The Repair Method You Have to Collect Specializing in Treatment of Concrete Cracks

Introduction

The Repair Method You Have To Collect Specializing In Treatment Of Concrete Cracks

According to the current situation of on-site investigation and observation, the cracks in the side walls of the tunnel door opening are repaired by grouting and caulking. The inside of the crack is sealed and bonded by grouting, and the outside is grooved to cut out 3cm wide and 2cm deep grooves and repaired with special grouting materials to eliminate safety and quality risks and maintain the overall appearance and integrity.
Use the method of minimal damage – the method of pouring low-viscosity modified epoxy resin reinforcement by pinhole oblique side drilling method; pinhole method high-pressure grouting materials: HK-UW-3 and HK-WG21; material: fast curing solvent-free ring Oxygen resin chemical grouting materials;
Cleaning: Use a wire brush to clean the surface, then use an air compressor to blow the surface clean, check and analyze the cracks in detail, and determine the location, spacing and depth of the drilling.
Drilling: Use high-power impact electric hammer and other drilling tools to drill along the two sides of the crack, the hole distance is 25-30cm, the drill diameter is 10-14mm, the drilling angle should be ≤45°, and the drilling depth should be ≤2% of the structure thickness /3, the drilling must pass through the cracks, but the structure must not be pierced (except for grouting after the structure), and the distance between the drilling and the cracks is ≤ 1/2 the thickness of the structure.
Seam cleaning: Use an air compressor to blow air into the grouting nozzle to clean the fine dust in the seam and observe the cracks.
Buried mouth: Install the grouting mouth (also known as the water-stop needle) in the drilled hole, and tighten it with a special inner hexagonal wrench to expand the expansion bolt behind the needle, seal the surface of the crack, and observe holes and pressure relief vents.
Grouting: Use a high-pressure grouting machine to pour epoxy resin slurry into the grouting hole (mouth), gradually pouring from bottom to top or from one side to the other. When the adjacent hole or crack surface observes that the hole starts to grout, keep the pressure 10 -30 seconds, use the method of controlling the grouting, observe the situation of the grout in the seam, and then set the time for refilling
Remove the mouth: After the grouting is completed, confirm that the epoxy resin is completely cured and then remove or knock off the exposed grouting mouth. the
Grooving: Use a fixed width grooving machine to cut the cracks, and then use special grouting materials to repair the grooves. When the strength and color meet the same requirements as the second lining concrete surface, use a grinder to clean the surface and basically restore the original surface color.

crack prevention control

1. Improve the design accuracy and at the same time strengthen the advanced geological forecast work, strengthen the geological work in the early stage of the project,
Provide detailed engineering geological and hydrogeological exploration data for the design, improve the quality of the design, and at the same time strengthen the advanced geological forecasting work during construction, and provide accurate data basis for unfavorable areas. the
2. Control the entry of materials and strictly control the quality and technical standards of raw materials
(1) Cement: Different brands, different specifications, and different batches of cement cannot be mixed; ordinary Portland cement is often used on the construction site, but the amount of cement per unit should be reduced as much as possible
(2) Crushed stone: according to the inner diameter of the pumping pipeline, choose as large a particle size gravel as possible; strictly control the mud content to not more than 1%, the content of needles and flakes to not more than 15%, and the particle size to 5 -31.5mm is appropriate, the maximum not exceeding 40mm.
(3) Sand: use well-graded medium sand, the fineness modulus should be 2.3-3.0, the particle size is less than 0.135mm, the proportion of the content should be 15%-20%, and the mud content should be strictly controlled at 3 %; in order to facilitate concrete transportation, pumping and pouring, the sand rate is 35%-45%. the
(4) Water: It is best to choose drinking water.
(5) Admixture: The type and dosage of the admixture must be carefully selected during construction. The high-efficiency water reducer can effectively reduce the mixing water, reduce the heat of hydration, and delay the release rate of the heat of hydration, thereby reducing temperature cracks, but the dosage Too much can cause swelling and cracking of the concrete.
3. Strictly control the construction operation of each channel of the tunnel to improve the construction quality
(1) Strengthen the detection of tunnel excavation sections, strictly control over- and under-excavation, and create good conditions for later lining construction. the
(2) Under the premise of ensuring that the shape of the excavated section meets the design requirements, the primary support should be strictly controlled so that the shotcrete cannot encroach on the clearance of the secondary lining, causing the thickness of the lining to fail to meet the design requirements. the
(3) Before the construction of the inverted arch and the low side wall, the base slag, sundries, and accumulated water must be cleaned up, so as to avoid different degrees of subsidence and deformation of the concrete after forming, which will affect the quality of the secondary lining in the later stage.
(4) The construction time of the secondary lining should be carried out when the deformation of the surrounding rock and primary support is basically stable. When the deformation of the surrounding rock is large and the rheological characteristics are obvious, and the secondary lining needs to be carried out in advance, the primary support or lining structure must be strengthened. the
(5) For the secondary lining concrete pouring, technicians should stand by during the whole process, and it is strictly forbidden to add water to the concrete during transportation and pumping.
4. Control and selection of concrete mix ratio
(1) Strictly measure according to the construction ingredient list, regularly check and correct the metering device; strengthen the detection of the moisture content of the sand and gravel, and adjust the water consumption for mixing in time.
(2) Improve the aggregate gradation, add fly ash or high-efficiency water reducer to reduce the amount of cement and reduce the heat of hydration. the
(3) Add a certain amount of admixtures with the functions of reducing water, increasing plasticity, and retarding to the concrete to improve the fluidity and water retention of the concrete mixture, reduce the heat of hydration, and delay the appearance of the heat peak.
(4) Control the temperature of the concrete into the mold; during summer construction, when the temperature is higher than 30 °C, the sand and gravel mixer should set up a sunshade, and wash the gravel with cold water to cool down; try to arrange concrete pouring at night.

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