Repair technology for the most common quality defe

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Repair technology for common quality defects of cast-in-place concrete during the construction of cast-in-place concrete structural members, we are often affected by many factors, such as unreasonable concrete mix design, poor on-site mixing and preparation conditions, inaccurate concrete pouring and tamping, improper maintenance measures, backward construction technology, etc., resulting in some common quality defects on concrete structural members. Such as: pitted surface, exposed reinforcement, holes, gaps and interlayer defects on the concrete surface, lack of edges and corners, cracks, insufficient concrete strength, surface sanding, punch, uneven beam column joints, etc. In order to eliminate the adverse effects of these quality defects on concrete structural members, scientific, reasonable and effective measures must be taken to meet the quality and technical requirements of concrete structural members. The following is about the common quality defects of cast-in-place concrete, and briefly talk about the new technology of repairing and strengthening

1. Pockmarked surface

generally speaking, pockmarked surface refers to the phenomenon that the local surface of concrete structural members is lack of slurry and rough, and there are many small pits and pockmarks, but no reinforcement and stones are exposed. It is one of the most common quality defects of cast-in-place concrete structural members

patching technology of pockmarked surface. Pockmarked surface mainly affects the appearance of components. If the area of pockmarked surface is small or the surface of structural components is painted, it may not be treated; The parts with large area shall be repaired, that is, the pitted parts shall be brushed with clean water on the beam part that cannot move the electronic universal testing machine. After being fully wetted, they shall be brushed with cement mortar or 1:2 cement mortar, troweled and polished

2. Honeycombs

honeycombs refer to holes or holes that are similar to honeycombs formed between aggregates due to local looseness, less mortar and more stones in concrete components

repair technology of honeycomb. If the concrete component has small honeycomb, it can be washed with water first, and then repaired with 1:2 or 1:2.5 cement mortar, troweled and compacted; If it is a large peak pit, the weak loose particles shall be chiseled off first, the formwork shall be erected after cleaning, and the fine aggregate concrete with twice the strength grade shall be carefully filled and tamped; The grouting pipe and exhaust pipe can be embedded in the deep honeycomb, and the principle that the direction of surface sanding is circling should be clear to everyone. After grouting, the concrete should be poured and sealed, and then the cement grouting treatment should be carried out

3, hole

3 The material steel can also explain that the hole refers to that there is a large gap in the concrete component structure, there is no concrete or honeycomb locally, and the reinforcement is partially or completely exposed, which is the most serious quality defect of cast-in-place concrete

hole repairing technology. For the reinforcement of the hole accident, the method of treating the construction joint can be adopted on the surface of the old concrete. The loose concrete and protruding stones at the hole shall be removed. The top of the hole shall be chiseled into an inclined plane to avoid forming a dead corner. Then, it shall be brushed with water and kept wet for 72h. After that, it shall be tamped with fine aggregate concrete with a strength grade higher than the original concrete. The water cement ratio of the concrete should be controlled within 0.5, and aluminum powder with one tenth of the cement content should be mixed and tamped in layers to avoid cracks on the contact surface of the new and old concrete

4. Exposed reinforcement

exposed reinforcement refers to that the main reinforcement, negative moment reinforcement or stirrup in the concrete member are partially exposed on the concrete surface. The phenomenon of exposed reinforcement is also one of the common quality defects of cast-in-place concrete structural members

repair technology of exposed reinforcement. The main measures are to protect the reinforcement and concrete from erosion. For the parts with small exposed reinforcement at the slab bottom and beam side, chisel the loose concrete around the exposed reinforcement, clean it with a steel wire brush, brush the exposed reinforcement with antirust paint, and then apply 1:2 cement mortar on the surface. If the exposed reinforcement is deep, the interface shall be treated and then filled and compacted with high-grade fine aggregate concrete

5. Missing edges and corners

missing edges and corners refer to the local damage, falling, irregular and defective edges and corners of concrete beams, columns, wallboards and right angle edges at holes

repair technique for missing edges and corners. If the missing edges and corners are small, clean them with clean water, brush them with steel wire brush, fully wet them, and then wipe them neatly with 1:2 or 1:2.5 cement mortar. It is also possible to chisel out the unsound concrete and protruding aggregate particles, wash them with water, wet them, and then repair them with fine aggregate concrete one level higher than the original concrete for careful maintenance; When the missing edges and corners are large, the loose part of the concrete shall be chiseled off, the interface shall be cleaned and fully wetted before the formwork is erected, and the maintenance shall be strengthened with fine aggregate concrete one level higher than the original concrete. The formwork shall be removed for maintenance after reaching a certain degree of strength, and their leading products are aluminum foil rolled strips and general 1xxx series and 3xxx series alloy plate strips

6. Construction joint interlayer

construction joint interlayer means that the concrete at the construction joint is not well combined, there are gaps or sundries, resulting in poor structural integrity and dividing the structure into several unconnected parts

repair technology of construction joint interlayer. After the occurrence of gap or interlayer, the loose concrete shall be chiseled, and the cement mortar or fine aggregate concrete shall be used for strong filling or grouting. When the surface crack is fine, clean the crack with clean water and wipe the water slurry after fully wetting. The interlayer shall be treated carefully. Before reinforcement, temporary supports shall be erected for reinforcement before chiseling. The sundries and soft concrete in the interlayer shall be removed, washed with clean water, fully wetted and then poured. Fine aggregate concrete with a higher strength grade or concrete stone reducing mortar shall be used for tamping and curing

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