With the rapid development of the domestic economy, along with the advancement of huge infrastructure construction such as the Belt and Road Initiative, as the core of infrastructure construction, the development of the cement industry has ushered in unprecedented development opportunities. Concrete technology cannot be separated from water compounds such as cement.
Since the advent of cement, concrete materials have become the most widely used building materials and are widely used in bridges, tunnels, roads, construction and other fields. With the development of society, many super projects such as high-rise and super-high-rise buildings, undersea tunnels, and cross-sea bridges are constantly emerging, which have put forward higher requirements for the various properties of concrete.
Ultra-high-performance concrete is a new material that appears after high-strength and high-performance concrete with superior mechanical properties and durability. It is generally believed that ultra-high performance concrete is a high-tech concrete composed of a dense material system with uniformly distributed ultra-fine particles and fiber reinforced materials. It has the characteristics of high strength, good durability, excellent tensile strength and fracture toughness, and can mostly replace The trend of steel is called "steel-like concrete".
Raw materials for ultra-high performance concrete technology
1. Cementitious materials
The initial cementing system is mainly composed of cement and silica fume. Silica fume has excellent In the research process of ultra-high performance concrete, silica fume has always played an irreplaceable role. The quality of silica fume even plays a decisive role in the performance of ultra-high performance concrete. With the deepening of research, the role of ultrafine fly ash, phosphate slag powder, rice husk ash and other materials has gradually emerged.
2. Aggregate
In ordinary concrete, aggregates are divided into coarse aggregate and fine aggregate, which are used according to a certain gradation. In ultra-high performance concrete, the method of removing coarse aggregate was chosen. As for fine aggregate, quartz sand with similar mechanical properties to the slurry was considered to significantly reduce the pores between the slurry and aggregate interface caused by the shrinkage of the slurry. and microcracks.
3. Admixtures
Admixtures are an important part of ultra-high performance concrete. The ultra-low water-binder ratio and porosity of ultra-high performance concrete are all due to the development of admixture technology. be realized later.
1. High-performance water-reducing agent
The ultra-high water-reducing rate of high-performance water-reducing agent effectively reduces the water-binder ratio of ultra-high-performance concrete, while improving fluidity and reducing It prevents concrete shrinkage and is one of the inseparable materials for ultra-high performance concrete. Huawei brand polycarboxylic acid high-performance water-reducing agent has the characteristics of high water-reducing rate, high slump retention, high reinforcement, low shrinkage, etc. It has good adaptability and is widely used in high-strength, high-fluidity, and high-performance concrete technology.
2. Expansion agent
It can compensate the volume shrinkage of ultra-high performance concrete to a certain extent.
3. Shrinkage reducing agent
Further reduce the risk of cracking and stabilize the volume of ultra-high performance concrete from different aspects
4. Fiber
Fibers such as steel fiber, rock fiber, ceramic fiber, alkali-resistant glass fiber, carbon fiber, synthetic fiber, etc. can be added to greatly increase the flexural strength and fracture toughness required for ultra-high performance concrete technology. The irregularly distributed fiber skeleton in the three-dimensional direction greatly limits the development of micro cracks and the generation of macro cracks.
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