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The Amazing Reaction of Cement: Do You Know How Concrete Hardens into Stone?
The reason why concrete is widely used is not only because of its plasticity and economy, but also because of the wonderful process it exhibits in chemical reactions. Concrete is a composite material consisting of aggregates combined with a fluid cement that hardens over time into a solid structure. This material is second only to water in global usage and is the most widely used building material in the world. Every year, nearly twice as much concrete is used as steel, wood, plastic and aluminum combined.
The hardening process of concrete is called hydration, and it's this process that allows concrete to form a strong bond, binding the various materials together into a durable, stone-like material.
The process begins by mixing dry Portland cement and water to form a flowable slurry. This paste pours easily into the mold and cures over time. During the hardening process, the reaction between cement and water creates a crystalline structure that tightly connects all the components, ultimately forming a stable concrete.
The hydration reaction is an exothermic reaction, which means that the surrounding temperature significantly affects the rate at which concrete sets.
Of course, this process is not set in stone. When making concrete, various additives are often added, such as pozzolans or superplasticizers, to improve the physical properties of the wet mix, adjust the curing time, or change the characteristics of the final product. Most concrete structures also have reinforcing materials such as steel bars embedded in them to increase their tensile strength; this is known as reinforced concrete.
History of Concrete
The history of concrete use dates back to ancient times, when humans began to use various materials to build stable structures. According to archaeological research, concrete floors appeared in the Royal Palace of Tirians in Greece as early as 1400-1200 BC. As early as 700 BC, the ancient Nabataeans discovered the benefits of hydraulic lime and began using concrete to build complex structures.
The use of concrete reached its peak during the Roman period, when Roman architects invented concrete made from flint, volcanic ash and other aggregates, greatly improving the durability and functionality of structures. Many of the elegant and solid buildings from ancient Rome still stand today. From the Colosseum to the Pantheon, these structures are examples of successful applications of concrete.
Constituents of concrete
The main components of concrete include cement, sand and water. Cement is the binder of concrete, which when mixed with water forms a paste that binds the aggregates together. Generally speaking, Portland cement is the most commonly used type of cement, and its main components are calcium silicate, calcium aluminate and calcium ferrite. These components react chemically with water and combine with the aggregate during the hardening process to form a strong structure.
In addition, the type and proportion of aggregates in the concrete formula will also affect the strength and durability of the final product. The coarse aggregate is usually crushed stone, while the fine aggregate is sand. Depending on construction requirements, the size and mix of these materials will be adjusted to suit different environments and loading conditions.
Amazing Features
One of the amazing properties of concrete is its ability to repair itself. In some cases, cracks in concrete can repair themselves through water reacting with unhydrated particles in the cement to form a crystalline structure. In addition, its durability also makes concrete perform well in marine environments. Ancient Roman concrete can still resist the erosion of seawater, which is difficult to match in modern concrete.
The evolution of concrete keeps pace with our changing construction needs, and future developments will likely involve more environmentally friendly and performance-optimized concrete materials.
Finally, as technology develops, more and more architects and engineers are seeking to reduce carbon dioxide emissions during concrete manufacturing and explore the use of various renewable materials in order to improve environmental impact. How do you think concrete will change and develop in the future?
