1950kg/m？ Apparent density of concrete ≤
Apparent density of concrete
In general design, the concrete is 1m? The mass of cement, coarse aggregate, fine aggregate, admixture, admixture and water is calculated in kg, and its density is about equal to the original concrete mass/1m? , generally in 2350~2450kg/m? .
The density of bubbles produced or specially designed in concrete due to air mixing or physical and chemical changes between substances is often small, such as foam concrete.
Extended data
History of concrete development
Archaeologists found that 5,000 years ago, the ancestors of Lingjiatan were not only able to make exquisite jade tools, but also began to plant rice, raise or hunt animals such as pigs, deer and birds to enrich their diet. In addition, in building construction, they learned the construction technology similar to reinforced concrete: "digging ditches to fill the fire soil and supporting the mud wall with wooden bones."
1900 World Expo showed the use of reinforced concrete in many aspects, which caused a revolution in the field of building materials. French engineer Ainabik 1867 saw monier's flowerpots, tubs and water tanks made of barbed wire and concrete at the Paris World Expo, and was inspired, so he tried to apply this material to building construction.
1879 began to manufacture reinforced concrete floors, and later developed into a set of concrete structural beams strengthened with steel hoops and longitudinal bars. Only a few years later, when he built an apartment building in Paris, he adopted improved reinforced concrete main columns, beams and floors, which are still widely used today.
1884, German construction company purchased monier's patent and conducted the first batch of reinforced concrete scientific experiments to study the strength and fire resistance of reinforced concrete. Bonding force between reinforcement and concrete. 1887, German engineer Collen first published the calculation method of reinforced concrete; Wilson, an Englishman, applied for a patent for reinforced concrete slab; American Hai Ete experimented with concrete beams.
From 1895 to 1900, France built the first batch of reinforced concrete bridges and sidewalks. 19 18 Abram published the famous water-cement ratio theory to calculate the strength of concrete. Reinforced concrete has become an important material to change the world landscape.
Concrete can be traced back to ancient times, and its cementing materials are clay, lime, gypsum, volcanic ash and so on. Portland cement appeared from 19 in the 1920s, and was widely used because of its good strength and durability, easily available raw materials, low cost, especially low energy consumption (see inorganic cementing materials).
At the beginning of the 20th century, someone published the theory of water-cement ratio, which laid the theoretical foundation of concrete strength. Later, lightweight aggregate concrete, aerated concrete and other concrete appeared one after another, and various concrete additives began to be used.
Since the 1960s, water-reducing agents have been widely used, and high-efficiency water-reducing agents and corresponding fluid concrete have appeared. Polymer materials entered the field of concrete materials, and polymer concrete appeared; A variety of fibers are used to disperse reinforced fiber concrete. Modern testing technology is also increasingly applied to the research of concrete material science.
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