Overview of fair-faced concrete
The fair-faced concrete building is a pouring molding, the surface does not do any decoration and painting, simple and gorgeous, thick and elegant, noble and simple, and the appearance texture is natural. It not only has the advantages of concrete itself, such as high strength, durability, weather resistance, etc., but also has a plain appearance, more taste and artistic effect, reflecting the trend of architectural decoration, advanced design and construction level.
It is the most environmentally friendly and green form of exterior wall and outdoor decoration practice, and its biggest feature is that after the concrete is poured, there is no longer any decoration, which is a method of expressing the plain appearance of concrete.
Fair-faced concrete features
1.Artistry
a.Natural and rich texture (smooth, rough) embodies the concept of modern people pursuing nature and returning to nature.
b.Easy to form (prefabricated, cast-in-place).
c.Expressive (color can be changed).
d.Strong imitation (imitation stone, imitation wood, imitation block).
e.Strong design (strong plasticity, can shape a variety of shapes).
2.Economical(Other additional decorations are omitted, and the construction period is shortened).
No plastering, saving labor, materials and construction period, avoiding plastering quality problems, and preventing potential safety hazards caused by the plastering layer falling off.
3.Diversity
Mirror fair-faced concrete, wood-grain fair-faced concrete (texture type fair-faced concrete), white fair-faced concrete (color fair-faced concrete type), bamboo mold fair-faced concrete (texture type fair-faced concrete), process fair-faced concrete or corduroy fair-faced concrete (manual or mechanical secondary processing), moire fair-faced concrete (concrete itself compactness and color difference zone to form a cloud).
Fair-faced concrete points
Essentials.
First, the formwork project.
1.The design of the template
The fair-faced concrete formwork and supporting structure must have sufficient stability, stiffness and strength to ensure that the structural shape, cross-sectional size and mutual position of the poured concrete meet the design requirements.
2.Template making
The formwork keel should not have joints, if it is really necessary to use the joint method, the number of joints of the same section should not exceed 50%; The size of the blanking of the formwork parts should be accurate and the incision should be smooth; Panels, ribs, back flutes and other components should be straightened before assembly, and should meet the requirements of strength and stiffness; The material of the wood formwork should be dry, and the incision should be planed; After the template is processed, it should be pre-assembled, and the surface flatness of the template, the cross-sectional size, the yin and yang angles, the height difference of the adjacent plate surface and the combination of the pull bolts should be checked, and the template should be numbered according to the pre-assembly.
3.The formwork installation shall comply with the following provisions
1) The installation of the formwork should meet the requirements of the deepening design of the layout of the formwork and the plate;
2) When the template is installed, it should be installed according to the template number;
3) There should be fixed measures at the root and top of the formwork when installing;
4) The installation of the opening template should be adjusted and fixed according to the positioning datum to ensure that the concrete is not displaced when poured;
5) The formwork support must be firm and stable, and the support point should be located in a firm and reliable place, and it should not be tied with the scaffolding;
4.Removal of formwork
When removing the mold, at least ensure that the strength of the concrete reaches more than 80% (the cantilever member must reach 100%), and it is best to start removing the mold after 100%. Use a wooden wedge when removing the mold, and do not use an iron rod to pry or hammer to knock it, and protect the corners of the components when removing the mold. The removed formwork should be placed gently, to prevent bruises, and cleaned and properly kept.
Point 2: Reinforcement engineering
1.Strictly control the accuracy of steel bar processing and binding;
2.In the process of rebar turning and binding, the rebar should avoid the tie bolt to ensure the smooth penetration of the tie bolt, ensure the position of the bolt eye is accurate, and communicate with the design for the rebar change measures that need to be taken;
3.The reinforcement protective layer cushion block should be placed in the plum blossom type, and the color of the reinforcement protective layer cushion block should be close to the color of fair-faced concrete;
4.Each rebar intersection should be tied, the wire should be tied no less than two turns, and the tail end should be towards the inner side of the member section.
Point 3: Concrete works
In order to ensure the quality of fair-faced concrete and construction requirements, quality control is carried out from the following aspects:
1.Raw materials
1) Cement should comply with the provisions of "General Portland Cement" (GB175-2007) and should be preferred. Grade 5 ordinary cement and 52Grade 5 Portland cement.
2) Fine aggregates should be selected with hard, clean, good gradation, low water absorption, small porosity of natural sand or artificial sand, aggregates should be selected with hard texture, good granular gradation of gravel and pebbles, coarse and fine aggregate quality should meet the relevant requirements of JGJ169 of the "Technical Regulations for the Application of Fair-faced Concrete".
3) Fly ash should be selected in accordance with the "fly ash used in cement and concrete", grade fly ash.
4) The amount of admixtures mixed into concrete and its adaptability to cement should comply with the provisions of the "Technical Specifications for the Application of Concrete Admixtures", and the dosage should be determined by testing. The content of harmful media such as chloride ions in admixtures should be strictly controlled. The admixture should have good adaptability with cementitious materials such as cement, and have little impact on the volume stability of concrete.
2.Mix design
Before the concrete production, the concrete mix design should be carried out according to the "Fair-faced Concrete Application Technical Regulations" for the slump expansion, slump loss, setting time, water secretion rate, air content and other tests of the concrete mixture, and the concrete test block should be formed to test the concrete compressive strength, impermeability, frost resistance and other properties.
Point 4: Detail processing
1. Arrangement of tie bolts
The plastic plug matched with the tension bolt should have sufficient strength, and the galvanized steel pipe sleeved in the PVC cylinder can effectively ensure the cross-sectional size and strength of the wall, so as not to cause hole deformation or slurry leakage, affect the flatness of the wall, and take out the plug after removing the mold.
According to the design requirements, a special plug is used for the tension bolt, and the surface texture of the plug is consistent with the texture of the wall.
2. Treatment of yin angle and yang angle mold.
The shady corner part of fair-faced concrete adopts a stereotyped yin corner mold, and the yin corner mold and the large template are overlapped with the open seam strip respectively, and the open seam strip is pulled on the frame of the template and the corner mold with bolts, so as to achieve the purpose of adjusting the joint.
The formwork of the sunny corner part overlaps each other, and there is a formwork clamp clamping, that is, it can meet the construction requirements; The yin corner part is directly processed into a yin corner template with a laminated multi-layer board and a visa board according to a 45-degree bevel.
In order to prevent cement mortar from seeping out from the joints of the sunny corner, the junction of the template end on one side and the template surface on the other side should be pasted with a sealing strip to prevent slurry leakage.