A, concrete surface pits, exposure, honeycomb, holes.
1. Phenomenon:
(1) The local surface of concrete is rough with many small pits.
(2) The main reinforcement, auxiliary reinforcement or stirrup in the structure is exposed.
(3) There are many stones in local concrete, forming honeycomb holes.
(4) The concrete structure has cavities, and there is no concrete locally, so the honeycomb is particularly large.
2. Governance:
(1) The pitted surface shall be scrubbed with clean water, and leveled with cement slurry or cement mortar after it is fully wetted.
(2) Clean up the concrete and rust on the exposed reinforcement, and then smooth it with cement mortar (1:2 ratio). If the exposed tendons are deep, the weak concrete should be removed and cleaned, compacted with higher-grade pisolite concrete, and carefully maintained.
(3) The small honeycomb can be washed with water first and repaired with 1:2 cement mortar; For large beehives, loose stones and protruding particles should be removed first, and the horn mouth should be chiseled, then washed and soaked with clear water, then compacted with high-grade pisolite concrete and carefully maintained.
(4) It is necessary to work out the reinforcement scheme together with the design unit, and then deal with it according to the approved scheme. When dealing with the holes in the beam, the bottom of the beam should be braced with supports, and then the loose concrete in the hole should be chiseled off and cut into an oblique shape for pouring concrete. Rinse with clear water and keep it moist for 72 hours, and then pour high-grade pisolite concrete. Bean stone concrete is mixed with one ten thousandth of aluminum powder. Strengthen maintenance after pouring. Sometimes concrete is poured after formwork support, because the hole is very big.
Second, the construction joints are not well combined.
1. phenomenon: the concrete at the construction joint is not well combined, and there are cracks or sundries, resulting in poor structural integrity.
2 governance:
(1) When the cracks are fine, the cracks can be washed with clear water, and plastering can be carried out after the cement slurry is fully wet.
(2) Before reinforcement, such as beams and columns, temporary supports should be erected for reinforcement before chiseling. Clean it up, fully wet it, then pour high-grade pisolite concrete, tamp it and maintain it carefully.
Third, lack of edges and corners.
1. Phenomenon: At the right angles of beams, slabs, columns, walls and holes, concrete is partially broken, irregular and has angular defects.
2. Treatment: When the missing edges and corners are small, brush them with a steel wire brush, fully moisten them with clear water, and then clean them with 1:2 cement mortar. For larger missing corners, the fake concrete shall be chiseled off, washed and wetted with water, and then the formwork shall be repaired with higher-grade pisolite concrete, and the maintenance shall be strengthened.
Fourth, the concrete surface is uneven.
1. phenomenon: the thickness of concrete slab is inconsistent, the surface is uneven, and there are even pits and footprints.
2. Treatment: local unevenness can be repaired with pisolite concrete or 1:2 cement mortar.
Verb (abbreviation of verb) Axial displacement of concrete structural members
1. Phenomenon: Axis displacement of foundation, wall, beam and column, and displacement of embedded parts exceed allowable deviation value.
2. Governance:
(1) If the deviation value does not affect the quality requirements of structure construction, it may not be treated; When only a small amount of local planing and repair treatment is needed, it should be repaired in time. Generally, 1:2 or 1:2.5 cement mortar or pisolite concrete with higher label can be used for repair.
(2) When the deviation value affects the quality requirements of structure construction, the treatment scheme should be studied and processed in conjunction with relevant departments.
Six, concrete column, wall, beam shape deviation, poor surface roughness.
1. phenomenon: the vertical deviation and surface flatness of concrete shapes such as columns, walls and beams exceed the allowable deviation value.
2. Governance:
(1) When the deviation value is small and does not affect the construction quality of structural engineering, it can generally be ignored; If only a small amount of demolition is needed to meet the quality of decoration construction, it can generally be treated before decoration.
(2) When the vertical deviation value exceeds the allowable value and affects the quality requirements of structural engineering, the concrete with large deviation value shall be dismantled and reworked after formwork removal.
Seven, concrete strength is low, poor uniformity.
1. Phenomenon:
(1) The average compressive strength of the same batch of concrete blocks is lower than the design strength grade of 0.85 or 0.90.
(2) The strength value of the lowest group of test blocks in the same batch of concrete is lower than the design strength grade of 0.9.
(3) It is not normal that the strength values of individual test blocks in the same batch of concrete are too high or too low.
(4) During winter construction, the test blocks cured under the same conditions can't meet the strength requirements of formwork removal or heat preservation expected in the winter construction scheme.
2. Governance:
(1) When the pressure test result is far from the requirements, or the test block is qualified and has doubts about the actual strength of the concrete structure, or the test block is lost, the number is confused, and the test block is forgotten to be made. Methods such as rebound instrument and ultrasonic wave can be used to measure the strength of concrete.
(2) If the concrete strength is unqualified, the test block can be chiseled from the concrete structure, carefully smoothed, and the actual strength of concrete can be measured by a testing machine. Bored test blocks shall be representative and shall not affect the use and safety of the structure.
(3) When the concrete strength is low and can't meet the requirements, the safety of the structure can be checked according to the actual strength, and the relevant design unit will study and put forward the treatment scheme, such as delaying the time to bear the load, reducing the load value or taking reinforcement measures.
(4) In winter construction, if it is found that the early strength of concrete increases too slowly, measures should be taken in time to strengthen heat preservation, and steam, hot sand and electric blanket should be used for covering heating or raw furnace heating.
Eight, the concrete protective layer is damaged or the concrete protective performance is poor.
1. Phenomenon: When the protective concrete of the structure is damaged or its protective performance is poor, the steel bars will rust, and the rust will expand, resulting in concrete cracking.
2. Governance:
(1) Concrete cracks can be filled with epoxy resin.
(2) Rust should be removed from corroded steel bars, and the concrete with poor combination with steel bars should be chiseled, rinsed with clear water and fully wetted, and then poured with high-grade pisolite concrete to strengthen maintenance.
(3) Concrete cracks caused by large-area steel corrosion shall be studied and formulated jointly with the design unit and processed after approval.
Nine, concrete shrinkage cracks
1. phenomenon: cracks mostly appear on the surface of newly poured structural members exposed to air, including plastic shrinkage, subsidence shrinkage, drying shrinkage, carbonization shrinkage, condensation shrinkage and other shrinkage cracks, which are neither deep nor wide.
2. Governance:
(1) If the concrete is still plastic, it can be plastered or vibrated again, and the maintenance should be strengthened.
(2) If the concrete has hardened, dry cement powder can be sprinkled into the cracks, and then water is added for wetting, or a thin layer of cement mortar can be applied to the surface.
(3) The crack surface can also be sealed with epoxy mortar or epoxy glass cloth.
Ten, concrete temperature cracks
1. phenomenon: the temperature cracks are irregular, and the temperature cracks of large-area structures are often criss-crossed; The temperature cracks in beam and slab are mostly parallel to the short side. The crack through temperature is usually parallel or almost parallel to the short side. The crack width is generally below 0.5 mm, and surface temperature cracks often appear during construction. After pouring for 2 ~ 3 months or more, penetrating temperature cracks appear, which widen in winter and become thinner in summer. Along the height direction of the section, cracks are mostly wide at the top and narrow at the bottom, some have the structure of wide at the bottom and narrow at the top, and some have shuttle-shaped cracks with wide middle and narrow at both ends.
2. Treatment: The surface cracks can be closed by brushing epoxy mortar twice or pasting epoxy glass cloth, plastering and spraying cement mortar. For waterproof and impervious structures, the through cracks with a width greater than 0. 1mm should be repaired by grouting mud or epoxy grouting, or by both grouting and surface sealing. Less than 0. 1m
M cracks, can not be treated or only surface treatment.
Eleven, concrete subsidence cracks
1. phenomenon: subsidence cracks are mostly deep or penetrating cracks, some in the upper part and some in the lower part, generally perpendicular to the ground or developing at an angle of 30 ~ 45. Large penetrating settlement cracks often have a certain deviation up and down or left and right, and the crack width is related to the load and uneven settlement value, but has little to do with the temperature change.
2. Governance: Cooperate with relevant departments such as design to properly strengthen the structure.
XII. Tensile Cracks of Concrete
1。 Phenomenon: cracks often appear on the upper surface or end of prestressed roof panels, wallboard and trough plates. Cracks often appear at the ends of prestressed crane beams and trusses. Most of the plates are transverse cracks with a plate angle of 45; The transverse rib at the end is close to the crack in the longitudinal rib and basically parallel to the rib height; The crack at the end of the longitudinal rib is inclined. In addition, longitudinal cracks along the direction of prestressed tendons often appear in the end anchorage zone of prestressed crane beams, trusses and other components, and extend intermittently for a certain length, and rectangular beams sometimes run through the whole beam. Vertical cracks sometimes appear at the end of truss, and transverse cracks often appear on the upper chord of arch truss.
2. Treatment method: slight tensile cracks can be closed without any treatment or by brushing epoxy mortar and pasting epoxy glass cloth. Serious cracks will obviously reduce the stiffness of the structure, and should be strengthened by prestress or reinforced concrete enclosure and steel hoop.
XIII. Chemical Cracks in Concrete
1. Phenomenon:
(1) The surface of beams and columns is parallel to the longitudinal cracks of steel bars; Cracks appear at the bottom of the plate member along the reinforcement position, and there are mottled yellow rust in the cracks.
(2) There are large cracks on the concrete surface, and the cracks are irregular.
(3) Irregular cracks appear after concrete pouring for half a year or more, and the cracks are in a large grid shape, with the center protruding and spreading around.
(4) About two months after concrete pouring, round or quasi-round cracks and spalling with different sizes appear, which are similar to "beans" and contain white and yellow particles.
2. Treatment method: For the expansion cracks caused by the corrosion of steel bars, the salty concrete around the main bars should be chiseled, derusted by sandblasting, and then repaired by sprayed concrete or covering.
Fourteen, concrete frost heaving cracks
1. phenomenon: cracks with different widths appear on the surface of structural members along the direction of main reinforcement and stirrup, and the depth can generally reach the main reinforcement. In post-normal stress members, longitudinal cracks appear along the direction of prestressed tendons.
2. Treatment method: ordinary cracks can be sealed with epoxy mortar; For wide and deep cracks, repair or paste epoxy glass cloth with epoxy mortar; For serious cracks, chisel off loose concrete, weld steel wire, then re-pour a layer of fine stone concrete and strengthen maintenance.
15. Cracks in production, transportation and installation of concrete members
1. Phenomenon: In the process of manufacturing, demoulding, transportation, assembly, stacking and hoisting, concrete structural members, especially slender and thin-walled structural members, appear various cracks in the longitudinal direction, transverse direction, oblique direction, vertical direction, horizontal direction, facing direction, deep penetration or penetration. The depth, location and strike of cracks vary with each other, and the width, depth and length of cracks are different and irregular.
2. Treatment method: Generally, longitudinal cracks can be repaired with cement slurry or epoxy cement. When the crack is wide, a splayed groove should be chiseled along the crack first, and then caulking should be done with cement mortar or epoxy mastic. Loose concrete in longitudinal cracks at the corners of members shall be removed, and then repaired with cement mortar or fine stone concrete. For the transverse cracks with fine surface, the cracks can be cleaned first, and then painted with epoxy mortar or sealed with epoxy glass cloth after the surface is dry. When the cracks are deep, epoxy resin or condensed cement slurry, steel wire mesh cement or steel plate hoop are used for treatment. For members with cracks running through the whole section, the treatment scheme should be studied with the design unit and processed after approval.
Sixteen. Transverse cracks and longitudinal cracks of prestressed circular hole floor slab
1. Phenomenon:
The transverse crack width of (1) slab is greater than 0.2mm, which generally extends from the surface to the side rib and mostly occurs in the middle of slab span. This kind of crack usually cracks on the surface of the plate, and both sides appear at the same time. There are many serious side cracks, which develop downward from the board surface to the protruding part below the board side.
(2) After heating and curing, intermittent longitudinal cracks appear on the side ribs on both sides of the panel. There are several panels on both sides at the same time, the length is generally 50-300mm, which can reach more than 1000mm in severe cases, the width is generally greater than 0.2mm, and the depth is shallow, generally not exceeding 1/6 rib height.
2. Governance:
(1) When the crack width is less than 0.2mm and does not extend to the plate side, it can be sealed with cement slurry and accepted. If it exceeds this limit, it should be treated as unqualified.
(2) When the total length of cracks is not more than one-third of the plate length and the width is not more than 0. 15mm, cement slurry can be used for caulking acceptance.
Seventeen, prestressed circular hole floor slab cracks
1. phenomenon: transverse cracks appear within the range of 100mm from the plate end, with a width of about 3-5mm, with intermittent cracks and few transverse cracks along the plate bottom.
2. Treatment: The bottom crack at the end of the plate is located in the supporting part of the plate, which is easy to cause shear damage of the plate and is not allowed. The board should be used as unqualified products or waste products.
Eighteen, prestressed round hole bottom steel wire broken wire, slippery wire, live wire.
1. Phenomenon:
(1) Cold-drawn low-carbon steel wire suddenly broke during component forming.
(2) After the steel wire is loosened, the steel wire retracts too much.
(3) After the steel wire is released, it becomes loose in the concrete.
2. Governance:
(1) If the number of broken wires does not exceed 5% of the total, it may not be treated; If it exceeds 5%, it is necessary to consider reducing the bearing capacity of the plate.
(2) According to the number of sliding wires, the sliding wire board can be degraded for use. However, if the number of slip lines is too large to meet the minimum allowable bearing capacity requirements, they should be treated as waste.
19. The quality of concrete pile is poor.
1. Phenomenon: poor compactness of concrete, large porosity in some areas, honeycomb in some areas, collapse of inner wall of holes, etc.
2. Treatment: Concrete honeycomb and holes can be treated as follows:
(1) Small honeycomb can be washed with water first and repaired with 1:2 cement mortar; For large beehives, loose stones and protruding particles should be removed first, and the horn mouth should be chiseled, then washed and soaked with clear water, then compacted with high-grade pisolite concrete and carefully maintained.
(2) It is necessary to work out the reinforcement scheme together with the design unit, and then deal with it according to the approved scheme. When dealing with the holes in the beam, the bottom of the beam should be braced with supports, and then the loose concrete in the hole should be chiseled off and cut into an oblique shape for pouring concrete. Rinse with clear water and keep it moist for 72 hours, and then pour high-grade pisolite concrete. Bean stone concrete is mixed with one ten thousandth of aluminum powder. Strengthen maintenance after pouring. Sometimes concrete is poured after formwork support, because the hole is very big.
For more information about project/service/procurement bidding, and to improve the winning rate, please click on the bottom of official website Customer Service for free consultation:/#/? source=bdzd