The improvement of the quality and performance of special concrete will have an immeasurable effect on the development of the world economy and the saving of energy resources. Because concrete constitutes almost all the buildings developed by mankind in recent times.
In this article, we will introduce 8 kinds of special concrete in terms of characteristics, proportions, and applications. We hope that the market will pay more attention to the commercial concrete and jointly promote the green and sustainable development of the national economy.
Special Concrete丨Permeable Concrete
Permeable concrete is concrete with a permeability rating of not less than P6. That is, it can resist the action of 0.6 MPa hydrostatic pressure without permeability. By improving the compactness of concrete, impermeable concrete improves the pore structure, thus reducing the infiltration channels and improving the impermeability. Its common proportioning methods are as follows.
Water-rich slurry method
Relying on the use of a smaller water-cement ratio, higher cement dosage, and sand ratio to improve the quality and quantity of cement slurry to make the concrete denser.
Aggregate grading method
By improving the aggregate grading, the aggregate itself achieves the maximum degree of dense stacking state. At the same time, strict control of the water-cement ratio, water consumption, and the compatibility of the mix, so that the concrete structure is dense and improves impermeability.
Admixture method
The admixture method is widely used because of its simple construction, low cost, and reliable quality compared with the previous two methods. It is in the concrete mixed with the appropriate varieties of admixtures to improve the concrete endospore structure, isolate or block various pores, cracks, water seepage channels, etc., in order to improve the purpose of concrete seepage resistance.
The use of special cement
The use of non-shrinkage impermeable cement, expansion cement, etc. to mix concrete, can improve the pore structure within the concrete, and effectively improve the density of concrete and seepage resistance.
Special Concrete丨Heat Resistant Concrete
Heat-resistant concrete is a special concrete that can maintain the required physical and mechanical properties under the action of high temperatures (200 ~ 900 ℃) for a long time. According to the different cementing materials used, heat-resistant concrete is mostly used for blast furnace foundation, coke oven foundations, thermal equipment foundations, and enclosure structures, lining, chimney, etc. Common types are as follows.
Slag cement heat-resistant concrete
Slag cement as the cementitious material, andesite, basalt, heavy slag, clay crushed brick, etc. as heat-resistant coarse and fine aggregates, and burnt clay, brick powder, etc. for grinding fine admixtures, and then add the right amount of water to prepare. Slag cement heat-resistant concrete formulated by the limit use temperature of 900 ℃.
Aluminate cement heat-resistant concrete
Using high alumina cement or sulfate cement, heat-resistant coarse and fine aggregates, high refractoriness grinding admixture, and water preparation. Aluminate cement heat-resistant concrete limit use temperature of 1300 ℃.
Water glass heat-resistant concrete
Water glass as a cementing material, mixed with sodium fluorosilicate as a hardener, heat-resistant coarse and fine aggregates can be used for crushed iron ore, magnesium bricks, chrome magnesium bricks, talc, coke stones, etc. Water glass heat-resistant concrete limit use temperature of 1200 ℃.
Phosphate heat-resistant concrete
Aluminum phosphate and high alumina refractory materials or zircon prepared from coarse and fine aggregates and finely ground admixtures. This concrete has high-temperature toughness, good wear resistance, high refractoriness, and its ultimate use temperature of 1500 ~ 1700 ℃.
Special Concrete丨Acid Resistant Concrete
Most of the corrosion of concrete is acidic medium corrosion. In the acidic medium under the action of corrosion resistance of concrete that is acid-resistant concrete. Acid-resistant concrete is widely used in the chemical industry for acid-proof tanks, electroplating tanks, etc. Common types are as follows
Water glass acid-resistant concrete
By water glass as a binder, sodium fluorosilicate as a hardener, and acid-resistant powder and acid-resistant coarse and fine aggregates in a certain proportion of the preparation. Water glass acid concrete can resist the erosion of all kinds of acids except hydrofluoric acid. Especially, it has good corrosion resistance to sulfuric acid and nitric acid and has high strength. It is mostly used in flooring chemical workshops, acid washing tanks, acid storage pools, etc.
Sulfur acid-resistant concrete
Sulfur as cementing material, polysulfide rubber as a toughening agent, mixed with acid-resistant powder and fine aggregate, boiled into sulfur mortar by heating (160～170℃), and then filled into acid-resistant coarse aggregate after cooling, which is sulfur acid-resistant concrete. Its compressive strength can reach more than 40MPa, and it is often used in ground, equipment foundations, acid storage tanks, etc.
Special Concrete丨Polymer Concrete
Polymer concrete is concrete made by combining organic polymers, inorganic cementitious materials, and aggregates. Compared with ordinary cement concrete, it has the advantages of high strength, corrosion resistance, wear resistance, and strong bonding. Common types are.
Polymer-impregnated concrete
The hardened concrete is dried and immersed in organic monomers, and the monomers within the pores of the concrete are polymerized by heating or radiation so that the concrete and the polymer form a whole, called polymer-impregnated concrete.
As the polymer fills the pores and micro-cracks inside the concrete, it increases the compactness of the concrete, improves the bond strength between cement and aggregate, and reduces the stress concentration. Polymer-impregnated concrete is suitable for special components requiring high strength and durability, especially for reinforced pipes, unreinforced pipes, and pits for transporting liquids.
Polymer Cement Concrete
It is made by mixing cement with polymer emulsion and mixing with sand or other aggregates. The production process is similar to that of ordinary concrete, making it easy to construct on-site. Polymer cement concrete is mostly used for seamless floors and is also commonly used for concrete pavements and airport runway surfaces and waterproofing layers for structures.
Special Concrete丨Fiber Concrete
Fibrous concrete is made of concrete as a matrix, mixed with various fiber materials. The purpose of incorporating fiber is to improve the tensile, flexural, and impact toughness of concrete, but also can effectively improve the brittle nature of concrete. Commonly used fiber materials are steel fibers, glass fibers, asbestos fibers, carbon fibers, and synthetic fibers. Fiber concrete is currently mainly used for complex stress structural elements, and high-impact resistance requirements of the project, such as aircraft runways, highways, bridge decks, pipelines, etc.
Special Concrete丨Radiation-proof concrete
Concrete that can shield the x, γ rays, etc. that are harmful to the human body is called radiation-proof concrete. It is prepared with cement, water, and heavy aggregates. Its apparent density is generally above 3000kg per cubic meter. The heavier the concrete, the better the performance of its protection against x, γ rays. And the thickness of the protective structure can be reduced.
But for protection against neutron streams, in addition to the need for concrete is very heavy, concrete also needs to contain a sufficient amount of the lightest element – hydrogen. Radiation-proof concrete is mainly used in the atomic energy industry and the application of radioisotopes in devices such as reactors, gas pedals, radiochemical devices, customs, hospitals, and other protective structures.
Special Concrete丨Fair-faced concrete
Fair-faced concrete is also called Architecture Concrete, Exposed Concrete, or Fair Faced Concrete (decorative concrete).
Its most important feature is that after the concrete is poured, there is no longer any painting on the outside, and no tiles, stone, and other materials are pasted, which is a way to show the plain face of the concrete. However, due to the fear that it will be soaked by rain or deterioration, it may be sprayed with a waterproof protective film.
As the technology continues to improve, the status of fair-faced concrete continues to rise in the minds of architects – the surfaces are becoming smoother and flatter, the tones more homogeneous, and the joints on the surface neater. There is also a growing public recognition of the artistic expression of fair-faced concrete.
Special Concrete丨Colored Concrete
Colored concrete is also known as surface-colored concrete. It is usually made of colored cement or white cement with pigments in a certain proportion to form a colored finish, and then ordinary concrete is poured on it. In addition, it is also possible to take a dry sprinkle coloring hardener on the surface of newly poured concrete to show color or use chemical coloring agents to penetrate into the capillaries of hardened concrete to generate insoluble and anti-abrasive colored precipitates to show color.