Knowledge points: construction technology of cast-in-place (prestressed) concrete pool
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I. Construction Scheme and Process
1. integral cast-in-place reinforced concrete pool structure construction technology
Measurement and positioning → earthwork excavation and foundation treatment → cushion construction → waterproof layer construction → bottom slab casting → pool wall and roof support column casting → roof slab casting → function test.
2. Process flow of cast-in-place reinforced concrete pool with unit combination
Earthwork excavation and foundation treatment → column pouring → impervious layer construction at the bottom of the pool → concrete cushion construction at the bottom of the pool → waterproof layer construction in the pool → block pouring of the pool wall → block pouring of the bottom plate → sealing of the bottom plate → waterproof layer construction of the pool wall → function test.
Second, the key points of construction technology
1. Formwork and supporting structure
When through-wall bolts are used to balance the lateral pressure of concrete pouring on the formwork, bolts with detachable ends or bolts that can be pulled out during formwork removal should be selected. For cast-in-place reinforced concrete beams and slabs with a span of not less than 4m, the formwork shall be arched according to the design requirements; When the design has no specific requirements, the springing height should be11000 ~ 3/1000 of the span.
2. Water stop device
Plastic or rubber waterstop joints should be hot-jointed, and overlapping is not allowed; The seam of metal water stop should be folded with bite or lap according to its thickness, and the lap length should not be less than 20 mm, and the bite or lap must be welded on both sides. Do not pierce the water stop or nail it in place.
3. Arrangement and installation of unbonded prestressed tendons
(1) The number and arrangement of anchor bars shall meet the design requirements; When there is no requirement in the design, it shall be ensured that the length of unbonded prestressed tendons in the tensioning section shall not exceed 50m, and the number of anchoring tendons shall be even.
(2) The anchoring positions of two adjacent unbonded prestressed tendons should be staggered by anchoring tendons; Take half of the number of anchor bars as the number of unbonded prestressed bars; The calculated length of each unbonded prestressed tendon should consider the width of an additional anchor tendon, the stretching working length at both ends and the anchoring length.
4. Tension of unbonded prestressed tendons
When the length of unbonded prestressed tendons in tensioning section is less than 25m, one end shall be tensioned; When the length of unbonded prestressed tendons in tensioning section is more than 25m and less than 50m, tensioning at both ends should be adopted; When the length of unbonded prestressed tendons in tensioning section is more than 50m, segmental tensioning and anchoring should be adopted.
5. Anchor sealing requirements of prestressed tendons
(1) The thickness of the protective layer of the protruding anchor end anchorage should not be less than 50m；;
(2) The thickness of the protective layer of exposed prestressed tendons should not be less than 50mm；;
(3) The strength grade of anchorage concrete should not be lower than that of corresponding structural concrete, and should not be lower than C40.
6. Dismantle the formwork and bracket
Side formwork shall be removed only when the strength of concrete can ensure that its surface and edges and corners are not damaged by formwork removal; Before the concrete block cured under the same conditions as the structure reaches the specified strength, the bottom die shall not be removed.
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