The original author: Feng Yonglu source:" Gansu science and technology" twenty-second volume eleventh2006November
Pick to: introduces water mirror concrete construction technology, standard, the main quality defects of concrete and how to prevention and elimination of common quality defects.
Key words: mirror surface concrete; quality problems; prevention and elimination
CLC: TU271. 1
Clear water concrete embodiment of people's pursuit of natural, regression nature of a concept. In the recent years in industrial and civil buildings are gradually applied. Below I water mirror concrete construction technology and the quality common fault and prevention and elimination on their own point of view.
1water mirror concrete construction technology
The current water mirror concrete construction technology of more often use template panel material has2 kinds: first, material properties of not less than Q235A, thickness5mm of high-quality cold-rolled steel plate or Baosteel raw plate after cutting, should adopt the gold processing planing edge processing or the cutting front panel front. The large wooden plywood, wood template dorsal rib material, according to the design drawings size stereotypes production, and then in the field, the overall assembly design; template surface paste LMM thick PVC affixed to the plate, or the use of specular bamboo plywood ( quality plywood ), to ensure smooth contact surface with concrete; column beam angle set wood line chamfer, wood used small screw fixation in beam column template corner, wood in the fixed prior to use paper tape comprehensive paste, to ensure the smooth wood surface; the channel steel, steel pipe hoop and the puller bolt for concrete reinforcement, by calculating the selected proper reinforcement method. Template design should be designed into an integral type large template or assembled large formwork, the concrete match ratio to optimization design, engineering construction through test and experiment with the selected suitable concrete color and the color matching mix. Sand, stone material selection of the same origin, the same color material, cement manufacturers use the same, the same strength grade of cement, admixture and additive for the same manufacturers, the same brand.
2clear water mirror surface concrete standards
The present concrete water still does not have unified quality acceptance criteria and construction technology, I think in general to meet specifications for concrete construction on the basis of perception, the surface is mainly have the higher quality requirements.
     (1) the geometry size is accurate, the corner edge founder, straight, not defect, rounded and.
(     2) the surface of concrete topstitching, concave lines straight, distribution, coordination, joint dislocation is less than or  equal to 1mm; to pulling bolt arrangement and lines should be relative, neat and orderly.
     (3) the surface of concrete compacting flat, smooth, glossy, color uniform, no pollution.
     (4) a concrete surface without cellular, pitted, bubble, hole, slag, no exposed tendons, hidden gluten, no belt, splash, a small patch.
    (5) embedded iron parts, preformed hole, embedded box position correctly, tidy and.
3clear water concrete are the main quality problems have
    (1) column slurry leakage, root rot. (2) concrete surface template patchwork obviously, concrete dislocation. (3) the beam column line angle of slurry leakage, sand. (4) the concrete surface wrinkling. (5) the concrete surface bubbles. 6) concrete surface color inconsistencies, matt. (7) embedded parts rough, skew, invagination. (8) bolt bore surrounding leak slurry, sand. (9) conservation and protection does not reach the designated position. Following the quality defects prevention and elimination to talk about some of view:
3.1column root leakage prevention and elimination
First, column template support, coping column root template support with1:2cement mortar screeding, leveling layer to use level inspection, to ensure that the horizontal flat (applied to the cap surface, floor level on the column ); column, wall template foot screed shoulds not be too thick, usually 30mm, width of 100mm. In second, the mouth of the template column all hands pushing, ensure the mouth under the founder of straight, column template bottom to paste a double-sided foam tape ( and the column edge size Qi ), Eli template and the leveling layer extrusion closely; third, column root should be set flush water drainage hole, the template removal, pouring concrete prior to the mortar will drain Kong Yuzhu root template around plugging firmly; fourth, to column and column joints, in the lower cylinder, template root parts of paste two a certain thickness of the surface tape, support reinforcement templates, can ensure the template bottom and cylindrical squeeze tightly; fifth, pouring concrete must be connected with the slurry processing, namely in the column root even pouring a layer 5 ~10cm thick with the mixture ratio of cement mortar, is strictly prohibited without the ground slurry pouring concrete.
The 3.2joints of clear, concrete dislocation prevention and elimination
The first, want to use specifications, thickness of wood veneer, wood, on the clear water mirror surface concrete construction process of template and the template, the choice of system is very important. Plywood using phenolic coated plywood template, the template quality selection of main material, surface with strong waterproof phenolic resin impregnated paper, smooth, high strength, light weight, strong waterproof performance, especially for concrete engineering, reinforced with wood and uniform large presses, to ensure accurate dimension unification. Stencil thickness before use to check carefully, ensure that the thickness of material to one component; second, template assembled, the wood reinforcement to Pinfeng template is vertically arranged; third, the gap between to use putty paste up after2cm wide transparent adhesive tape; fourth, large combined formwork joints should be the edge of the template by hand to push, and then paste on the double-sided adhesive tape, ensure the homogeneous and joint; fifth, steel pipe for use in reinforcement hoop hoop bending, deformation or slot is strictly prohibited, and must have sufficient strength and stiffness, to ensure water mirror concrete surface roughness.
3.3column beam line angle of slurry leakage, sand and not straight prevention and elimination
First, wood to ensure uniform size, smooth lines, in the factory before use after, unified by a pick, bending deformation and cracking are prohibited the use of wood on the brush, plastic and tape paper paste to special construction, responsible person, wood paste paper tape to wide, on each side of a wood strip width the side 2cm, to double head, if found to have paper tape bubble phenomenon, with acupuncture break to exhaust gas, wood line installation and template contact site to paste the double-sided foam tape, when so mounted and template squeezing compaction, wood sponge tape and wood edges to flush, banned both between the uneven situation; second, wood to wood line line, one by one to pick, ensure that the specifications of the nail in the same components, wood generally fixed in facet templates, nail spacing200 ~ 250mm, to ensure that the wood in support of a large surface template deformation, wood joints for all45 degree angle joint, does not allow direct docking, wood lines on the head office straight narrow tape affixed to the whole.
3.4concrete surface wrinkle prevention and elimination
In order to achieve concrete surface of the mirror effect, in the wood, the template seams are to use adhesive tape paste, because construction adhesive tape paper wrinkling caused concrete surface wrinkling, as do the work of prevention and elimination of paper tape, to prevent wrinkling. First, an adhesive tape paper, as far as possible in one time, no tear reposting, really need to stick again, need to change the paper tape, from one side to the other side to catch the stick; second, wood can be suitable in universal adhesive, to increase the adhesive force, tape paper if there are bubbles, according to second part of the method of elimination.
3.5concrete surface air bubble prevention and elimination
Clear water mirror surface concrete formwork in the concrete pouring process of drainage, permeability is poor, so the concrete tamping quality level greatly depends on the concrete surface air bubble number. The first, should be stratified by pouring concrete bar examination, the layer thickness, such as 50cm layer, measuring every 50cm brush red and blue mark, when measuring upright in the concrete surface, outside leakage measuring length to test the layer thickness, and equipped with check, pouring with lighting, thickness of stratification should meet the requirements, the first layer of concrete vibration compacting concrete surface is level, until it is no longer a significant sink and bubbles are generated so far, and then cast the second layer of concrete, pouring concrete in upper, lower concrete should be inserted around 5cm, to eliminate the two layer between the joints; second, concrete vibrator shall be inserted points evenly, quick slow pull, each interpolation point to master the general vibration time, vibration time20 ~ 30S, too short is not easy to ramming and bubble discharge, long may cause concrete segregation phenomenon, resulting in inconsistent color concrete surface; third, concrete vibrator, vibrator and abuts the template vibrated, will most likely be bubble rushed to the template edge, but not conducive to the bubble discharge, so the vibration rod should be associated with the template is maintained about 150 to 200mm gap, in favor of the bubble discharge; fourth, concrete slump, workability and water-reducing agent in concrete vibrator to produce certain effect, we can choose reasonable admixture, appropriately increase the concrete mixing time, increasing collapse Fall of method for concrete vibrator, in at the same time, to reduce the concrete bubbles have certain benefits.
3.6concrete surface color inconsistencies, luster, prevention and elimination
Concrete surface color uniform, smooth, glossy clear water mirror surface concrete is a notable feature, how to prevent concrete surface of inconsistent color or dull becomes more important, according to the previous construction experience, the first, in the wood plywood is adhered with a layer of smooth smooth PVC affixed to the plate, the adhesive coating to be used special rubber scraper, ensure the sticking surface coating uniformity, thickness, glue too thick can consider adding thinner, and be ready to rubber hammer, paste after tapping the sticking surface, exhaust gas, the solid paste. Template paste PVC plate after pouring out concrete generally has good gloss, this method in many engineering verified and applied; or use a mirror panel, also can achieve the same effect. Template installed before brushing mold release agent, release agent to uniform thickness, repeatedly wiping the surface of the template to no runny release agent. Second, related to the concrete mixture ratio, i.e. the same number of concrete, concrete used in wood, cement manufacturers, with the same brand, same lot number, stirring concrete must be in strict accordance with the ratio of construction, material measurement should be accurate; third, selection of additives are also important, part of the admixture of concrete in color appearance caused a certain degree of influence, the concrete mixture ratio determination, in the construction of formal project, to do some model wall, if there is a problem, mix make appropriate changes and adjustment; fourth, the admixture of the concrete mixing time should be extended, so as to fully mixing evenly, fully dissolve; fifth, in ensuring the vibration compacting concrete case, not a long time after vibration and repeated vibration, so as to avoid concrete segregation, resulting in concrete surface color is different, because if the component surface laitance thicker, but adding an appropriate clean gravel then moderate two vibration approach, avoiding the surface layer concrete and the lower concrete color inconsistencies; sixth, without affecting the flow of materials used in the case of late, as a template, the template member in full maintenance, to prevent premature loss of water, on the other hand, can be avoided by watering and maintenance caused by mixed with sand, dust sewage to flow to the concrete accident The surface of the member, causing pollution, affect perception, of course component maintenance may also be considered after stripping immediately overlying the plastic film approach, using concrete surface of steam condensate natural conservation.
3.7embedded parts rough, skew, invagination of the prevention and elimination of
Clear water mirror surface concrete because of its smooth appearance, bright as a characteristic, be good to hear or see, in many power plants and other industrial construction has been more construction application and industrial construction projects, a significant feature is the civil engineering of embedded parts, construction difficult, and also appeared in a series of uneven, skew, as embedded parts invagination of quality problems such as how to ensure the embedded iron parts location accuracy, surface and concrete with a plane to become everybody care about more topic. First, because of the embedded part has a lot of anchor bar or other anchors for electric arc welding, and the welding heat stress are easy to produce deformation, embedded parts, for planar buried piece surface caused by inequality, therefore embedded parts in the factory for the project, must be by a block-by-block check, for the deformation of the jack pressure correction; second, leaving the plant qualified embedded parts shall apply suitable mounting method, can guarantee the embedded parts in concrete pouring is not easy to occur when skew, invagination and other quality problems. At present, the better way is to first in the matched template. Iron position, then the iron and the modules in the same location on the borehole, the embedded part and the template is padded between2mm thick sponge, prevent between two clamping slurry, with a diameter of4mm bolt embedded parts fastened to the surface of the template, stripping, first remove the template outer nut, bolt after template removal, resection, using hand-held grinders grind.
To ensure that buries itself founder, size accurate, no burr, for plane steel embedded parts with Shears Scissor, for angle steel and other steel embedded parts of the cutting machine cut. The embedded parts production and installation construction method of embedded parts surface roughness, and the concrete surface level, look good.
3.8bolt bore surrounding leak slurry, sand and eliminating method
In the power plant and other industrial buildings, column beam section are larger, the bolt reinforcement is a good way to prevent the member up to die, but to clear water mirror surface concrete engineering, bolt holes around the quality defects of concrete surface, will no doubt greatly influence the visual appearance, for the elimination of column beam reinforcement with column for bolt the surrounding slurry leakage sand, thereby causing the column surface visual appearance defects, on one hand, can consider not used for bolt, and the other reinforcement approach way to avoid bolt hole. For the column and single beam member, adopts channel steel reinforcement, steel in component used for bolt reinforcement, the channel steel specifications, to pulling bolt diameter and reinforcement spacing through calculation to determine, at the same time frame column using scaffolding system on top, namely column scaffold directly abutting the two column reinforcement the channel, can greatly increase the assurance coefficient, for the beam slab cast-in-place beam, appropriate encryption support rod, preventing deformation, at present this construction method in Jingyuan power plant project phase three2x300MW main plant construction has obtained good effect. On the other hand, if you do need to adopt to pulling bolt ( such as wall and other components ), can be used in the component template on both sides of the corresponding position of drill pipe hole than PVC LMM ( PVC tube diameter than the bolt2 ~3mm, PVC tube strength is higher ), to pulling bolt from the PVC pipe passes through ( PVC tube length to be out of the template on both sides of 4~ 5cm ), PVC pipe and surrounding the platen junction with adhesive tape. Such basic can avoid the bolt hole leakage around the slurry sand, to pulling bolt can also draw turnover utilization.
3.9conservation and protection does not reach the designated position control
Concrete curing time is more than 7days. For horizontal exposed slab, beam concrete surface by using covering geotextile, and water conservation, or covered with plastic film bag curing press. Beam column side elevation after template removal or repair in time after completing the brushing concrete curing liquid. Concrete protection, in the removal of concrete surface stains, as well as the surface patch is completed, in the concrete surface coating liquid conservation, finished in the concrete surface to form a layer of transparent protective film, and then the film wrapping and plywood corner protection.
In this paper, the clear water mirror surface concrete construction nine aspects of prevention and elimination of common quality problems in construction practice method is my area a little experience, is willing to work with the vast number of engineering and technical personnel continue to research, promote the level of technology of clear water mirror surface concrete progress and improvement.