The bulk density of concrete varies with the grade of concrete. Capacity is calculated according to the mixture ratio of concrete and the proportion of various materials that make up concrete per cubic meter. The bulk density of concrete generally refers to the bulk density of fresh wet concrete. For example, prepare C25 concrete. After many trial mixes, it is finally determined that the concrete composition material is: cement: water reducer: sand: crushed stone: water =1:0.022:1.59: 3.39: 0.47 = cement 372kg( 15.4%)+ water reducer (8.2kg).
Concrete is one of the most important civil engineering materials. It is a kind of artificial stone which is made of cementing material, granular aggregate (also called aggregate), water, additives and additives added when necessary, mixed evenly, compacted, cured and hardened in a certain proportion. Concrete has the characteristics of abundant raw materials, low price and simple production technology, so its consumption is increasing. At the same time, concrete also has the characteristics of high compressive strength, good durability and wide range of strength grades. These characteristics make it widely used, not only in various civil engineering, but also in shipbuilding, machinery industry, marine development, geothermal engineering and so on. Concrete is also an important material.
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.