by William M. Kelly
Chapter 5: Cement
Cement manufacture involves the processing of selected raw materials, either natural whole rock or a specific combination of rock materials, to make a synthetic mineral mixture that will bind to an aggregate filler and yield a durable, physically and chemically stable, and strong product. Generally, the term refers to “hydraulic” cement, primarily portland cement, which has the property of hardening under water and which is the chief binding agent for concrete and masonry. Portland cement concrete is one of the principal materials used in infrastructure, commercial, and residential construction. In 1818, engineer Canvass White found bedrock in Madison County, New York, that could be processed into hydraulic cement. Cement from this and other limestone units found in Cayuga and Onondaga counties were used in the construction of the original Erie Canal (1817–1825). In 1871, the first landmark building constructed with reinforced concrete was erected in Port Chester, New York (Auburn Univ. 2007).
Historically, New York produced two types of cement, which differed primarily in the raw material sources. “Natural” cement was made from whole-rock limestone formations, which contain between 54 and 75 percent calcium and magnesium carbonates and 20 to 40 percent silica, alumina, and iron oxides. Portland cement is made from limestone with higher calcium carbonate content, perhaps as high as 95 percent, and lower amounts of accessory minerals. Other rock, mineral, or chemical admixtures are introduced to portland cement to produce the proper chemical composition. Natural cement was first made from “waterlime” rock in 1823, in an accidental discovery during the construction of the Delaware and Hudson Canal in Ulster County. It was noticed that the lime calcined from certain rocks in the Rosendale area would harden under water rather than slake (Ries and Eckle 1901). In 1899, there were 29 cement works in New York that produced 4,689,167 barrels of 136-kilogram (300-pound) capacity, that were valued at $2,813,500 (2009 value: $71,594,555).
The Rosendale region produced what was recognized as the best natural cement in the United States. Here, strata in the Upper Silurian Rondout Formation were utilized. The strata had a workable aggregate thickness of up to 30 feet. Large room and pillar mines that extended 300 meters (1,000 feet) across the face (along strike) and down dip for 249 to 365 meters (800—1,200 feet) yielded the raw material. The Rondout was also quarried for natural cement at Howe’s Cave in Schoharie County. Other New York “waterlimes” were also used for natural cement production. In central New York, the natural cement rock was found at the top of the Manlius Formation in Onondaga and Madison counties. In the western part of the state, quarries in Erie County once rivaled the Rosendale mines. The rock used here was the Upper Silurian Bertie Dolostone of the Salina Group (Newland 1921).
Portland cement production in New York began in 1881 at Beacon, Dutchess County. Raw materials were derived from the Kingston area. This enterprise was so successful that another plant was opened closer to Kingston in 1883. Statewide, the industry grew rapidly during the 1890s and by 1902, production exceeded a million barrels per annum (Newland 1921). In 1906, the portland cement industry surpassed natural cement production (2,423,724 bbls. vs.
1,691,565 bbls.), although the latter persisted in New York until 1970 when the last of the Rosendale quarries was closed. Originally, the locus of portland cement manufacturing was in the Hudson River Valley south of Albany. These plants drew on units (e.g., Manlius, Coeymans, Becraft, Alsen) of the Lower Devonian Helderberg Group. These rocks were used for portland cement in Schoharie County as well. In Glens Falls, Washington County, rocks of the Ordovician Black River–Trenton Groups were quarried for this use. In central New York, portland cement plants used the Tully Formation in Tompkins County and the Manlius, Coeymans, and lower Onondaga Formations in Onondaga County.
Portland cement comprises the majority of New York hydraulic cement output with most of the remainder being masonry cement. Most of the portland cement is used in concrete. Approximately 1 ton of portland cement is used to make 4 cubic yards of concrete. In general, ready-mix concrete is the primary use of portland cement in New York. Concrete product manufacture is the next-largest use in concrete blocks; concrete pipe; prestressed, precast concrete; and other concrete products. Highway contractors and building material dealers account for the remainder (Johnson 1985). Quantities of cement shipped to customers in New York, from all sources, are shown in Table 7.
Cement Shipments to Final Customer, by Destination and Origin in 2007. (Data from U. S. Geological Survey [van Oss 2009]).
The primary ingredient needed for cement manufacture is slaked lime (CaO), which is produced from the mineral calcite (CaCO3) in limestone although in theory marble or marl could be used. Secondary raw materials must be added to provide silica (SiO2) and alumina (Al2O3) that are needed for the growth of the synthetic minerals that will form the cement. Iron, as ferrous oxide (FeO), is also needed in the raw materials or must be added. Although the source of these secondary components can be diverse, the final ratio of silica to alumina plus iron oxide must be tightly controlled (Ames et al. 1994). Traditional sources of these additional materials in New York have been clay and shale, which occur widely and often in association with the limestone units. While there is considerable flexibility in the choice of raw materials for cement, the chemical and physical properties of the raw feed to the kiln exert a large effect on costs. There are some rocks in the state, so-called “impure limestone,” which have approximately the correct blend of lime, silica, alumina, and iron to be used directly without additives. These were the rocks that were the raw material to New York’s natural cement industry. However, a rock that has exactly the correct blend of ingredients for modern cement is very rare.
In addition to the raw materials described above, a source of sulfur as SO3 is required. This is added to control the setting time of concrete made with the cement. A common source of SO3 is gypsum (CaSO4•2H2O), which was mined in western New York until very recently. To a degree, synthetic gypsum, derived from sulfur dioxide (SO2) flue gas scrubbers on power plants, has supplanted natural gypsum (Ames et al. 1994). Source materials for cement manufacture can contain components, within limits, other than those described. However, if present in amounts above prescribed levels, they become deleterious. Magnesium compounds such as the mineral dolomite (CaMgCO3) are the most common of the unwanted materials. Magnesia (MgO) is beneficial in the kiln feed in amounts less than 4 percent in that it acts as a flux and is considered to be tolerable. However, amounts in excess of that are intolerable because the formation of magnesium minerals, such a periclase, in concrete cause expansion and disruption of the concrete, which can lead to failure (Ames et al. 1994).
Various physical and chemical environments require that several different types of portland cement be manufactured. Eight types of cement (five primary, three air-entraining) are produced in New York. The types and uses are listed in Table 8.
Types and Characteristics of Portland Cement.
Types IA, IIA and IIIA are cements used to make air-entrained concrete. They have the same properties as Types I, II, and III, except that they have small quantities of air-entrained materials combined with them. Although, as indicated by historical references, some ancient and early-twentieth-century concretes were accidentally air entrained, the New York State Department of Public Works and the Universal Atlas Cement Company were the first to recognize that certain natural organic materials, primarily wood and animal by-products, would greatly increase the resistance of concrete road surfaces to freeze—thaw and de-icing chemicals (Whiting and Stark 1983; Rixom and Mailvaganam 1986). The most commonly used materials to encourage air entrainment are salts of wood resins, synthetic detergents, salts of petroleum acids, and salts of fatty or resinous acids (Dolch 1984).
Blended cements are also produced in New York. Blended cement is a mixture of portland cement and blast furnace slag or of portland cement and a pozzolan (most commonly fly ash). The use of blended cements in concrete reduces the amount of water required for the mix and diminishes bleeding, improves workability, enhances sulfate resistance, and inhibits the alkali-aggregate reaction. Blended cements also reduce the heat evolved during hydration, thus reducing the chances for thermal cracking upon curing.
Cement producers are located in Albany, Greene, and Warren counties. All of the facilities are foreign-owned. The mine and cement plant in Albany County is operated by the French-owned Lefarge Group. Lefarge in North America is the largest diversified supplier of construction materials in the United States and Canada and is the world’s leading cement manufacturer. The mine from which the raw materials are extracted in Albany County is the largest producer of crushed stone in the state (Figure 21). The cement producers in Warren and Greene counties are operated by the Heidelberg Cement Group, a German-owned company. The 550,000 tpy Warren County cement plant uses modern preheater technology and supplies cement by truck, rail, and barge throughout eastern New York and New England. Cement and slag grinding capacity at the company’s Greene County plant augments the cement plant’s capacity and produces blended products. A second cement plant in Greene County is owned by Holcim, a Swiss-owned company. Holcim also owns reserves on Becraft Mountain and recently spent $58 million in a futile attempt to open a new, state-of-the-art plant to replace its existing operation.
Cement and construction aggregate quarry, Ravena, New York. Note trucks and equipment at center for scale.