Foundations of Construction: The construction magic of Portland cement                             

portland cement
“The Canadian Portland Cement Company, Marlbank Works” with kiln featured. Marlbank, Ontario circa 1895, Deseronto Archives/Wikimedia Commons

By Susanna McLeod

Special to Ontario Construction News

Time for a quick quiz, and here are the clues: this material is produced internationally for the construction industry and at plants across Canada and Ontario. The solid substance is processed into powder and then hardened again. Its uses as versatile building supply are nearly infinite.

Any guesses? Lumber? No, good choice but not right. Some sort of resin? Another interesting response but still not the thing we’re looking for. Ready for the answer? It is cement. Specifically, Portland cement.

From skyscrapers to home foundations, highways to pipes, and ornamental statues to street light poles, and so much more, cement is the champion. For well over a century in Canada, Portland cement has been an essential part of the all-purpose concrete. In 2018, Canadian firms produced the enormous number of nearly 13.6 million metric tonnes of Portland cement.

The Statistics Canada cement survey conveyed that the total was up by 6.7% for national and export production. Four-and-a-half million metric tonnes were exported in 2018, up 11.4% from the previous year. (On top of that, just over 355,000 metre tonnes of masonry and other types of cement were produced that year.)

Recognized as the inventor of Portland cement, Joseph Aspidin of Leeds, England received Patent No. 5022 on October 21, 1824. (Portland cement received its name because it resembled the colour of limestone found on the Isle of Portland.) Titled “Aspidin’s Improvements in the Modes of Producing an Artificial Stone,” the patent contained a description of his methods.

Locating the limestone, Aspidin produced a powder or pool, mixed it with “argillaceous earth or clay” and placed it into a pan to dry. “Then I break the said mixture into suitable lumps, and calcine them in a furnace similar to a lime kiln till the carbonic acid is entirely expelled,” Aspidin writes. The heated mixture “is to be ground, beat or rolled into a fine powder, and is then in a fit state for making cement or artificial stone.”

Shipped from England to Canada in the 1800s, cement was transported in wooden barrels to feed the hungry colonial building boom. While a type of cement may have been used for Rideau Canal construction in the 1830s, “the first official records of the cement industry in Canada refers to production from a Quebec limestone in 1856,” said Earle A. Ripley et al in the book, “Environmental Effects of Mining.” By 1889, “the first production of Portland cement was by C.B. Wright and Sons of Hull, Quebec, and Napanee Cement Works of Napanee, Ontario.” Four years later, Vancouver was home to the first cement plant in western Canada.

“In 1950 there were three cement plants in operation in Ontario, with five kilns having a total rated capacity of 1,090,000 tons per year (of Portland cement),” according to D.F. Hewitt in “The Portland Cement Industry in Ontario,” Industrial Mine Report No. 25, 1968. By 1967, the number had tripled, and the industry never looked back.

Modern processing of Portland cement demands precise proportions of ingredients with frequent testing for best quality. After materials are blended, “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,” described R.A. Serne’s entry in The Canadian Encyclopedia. When cool, the clinker is crushed into powder and “a small amount of gypsum is added to regulate the initial chemical reaction of the cement.”

To satisfy diverse construction needs, five types of Portland cement are produced: general purpose; moderate sulfate resistance; high early strength (for cold weather concrete); low heat; and high sulfate resistance. An added type, white, is also made for decorative uses.

Cement by itself cracks and shrinks; it becomes a durable binder when water and the familiar aggregates of sand, gravel and rocks are mixed in to form concrete. Indispensable across the country, Canada’s utilization is small compared to China, “estimated to consume the largest amount, 400 million tons, with Japan and the United States running second and third at 90 million tons and 80 million tons respectively,” stated Serne. “This places Canada well behind the top ten world producers of Portland cement.”

Production of concrete creates a sizeable carbon footprint. The Canadian cement industry is tackling the problem full-on, developing new carbon capture technology. A Canadian firm based in Nova Scotia has developed a process in which liquefied CO2 is “injected into the concrete mix, causing it to react with calcium ions and water to produce limestone,” said Government of Canada in Canada in “CarbonCure Technologies strengthens concrete and the fight against global warming.” The remarkable invention “can be installed in a single day and requires no changes in materials or production processes.”

Durable, irreplaceable, and with a reduced carbon footprint, Portland cement and concrete perform industrial-strength magic.

©2019 Susanna McLeod. McLeod is a Kingston-based freelance writer who specializes in Canadian history.


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