The so-called ultra-high performance concrete, referred to as UHPC, refers to the general name of cement-based composites with compressive strength above 150MPa and ultra-high toughness and ultra-long durability in the world. Among them, the more representative ultra-high performance concrete material is reactive powder concrete RPC, which was proposed by French scholars in 1993. It is mainly composed of silica fume, cement, water reducer, fine aggregate and steel fiber. It is constructed according to the principle of greater compactness, so that the defects (pores and micro cracks) in the material can be reduced to less. So what are its performance characteristics! Don't worry, Chengdu UHPC ultra high performance concrete editor will answer for you:

UHPC functional concrete is a special engineering material with strength, toughness and high durability. It has a good application prospect in the fields of national defense engineering, marine engineering, nuclear industry, special security and protection engineering, and municipal engineering. The test shows that its flexural strength is three times that of ordinary C50 concrete, the shrinkage decreases by 50%, and it is still intact after 700 freeze-thaw cycles. It is called "never crack" concrete.
UHPC material components do not contain coarse aggregate, and the particle size is generally less than 1mm. It has strength and excellent durability due to its high compactness. The research shows that the compressive strength of UHPC can reach more than 200MPa, and the durability of UHPC can reach more than 200 years. In addition, because the dispersed fine steel fibers in UHPC can greatly slow down the expansion of micro cracks in the material, so that the material shows toughness and ductility.

The following figure shows the dimensional comparison of equal bending strength of different materials.


Compact packing: This is one of the basic principles of all dense powder material design. The high compactness and good working function of UHPC make the surface in contact with the formwork have a high finish. It is difficult for external harmful media to invade into UHPC, and the colorants and other components in UHPC are not easy to precipitate out. Using this feature, UHPC can be used as the external decoration material of buildings.
2. How to select fibers for UHPC?

Considering the cost performance, metal fiber can be selected first, followed by long and short metal fiber. When different fibers are mixed, they shall be selected reasonably after careful test.

3. Why is it not recommended that UHPC use large aggregates?

This involves the problems of material fracture mechanics, including the original crack size and defect density; It also involves the problems of material homogeneity, such as the spatial distribution of large particles; It also involves the problems in porous materials. Unless it is necessary (or the section size of the component is large enough), it is generally not suitable to use aggregates > 5mm (unless it is really necessary, such as shrinkage reduction, temperature reduction, cost reduction, etc.)!

4. Where is UHPC suitable?

Where conventional concrete can not meet the requirements! Where there are high requirements for impermeability, frost resistance and salt corrosion resistance; where there are high requirements for earthquake resistance, explosion resistance and crack resistance, oil and gas transmission pipelines can be made by using the high tensile strength and corrosion resistance of UHPC to replace large-diameter thick wall steel pipes with high cost, which can significantly improve the durability of the pipeline and reduce the cost; super long-span structure and large crack resistance For shell structure, curved surface structure, repair and reinforcement of old structures, UHPC has been used as the outer protective layer of steel structure of offshore oil platform, which can greatly improve the service life of pillars in water level change area; it is used in military and security fields to manufacture anti explosion and anti impact devices.
5. How to improve the basic quality of UHPC?

The cube (100mmx100mmx100mm) without fiber base material has a compressive strength of not less than 150MPa, a tensile strength of not less than 5MPa, a permeability of two orders of magnitude lower than C80, and no visible bubbles; these are also entry-level quality requirements. In addition, common deterioration problems of conventional concrete (including HPC) should be exempted (including reinforcement erosion, freeze-thaw damage, alkali aggregate reaction and sulfate corrosion), such UHPC can deserve the title of real UHPC; if it is still troubled by these deterioration phenomena, it can not deserve the title of UHPC.

6. Can UHPC's anti-wear and fire resistance be much higher than C80?

The anti-wear and fire resistance of cement-based materials need special design, which has no fixed relationship with the compressive strength or compactness of the materials. The anti-wear and fire resistance of UHPC can be designed very excellent, but compared with C80, it is not easy to achieve the promotion of orders of magnitude or several orders of magnitude.

7. Why doesn't the modulus of UHPC easily reach above 55gpa?

The elastic modulus of the material essentially depends on the main bonding bond type in the material. UHPC is still a cement-based material, and the bonding type has not changed essentially, so it is impossible to make significant progress. Adding high-strength and high hardness aggregate to UHPC can improve the elastic modulus to reach the level of 60-70gpa.

8. What kind of UHPC is more cost-effective?

According to the current domestic production level, UHPC materials with cubic compressive strength of 150 ~ 200MPa, tensile strength of 7 ~ 12MPa and permeability lower than C80 have higher cost performance; these indicators will change with the development of technology in the future.

9. What are the major weaknesses of UHPC?

Like other cement-based materials, it is not resistant to acid corrosion (including the corrosion of sulfate bacteria, which is much better than OPC). It has greater self shrinkage and stronger early cracking sensitivity in theory (not necessarily in practice).
10. Why steam curing UHPC?

It is mainly to eliminate the adverse effects of hydration in the later stage of UHPC, such as shrinkage, cracking, creep, etc.; in addition, it can improve the strength and density of UHPC. Full steam curing (also known as damp heat curing, heat curing, "heat treatment", etc.) It can make the cementitious materials that can be hydrated at normal temperature complete hydration as soon as possible and reduce the later changes. Therefore, if there is a prerequisite for steam curing, steam curing should be done as much as possible, and there is no need to blindly pursue the non steam curing technology. The non steam curing does not always mean improving the predecessors. We should adapt to the circumstances and materials.
11. What kind of display (pictures) does UHPC have in detail?

Water purification concrete surface:
Sand blasting surface:

Cave rock wind:

Imitation wood grain:

Imitation brick type:

Burnt stone type:
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