The Advantages of Fiber in Concrete

Concrete is popular in the construction industry because it can be made from local materials, is relatively cheap, and can be cast into building components of various shapes. It not only reflects the beauty of the building structure but also has relatively high compressive resistance.

Problems with concrete buildings

Concrete is made of brittle materials such as cement. The characteristics of the material used for pouring determine its low tensile strength. Therefore, when some compressive components are used in actual projects, their low compressive strength can lead to cracks appearing when they are compressed, causing the components to break and compromising the overall stability of the building. During the construction process, the mechanical properties of concrete decrease, primarily due to various factors in the concrete raw materials, pouring, maintenance, and transportation processes.

Concrete has a large self-weight, and the higher the strength of concrete, the more obvious its brittleness. Therefore, concrete cannot meet the stability requirements of large-span structures. Secondly, concrete has low durability. Concrete in the natural environment cannot always be kept in a constant temperature and humidity state. Too high a temperature will damage the concrete and expand and destroy the internal structure, while too low a temperature will cause the concrete to shrink and produce many cracks.

The future of concrete

With the continuous development of construction technology, research has begun in the direction of high-performance, compression-resistant, crack-resistant, and durable concrete. With the continuous research and exploration of the building materials industry, it has been found that adding fibers to concrete can improve the performance of concrete to the above standards.

Advantages of fiber reinforced concrete

The essential shortcoming of concrete is that its materials cannot improve it. Fibers improve the performance of concrete through their unique properties, such as high elastic modulus and high tensile strength, but they do not change the chemical properties of the concrete's materials, and therefore do not destroy the internal structure of concrete.

Inhibit Cracks

Fibers have high physical and mechanical properties, such as elastic modulus and tensile strength. Adding them to concrete can effectively inhibit and prevent the occurrence of cracks. Compared with other fibers, the elastic modulus of carbon fiber is 1-5 times higher than other fibers, and the tensile strength is 1-10 times higher than other fibers. Carbon fiber is also resistant to high temperatures and corrosion.

During concrete pouring and curing, especially in bending members, non-standard temperature and humidity conditions will cause initial cracks in the concrete. Under pressure, stress concentration will form at the tip of the initial crack in the concrete. There are cracks in the concrete. When the stress distribution of the entire specimen is uneven, the cracks will continue to expand, eventually causing damage to the concrete, which has become a safety hazard in real life. After adding carbon fiber to concrete, when the concrete is compressed, the carbon fiber can absorb part of the stress concentration at the tip of the crack and transfer the stress to the entire part of the concrete through the fiber, thereby inhibiting the generation and expansion of cracks.

Enhanced Mechanical Properties

Various defects will occur during concrete mixing and pouring, such as a small amount of bubbles generated during mixing remaining inside the concrete. When the bubbles disappear, original defects will be formed in the concrete, reducing the compressive strength of the concrete. When carbon fiber is added to concrete, the light and fine carbon fiber is randomly distributed in the concrete, and the bonding force and friction between itself and the concrete matrix tightly connect the aggregates. And because the carbon fiber is small in size, it can fill the pores generated by concrete mixing, making the aggregates denser, thereby improving the compressive strength of the concrete.

Toughening Effect

The higher the strength of concrete, the more obvious its brittleness. The addition of carbon fiber can improve the brittle structure of concrete and increase its toughness. When concrete is subjected to external loads, its internal initial defects will slowly expand into cracks. When the cracks are large, carbon fiber builds a bridge between the cracks and can absorb part of the stress. Because carbon fiber has good physical and mechanical properties, the specimen continues to expand the cracks under the action of pressure, first overcoming the bonding force and friction between the carbon fiber and the concrete matrix. In this process, the carbon fiber absorbs a lot of energy, prolongs the crack expansion time, inhibits the crack expansion, and improves the toughness of concrete.

Fiber concrete performance