One thing I noticed doing masonry and learning about foundations was just how ubiquitous the use of cement and concrete is. The mortar used between the stones contains cement. The concrete we pour between the stones and the insulation of the knee wall contains cement. The foundation of nearly every building is made with concrete, and therefore cement.
Just to clarify, cement is burnt lime mixed with clay, silica, iron oxide, and aluminum oxide. When mixed with water, cement will set and harden. It is the binding ingredient in concrete, which is cement mixed with an aggregate for a stronger hold. Sand and gravel are the most common aggregates.
Concrete is a staple in modern construction of basically any structure. Bridges, buildings, side walks, and road ways, for example, all use this material. We can shape it into distinctive and specialized forms, and use it to support massive loads (with the right reinforcement). It's durability and resistance to weather also make it a very popular building material. Despite these advantages, I think it's important to know the price we pay to use this material.
Manufacturing concrete is extremely energy intensive. The limestone used to make it mostly comes from mines. This involves heavy use of fossil fueled equipment as well as the explosives. The limestone must then be transported to a factory, at which large grinders and crushers break the stone into smaller chunks. This process takes several stages to get the stone to the right size. The stone is then mixed with other ingredients, including iron ore, and passed through huge kilns that heat it to about 2,700 degrees Fahrenheit. The remaining material (a lot of gases burn off in the kiln) is cooled and then ground into extremely fine powder and mixed with more limestone and gypsum. This material is then packaged and sold as cement.
There is an environmental cost as well. Often, limestone deposits occur around karst, a topographical formation that is caused by dissolving limestone, which forms underground sink holes and caves. Ground water often flows through these formations, and when mining operations happen at these sites the flow of ground water is disrupted. Mining crews sometimes remove the ground water to gain access to the mining site, and this lowers the water table. Removing the rock and water from a limestone also removes the under ground support for the rock and dirt on the surface. This can cause sinkholes. These can be dangerous for mining crews and people living in the surrounding area.
Cement is also extremely alkaline. It burns when it touches your skin, and you have to rinse your hands in vinegar to neutralize it. You don't want to breathe it in either. The particles are so fine, they could easily coat your lungs and I'm sure that damage would be hard to reverse.
Right now, concrete is too essential to our building industry to replace. There are few materials as versatile and easy to work with. But I hope that we can work towards finding alternatives, or alternative ways to process the cement. The cost in terms of fossil fuels is very high, and the water supply is definitely not something we should be jeopardizing.
Just to clarify, cement is burnt lime mixed with clay, silica, iron oxide, and aluminum oxide. When mixed with water, cement will set and harden. It is the binding ingredient in concrete, which is cement mixed with an aggregate for a stronger hold. Sand and gravel are the most common aggregates.
Concrete is a staple in modern construction of basically any structure. Bridges, buildings, side walks, and road ways, for example, all use this material. We can shape it into distinctive and specialized forms, and use it to support massive loads (with the right reinforcement). It's durability and resistance to weather also make it a very popular building material. Despite these advantages, I think it's important to know the price we pay to use this material.
Manufacturing concrete is extremely energy intensive. The limestone used to make it mostly comes from mines. This involves heavy use of fossil fueled equipment as well as the explosives. The limestone must then be transported to a factory, at which large grinders and crushers break the stone into smaller chunks. This process takes several stages to get the stone to the right size. The stone is then mixed with other ingredients, including iron ore, and passed through huge kilns that heat it to about 2,700 degrees Fahrenheit. The remaining material (a lot of gases burn off in the kiln) is cooled and then ground into extremely fine powder and mixed with more limestone and gypsum. This material is then packaged and sold as cement.
There is an environmental cost as well. Often, limestone deposits occur around karst, a topographical formation that is caused by dissolving limestone, which forms underground sink holes and caves. Ground water often flows through these formations, and when mining operations happen at these sites the flow of ground water is disrupted. Mining crews sometimes remove the ground water to gain access to the mining site, and this lowers the water table. Removing the rock and water from a limestone also removes the under ground support for the rock and dirt on the surface. This can cause sinkholes. These can be dangerous for mining crews and people living in the surrounding area.
Cement is also extremely alkaline. It burns when it touches your skin, and you have to rinse your hands in vinegar to neutralize it. You don't want to breathe it in either. The particles are so fine, they could easily coat your lungs and I'm sure that damage would be hard to reverse.
Right now, concrete is too essential to our building industry to replace. There are few materials as versatile and easy to work with. But I hope that we can work towards finding alternatives, or alternative ways to process the cement. The cost in terms of fossil fuels is very high, and the water supply is definitely not something we should be jeopardizing.
http://education.seattlepi.com/environmental-hazards-limestone-mining-5608.html
http://www.cement.org/cement-concrete-basics/how-cement-is-made
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