Joseph Aspdin, an English mason, is generally credited with the invention of portland cement. In 1824 he obtained a patent for his product, which he named portland cement because it produced a concrete the colour of limestone quarried on the Isle of Portland. The name is used worldwide, with many manufacturers adding their own trade or brand names. Canadian production began in Hull, Québec, in 1889. Before that time portland cement was imported from England in wooden barrels. Plants were soon established at Napanee and Shallow Lake, Ontario, and on Montréal Island. The first plant in the western provinces was built in Vancouver in 1893.
Materials used in MANUFACTURING portland cement must contain appropriate proportions of lime, silica alumina and iron components. During manufacture, frequent analyses are made to ensure a uniformly high-quality product. The raw materials are pulverized and mixed in the desired proportions. After blending, the prepared mix is fed into the upper end of a rotary kiln, where it is burned or fired at temperatures of 1400-1650°C and changed into portland cement clinker. The clinker is then cooled and pulverized. During this operation, a small amount of GYPSUM is added to regulate the initial chemical reaction of the cement. This pulverized product is finished portland cement, ready for use in making concrete.
Different types of portland cement are manufactured in Canada to meet physical and chemical requirements for specific purposes. The Canadian Standards Association provides for 5 types of portland cement for specific purposes; ie, normal, moderate and high early strength, low heat of hydration, and sulphate-resisting. Normal portland cement is the type most commonly manufactured; high early strength and sulphate-resisting types are usually available. Like moderate and low heat of hydration forms of portland cement, other special cements (masonry, oil well, expansive, regulated set) may not always be readily available from manufacturers because of low demand.
In 1996, 9 Canadian cement companies operated 20 plants. Five of the 9 companies are foreign affiliated and controlled 83% of Canadian clinker capacities as of 1995. The oldest cement kiln was built in the 1950s, but most are around 15 years old. Total clinker capacity of the 20 plants is 15.4 million t and finish grinding capacity, 17 million t. Regionally, Ontario and Québec combine to have the majority of capacity - over 60% of the totals. Lafarge Canada Inc. is Canada's largest cement company, with slightly less than one-third of the nation's capacity. The next 2 largest producers, St Lawrence Cement Inc and St Mary's Cement Co, combine to account for an additional 37% of Canada's capacity.
Canadian cement plants tend to be modern and larger than other North American facilities. Slightly over half of Canadian capacity is coal-fired; initiatives to conserve energy should increase this proportion and continue the increased use of waste fuel alternatives. The Canadian cement manufacturers now use a mix of wet and dry-process technology that contributed to a 24% reduction in overall energy consumption during the period 1974-1994. The Canadian industry is strongly regionalized, with most plants located in high-population areas. High transportation and energy costs strongly influence plant location and economic viability.
Cement consumption in Canada (producers' shipments plus imports less exports) has been variable over the past decade at a 6.5 to 7.5 million t range. At this level, the value of production was estimated at about $700 million. Primary sources of demand are from Ontario with relatively equal participation by Québec, the Prairie provinces and British Columbia. Total world consumption of portland cement was 1.37 billion t in 1994. China is estimated to consume the largest amount, 400 million t, with Japan and the United States running second and third at 90 million t and 80 million t respectively. This places Canada well behind the top ten world producers of portland cement.
Although individual companies do research on cement production, much experimentation on the use and application of cement and concrete is done through the Canadian Portland Cement Association, an industry-supported, nonprofit organization, the purpose of which is to improve and extend the uses of cement and concrete through scientific research and engineering fieldwork. The association is active throughout Canada and offers detailed information on concrete use, design and construction.
Author R.A. SERNE
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