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Concrete was poured during the severe winter of 1999-2000. 1 The determination of concrete mix ratio and material selection 1.1 Mixing ratio According to the design requirements of strength grade and impermeability grade, the concrete mix ratio with good workability and pumpability is determined through tests, and the slump of pump concrete should be controlled at (160) In the range of ±20mm, the winter construction will adjust the amount of antifreeze in time according to the change of temperature.
1.2 The choice of materials must use low-alkali cement, winter planting preferred ordinary Portland cement. The bottom plate is suitable for strength grade 32.5 slag cement (its low hydration heat and long setting time) to reduce the difference between the internal temperature and the surface temperature to avoid cracking and ensure the impermeability.
Select water reducing agent, retarder, air-entraining agent and anti-freeze agent according to the requirements of design strength grade, impermeability grade and the workability and uniformity of concrete required for construction. To compensate for concrete shrinkage, appropriate amounts of micro-expansion agents (such as CEA) should also be added to the concrete.
In order to ensure the pumpability of concrete, fly ash and ground slag powder are added, and the amount of cement is also reduced to avoid the excessive bleeding rate of cement. 2 Mixing requirements for self-waterproof concrete (1) Determine the moisture content of sandstone in time to adjust the amount of concrete mixing water.
(2) Concrete mixing equipment must be kept clean. (3) The concrete mixing time must not be lower than the specification.
In the winter construction, the concrete heating water and the aggregate heating shall be determined according to the thermal calculation, and shall not exceed the specified value of the specification. 3 Self-waterproof concrete pouring (1) The slump test should be done frequently after entering the site. Unqualified persons are strictly prohibited to use the concrete in order to ensure the concrete entering temperature.
(2) The pouring method of concrete must be reasonable to avoid cold seams. (3) Due to the large slump of the pumped concrete, the floor concrete adopts the "push-casting method", that is, 'a slope, thin layer pouring, sequential advancement, followed by pouring to the top'.
The concrete poured on the slope formed by the natural runny is used to avoid the frequent removal or extension of the conveying pipe, so as to increase the pumping efficiency, simplify the bleeding treatment of the concrete and ensure that the spacing between the upper and lower concretes does not exceed the initial setting time. (4) In the concrete construction of the floor slab, two vibration points shall be arranged on the upper and lower layers of each casting belt according to the slope formed during pumping.
In order to prevent the concrete from building up at the unloading point, the concrete at the material inlet is first vibrated to form a natural flow gradient, and then fully vibrated to increase the ultimate tensile strength of the concrete and prevent the occurrence of cracks due to concrete sinking. (5) The wall concrete should be layered and continuously poured, and the pouring thickness of each layer should be controlled at about 300mm.
(6) Self-tightening method should be adopted for self-waterproof concrete. The key is to accurately grasp the time of the second vibration. The specific method is that after the first time after entering the mold, the vibrating rod is inserted into the vibrator before the concrete is not initially set and the next layer of concrete is poured to further vibrate the concrete and drive out the air bubbles.
(7) After vibrating for the second time, first use a long scraper to level off according to the elevation, then use a wooden trowel to press repeatedly to make the surface dense. Finally, use a steel trowel to calender the surface to prevent cracks on the concrete surface. Insulation coverage. (8) The concrete shall be maintained with integrated heat storage method and shall be maintained for 7 days with the mold.
After the mold is removed, the insulation is covered in time. During the curing of concrete, temperature monitoring should be strengthened, and problems should be found and measures taken promptly.
4 Setting of post-pouring belt and construction joints Four continuous through-pouring belts are provided on the floor and outer wall panels as temporary shrinkage joints. The structure is divided into 7 pouring blocks (the total amount of floor concrete per block is 1300 square meters. Meters around). In order to speed up the construction progress, CEA admixtures were added and poured before pouring (closed after the top floor of the basement was closed for 15 days).
In order to ensure the impermeability, two horizontal construction joints were installed at 500 mm above the floor and 200 mm above the top floor of the underground. 5 Post-pouring belt and construction joints treatment (1) The post-pouring belt and construction joints are the weak links for self-waterproofing of concrete structures. For this reason, there are not only grooves (for floor soles only), but also for joints (for wall only joints). , steel plate sealing tape and cutting hair processing, air compressor blowing, in the pouring of new concrete before pouring, should also be brushing 4mm EE-2 interface treatment agent, shop 50mm thick concrete with the same grade of stone-reducing mortar, Fully vibrate nearby when pouring new concrete.
(2) The base cushion layer at the post-pouring zone should be reduced by 100mm to facilitate the handling of ice and snow, garbage disposal and seams. Before the construction of the floor concrete, brush a layer of 3mm thick polyurethane waterproof layer on the cushion (should be wide 300mm on both sides of the rear pouring belt) to enhance the anti-seepage effect.
(3) Through the center of the wall bolt, the water ring is welded and the water stop ring is fully welded. The wooden end of the bolt needs to be provided with a wooden spacer (20mm x 20mm x 1.2mm or diameter 20mm x 1.2mm), which is removed along with the template. Formed concrete is concave (1.2mm deep) at the bolt. After the mold is to be removed, the steel bar is cut along the flat recesses, the anti-rust paint is applied first, then a layer of 3mm thick EE-2 interface treatment agent is applied, and then blocked with an expansion waterproof mortar, and the light is collected and cured. 7d.
(4) The selection of post-cast concrete belts should be performed during the early spring when the temperature is low, so as to avoid excessive temperature stress. (5) In order to prevent construction water and snow water from flowing into the post-strip zone around the floor, a water wall with a width of 60mm and a height of 300mm shall be added at 500mm on both sides of the post-sweeping belt, and waterproof mortar shall be applied on both sides of the wall.
Self-waterproof concrete winter construction technology for basement
The total construction area of ​​Lenovo Computer Building is 71699.8 square meters. The basement is made of a sampan plate, with a depth of 11.0m, a floor thickness of 600mm and a wall thickness of 350mm. The concrete strength and impermeability grades are C40 and P8, respectively. There is no soft waterproof layer.
Release Date:2009/3/25 14:37:21