Especially for the thick concrete slope protection board, because it is mostly needle-shaped flat-seam structure, it is difficult to realize flat-seam after flat-seam, and it can only be controlled by formwork; The formwork is supported on the gravel cushion, so it is impossible to use the plane vibrator, which makes the surface flatness difficult to control. In order to ensure the construction quality of concrete slope protection, a set of scientific and reasonable construction technology and quality assurance measures must be carefully formulated and strictly implemented.
1 concrete slope protection construction technology
Surface treatment of foundation → laying gravel cushion → formwork support and expansion joint installation → concrete mixing, transportation, warehousing, vibrating and screeding → formwork removal → maintenance.
1. 1 basic surface treatment
The top edge line of toe tooth wall is the bottom edge line of slope protection, and its position accuracy directly affects the appearance quality of slope protection. Must be strictly controlled in the embankment foot construction stage; Backhoe excavators cut slopes in time as the embankment surface rises; A large area of embankment slope is compacted by bulldozers, backhoes and other equipment. The compaction degree of the inverted trapezoidal backfill area between the toe of the embankment and the embankment body is one of the key indexes of construction control, and the electric impact rammer should be used for layered compaction. Hand-hanging line for precise slope repair.
1.2 gravel cushion laying
Gravel cushion should be uniform, smooth and dense. When laying, machinery is given priority to, supplemented by labor. The elevation of the top surface of cushion is controlled by the control line hung out in advance.
1.3 formwork support and expansion joint installation
1.3. 1 template preparation font split slope protection construction is mostly horizontal construction. In order to ensure the verticality and surface smoothness of the slope protection block, the formwork shall adopt high-rigidity channel steel as far as possible, and the height of the channel steel is the same as the thickness of the slope protection concrete slab. A certain number of wooden formwork shall be configured to meet the needs of slope protection length change. The transverse formwork and the longitudinal formwork are connected and fixed by bolts. The bolt spacing is determined according to the size of the drawing block. Use steel bars as triangular fasteners to fix the template position. According to the width of the block, the fixing fixture is made, and the steel bars are welded at both ends of the angle steel, so that the side formwork of the slope protection can be clamped at the same time to ensure the width of the slope protection block. Prepare wooden wedge to fix formwork joints, and fix formwork spacing on each side with wood square. 1.3.2 Setting-out is the key to improve the appearance quality of slope protection. According to the construction drawings, measure and set out the formwork installation, hang up the whole line, and measure the elevation of the top surface at the same time to ensure that the top edge of slope protection, that is, the top line of embankment, is in a straight line. 1.3.3 When installing, calculate the top elevation of the edge line of the casting block according to the slope ratio. Formwork parallel to the dike axis direction is supported by long formwork, and short formwork jumping blocks along the slope are installed between formwork supported by long formwork. After the formwork support is completed, the control line put in advance is used for precise adjustment to ensure the accurate position of the upper and lower edges and the top surface of the formwork. 1.3.4 The expansion joint foam board is cut with a table saw, and the cutting width is slightly smaller than the thickness of the slope protection, which is convenient for installation. This can solve the shortcomings of burr and nonlinearity in cutting surface with wallpaper blade, and also greatly reduce material loss and working strength. First, the foam board is embedded in the joint surface of the concrete structure to be poured first, and it is nailed firmly with cement steel nails or glued on the joint surface with engineering glue. The surface of the foam board must be flush with the concrete pouring surface. 1.3.5 Maintenance In order to prevent rust and facilitate form removal, the steel formwork panel should be coated with release agent. After each form removal, the formwork shall be cleaned in time and stored properly.
1.4 concrete mixing, transportation, vibrating and screeding
1.4. 1 Prepare a set of concrete tools for construction in advance. The front line of slope protection construction is long, so it needs to be equipped with generators. Small generators can basically meet the needs of construction. Make a car that integrates a hoist and a generator, which can turn around and carry tools such as lamps, generator oil, water, cables and brake boxes. According to the construction intensity, prepare concrete supporting tools such as electric trowel and hand trowel. The scraping bar is made of square steel welded handles at both ends. When the slope is long, chute should be made for blanking, and large plastic sheets should be prepared to prevent the rain from wetting the warehouse surface and causing unnecessary losses. 1.4.2 quality control of raw materials All raw materials are inspected and tested regularly as required, and stored in a standardized manner. When mixing, control the quality of concrete components (water, aggregate, cement and admixture) in strict accordance with the mixture ratio to ensure that the quality of finished concrete meets the design requirements. 1.4.3 concrete mixing concrete adopts centralized mixing, and the mixing intensity of the mixing system meets the requirements of peak monthly strength. 1.4.4 The daily strength of concrete transportation is generally not large because the pouring speed is mainly determined by the pressing speed. However, when the transportation distance is far away, concrete tankers or dump trucks can be selected to transport concrete, so as to shorten the transportation time of concrete as much as possible and seal the carriage to prevent slurry leakage during transportation. Keep the transportation road unblocked to avoid bleeding and aggregate separation caused by bumps and vibrations. 1.4.5 concrete pouring shall be carried out in parallel by "jumping block method". After returning to the empty pouring section, the next layer will be poured, and the concrete will be poured from bottom to top longitudinally. Before pouring, the slope surface should be watered and wetted, so as to prevent the gravel material in the cushion layer from absorbing a large amount of water in the concrete, resulting in insufficient hydration reaction of cement and affecting the strength of concrete. Before pouring the empty section, cover the poured slope protection blocks on both sides of the empty section with materials such as film to avoid being polluted by cement slurry or damaged by collision of machines and tools, which will affect the appearance quality of slope protection. At the same time, protect the installed flat-fell seam foam board. 1.4.6 concrete shall be closed, and the vibrated concrete shall be closed manually after it is put into storage. The pouring sequence is from bottom to top. When pouring, it should be smooth with the pouring, and it is not allowed to accumulate. The vibrating time of the internal vibrator shall be subject to the fact that the concrete does not sink obviously, bubbles do not appear and the slurry begins to pan. When the vibrator cannot be used, it should be tamped manually. After the completion of concrete vibrating, the hanging line should be corrected again to ensure that the formwork does not go away. If there is any problem with formwork, the correction should be completed before the initial setting of concrete. Scrape the concrete surface on the top surface of the side formwork with a special scraper, initially scrape the concrete surface of the slope protection, and then smooth it with an electric trowel. According to the temperature and the actual solidification of the slope protection surface, it is manually smoothed and calendered several times to ensure the appearance quality of the slope protection concrete. 1.4.7 screeding of concrete After the slope protection concrete is screeded with a scraper, the surface setting hardening time always changes due to the influence of temperature and water cement ratio. It is necessary to master the pressing time according to experience. First, install the sand table on the electric trowel, tie a rope to the top of the dike and pull it up and down to make the slope smooth, then use the electric trowel to press the light twice, and use the hand trowel to finely treat the corners, and remove the concrete at the top of the template to prevent the concrete corners from being damaged during formwork removal.
1.5 template removal
When concrete is dismantled, it can be dismantled without hurting edges and falling corners. After slowly removing the bracket, slowly remove the template outward. If it is found that the removed formwork is out of welding or deformed, it should be repaired in time, and the removed steel bar connectors should be placed centrally.
1.6 concrete curing
Adopt the way of keeping in good health with plastic film to control the evaporation of water well. After pouring the final set, quickly cover it with film for curing, and spray water to moisturize it in time in extremely hot and high temperature season. Pedestrians and piles are not allowed on the film, and the curing time is not less than 14d.
1.7 concrete surface protection
After the concrete pouring of slope protection is completed, necessary protection shall be carried out, warning signs shall be set up, and special personnel shall be assigned to patrol to avoid mechanical crushing and cattle and sheep trampling. The edges and corners of the pouring block should also be protected so as not to affect the appearance quality of the slope protection.
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