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95-567: The Great Stone Dam (also called the Lawrence Dam or Lawrence Great Dam ) was built between 1845 and 1848 on the site of Bodwell's Falls on the Merrimack River in what became Lawrence, Massachusetts . The dam has a length of 900 feet (270 m) and a height of 35 feet (11 m). Lawrence is in Essex County, Massachusetts , approximately 25 miles (40 km) north of Boston and only

190-399: A changing climate led in 2007 to $ 3.5 million in improvements and repairs, including replacement of the old plywood flashboards with a more reliable metal and rubber-bladder washboard structure (for better flood and water level control), as well as improving fish migration. In 2008 repairs were delayed by exceptionally heavy rains which highlighted the necessity of the repairs. The development

285-554: A chemical reaction between the dry ingredients and water. The chemical reaction results in mineral hydrates that are not very water-soluble. This allows setting in wet conditions or under water and further protects the hardened material from chemical attack. The chemical process for hydraulic cement was found by ancient Romans who used volcanic ash ( pozzolana ) with added lime (calcium oxide). Non-hydraulic cement (less common) does not set in wet conditions or under water. Rather, it sets as it dries and reacts with carbon dioxide in

380-546: A mortar made of sand and roughly burnt gypsum (CaSO 4 · 2H 2 O), which is plaster of Paris, which often contained calcium carbonate (CaCO 3 ), Lime (calcium oxide) was used on Crete and by the Ancient Greeks . There is evidence that the Minoans of Crete used crushed potsherds as an artificial pozzolan for hydraulic cement. Nobody knows who first discovered that a combination of hydrated non-hydraulic lime and

475-511: A "New City on the Merrimack", which would later become known as Lawrence . Land was acquired from towns on both sides of the Merrimack River ( North Andover , Andover and Methuen ) 11 miles downstream from Lowell. However, water power required a fall greater than the 5 feet (1.5 m) provided by the natural river drop; to achieve a usable water height of no less than 30 feet (9.1 m),

570-437: A 2002 statewide water assessment stated that elevated counts of E. coli and fecal coliform contributed to the river's largest cause of water quality violations. By the 2000s, the largest pollution concern was combined sewer overflow . Wildlife has been impacted through the contamination of shellfishing beds as well as habitat contamination, and aquatic life has been affected due to excess lead , zinc , and other metals in

665-411: A dam of unprecedented size would be required. Initially known as "The Merrimack Water Power Association" (1843) under Samuel Lawrence and Daniel Saunders, the association had identified that "there lay a tract of land resting upon foundations of imperishable blue stone and so shaped and environed by nature as to be a rare site for a permanent dam and a connected system of canals, and for the building of

760-616: A double flood of rain and melting snow and ice swelled the Merrimack at Lowell to 68.4 feet (20.8 m), 10 feet (3 m) higher than the 2006 flood. Part of the Jack Kerouac book Doctor Sax is set during this event. In addition to the 1936 flood, the 1852 flood, and the Mother's Day Flood of 2006, the New England Hurricane of 1938 and floods in October 1996 and April 2007 round out

855-692: A few miles south of the New Hampshire border ( Salem ), located in the Merrimack Valley . The dam is 11 miles (18 km) downstream from Lowell and is visible from Route 28 (Broadway) in Lawrence and from behind the Pacific Paper Mill (now defunct). The dam feeds two canals ( North , re-built in 1848, and South, completed in 1896). At their peak, the North Canal provided up to 13,000 horsepower and

950-432: A fine powder. This product, made into a mortar with sand, set in 5–15 minutes. The success of "Roman cement" led other manufacturers to develop rival products by burning artificial hydraulic lime cements of clay and chalk . Roman cement quickly became popular but was largely replaced by Portland cement in the 1850s. Apparently unaware of Smeaton's work, the same principle was identified by Frenchman Louis Vicat in

1045-482: A foot of rain with some areas receiving as much as 17 inches (43 cm). According to The Boston Globe , around 1,500 people evacuated their homes to escape the flood. This flood also prompted the Massachusetts city of Lowell to install a modern (albeit temporary) flood control gate comprising square steel beams at the site of the historic Francis Gate , a 19th and 20th-century wooden flood gate. When lowered,

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1140-432: A form of hydraulic cement, is by far the most common type of cement in general use around the world. This cement is made by heating limestone (calcium carbonate) with other materials (such as clay ) to 1,450 °C (2,640 °F) in a kiln , in a process known as calcination that liberates a molecule of carbon dioxide from the calcium carbonate to form calcium oxide , or quicklime, which then chemically combines with

1235-669: A half-century. Technologies of waste cementation have been developed and deployed at industrial scale in many countries. Cementitious wasteforms require a careful selection and design process adapted to each specific type of waste to satisfy the strict waste acceptance criteria for long-term storage and disposal. Modern development of hydraulic cement began with the start of the Industrial Revolution (around 1800), driven by three main needs: Modern cements are often Portland cement or Portland cement blends, but other cement blends are used in some industrial settings. Portland cement,

1330-612: A high-tech fish ladder intended to promote fish migration, especially salmon . Fish numbers in the river are higher than before, but time has shown that although the presence of a ladder is better than not having one, the dam—as do all unnatural river obstructions—has had a detrimental impact on natural resources. Although hydroelectric power has often been billed as a sustainable green energy source, continued sustainability relies on developing better ways of supporting nature, fish habitat and fundamental ecological services. The need to work in partnership with nature and be more responsive to

1425-479: A manufacturing city"; this tract was at Bodwell's Falls. In 1845, Abbott Lawrence, Nathan Appleton , Patrick T. Jackson , John A. Lowell , Ignatius Sargent , William Sturgis and Charles S. Storrow incorporated as the Essex Company with a charter to develop water power for planned textile mills along the Merrimack River by building a dam at the preferred site. In addition to being a company director, Storrow

1520-787: A market for use in concrete. The use of concrete in construction grew rapidly from 1850 onward, and was soon the dominant use for cements. Thus Portland cement began its predominant role. Isaac Charles Johnson further refined the production of meso-Portland cement (middle stage of development) and claimed he was the real father of Portland cement. Setting time and "early strength" are important characteristics of cements. Hydraulic limes, "natural" cements, and "artificial" cements all rely on their belite (2 CaO · SiO 2 , abbreviated as C 2 S) content for strength development. Belite develops strength slowly. Because they were burned at temperatures below 1,250 °C (2,280 °F), they contained no alite (3 CaO · SiO 2 , abbreviated as C 3 S), which

1615-413: A month for Rosendale cement made it unpopular for constructing highways and bridges, and many states and construction firms turned to Portland cement. Because of the switch to Portland cement, by the end of the 1920s only one of the 15 Rosendale cement companies had survived. But in the early 1930s, builders discovered that, while Portland cement set faster, it was not as durable, especially for highways—to

1710-579: A permit allowing landfill water to be dumped into the Merrimack River. Politicians are also seeking increased federal funding to update water infrastructure for the Merrimack River, as the river's current sewer infrastructure has resulted in the dumping of over 100,000 gallons of untreated water into the river. The Merrimack is listed as one of the Navigable Waters of the United States, subject to Section 10, Rivers and Harbors Act Jurisdiction. While

1805-682: A pozzolan produces a hydraulic mixture (see also: Pozzolanic reaction ), but such concrete was used by the Greeks, specifically the Ancient Macedonians , and three centuries later on a large scale by Roman engineers . There is... a kind of powder which from natural causes produces astonishing results. It is found in the neighborhood of Baiae and in the country belonging to the towns round about Mount Vesuvius . This substance when mixed with lime and rubble not only lends strength to buildings of other kinds but even when piers of it are constructed in

1900-443: A result of the pollution from textile mills and other human-related waste. In the 1960s, the Merrimack River was one of the ten most polluted waterways in the United States due to years of unmediated dumping of raw sewage , paper and textile mill discharge, and tannery sludge. Phthalates , a group of chemicals used in the manufacture of plastics and detrimental to human bodily systems, were identified in high concentrations within

1995-563: A section depicting the fictional Pre-Columbian arrival of 9th century Irish and English travelers at the Merrimack River and their interactions with local Native Americans . Cement A cement is a binder , a chemical substance used for construction that sets , hardens, and adheres to other materials to bind them together. Cement is seldom used on its own, but rather to bind sand and gravel ( aggregate ) together. Cement mixed with fine aggregate produces mortar for masonry, or with sand and gravel , produces concrete . Concrete

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2090-726: A very advanced civilisation in El Tajin near Mexico City, in Mexico. A detailed study of the composition of the aggregate and binder show that the aggregate was pumice and the binder was a pozzolanic cement made with volcanic ash and lime. Any preservation of this knowledge in literature from the Middle Ages is unknown, but medieval masons and some military engineers actively used hydraulic cement in structures such as canals , fortresses, harbors , and shipbuilding facilities . A mixture of lime mortar and aggregate with brick or stone facing material

2185-422: Is hydraulic cement , which hardens by hydration of the clinker minerals when water is added. Hydraulic cements (such as Portland cement) are made of a mixture of silicates and oxides, the four main mineral phases of the clinker, abbreviated in the cement chemist notation , being: The silicates are responsible for the cement's mechanical properties — the tricalcium aluminate and brownmillerite are essential for

2280-512: Is pozzolanic , so that ultimate strength is maintained. Because fly ash addition allows a lower concrete water content, early strength can also be maintained. Where good quality cheap fly ash is available, this can be an economic alternative to ordinary Portland cement. Portland pozzolan cement includes fly ash cement, since fly ash is a pozzolan , but also includes cements made from other natural or artificial pozzolans. In countries where volcanic ashes are available (e.g., Italy, Chile, Mexico,

2375-400: Is 1,629 feet in length. The overflow of water is 900 feet wide from wing to wing, the crest line curving slightly upstream. A solid filling of earth, backing the masonry and sloping back, one foot in six, protects the structure. The south wing wall is 324 feet long and the north wing 405 feet. The original cost of the structure, at the time of building when prices of labor and material ruled low,

2470-520: Is a major emitter of global carbon dioxide emissions . The lime reacts with silicon dioxide to produce dicalcium silicate and tricalcium silicate. The lime also reacts with aluminium oxide to form tricalcium aluminate. In the last step, calcium oxide, aluminium oxide, and ferric oxide react together to form brownmillerite. A less common form of cement is non-hydraulic cement , such as slaked lime ( calcium oxide mixed with water), which hardens by carbonation in contact with carbon dioxide , which

2565-569: Is about 4.4 billion tonnes per year (2021, estimation), of which about half is made in China, followed by India and Vietnam. The cement production process is responsible for nearly 8% (2018) of global CO 2 emissions, which includes heating raw materials in a cement kiln by fuel combustion and release of CO 2 stored in the calcium carbonate (calcination process). Its hydrated products, such as concrete, gradually reabsorb atmospheric CO 2 (carbonation process), compensating for approximately 30% of

2660-417: Is completely evaporated (this process is technically called setting ), the carbonation starts: This reaction is slow, because the partial pressure of carbon dioxide in the air is low (~ 0.4 millibar). The carbonation reaction requires that the dry cement be exposed to air, so the slaked lime is a non-hydraulic cement and cannot be used under water. This process is called the lime cycle . Perhaps

2755-555: Is constantly fed into a rotary kiln, it allowed a continuous manufacturing process to replace lower capacity batch production processes. Calcium aluminate cements were patented in 1908 in France by Jules Bied for better resistance to sulfates. Also in 1908, Thomas Edison experimented with pre-cast concrete in houses in Union, N.J. In the US, after World War One, the long curing time of at least

2850-606: Is known as the Merrimack Valley . Several U.S. naval ships have been named USS  Merrimack and USS Merrimac in honor of this river. The river is also known for the early American literary classic A Week on the Concord and Merrimack Rivers by Henry David Thoreau . The etymology of the name of the Merrimack River—from which all subsequent uses derive, such as the name of the Civil War ironclad—remains uncertain. There

2945-578: Is located along the river's banks in New Hampshire. On the Merrimack River's banks are a number of cities built to take advantage of water power in the 19th century, when textile mills dominated the New England economy: Concord , Manchester , and Nashua in New Hampshire, and Lowell , Lawrence , and Haverhill in Massachusetts. At the mouth of the river is the small city of Newburyport . Prior to

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3040-667: Is more usually added to Portland cement at the concrete mixer. Masonry cements are used for preparing bricklaying mortars and stuccos , and must not be used in concrete. They are usually complex proprietary formulations containing Portland clinker and a number of other ingredients that may include limestone, hydrated lime, air entrainers, retarders, waterproofers, and coloring agents. They are formulated to yield workable mortars that allow rapid and consistent masonry work. Subtle variations of masonry cement in North America are plastic cements and stucco cements. These are designed to produce

3135-403: Is present in the air (~ 412 vol. ppm ≃ 0.04 vol. %). First calcium oxide (lime) is produced from calcium carbonate ( limestone or chalk ) by calcination at temperatures above 825 °C (1,517 °F) for about 10 hours at atmospheric pressure : The calcium oxide is then spent (slaked) by mixing it with water to make slaked lime ( calcium hydroxide ): Once the excess water

3230-483: Is responsible for early strength in modern cements. The first cement to consistently contain alite was made by William Aspdin in the early 1840s: This was what we call today "modern" Portland cement. Because of the air of mystery with which William Aspdin surrounded his product, others ( e.g., Vicat and Johnson) have claimed precedence in this invention, but recent analysis of both his concrete and raw cement have shown that William Aspdin's product made at Northfleet , Kent

3325-457: Is some evidence that it is Native American. In 1604 the natives of later New England told Pierre Dugua, Sieur de Monts , who was leading a colony of French language speakers to Acadia (later Nova Scotia ), of a beautiful river to the south. The French promptly pronounced its native name as Merremack . In 1605 Samuel de Champlain followed this lead, found the river and renamed it Riviere du Gas . The French and their name did not remain on

3420-474: Is the most widely used material in existence and is behind only water as the planet's most-consumed resource. Cements used in construction are usually inorganic , often lime - or calcium silicate -based, and are either hydraulic or less commonly non-hydraulic , depending on the ability of the cement to set in the presence of water (see hydraulic and non-hydraulic lime plaster ). Hydraulic cements (e.g., Portland cement ) set and become adhesive through

3515-438: Is to make concrete. Portland cement may be grey or white . Portland cement blends are often available as inter-ground mixtures from cement producers, but similar formulations are often also mixed from the ground components at the concrete mixing plant. Portland blast-furnace slag cement , or blast furnace cement (ASTM C595 and EN 197-1 nomenclature respectively), contains up to 95% ground granulated blast furnace slag , with

3610-474: The Isle of Portland , Dorset, England. However, Aspdins' cement was nothing like modern Portland cement but was a first step in its development, called a proto-Portland cement . Joseph Aspdins' son William Aspdin had left his father's company and in his cement manufacturing apparently accidentally produced calcium silicates in the 1840s, a middle step in the development of Portland cement. William Aspdin's innovation

3705-411: The "Merrimake" and "Merrymake" of a 1721 land grant at Penacook, New Hampshire . William Wood's New England's Prospect of 1634 calls the river the "Merrimacke" and locates it eight miles beyond Agowamme ( Ipswich, Massachusetts ). It hosts, he says, "Sturgeon, Sammon and Basse, and divers other kinds of fish." Merrimac, Massachusetts , settled in 1638 and originally part of Amesbury, Massachusetts ,

3800-588: The 1960s. Today the dam is the site of a hydroelectric plant, completed in 1981, which is owned by Central Rivers Power USA (now parent company of the Essex Company, which still owns the dam) and the Lawrence Hydroelectric Associates. In part due to the successful use of the river's power to develop the industrial potential of the city of Lowell, a consortium of local industrialists ( Abbott Lawrence , Edmund Bartlett, Thomas Hopkinson of Lowell, John Nesmith , and Daniel Saunders) set out to create

3895-487: The 1970s the Lawrence Hydroelectric Associates began the construction of a $ 28-million power plant at the south end of the Great Stone Dam that would ensure energy production and preserve the architectural integrity of the dam. In 1981, the project was completed allowing the generation of 16.8 MW of power, far more than the 15,000 horsepower (11 MW) the dam provided in its heyday. The plant's development included

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3990-517: The Art to Prepare a Good Mortar published in St. Petersburg . A few years later in 1825, he published another book, which described various methods of making cement and concrete, and the benefits of cement in the construction of buildings and embankments. Portland cement , the most common type of cement in general use around the world as a basic ingredient of concrete, mortar , stucco , and non-speciality grout ,

4085-501: The Francis gate seals the city's canal system off from its source on the Merrimack. The Great Gate, as it is also called, was built in 1850 under the direction of James B. Francis . Considered unnecessary when it was first constructed, "Francis' Folly" first saved the city in 1852 and subsequently in 1936. The most significant flood in the recorded history of the Merrimack was in March 1936, when

4180-464: The Gulf of Maine between the city of Newburyport and the town of Salisbury . In addition to the Merrimack River mainstem, there are dozens of sub-basins in New Hampshire and Massachusetts making up the watershed. The U.S. Geological Survey categorizes them into six fourth-level sub-basins using hydrological codes with the prefix 0107. The following are some of the other significant rivers found within

4275-431: The Merrimack River is prone to minor flooding , on May 15, 2006, rainfall raised the river more than 8 feet (2.4 m) above flood stage, forcing evacuations, damaging property, and breaking the main sewage pipeline in the city of Haverhill, Massachusetts , dumping 35 × 10 US gallons (1.3 × 10  L) of raw sewage waste into the river per day. Reports of total rainfall vary, but most areas appear to have received around

4370-433: The Merrimack River. Currently, there are six sanitary sewer systems from which untreated sewage flows directly into the Merrimack River due to infrastructure issues within the sewage system. Recent research has identified mercury contamination as a significant threat to fish and aquatic life in the Merrimack River. This research analyzes how biological mercury hotspots and watershed transport of mercury might contribute to

4465-760: The Merrimack. The natives dwelling along the river at the time of European exploration included the Agawam and Naumkeag on the lower reaches, the Pawtucket at Lowell, Massachusetts , the Nashua , Souhegan and Namoskeag around Manchester, New Hampshire , the Pennacook northward from Bow, New Hampshire , and the Winnepisseogee at the source, Lake Winnipesaukee . According to Joseph B. Walker, relying on Chandler Eastman Potter's The History of Manchester (1856), Merremack contains

4560-526: The New York Commissioner of Highways to construct an experimental section of highway near New Paltz, New York , using one sack of Rosendale to six sacks of Portland cement. It was a success, and for decades the Rosendale-Portland cement blend was used in concrete highway and concrete bridge construction. Cementitious materials have been used as a nuclear waste immobilizing matrix for more than

4655-457: The Philippines), these cements are often the most common form in use. The maximum replacement ratios are generally defined as for Portland-fly ash cement. Portland silica fume cement. Addition of silica fume can yield exceptionally high strengths, and cements containing 5–20% silica fume are occasionally produced, with 10% being the maximum allowed addition under EN 197–1. However, silica fume

4750-471: The South Canal 2,000 horsepower; the Essex Company sold "mill rights" to its water power, allowing mills to use the energy provided. The North Canal existed before the dam, but was redeveloped both to better feed the mills and to accommodate the 30-foot (9.1 m) drop caused by the dam. About a mile in length, the canal had a guard lock and three lift locks with mitered gates. The locks were abandoned in

4845-523: The US Army, supervised the construction. The exact construction is outlined as follows: The dam is constructed of huge granite blocks, laid in hydraulic cement firmly embedded and bolted upon the river rock bed. The thickness at the base is 35 feet, narrowed gradually to about 13 feet below the crest stone. The greatest height of masonry is 22 feet and the average plunge of water 25 to 26 feet without flashboards. The masonry, including wings extending inland,

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4940-603: The absence of pozzolanic ash, the Romans used powdered brick or pottery as a substitute and they may have used crushed tiles for this purpose before discovering natural sources near Rome. The huge dome of the Pantheon in Rome and the massive Baths of Caracalla are examples of ancient structures made from these concretes, many of which still stand. The vast system of Roman aqueducts also made extensive use of hydraulic cement. Roman concrete

5035-623: The air. It is resistant to attack by chemicals after setting. The word "cement" can be traced back to the Ancient Roman term opus caementicium , used to describe masonry resembling modern concrete that was made from crushed rock with burnt lime as binder. The volcanic ash and pulverized brick supplements that were added to the burnt lime, to obtain a hydraulic binder , were later referred to as cementum , cimentum , cäment , and cement . In modern times, organic polymers are sometimes used as cements in concrete. World production of cement

5130-460: The available hydraulic limes, visiting their production sites, and noted that the "hydraulicity" of the lime was directly related to the clay content of the limestone used to make it. Smeaton was a civil engineer by profession, and took the idea no further. In the South Atlantic seaboard of the United States, tabby relying on the oyster-shell middens of earlier Native American populations

5225-476: The confluence of the Pemigewasset and Winnipesaukee rivers. From there, the river flows south through Concord, Manchester, and Nashua, entering Massachusetts at the town of Tyngsborough , where it turns northeast and winds past or through Chelmsford , Lowell, Dracut , Tewksbury , Andover , Methuen , Lawrence, North Andover , Haverhill, Groveland , West Newbury , Merrimac , and Amesbury , to its mouth at

5320-536: The construction of the Middlesex Canal , Newburyport was an important shipbuilding city, in a location to receive New Hampshire timber that had been floated downriver. The Merrimack River watershed covers 5,010 square miles (12,980 km ) in southern New Hampshire and northeastern Massachusetts. It is the fourth largest river basin in New England . The river begins in the city of Franklin, New Hampshire , at

5415-426: The dam and surrounding industrialization, were so popular that it took less than one month to acquire capital of 1 million dollars. Gilmore & Carpenter won the contract to build the dam. The construction commenced and finished on the same day (September 19) three years apart (one source states it was the same hour) from the first stone laid in 1845 to the last in 1848. Charles H. Bigelow, who had been an engineer in

5510-492: The dam is a popular fishing location for breeds such as white perch , American shad , river herring , and in season, striped bass , also known as "stripers", as the area has a larger concentration of fish due to the dam and an easily accessible shoreline for both boaters and shoreside anglers. Merrimack River The Merrimack is an important regional focus in both New Hampshire and Massachusetts. The central-southern part of New Hampshire and most of northeast Massachusetts

5605-420: The development of new cements. Most famous was Parker's " Roman cement ". This was developed by James Parker in the 1780s, and finally patented in 1796. It was, in fact, nothing like material used by the Romans, but was a "natural cement" made by burning septaria – nodules that are found in certain clay deposits, and that contain both clay minerals and calcium carbonate . The burnt nodules were ground to

5700-607: The earliest known occurrence of cement is from twelve million years ago. A deposit of cement was formed after an occurrence of oil shale located adjacent to a bed of limestone burned by natural causes. These ancient deposits were investigated in the 1960s and 1970s. Cement, chemically speaking, is a product that includes lime as the primary binding ingredient, but is far from the first material used for cementation. The Babylonians and Assyrians used bitumen (asphalt or pitch ) to bind together burnt brick or alabaster slabs. In Ancient Egypt , stone blocks were cemented together with

5795-608: The elements merruh ("strong") and auke ("place"—a recognizable locative ending), and means "the place of strong current,- a term not inappropriate, when we consider ... the river's rapids ...." Potter was an authority on Native American affairs in colonial New England. By contrast, in A Week on the Concord and Merrimack Rivers , Henry David Thoreau implies that "its name signifies the Sturgeon River." Walker goes on to cite spellings of "Merimacke", "Merimack" and "Merrimacke" in "the colonial records of Massachusetts", as well as

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5890-482: The end of World War II, the economic, social and industrial landscapes within which the mills relied on the dam's power were changing. Complex interrelated forces including geographical migration of the textile industry and development of an increasingly influential "consumer economy" with high shopper expectations, demanding price models and rapidly evolving fashion tastes, plus the development of energy and industrial technologies, all led to widespread mill closures, making

5985-499: The exposure of aquatic life to chemical pollution within the Merrimack River. Additionally, the use of road salt in the winter has remained a major pollutant since the 1970s, and chloride contamination in the Merrimack River continues to impact aquatic life. United States politicians from New Hampshire and Massachusetts are calling for the United States Environmental Protection Agency (EPA) to reassess

6080-461: The first decade of the nineteenth century. Vicat went on to devise a method of combining chalk and clay into an intimate mixture, and, burning this, produced an "artificial cement" in 1817 considered the "principal forerunner" of Portland cement and "...Edgar Dobbs of Southwark patented a cement of this kind in 1811." In Russia, Egor Cheliev created a new binder by mixing lime and clay. His results were published in 1822 in his book A Treatise on

6175-402: The formation of the liquid phase during the sintering ( firing ) process of clinker at high temperature in the kiln . The chemistry of these reactions is not completely clear and is still the object of research. First, the limestone (calcium carbonate) is burned to remove its carbon, producing lime (calcium oxide) in what is known as a calcination reaction. This single chemical reaction

6270-535: The historical innovation and social marvel beneath their feet. The Lawrence History Center (located in what were the offices of the Essex Company ) has significant displays on the dam and its creation. The construction of the dams and canals might have been more expensive if not for the easy availability of cheap labor, often Irish immigrants , who worked in what could be appalling and unsafe conditions which contributed to injury and sometimes death. Increasingly from

6365-553: The impact of its development. It stands as testament to the heyday of great innovation and innovators, to a time of economic and social development, to the Essex Company itself, and most importantly to an immigrant city born in and of the American Industrial Revolution . It was further included in the North Canal Historic District in 1984. Because of the impact on the depth and flow of the river, and

6460-426: The initial CO 2 emissions. Cement materials can be classified into two distinct categories: hydraulic cements and non-hydraulic cements according to their respective setting and hardening mechanisms. Hydraulic cement setting and hardening involves hydration reactions and therefore requires water, while non-hydraulic cements only react with a gas and can directly set under air. By far the most common type of cement

6555-506: The large mill pond caused by the dam, the area above and below the dam have enhanced recreational opportunities. A large area for sailing , kayaking and boating is located immediately upstream from the dam, supported by a large boat house housing the Greater Lawrence Community Boating Program (as well as a water rescue station). Despite conservationist concerns over fish numbers, the area immediately below

6650-404: The low pH (8.5–9.5) of its pore water) limited its use as reinforced concrete for building construction. The next development in the manufacture of Portland cement was the introduction of the rotary kiln . It produced a clinker mixture that was both stronger, because more alite (C 3 S) is formed at the higher temperature it achieved (1450 °C), and more homogeneous. Because raw material

6745-465: The most endangered rivers in the United States, as named by the American Rivers nonprofit in 2016. Current concerns include stormwater runoff , urban stormwater, high levels of bacteria, combined sewage runoff, phosphorus creating harmful algal blooms , reduced oxygen levels, illicit sewage discharges, and litter . Combined sewer overflows (CSO) are the largest contributors to waste discharge into

6840-404: The official spelling be "Merrimack". Prior to glaciation, the Merrimack continued its southward course far beyond the present day New Hampshire-Massachusetts border to enter the Gulf of Maine near Boston . Upon the glacier's retreat, debris deposited north of Boston filled the lower Merrimack Valley, redirecting the river into its current northeast bend at Lowell. The Neville archaeological site

6935-465: The other materials in the mix to form calcium silicates and other cementitious compounds. The resulting hard substance, called 'clinker', is then ground with a small amount of gypsum ( CaSO 4 ·2H 2 O ) into a powder to make ordinary Portland cement , the most commonly used type of cement (often referred to as OPC). Portland cement is a basic ingredient of concrete , mortar , and most non-specialty grout . The most common use for Portland cement

7030-467: The point that some states stopped building highways and roads with cement. Bertrain H. Wait, an engineer whose company had helped construct the New York City's Catskill Aqueduct , was impressed with the durability of Rosendale cement, and came up with a blend of both Rosendale and Portland cements that had the good attributes of both. It was highly durable and had a much faster setting time. Wait convinced

7125-415: The power the dam provided obsolete for current needs while also wholly inadequate for newer development. While these and other changes reduced demand for the dam's energy, demand for hydroelectric power was growing: the Great Stone Dam was both literally and figuratively well placed to be as much a part of the future as it had been of the past if investment could be found for the necessary modernization. In

7220-447: The rest Portland clinker and a little gypsum. All compositions produce high ultimate strength, but as slag content is increased, early strength is reduced, while sulfate resistance increases and heat evolution diminishes. Used as an economic alternative to Portland sulfate-resisting and low-heat cements. Portland-fly ash cement contains up to 40% fly ash under ASTM standards (ASTM C595), or 35% under EN standards (EN 197–1). The fly ash

7315-472: The river in 1973. A 1976 study of the chemical dynamics of the Merrimack River found that at that time, the biggest pollution source was road salt . Although the river underwent significant restoration efforts from the 1970s onwards, a 1997 study found that the river continued to suffer from the long-term effects of pollution. The study identified that the river had elevated bacteria counts, low dissolved oxygen , and high nutrient levels . A few years later,

7410-438: The river's infrastructure, there was a noticeable change in wildlife and aquatic life. Birds, fish, and other animals returned to inhabit the river, with citizens noting specifically seeing much more American shad , striped bass , trout , and Atlantic salmon . The involvement of local volunteers in monitoring and maintaining the river has provided effective restoration efforts over the years. The Merrimack River remains one of

7505-442: The river's most serious flood events, measured at Lowell. The Francis Gate had been left in place after being dropped in 1936, so it prevented flooding in 1938 as well. In 2007, the steel beam system was again assembled in place. The song "Merrimack River" and its instrumental reprise are featured on the 2009 album Amanda Leigh by Nashua, New Hampshire, native Mandy Moore . Anya Seton 's historical novel Avalon includes

7600-538: The river. In addition, human recreational activities such as swimming and boating have been restricted in certain areas of the river due to high contamination levels. The Federal Clean Water Act of 1972 led to significant improvement for the Merrimack River. The law required sewage to be treated before being discharged into waterways. Federal funding allowed officials to create the river's infrastructure, specifically funding for wastewater treatment plants (U.S. Army Corps of Engineers 2006). Following these changes in

7695-407: The sea, they set hard underwater. The Greeks used volcanic tuff from the island of Thera as their pozzolan and the Romans used crushed volcanic ash (activated aluminium silicates ) with lime. This mixture could set under water, increasing its resistance to corrosion like rust. The material was called pozzolana from the town of Pozzuoli , west of Naples where volcanic ash was extracted. In

7790-503: The six major sub-basins in the watershed, listed moving downstream along the Merrimack: Since 1951, the Merrimack River has seen many alterations and pollutants. It was dammed and canalled , as well as used as a dumping spot for industrial waste . The Merrimack was essential for textile mill complexes, which used the river for discharge from their factories. Citizens recall that the river had unusual colors, smells, and vegetation as

7885-471: The stonework have ever been needed. At the time of its construction it was the largest dam in the world, and it remains one of the significant landmarks defining the city to which its creation gave birth. It was so significant to the city at the time, a celebration was held in honor of its semi-centennial in 1895, yet now may be less celebrated, as at the site of the dam there is no viewing platform, monument or historical marker giving passersby information about

7980-444: Was a true alite-based cement. However, Aspdin's methods were "rule-of-thumb": Vicat is responsible for establishing the chemical basis of these cements, and Johnson established the importance of sintering the mix in the kiln . In the US the first large-scale use of cement was Rosendale cement , a natural cement mined from a massive deposit of dolomite discovered in the early 19th century near Rosendale, New York . Rosendale cement

8075-441: Was about $ 250,000. The construction was innovative for the time as it used hydraulic injections of concrete into the spaces between the granite stones. This has led to the dam's reliability and durability, as despite several severe floods no repairs to the dam itself have ever been required, although repairs were made in 1894 to the wooden flashboards and the flashboard system was updated in 2007 to improve water control. No repairs to

8170-453: Was called West Amesbury until 1876, at which time it adopted its current name and spelling. Merrimack, New Hampshire , was incorporated in 1746, spelling its name "Marrymac" in the record of its first town meeting. It was referred to as "Merrimac" into the early 19th century: in the 1810 decennial census, it was spelled "Merrimac", but in the 1820 census and afterward, "Merrimack". In 1914, US Congressman John Jacob Rogers (MA) petitioned that

8265-487: Was carefully planned to ensure longevity and capacity for the 19th century achievement. It remains owned by the Essex Company which itself is now owned by Central Rivers Power USA, in partnership with Lawrence Hydroelectric Associates. Added to the National Register of Historic Places in 1977, the Great Stone Dam is considered one of the greatest engineering projects of the 19th century due to its size, its method and

8360-479: Was counterintuitive for manufacturers of "artificial cements", because they required more lime in the mix (a problem for his father), a much higher kiln temperature (and therefore more fuel), and the resulting clinker was very hard and rapidly wore down the millstones , which were the only available grinding technology of the time. Manufacturing costs were therefore considerably higher, but the product set reasonably slowly and developed strength quickly, thus opening up

8455-468: Was developed in England in the mid 19th century, and usually originates from limestone . James Frost produced what he called "British cement" in a similar manner around the same time, but did not obtain a patent until 1822. In 1824, Joseph Aspdin patented a similar material, which he called Portland cement , because the render made from it was in color similar to the prestigious Portland stone quarried on

8550-494: Was extremely popular for the foundation of buildings ( e.g. , Statue of Liberty , Capitol Building , Brooklyn Bridge ) and lining water pipes. Sorel cement , or magnesia-based cement, was patented in 1867 by the Frenchman Stanislas Sorel . It was stronger than Portland cement but its poor water resistance (leaching) and corrosive properties ( pitting corrosion due to the presence of leachable chloride anions and

8645-622: Was formalized by French and British engineers in the 18th century. John Smeaton made an important contribution to the development of cements while planning the construction of the third Eddystone Lighthouse (1755–59) in the English Channel now known as Smeaton's Tower . He needed a hydraulic mortar that would set and develop some strength in the twelve-hour period between successive high tides . He performed experiments with combinations of different limestones and additives including trass and pozzolanas and did exhaustive market research on

8740-405: Was rarely used on the outside of buildings. The normal technique was to use brick facing material as the formwork for an infill of mortar mixed with an aggregate of broken pieces of stone, brick, potsherds , recycled chunks of concrete, or other building rubble. Lightweight concrete was designed and used for the construction of structural elements by the pre-Columbian builders who lived in

8835-463: Was the lead engineer for the Essex Company and is credited as the designer and engineer of the dam. Previous to incorporating as the Essex Company, the group of men had been known as the "Boston Associates" and had made similar developments upstream in Lowell, where a dam of similar (but smaller) size had already been built, giving rise to that industrial city. The plans set forth by the Essex Company, for

8930-407: Was used in house construction from the 1730s to the 1860s. In Britain particularly, good quality building stone became ever more expensive during a period of rapid growth, and it became a common practice to construct prestige buildings from the new industrial bricks, and to finish them with a stucco to imitate stone. Hydraulic limes were favored for this, but the need for a fast set time encouraged

9025-720: Was used in the Eastern Roman Empire as well as in the West into the Gothic period . The German Rhineland continued to use hydraulic mortar throughout the Middle Ages, having local pozzolana deposits called trass . Tabby is a building material made from oyster shell lime, sand, and whole oyster shells to form a concrete. The Spanish introduced it to the Americas in the sixteenth century. The technical knowledge for making hydraulic cement

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