1840s, earning him recognition for the development of "modern" Portland cement. Reinforced concrete was invented in 1849 by Joseph Monier . and the first reinforced concrete house was built by François Coignet in 1853. The first concrete reinforced bridge was designed and built by Joseph Monier in 1875. Prestressed concrete and post-tensioned concrete were pioneered by Eugène Freyssinet ,

9999-510: Was taken offline as a safety precaution. The drought in Australia caused water levels to drop to 14% capacity, the lowest since it was built. The cessation of water supply was meant to protect the dam from potential blue green algae blooms in the coming summer months. The operators continued to release between 8–10 megalitres (1.8 × 10 ^ –2.2 × 10 ^  imp gal; 2.1 × 10 ^ –2.6 × 10 ^  US gal) per day to service

10100-416: Was to plant as many fish as possible into as many bodies of water as possible. Now, with knowledge of the detrimental effects fish stocking has on invertebrate and amphibian populations, it is conducted much more selectively. Today, much more thought is put into introducing non-native species as they can severely damage the populations of fragile natives; practices lean more towards sustainability. Stocking

10201-625: Was used for construction in many ancient structures. Mayan concrete at the ruins of Uxmal (AD 850–925) is referenced in Incidents of Travel in the Yucatán by John L. Stephens . "The roof is flat and had been covered with cement". "The floors were cement, in some places hard, but, by long exposure, broken, and now crumbling under the feet." "But throughout the wall was solid, and consisting of large stones imbedded in mortar, almost as hard as rock." Small-scale production of concrete-like materials

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