What is UHPC Ultra High Performance Concrete

Ultra high performance concrete (UHPC) is a new type of cement-based composite material developed in the past thirty years, which has ultra-high mechanical properties and durability, as well as good toughness, bonding performance, impact resistance, and fatigue resistance. In recent years, with the continuous maturity of UHPC preparation technology, its superiority in performance has gradually been recognized by the public. UHPC has become a research hotspot in the field of concrete, widely used in structures, decoration, reinforcement, rapid repair, paving, joint filling, and so on.

1、 UHPC Overview

UHPC is a special concrete with ultra-high strength, ultra-low water absorption, ultra-strong durability, and corrosion resistance. The UHPC currently used in the field of architectural design (different from the structural field) has a compressive strength greater than 120MPa and a flexural strength greater than 25MPa. Although UHPC can achieve high compressive strength, for slender building components, the main utilization is the flexural strength of UHPC. In practical applications, the ultra-high strength of UHPC matrix is further enhanced and toughened by small amounts of polyvinyl alcohol resistant fibers or steel fibers.

2、 Basic Configuration Principles of UHPC

By improving the fineness and activity of organizational components and avoiding the use of coarse aggregates, the internal pores and microcracks of the material are minimized to achieve ultra-high strength and durability. Using higher-order raw materials such as water, sand, cement, silica fume, fibers, and admixtures, through micro continuous grading technology, ultra-efficient water reducing agents and fibers, fully utilizing the chemical and geometric characteristics of ultrafine particles and carefully selected particles, and enabling these particles to achieve close stacking and strong molecular binding force of the matrix through accurate mixing, pouring, and curing.

3、 Physical characteristics of UHPC

Compressive strength ≥ 120MPa;

Fiber reinforcement, improving toughness, with a flexural strength of ≥ 25MPa;

Extremely low water cement ratio → high density → low porosity → dense microstructure;

Excellent durability and extremely low water absorption;

Excellent resistance to chloride intrusion;

Extremely high freeze-thaw cycling performance;

Excellent resistance to sulfide or acid corrosion;

Also known as Reactive Powder Concrete RPC.

4、 Application characteristics of UHPC

Mechanical properties - ultra-high compressive and flexural strength;

High durability - disconnected porosity of 2%, resistant to extremely strong chemical corrosion;

Excellent aesthetics - replicate the surface and geometric patterns of the mold, with a delicate texture that is comparable to an artwork;

Good plasticity - can achieve arbitrary curved surfaces and hollow shapes, making it the most ideal material for achieving architectural aesthetics;

Self Cleanliness - The material is dense and has strong hydrophobicity and stain resistance, giving it the ability to self clean.

Sustainability - Special structures can solve environmental issues and reduce life cycle costs, such as reducing building costs, mold costs, labor costs, and maintenance costs, improving the safety, construction speed, and life cycle of construction sites.

5、 UHPC Advantages

1. Compressive performance. By improving the fineness and activity of the components and avoiding the use of coarse aggregates, the internal defects (pores and microcracks) of the material are minimized to achieve ultra-high strength and durability. The strength of UHPC products is 6-8 times higher than that of traditional concrete. The compression test results indicate that the material performance is linear before reaching the maximum stress, and there is no damage to the material at this stage.

2. Bending resistance. Add 2% metal fibers to make each cubic meter of concrete contain 50 million fibers, which have the ability to absorb deformation. When the material bends and cracks, it exhibits excellent ductility, with many cracks appearing in the stress area but not overall fracture.

3. Durability. The microstructure of UHPC products is sealed, which makes them highly resistant, corrosion-resistant, and chemically aggressive, making them a durable material with ultra-high performance. UHPC products can be used under severe corrosive environmental conditions without damage, such as salt, acidic solutions, and seawater, and have self-healing properties.

4. Aesthetics. The high density and good working performance of UHPC make the surface in contact with the template have a high smoothness. It is difficult for harmful external media to penetrate into UHPC, and the colorants and other components in UHPC are also difficult to precipitate outward. By utilizing this feature, the surface and geometric patterns of the mold can be replicated and UHPC can be used as an exterior decoration material for buildings.

5. Plasticity. Unlike other types of concrete, UHPC products can be used to manufacture irregular plates with various curvatures and large panels with a hollowing rate of over 50%. UHPC products can also incorporate light and shadow elements into their design, which is impossible to achieve with other steel plate and laser cutting solutions. Meanwhile, due to its high fluidity, it can be cast into extremely complex and versatile shapes.

6. Self cleanliness. The self-cleaning performance of UHPC products is mainly based on two reasons. Firstly, its dense density and ultra-low porosity enable UHPC products to resist chemical corrosion and chloride ion intrusion; The second is to use protective agents targeting UHPC to achieve surface hydrophobicity and stain resistance.

6、 Installation nodes for UHPC tablets

For regular sized flat plates, it is recommended to use a back bolt type dry hanging installation: during the pouring and production of the plate, sleeves and screws are pre planted to fix the hanging parts, and then connected to the main structure with the help of keels and embedded parts; For flat or irregular plates with larger plate sizes, it is recommended to attach a steel frame on the back to resist bending moments and facilitate installation and transportation.