From May 1, 2023, the Ministry of Housing and Urban-Rural Development's new regulations "Seamless Construction Standard for Ultra-long Concrete Structures" JGJ/T492-2023 have been implemented! Among them, the specification focuses on the process points of the warehouse jumping method, which provides a basis for the replacement of the post-pouring belt scheme for various engineering projects.
In the construction of ultra-long concrete structures, how to solve the cracking problems caused by cold shrinkage and dry shrinkage of super-large concrete structures, as well as the hazards caused by tensile stress, is a technical problem. Since Professor Wang Tiemeng based on the design principle of "resistance and release", the construction method of jumping warehouse has been widely used in the construction of super-large volume concrete.
Post-pouring belt VS jumping method
The post-pouring belt is a reserved construction interval zone set up to prevent cracks in concrete due to temperature, shrinkage and uneven settlement of the foundation. In the long-term engineering practice, there have always been common construction problems that are difficult to solve in the post-pouring belt:
- Quality-wise
- It is difficult to clean up the garbage at the post-pouring zone, the steel bars are easy to corrode, and the interface between the old and new concrete is easy to produce penetrating cracks.
- Progress-wise
- The construction of mechanical and electrical, municipal and curtain wall and other professional projects at the location of the post-pouring belt has been delayed, affecting the entire construction period.
- Security aspects
- The position of the post-pouring belt is cantilevered on both sides, which brings hidden dangers to construction safety and structural safety.
Post-pouring tape
The method of pouring concrete at intervals divides the ultra-long concrete structure into multiple units of a certain scale, and is an effective measure to prevent concrete cracks and facilitate construction by releasing internal and external stress. The warehouse jumping method replaces the post-pouring belt, and the seamless construction effectively solves the problem of crack control and seepage prevention of super-large concrete:
- Quality-wise
- The position process of the construction joints of the warehouse jumping method is simple, and it is easy to control the penetration cracks at the interface of the old and new concrete compared with the post-pouring belt.
- Progress-wise
- The vaulting method makes the whole structure formed in advance, which is conducive to the early construction of basement transportation and other professional projects.
- Security aspects
- The jumping method makes the structure as a whole formed in advance, and avoids the potential safety hazards of the cantilevered state on both sides of the post-pouring belt.
Position hopping method
The basic idea of the vault jumping method is "combination of resistance and discharge, first release and then resistance", using the principle of "resistance and release" characteristics of concrete that is easy to release the internal stress before the performance is not stable and completely solidified in about seven days, as shown in the following schematic diagram, the large-volume concrete is divided into several blocks according to the construction joint, and the division form of each part of the warehouse grid, the location of the construction joint is left and the construction sequence is determined according to the construction partition, and the interval is poured one grid.
Example of position splitting using the position hopping method
The node practice of post-pouring belt VS vaulting method is simplified and the process is simple, which helps the quality control of engineering projects and reduces costs and increases efficiency.
Post-pouring belt nodes
Position hopping nodes
The technical specification on which the warehouse jumping method is currently based is the "Technical Specification for the Warehouse Jumping Method for Super-large Volume Concrete Structures" T/CECS640-2019, which has been implemented since April 1, 2020, and more elaborates on the materials, mix ratio, preparation and transportation, concrete construction, temperature monitoring and control in the construction process of the warehouse jumping method.