Honeycomb: That is, the concrete structure is locally puffy, with little mortar and many stones, and the gaps between the stones form a honeycomb-like hole.
- Improper concrete proportions or inaccurate measurement of materials, resulting in low mortar and high gravel.
- Insufficient mixing time, unmixed, poor compatibility and lack of vibration density.
- Concrete segregation due to too high a drop height.
- No layering of material, poor tamping, missed vibrations or insufficient tamping time.
- The joints of the formwork are not tightly plugged and the slurry is lost.
- The reinforcement is dense, and the stone used is too large in particle size or too small in slump.
- Strict control of the ratio, strict metering and frequent inspections.
- Concrete mixing should be full and uniform, and slump should meet the requirements.
- Discharge height more than 2m to use a skewer or chute, vertical members of the root should be poured in the same ratio of reduced stone mortar before pouring concrete (generally 30 ~ 50 mm is appropriate).
- Pouring of concrete shall be done in layers of material and tamping to prevent leakage of vibrations.
- Plug up the joints of the formwork and check and correct the slurry leakage at any time during pouring.
- For small honeycombs, wash and clean 1:2 or 1:2.5 cement mortar to level and compact.
- Larger honeycomb, chiseled to remove weak loose particles, washed and supported, carefully filled and compacted with a higher strength grade of fine stone concrete.
- Deeper honeycomb can be treated by burying slurry pipe and exhaust pipe inside, applying mortar on the surface or cement slurry after sealing the poured concrete.
Pocked surface: I.e., lack of slurry and many small pits and pocked spots appear on the local surface of concrete, forming a rough surface, but without the phenomenon of exposed reinforcement.
- The surface of the formwork was rough or not cleaned of debris, the steel formwork isolator was not brushed or not evenly brushed, and the concrete surface was sticky when the formwork was dismantled.
- The wooden formwork was not sufficiently wet, and the water on the surface of the concrete was absorbed by the formwork, so that the water on the surface of the concrete was absorbed by the formwork and water loss appeared pitting.
- Slurry leaking from the formwork joints and joints.
- Uneven application of the formwork isolator, or omission or failure of the brush, resulting in pitting of the concrete surface to the formwork.
- Concrete tamping is not solid, air bubbles are not discharged, stopping on the surface of the formwork and forming pitting after demolition of the form.
- The surface of the formwork should be cleaned, no cement mortar and other debris should be stuck to it; before pouring concrete, the formwork should be fully moistened with water, and the gaps in the formwork should be blocked with double-sided adhesive strips.
- The formwork release agent should be long-lasting and evenly applied and should not be missed.
- Concrete shall be evenly stratified and compacted.
- If there are defects in the pock surface, the surface of the concrete for painting decoration, may not be treated, the surface without painting, the pock surface should be fully moistened after watering, using the original concrete ratio to stone mortar, the pock surface will be smoothed and polished.
Hole: That is, there is a large gap in the concrete components, local concrete or honeycomb is particularly large.
- Where the concrete is blocked from being poured upwards without being vibrated in places where the reinforcement is dense or where holes and embedded parts are left open.
- Serious segregation of concrete, piles of stones, severe run-off and lack of careful tamping.
- One feeding is too much and too thick, and the vibrator cannot vibrate, forming a hole.
- Drop debris such as tools, blocks of wood, mud, etc. Into the concrete to block the concrete.
- The use of fine concrete of a higher strength grade at reinforced areas, carefully layered or with manual tamping.
- There are reserved holes where material should be discharged from both sides at the same time, serious tamping.
- Timely removal of debris that has fallen into the concrete.
- Treatment: Remove loose concrete around the holes, rinse with high-pressure water, and carefully pour and tamp with fine concrete of a higher strength grade after erecting the mold.
Exposed reinforcement: That is, the main reinforcement, secondary reinforcement or hoop reinforcement within the concrete is partially exposed and not encased by the concrete.
- Displacement, too little or omission of the reinforcing steel protective pads during the pouring of concrete, resulting in the reinforcing steel clinging to the formwork.
- Small cross-section of members, dense reinforcement, stones stuck in the reinforcement prevented mortar from filling the formwork.
- Improper concrete proportions, segregation, lack of slurry leakage at exposed bars.
- Wooden formwork not moistened before pouring, sticking off protective layer of concrete during demoulding, etc.
- Before pouring concrete, check that the reinforcement and protective pads are correctly positioned and that the wooden formwork is sufficiently moistened.
- Coarse aggregates should be selected with the appropriate grain size when the steel is dense.
- Ensure that the concrete proportion and ease of preparation meet the design requirements.
- Processing method: The surface exposed tendons can be washed and wiped with 1:2 cement mortar on the surface, and the deeper exposed tendons should be treated at the interface and filled with high grade fine stone concrete and compacted.
Gap and interlayer: There are layers of loose concrete in the concrete.
- Where construction joints or deformed joints have not been jointed, the surface cement film and loose stones have been removed, or concrete has been poured without removing the layer of weak concrete and wetting it sufficiently.
- Construction joints where sawdust, soil, bricks and other debris are not removed or are not clean.
- Concrete was poured to an excessive height, without cascade and chute, resulting in concrete segregation.
- The bottom junction is not filled with joint mortar layer and the concrete at the joints is not well vibrated.
- Carefully deal with construction joints and deformation joints in accordance with the requirements of the construction acceptance specification.
- Joints should be cleaned and washed of sawdust, soil, bricks and other debris.
- Concrete pouring height greater than 2m should be set up with a skewer or chute.
- Pour the same proportion of reduced stone mortar (generally 30-50 mm) before pouring concrete at the joints and strengthen the concrete tamping at the joints.
When the gap interlayer is not deep, the loose concrete can be chiseled away, cleaned, and then filled with 1:2 or 1:2.5 cement mortar to fill in tightly.
When the gap interlayer is deeper, remove the loose part and internal inclusions, rinse with pressure water, then support the mold, powerfully fill the fine stone concrete or close the surface and press slurry treatment.
Lack of edges and corners: That is, the structure or component corners where the concrete is partially dropped, edges and corners have defects.
- Wooden formwork not sufficiently wetted with water or not wet enough; poor maintenance after concrete pouring, resulting in dehydration and low strength, or water-absorbent expansion of the formwork pulling the corners apart and sticking out the edges when dismantling the form.
- Premature removal of lateral non-load-bearing formwork for winter construction.
- The edges and corners are knocked off by external forces or heavy objects during mold removal, or the finished product is not well protected.
- The formwork has not been painted with a barrier, or has been painted unevenly or missed.
- Wooden formwork should be sufficiently moistened before concrete is poured and carefully watered for maintenance after concrete is poured.
- Concrete should have a strength of at least 1.2 mpa when removing lateral non-load-bearing formwork.
- Lifting of formwork to prevent impact on edges and corners, and protection of finished positive corners during transport to avoid damage.
- Processing method, the loose particles can be chiseled off, rinsed and fully moistened, depending on the degree of damage with 1:2.5 cement mortar patching and aligning, or support the inclined mold with a higher level of concrete tamping maintenance.
Concrete surface cracks: That is, there are certain regular cracks on the surface of concrete, and some even up and down cracks for slab components; irregular cracks on the surface of concrete, and continue to develop over time; longitudinal and deep cracks in large-volume concrete.
- The concrete is not cured in time after pouring, especially at high temperature and dryness, resulting in shrinkage cracks.
- Use of unqualified cement to mix concrete, resulting in irregular cracks that develop over time.
- Temperature cracks and shrinkage cracks are produced in large volume concrete.
- According to construction regulations for timely maintenance, within 12h after pouring to cover and watering, watering time of not less than 7d (for admixture of slow-setting admixture or impermeable concrete requirements of not less than 14d). If air-drying cracks occur on the surface of mass concrete after initial setting, secondary surface coating or compaction shall be carried out.
- All cement must be re-inspected before use.
- For large volume concrete before pouring, make sure to develop a proper temperature control program to control the difference between internal and external temperature within the specified value. The necessary protective measures should be taken when the temperature changes.
Concrete surface unevenness: The surface of concrete is uneven, or the thickness of the slab is uneven.
- After the concrete was poured, the surface was only smoothed with a shovel but not flattened with a trowel, resulting in a rough and uneven surface.
- The formwork is not supported on hard soil, or the bearing surface is insufficient, or the support is loose or soaked with water, resulting in uneven sinking of the freshly poured concrete during early curing.
- When the concrete has not reached a certain strength, the upper man operates or transports the material, causing the surface to be depressed and uneven or imprinted.
- Operate in strict accordance with construction specifications; after pouring concrete, level and calibrate it with trowels according to level control signs or bullet lines; after final setting, water it for curing.
- The formwork should be of sufficient strength, rigidity and stability to be supported on solid foundations, have sufficient support area and be protected from flooding to ensure that it does not sink.
- Concrete strength of 1.2 mpa or more, before walking on the casted structure.