Ultra-high-performance concrete (UHPC) is becoming popular in construction because of its outstanding qualities. The first one that was introduced was UHPC reactive powder concrete in the 1990s, and since then, the material has seen growth in its use. UHPC has cement characteristics except that the compressive strengths are minimized to 17000 pounds in one square feet. Other qualities such as flexibility, durability, and toughness are also specified. While using the concrete, fibres usually are added to ensure that specific requirements are achieved.
As mentioned earlier, UHPC was first introduced as reactive powder concrete. Reactive powder concrete is made by mixing Portland cement, fine sand, limestone quartz flour, reactive powders, water reducers, regular water, and other supplements. Usually, UHPC is minimized to 17000 pounds, but with the reactive powder concrete, the formula is stronger and can provide extra strength of 29000 pounds per square inch. The addition of matrix, a fine material, makes the final product dense, with a smooth surface. These materials are known and valued for the aesthetics they add and their ability to move the form details to a surface.
Fibres are responsible for strengthening and controlling cracking, thus increasing the lifespan of a building. There are various fibres in the market that can be used in UHPC, including PVA, high carbon steel, Carbon, and Glass. Sometimes, a combination of all the fibres can also be used. Among all the fibres in the market, steel stands out to be the most suitable UHPC. In buildings where some degree of fire resistance is required, polypropylene fibres are combined with steel fibres to provide the required resistance. One of the characteristics of UHPC is ductility, and this is important for concrete. It can deform and support the tensile loads even after they cracked. Other properties such as high compression and tensile enable this concrete to create strong bonds for short-length rebar embedment.
The constructions of this product are made simple with self-compacting qualities. As a result, instead of manually reinforcing steel, these materials already do the job. The matrix is dense with a small disconnected pore structure which leads to low permeability. This prevents the entrance of dangerous materials like chloride, which is more durable.
Today, UHPC products are becoming more accessible with their use made simple. Some of the manufacturers create UHPC that only requires the addition of water. The product is already pre-mixed, and adding water makes it ready.
Characteristics of UHPC
You might be wondering why most countries take advantage of UHPC in construction. Well, it is because of its strength and durability
Summary of this quality
The compressive strength is 17000 to 22000 psi which is 120 to 150 MPa
The flexural strength is 2200 to 3600 psi which measures 15 to 25 MPa
The modulus of elasticity is 6500 to 7300 ksi
Durability
UHPC has a long lifespan. Its durability is measured by how this material can survive in extreme conditions. Freeze and thaw resistance, abrasion resistance, and chloride resistance display this material’s durability. In general, this material has hard rock properties.
- Its freeze and thaw is 100% after 300 cycles
- The relative volume loss index for abrasion is 1.7
In summary, having looked at UHPC and its characteristics, it is true that it is the best concrete for constructions compared to traditional concrete.