The hydration process is exothermic, which means ambient temperature plays a significant role in how long it takes concrete to set. This time allows concrete to not only be cast in forms but also to have a variety of tooled processes preformed. The cement reacts with the water through a process called concrete hydration that hardens over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. Concrete is expected to be a key material for structures resilient to climate disasters, as well as a solution to mitigate the pollution of other industries, capturing wastes such as coal fly ash or bauxite tailings and residue. Significant research and development is being done to try to reduce the emissions or make concrete a source of carbon sequestration, and increase recycled and secondary raw materials content into the mix to achieve a circular economy. Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. This widespread use results in a number of environmental impacts. Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminum combined.
Concrete is the second-most-used substance in the world after water, and is the most widely used building material. A vast concrete structure – The Hoover DamĬoncrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time.
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