Rebar chemical reinforcement is usually by inserting steel reinforcement into the concrete structure, increasing the cross-section of beams, and adding new beams on columns. In the process of chemical rebar reinforcement and reconstruction, it is sometimes necessary to weld the imchemicaled reinforcement. However, the high temperature generated by welding may adversely affect the bonding properties and load-bearing capacity of the rebar chemical glue, causing the rebar chemical to slip, thereby affecting the reinforcement effect.

What is the effect of welding after rebar chemical?

For manual arc welding, the temperature of DC is about 1000~2000℃, while that of AC is 2400~2600℃. The thermal decomposition temperature of epoxy chemical reinforcement is generally about 180~300 °C. If no protective measures are taken for direct welding, the colloid will completely lose its adhesiveness, resulting in the anchoring of the chemical bar.

To sum up, it is not advisable to weld the bars after chemical without any protective measures, and the colloid cannot directly withstand the heat of welding.

How to solve the impact of high temperature welding?

When it is necessary to carry out welding after chemical, we can reduce the impact of high temperature welding by reasonably controlling the temperature of the colloid, appropriately increasing the anchoring depth, and using other connection methods.

2.1 Reasonably control the temperature of the colloid part

Relevant specifications and expert arguments show that welding is feasible with appropriate protective measures. The principle is to keep the temperature near the colloid in a relatively safe range through various measures, so as not to affect or less affect the performance of the colloid.

If individual steel bars really need post-welding, in addition to the cooling measures of intermittent welding, the distance between the welding part and the top surface of the glue injection hole should not be less than 15d, and should not be less than 200mm. At the same time, the exposed roots of the chemicaled tendons must be wrapped with multiple layers of wet wipes impregnated with ice water.

For batches of rebars, the principle of first welding and then rebars is still adhered to to ensure that the adhesive layer will not be damaged due to high temperature.

2.2 Appropriately increase the anchoring depth

The method of appropriately increasing the anchorage depth can not only improve the ultimate tensile bearing capacity of the chemical bar, but also reduce the slippage of the chemical bar, thereby reducing the influence of post-welding.

2.3 Adopt other connection methods

Other connection methods can be adopted, such as binding and overlapping, mechanical connection.

1) Binding and lap joints. Reinforcing bar overlap refers to the connection method in which two steel bars have a certain overlapping length with each other, and is bound by wire ties. The specification stipulates that when the diameter of the tensile steel bar is greater than 25 and the compression steel bar is greater than 28, it is not appropriate to use the lashing lap joint.

A. Advantages: simple construction, high efficiency, and no damage to steel bars.

B. Disadvantages: The waste of steel bars is too large, the skeleton is easily deformed, and the force transmission performance is the worst.

2) Mechanical connection. Mechanical connection of steel bars is a connection method in which the force in one steel bar is transmitted to another steel bar through the mechanical occlusion of the steel bar and the connector or the bearing effect of the end face of the steel bar.

A. Advantages: easy operation, fastest construction speed, continuous and infinite connection, best force transmission performance, super strong connection, stable and best quality.

B. Disadvantages: In comparison, the main cost is higher.

The choice of connection method needs to be combined with the actual situation, with reference to standard specifications, etc., to make a reasonable choice.

Rebar chemical works should be welded first and then chemicaled as much as possible. If the rebar needs to be welded after welding, intermittent welding can be used, the distance between the welding part and the top surface of the glue injection hole can be increased, and the exposed roots of the rebar can be wrapped with multi-layer wet wipes impregnated with ice water. Or use other appropriate connection methods, etc. So as to achieve a good chemical effect.