Special Concrete Knowledge: A科普 Guide - Beijing Mingsheng Weiyi

When most people think of concrete, they might envision a dusty, noisy construction site. Yet, in the minds of designers, concrete holds a magical allure. Its malleability and the inherent beauty that is as pure as its essence, are unmatched by any other material.

For most in the construction industry, specialty concrete is a familiar term, but few can articulate exactly what makes it special or to what extent. This article aims to provide a detailed introduction to specialty concrete, clarifying its characteristics and offering a general overview of its applications.

Radiation Shielding Concrete

Also known as shielding concrete or radiation-proof concrete, it has a high bulk density and is capable of blocking γ-rays, X-rays, or neutron radiation, making it difficult for radiation to penetrate.

The Application of Radiation-Proof Concrete

The rapid development and widespread application of nuclear technology have spurred prosperity in the power and other industries, but have also posed significant threats to the environment and human health. Safety concerns have garnered great attention. Nowadays, radiation shielding concrete is extensively used, particularly in the design of large-scale buildings for the nuclear industry. Moreover, with the advancement of high technology, there is a high demand for radiation shielding concrete in medical applications involving radioactive instruments, necessitating the use of special buildings that incorporate large amounts of radiation shielding concrete.

Company Project Cases: Atomic Energy Research Institute, Shanghai Huashan Hospital, etc.

Heavy-duty concrete

As everyone knows, the specific weight of normal concrete is around 23 kN/m³, while that of reinforced concrete is around 25 kN/m³. How heavy is heavy-duty concrete?

Under strength (C30) requirements and certain workability conditions (such as self-compacting), the current specific gravity is 60 kN/m3 (note: the apparent density of iron is 78 kN/m3 per cubic meter). If the workability of concrete is to be improved, such as for pumping requirements, the current specific gravity for pumpable heavy-duty concrete is 50 kN/m3. The specific gravity of heavy-duty concrete can be adjusted according to specific design needs, ranging from 25 to 60 kN/m3.

Section 3: Bridge Counterweight Concrete

Bridge ballast primarily consists of steel box girders or structures designed for load balancing. Its advantages include excellent fluidity, self-compaction, pumpable construction, simplicity, and quick project completion. It is particularly suitable for constructing irregular structures, offering much higher cost-effectiveness and efficiency compared to using flat iron and other materials.

Company Project Cases: Chizhou Yangtze River Bridge, Chongqing Eger Rock Bridge, Wuhan Qingshan Yangtze River Bridge, Zhuhai Honghe Bridge, etc.

Anti-float concrete with weight balancing

Anti-float concrete with counterweights is commonly used in buildings in areas with high water levels. It effectively addresses the issue of insufficient structural weight, ensuring structural anti-float counterweight and balanced counterweight for main and wing buildings, thereby effectively preventing uneven settlement problems.

Anti-float concrete with added weight is commonly used in underground parking garages, sunken plazas, underground stations, and the underground structures of main podium commercial complexes.

Company Project Cases: Beihai Museum, Shanghai Jinmao Tower, Zhongshan碧桂园 Project, etc.

Section 5: Balanced Concrete Components

The weighting materials, used as aggregates and with appropriate particle size grading, can be manufactured into weighting components of various shapes; the concrete density can reach 2.5~6.0t/m3; the weighting components can weigh from several tons to tens or even dozens of tons; aggregates can be provided as required for self-precasting or cast-in-place components; they are characterized by small volume, high specific gravity, excellent durability, and low cost, making them a complete substitute for cast iron weights. For example, they are used in electric railway counterweights, construction machinery weighting blocks, elevator weighting blocks, and large-scale weighing scales.

Ultra-light, high-strength concrete

The concrete has a density of around 1.5 tons per cubic meter and can achieve a strength of C80 or higher.

As a new building material, it boasts superior properties such as high compressive strength, strong resistance to deformation, high density, and low porosity, making it widely used in high-rise building structures, large-span bridge structures, and certain special structures. High-strength concrete is characterized by its high compressive strength, typically 4 to 6 times that of ordinary concrete, allowing for reduced cross-sectional areas of components. Therefore, it is well-suited for high-rise buildings.

Seven: Ultra-High Performance Concrete (UHPC)

Also known as Reactive Powder Concrete (RPC), "Ultra-High Performance Concrete" encompasses two aspects of 'ultra-high'—ultra-high durability and ultra-high mechanical properties. It boasts characteristics such as tensile and crack resistance, as well as resistance to high temperatures.

UHPC, known for its exceptional durability, boasts mechanical properties nearly equivalent to those of rigid structures when properly reinforced, while also offering excellent wear and blast resistance. Consequently, UHPC is particularly suitable for use in long-span bridges, blast-resistant structures (such as bank vaults), thin-walled structures, and environments with high wear and corrosion. UHPC has already been applied in various practical projects, including long-span pedestrian overpasses, highway-railway bridges (examples are listed in Table 3), thin-walled silos, nuclear waste containers, steel cable anchoring reinforcement plates, ATM protective shells, and more. It is anticipated that its applications will continue to expand.