The epoxy grouting technology of cracks is not only used in the basement, but also widely used in the repair and maintenance of various concrete.
Underground crack grouting is usually used to solve the infiltration of groundwater. Leakage of above-ground buildings is mainly to solve structural leakage, such as between concrete load-bearing walls and between columns. The grouting of above-ground buildings usually uses epoxy resin.
The resin grouting process has a reputation for structural maintenance technology. However, most concrete crack grouting is maintenance of the structure rather than maintenance. That is to say, the technology mainly grouts the resin to the defect site to maintain the concrete in a good state instead of repairing its design strength. Sealing cracks to protect steel bars is the most common practice.
Above-ground structural resin grouting is widely used worldwide, including horizontal and vertical structures.
Crack grouting has a large market in the United States. Recently, a California general contractor completed the resin grouting work for the San Francisco Bay Bridge. Grouting construction extends the life of the bridge to prevent corrosion and prevent further cracking.
Material selection
Because the construction of the above-ground building is to repair its structural strength, it is necessary to choose the so-called "structural epoxy resin" product. ASTM C881 covers seven different types of epoxy adhesives, and Type 4 adhesives are most commonly used.
Type 1 adhesive and Type 4 adhesive are load-bearing epoxy resins, Type 1 adhesives are used to bond new and old concrete, and Type 4 adhesives are used for bonding between existing buildings, 99% cracks. The grouting project uses a type 4 adhesive. Type 2 adhesives and Type 5 adhesives are non-load bearing, Type 3 adhesives are used for movable laminate structures, Types 6 and 7 are used for bonding preformed components.
ASTM C881 classifies epoxy adhesives into different grades based on viscosity and temperature range. Choosing the right resin formulation is critical to the success of on-site construction.
Usually, grouting workers use "ultra-low viscosity epoxy resin" (500~900 mPa·s), which is similar to the fluidity of motor oil.
Generally, the viscosity of epoxy resin is 300 mPa·s, but its tensile properties are not as good as ASTM standards. Attention should be paid to the brittleness of the epoxy resin. It is possible to inject a sample first and hit it with a hammer the next day. If it is pulverized, the crack repair is likely to fail.
construction
Although some grouting works are large in scale, their construction techniques are similar to those in civil basement projects.
The first step is to treat the crack and its surrounding parts with a wire brush or other brushing tool. For the above-ground buildings, the cracks should be sealed on both sides, so the base layers on both sides of the cracks should be treated.
The base treatment should be strictly required. When grouting the column or the shield wall, the pressure of the grouting may be very high, up to several hundred psi (1 psi ≈ 6.89 kPa), so the bond must be very strong.
experience
There are two types of injection equipment that can be used in aboveground structural grouting projects. One is to mix the resin and the catalyst through the nozzle, which gives the builder a great deal of flexibility in the progress of the project. Another type of equipment requires the builder to pre-mix the epoxy resin before grouting.
Before the grout begins, make sure that the prepared slurry is used up and the pot life of the slurry is checked. If used in large quantities, the actual slurry pot life may be less than the indicated time. Because the material reacts chemically during the grouting process, the more the amount of epoxy resin, the higher the temperature, the faster the reaction. On a 75 F (23.8 °C) basis, for every 15 F (9.4 °C) increase, the pot life will be halved.
Grouting should be carried out during the daytime when the climate is cool, at which point the width of the crack is greatest. The crack will also swell as the temperature changes and the temperature difference between day and night changes. Although the crack has a small degree of swell and the crack itself is relatively narrow, when the high modulus epoxy resin is grouted into the crack and the temperature drops sharply, it may cause the grouting to fail.
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