Sustainability Principles and Practice by Robertson Margaret;

Author:Robertson, Margaret;
Language: eng
Format: epub
Publisher: Routledge
Published: 2017-02-12T16:00:00+00:00

p.198

Foundations

A foundation transfers and distributes the load of a building to the earth below. Most building foundations involve concrete. Concrete is a mixture of cement, sand, coarse aggregates, and water. Humans use a lot of concrete, which generates a lot of greenhouse gas: cement production is the second largest industrial source of carbon dioxide emissions, after power generation. About 5 percent of all CO2 emissions worldwide are generated by the cement industry, more than the entire aviation industry (Calkins 2009, 105). Of those emissions, about half are from the chemical process of converting limestone and other carbonates to Portland cement and about 40 percent from the burning of fossil fuels used in the process.

Green building designers often specify a concrete mix with fly ash used as a substitute for part of the cement. Fly ash is a byproduct of burning ground coal to produce electricity. Like Portland cement, it will react and harden when mixed with water. Using fly ash as a cement substitute reduces demand for planet-warming cement and recycles what would otherwise be a waste product. Ground granulated blast furnace slag, a byproduct of steelmaking, is another waste product that can be substituted for cement. As with fly ash, it produces concrete with improved strength and durability.

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