In recent years, due to the diversification trend of construction works and public works, especially the increasingly complex binding of steel bars, coupled with the rising labor costs of concrete pouring, it has become difficult to find suitable workers. These factors have led to many problems in the construction process of ordinary concrete.
In recent years, due to the advancement of concrete raw materials, especially in the improvement of admixtures, high performance concrete (HPC) and self-compacting concrete (SCC) have emerged. These new types of concrete are made possible by the development of material technology.
The American Concrete Institute (ACI) defines high performance concrete (HPC) as outperforming ordinary or conventional concrete (which may be one or more). Its properties include high strength, high fluidity, high durability, high water tightness and self-filling. Self-compacting concrete (SCC) is a type with high fluidity and self-filling properties that are better than ordinary concrete, so SCC is actually a form of HPC. In addition, high-flow concrete refers to the type with higher fluidity than ordinary concrete, and it is also a form of HPC.
In the market, SCC and high-flow concrete are often confused by engineering professionals as the same. But in reality, there is a difference between the two. The main difference is that the SCC is characterized by high fluidity and self-filling, and does not require vibration or tamping during construction. On the other hand, high-flow concrete (which can be called when the slump is 18 cm) has high fluidity, but it is not necessarily self-filling, and it still needs to be compacted by vibrators during construction. So there is a clear difference between the two.
What is high-performance concrete?
According to the definition of high-performance concrete given by the American Concrete Institute (ACI), HPC (HPC-high performance concrete) is better than traditional concreteIt should be strength, modulus of elasticity, workability, fluidity, volumetric stability, durability, wear resistance, water tightness, integrity and other special properties (such as low heat of hydration) economy, etc. Therefore, the so-called high performance is the concrete developed for the general traditional concrete construction method can not meet the needs of the project, and the high-performance concrete may have one or several kinds of "high performance" to meet the needs of the project. In fact, we can think of "high-performance concrete" as a term for engineering materials in a broader sense.
What is self-filling concrete?
Self-compacting concrete (SCC) refers to the special concrete that is filled to the corners of the steel bar and between the steel bar and the steel bar and the template completely through its own gravity without vibration tamping during the pouring process. The "high performance" required by SCC is "self-filling and vibration-free tamping", and more specifically, SCC should be a type of HPC.
Workability refers to the nature of pouring and tamping in concrete construction operations. Workability refers to whether the concrete can be filled with all corners of the formwork completely and uninterrupted. The most useful simple tool for measuring workability on the construction site is to use a slump cone, which is a non-absorbent cone with an upper diameter of 4 inches, a lower diameter of 8 inches and a height of 12 inches. The level of slump is also most commonly used to specify the workability of concrete. At present, the slump used for construction in general engineering is about 15 to 18 cm, and this kind of concrete has moderate viscosity and good workability. In the United States, a slump greater than 20 cm is called high-fluidity concrete.
The difference between "high flow concrete" and "self-filling concrete" is that high flow concrete obviously only has high fluidity, but there is no clearance and filling of steel bars. The performance varies greatly, and there are often confusing explanations in the market.
Based on the above discussion, the types, composition conditions and uses of high-performance concrete are made into the following table:
This article is an excerpt from Dr. Lai Ruixing**'s "Self-Filling Concrete (S.).c.c.Filling Data Module".