In accordance with the characteristics of reinforced structures, fully utilize the potential of the reinforcement department. The reinforcement of concrete structures should ideally use hot-rolled steel with smaller proportional limit deformation, lower strength, and better weldability, such as HPB235 or HRB335 grades. The use of outdated or damp cement is strictly prohibited.
In the wet-outsourced steel reinforcement method, when using chemical slurry grouting for connection, the slurry composition should be pre-mixed before engineering application. Select slurry with good injectability, low shrinkage, high bonding strength, adjustable curing time, and good durability, with non-toxic or low-toxicity materials. The cement strength grade should not be lower than 42.5. For the steel sections, steel plates, flat bars, and steel pipes used in concrete structure reinforcement, it is advisable to choose carbon structural steel of grade Q235 or high-strength low-alloy structural steel of grade Q345.
For the prestressed reinforcement of large structures, high-strength steel can be used to reduce material consumption. However, it is necessary to elevate the working stress of the steel to the corresponding level through prestressing means to fully utilize the material's potential.
After the slurry solidifies, its bonding strength with concrete should exceed the tensile and shear strengths of the concrete in the bonded structure. No admixtures such as fly ash should be added to the reinforcing concrete. When the original components or the concrete strength of the components is high, and the same strength grade as the original structure is used, technical measures must be taken to ensure sufficient bonding strength between the new and old concrete. For concrete load-bearing components reinforced with bonded carbon fiber fabric or carbon fiber boards, the concrete strength grades should not be lower than C15 and C20, respectively, and the moisture content of the concrete at the bonding area should not exceed 4%.
Based on the characteristics of Chongqing reinforcing materials, it is advisable to use rapid-hardening, early-strength, and low-shrinkage silicate cement or ordinary silicate cement for the cement used in dismantling, and to opt for early-strength cement or micro-expansion cement.
Reinforcement of concrete structures typically involves arc welding with electrodes matched to the strength of the welding steel. When using reinforced concrete, micro-expansive concrete, or shotcrete for reinforcement, or when the concrete needs to be reinforced with early-strength, anti-freezing, or other additives, it is advisable to conduct a trial mix and inspect its strength before construction. In some cases, it is also necessary to inspect its properties such as shrinkage and erosion.
The concrete strength grade used for reinforcing concrete structures should be one level higher than that of the original component's concrete strength grade and should not be lower than C20.
