Contains the full lesson along with a supporting toolkit, including teachers’ notes.
In recent times, we have all become aware of the need to protect the environment. When we refer to the environment in this sense we usually mean the natural environment, the earth itself, trees, rivers and the surrounding atmosphere. This natural environment is distinguished from the built environment.
Over many years, scientists have developed theories to explain various features of the natural environment such as the sun’s light, rainbows, lightning, the air we breathe, and the way the wholeecosystem is interrelated. At the same time, as we construct the built environment, we use many of the earth’s natural resources. Our roads, bridges, railways, houses and office blocks all use steel and concrete. These widely used materials are produced byextracting and processing natural resources.
Using natural resources
CRH is a major company in the extractive industry and a world leader in the production of building materials. CRH produces bothprimary materials and value-added products for use by the construction industry all over the world. Value-added products include bricks, roof tiles and insulating materials. Primary materials are the basic products used for construction. Cement is a well known and widely used primary material. Cement is a key ingredient in concrete which is a vital product used in the construction of our built environment. The science of cement production is well known. Essentially, the basic raw material,limestone, is crushed and mixed with silica bearing materials, mainly shale, and heated to a high temperature. The output of this process is called clinker. This clinker is then ground with a small amount of gypsum to produce the final product – Portland cement.
Limestone (calcium carbonate, CaCO3) is a commonly occurring mineral in nature and there is little danger that it will run out. However, when it is broken down at high temperature in the kiln,calcium oxide and carbon dioxide are produced (CaCO3 → CaO + CO2). This process can be demonstrated in a laboratory by one person. However, millions of tonnes of cement are required each year, so it usually produced in bulk in a large manufacturing plant. Clearly, cement manufacturing must be carefully managed and controlled. This challenge falls to engineers and in this lesson we look at some of the activities in which they are engaged.