The forests of gleaming skyscrapers rising from most world urban centers today may be a symbol of modern human technological innovation and ingenuity, but some materials used in their construction are nearly as old as civilization itself. Roman structures built almost entirely from cement and aggregates are still standing two thousand years later. Builders today hope to achieve similar longevity using more environmentally friendly concrete.
Although the concept of a using a benign building material that is somehow in sync with nature is mostly an advertising strategy, the idea is not a total exaggeration. The material most people call concrete is made from crushed bits of rock or old recycled aggregate, and the sizes and amount of this material varies according to formula. It is most commonly machine mixed into a watery paste containing portland cement and additives.
Rock is by definition natural, but the cement slurry is not. Portland cement was invented during the Industrial Revolution, and is also used today in mortar, grout, and other products. For humans it is physically harmful, and skin contact can result in burns. It contains toxic chromium and silica, and the manufacturing process cannot be considered ecologically friendly because of high carbon discharges.
Other chemical additives are combined during manufacturing to enhance specific characteristics of the hardened product. Called admixtures, they are used to shorten the on-site drying period, use less water, increase or decrease permeability, and to add flexibility. While these substances are necessary and useful, they can include setretarders, aerators that form internal gas, plasticizers, and polymerics to increase tensile resistance.
Production of cement increases the possibility of water pollution, and makes safe disposal of demolished material necessary. Although made mostly from natural rock, the substance does not naturally decompose, but must be broken into smaller chunks using machinery. Once it has deteriorated, it must either be reinforced with fresh material or torn down. Recycling is increasing, and a considerable amount of re-purposed material is used in highway construction.
It is possible to achieve a carbon-negative manufacturing process using current technology, but doing so is comparatively expensive. Developing nations rely on this material, and do not welcome additional built-in construction costs. For most builders, using this material more efficiently and effectively is as important to preventing environmental damage as the efforts to make current cement factories less toxic.
Using concrete manufactured locally eliminates costly and high-emissions transportation, although what constitutes local is still debated. The substance can be an energy-efficient asset by creating a thermal mass, or large solid body that retains both heat or cold, which helps regulate interior temperatures throughout the day. While cities typically are hotter than countryside, aggregate surfaces can reflect sunlight and slightly reduce the heat index.
Longevity remains the greatest environmental benefit. Properly hardened material resists weathering and cracking, and can even be made more resistant to seismic shock. A structure designed to last decades may be initially more costly, but those expenses even out, making repairs and ultimately demolition more financially manageable. Improved cement production processes and advanced building design methods are helping to improve negative public opinion.
Although the concept of a using a benign building material that is somehow in sync with nature is mostly an advertising strategy, the idea is not a total exaggeration. The material most people call concrete is made from crushed bits of rock or old recycled aggregate, and the sizes and amount of this material varies according to formula. It is most commonly machine mixed into a watery paste containing portland cement and additives.
Rock is by definition natural, but the cement slurry is not. Portland cement was invented during the Industrial Revolution, and is also used today in mortar, grout, and other products. For humans it is physically harmful, and skin contact can result in burns. It contains toxic chromium and silica, and the manufacturing process cannot be considered ecologically friendly because of high carbon discharges.
Other chemical additives are combined during manufacturing to enhance specific characteristics of the hardened product. Called admixtures, they are used to shorten the on-site drying period, use less water, increase or decrease permeability, and to add flexibility. While these substances are necessary and useful, they can include setretarders, aerators that form internal gas, plasticizers, and polymerics to increase tensile resistance.
Production of cement increases the possibility of water pollution, and makes safe disposal of demolished material necessary. Although made mostly from natural rock, the substance does not naturally decompose, but must be broken into smaller chunks using machinery. Once it has deteriorated, it must either be reinforced with fresh material or torn down. Recycling is increasing, and a considerable amount of re-purposed material is used in highway construction.
It is possible to achieve a carbon-negative manufacturing process using current technology, but doing so is comparatively expensive. Developing nations rely on this material, and do not welcome additional built-in construction costs. For most builders, using this material more efficiently and effectively is as important to preventing environmental damage as the efforts to make current cement factories less toxic.
Using concrete manufactured locally eliminates costly and high-emissions transportation, although what constitutes local is still debated. The substance can be an energy-efficient asset by creating a thermal mass, or large solid body that retains both heat or cold, which helps regulate interior temperatures throughout the day. While cities typically are hotter than countryside, aggregate surfaces can reflect sunlight and slightly reduce the heat index.
Longevity remains the greatest environmental benefit. Properly hardened material resists weathering and cracking, and can even be made more resistant to seismic shock. A structure designed to last decades may be initially more costly, but those expenses even out, making repairs and ultimately demolition more financially manageable. Improved cement production processes and advanced building design methods are helping to improve negative public opinion.
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