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Pumping concrete in construction of the spillway

Spillway concrete pouring operation is the focus of quality control, in which section of the culvert and open channel section of the construction there is a big difficulty. Culvert section of the wall height 5.7m, cylindrical curved roof, a large height difference, open channel section of the steep slope of 1:2, on both sides of the wall height of 6m, is blasting in the middle of the mountain out of a groove, such as by - General construction of concrete construction technology, and its construction is very difficult. Therefore more economical and rational use of pumping concrete, reducing the part of the difficulty of construction and improve the progress of the project, saving the cost of certain expenses. 2.1 Concrete Pumping control points (1) raw materials of the main raw materials of concrete spillway pumping 32.5 ordinary portland cement, I fly ash, two with pebbles, KDNOF high concentration of superplasticizer, KDSF- A air-entraining agent. (2) Concrete Mixing Ratio qualified laboratory for the test with the work of pumping concrete through the different content, different ratio, for comparison, the only affordable, but also more reasonable, and can meet the design requirements mix. Mix pumping concrete spillway in Table 1. Table 1 pumping concrete spillway over the table l4 · Zhao Lan, Xu Yifang: pumping concrete in construction of the spillway (3) focus on the construction process control environment according to the terrain, construction of pumping concrete spillway with a fixed pump . Pump as much as possible on the nearby warehouse near the concrete pouring, minimizing duct length. Spices by mixing station, concrete delivery, the theoretical maximum throughput of 67m0 / h, diameter pipes 125mm, vertical pipe length of up to 150m. Slump of concrete out of machine regular monitoring and follow-site monitoring and control placement of the concrete slump, concrete tank due to transmission distance is not very different, have little effect on the concrete slump (negligible),[link widoczny dla zalogowanych], but influenced by temperature . According to monitoring data of the machine at any time to adjust concrete slump. Construction, concrete slump control in 15 ~ 17cm. Part of the monitoring data shown in Table 2. Table 2 Concrete Slump part of the monitoring results of the table put a pump seal rubber nipple, wet with water before pumping pipes, later puree (not the same ratio of coarse aggregate concrete) lubrication pumps and piping. Pump hopper before you let someone in charge of the stone taken out mixture and debris. 2.2 The effect of the double-doped construction technology, in particular with a capacity of 25% fly ash, the construction of better concrete workability, slump retention rate, pumping well, the phenomenon of plugging rare scene, the effective ensure the construction progress; another pumping concrete mixing a high concentration of superplasticizer, air-entraining agent, not only saves the cost of materials, the mechanical properties of hardened concrete can meet the design requirements. 3 Conclusion (1) should focus on the choice of water-reducing agent to maintain the plastic concrete (slump loss), loss rate, the lower concrete slump loss of the smaller (normal conditions, the loss of not more than 20ram, but in the temperature reach above 30 ℃, concrete slump loss increases), can pump the better. (2) the use of water-reducing agent reduces the water-cement ratio (generally available to 0.4), improve the early strength of concrete (up to 75% of the design label.) (3) selection of the secondary with a reasonable solution. The flakiness of the aggregate content,[link widoczny dla zalogowanych], the lower (preferably less than 8%), the better the workability of concrete pumping, the higher the intensity. (4) In general, pumping concrete should choose the low heat of hydration, setting time and a long, post-high strength cement. In the use of ordinary portland cement, fly ash content due to increase (up to 25%), in conjunction with the use of high concentration of superplasticizer, has played a lower heat of hydration, improve the workability,[link widoczny dla zalogowanych], to improve concrete late strength of multiple roles. (5) poor cohesion of the concrete in the pumping process easy to segregation. Mix in the choice of construction, in accordance with fine aggregate fineness modulus of sand is reasonably adjusted rate (low intensity pumping concrete in the rate of 40% sand),[link widoczny dla zalogowanych], with the use of pumping, make concrete cohesiveness and liquidity improved. (6) in the arrangement of concrete pumping pipe, generally horizontal tube under the tube length and the ratio of the vertical tube length should be 1 / 3, so that the level of control through the wall of the concrete and concrete counter friction to balance the pressure to avoid plugging accident. (7) the diameter concrete pipes should normally be three times larger than the maximum aggregate size (the project is 3.125 times), and wet with water before pumping pipe, pipe, after wetting with a puree to avoid plugging of concrete. Pump concrete pumping concrete and rapid construction of a combination of technology, comprehensive benefit significantly, to ensure pumpability of concrete and concrete pumping concrete cracking durability of the technology is the key. Spillway practice shows that the fly ash and superplasticizer I use is to ensure the quality of concrete and important measure to ensure the construction speed.
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