Description: With the rapid development of the construction industry, the application of pumping concrete has become an indispensable link in concrete construction. However, pumping concrete often has problems with one or the other, which brings trouble to the construction schedule and construction quality . This paper analyzes the causes of pumping concrete often problems and gives a series of solutions. 1 concrete admixture of cement adaptability (1) whether the stability of the cement ore lead to stable mineral composition, thus affecting the adaptability of concrete admixtures on the cement. (2) cement production process, such as shaft kiln and rotary kiln, how to control the quench measures in the cooling system, the temperature of gypsum grinding, etc., resulting in the change of mineral components, crystal phase state and gypsum morphology in cement, thus affecting To the concrete admixture of cement adaptability. (3) Absorption capacity of additives in cement: C3A> C4AF> C3S> C2S, the cement hydration rate is directly related to the mineral composition. (4) After the cement is stored for a period of time, the temperature is lowered, the high temperature adaptability of the concrete admixture is improved, and f-CaO absorbs the water in the air to convert into Ca (OH) 2, absorbs the CO2 in the air and turns into CaCO3, So that Mwo down, but also to improve the workability of concrete, so that the loss of fresh concrete slump slowed down, the concrete coagulation time slightly longer. (5) Ordinary portland cement requires slightly larger water than slag cement, which is good in water retention, but also has a relatively high slump loss. (6) Cement with high C3A content has fast slump loss and good water retention. (7) Hydrophilic admixture in cement is good in water retention; pozzolanic cement is poor in water retention and easy to excrete water. (8) temperature and humidity directly affect the concrete admixture of cement adaptability. (9) The proportion of sand, stone grading and the proportion of sand, stone, water and plastic also affect the adaptability of concrete admixture to cement. 2 concrete prone to bleeding, the reasons for the problem of segregation and solutions 2. 1 reasons (1) easy to bleeding when the fineness of cement; C3A low content of cement easy to bleeding; cement standard consistency of small water easy to bleeding; slag Bipu silicon easy to bleed water; volcanic silicate cement easy to bleed water; grade â… fly ash easy to bleed water; mixed with non-hydrophilic mixture of cement easy to bleeding. (2) small amount of cement easy to bleeding. (3) Low-grade cement is more likely to bleed water than high-grade cement (same dosage). (4) with the same level of concrete, high-grade concrete cement concrete cement than low marks more bleeding. (5) Unit of water is too large concrete easy to bleeding, segregation. (6) low strength concrete prone to bleeding (general) (7) sand rate of small concrete prone to bleeding, segregation phenomenon. (8) continuous gravel than the single gravel concrete bleeding small. (9) Concrete admixture of water retention, thickening, poor air permeability concrete prone to bleeding. (10) super-mixed concrete admixture of concrete prone to bleeding, segregation. 2.2 solution (1) the fundamental way is to reduce unit water consumption. (2) increase the sand rate, choose a reasonable sand rate. (3) increase the amount of water, cement or mixed amount of â…¡, â…¢ fly ash. (4) The use of graded gravel, and needle-shaped content of small. (5) to improve the performance of concrete admixtures, so that it has a better water retention, thickening, or appropriate to reduce the amount of concrete admixture (only on-site), mixing station if you reduce the amount of concrete admixtures, concrete collapse may occur New problem of rapid drop loss. 3 pumping concrete appears to grasp the bottom or the reasons for knot and solution 3.1 Causes (1) severe bleeding concrete prone to scratch or board knot (stick pan). (2) large amount of cement concrete prone to grasp the phenomenon. (3) large amount of concrete admixture tend to grasp the phenomenon of concrete. (4) sand rate is small, concrete prone to plate junction phenomenon. (5) Concrete admixture High water reduction rate, high bleeding rate, water retention, thickening, poor air entrainment effect of concrete prone to catch the bottom or the phenomenon of compaction. 3.2 solutions (1) to reduce water consumption per unit. (2) improve sand rate. (3) Addition of appropriate amount of admixture such as fly ash, reduce the amount of cement. (4) reduce the amount of concrete admixture. (5) increase the air admixture admixture, thickening, water retention. 4 pumping concrete slump loss causes and solutions 4. 1 reasons (1) concrete admixture and poor cement caused by slump loss loss. (2) The amount of concrete admixture is not enough, retarding, plastic preservation effect is not satisfactory. (3) the weather is hot, some admixtures fail at high temperature; the water evaporates quickly; the bubble spill causes the quick loss of fresh concrete slump. (4) The initial concrete slump is too small, the unit water consumption is too small, resulting in cement gypsum hydration is not enough solubility; In general, sl0 ≥ 20cm concrete slump loss is slow, otherwise, fast. (5) In general, the order of slump loss is: high alumina cement> Portland cement> ordinary portland cement> slag Portland cement> admixture cement. (6) The coordination of construction site and mixing plant is not good, pressure car, traffic jam time is too long, resulting in excessive loss of concrete slump. 4.2 solution (1) adjust the concrete admixture formula to make it compatible with the cement. Before construction, be sure to do concrete admixture and cement adaptability test. (2) adjust the concrete mix to improve the sand rate, water consumption, the concrete initial slump adjusted to 20cm above. (3) Add appropriate amount of fly ash instead of part of the cement. (4) increase the amount of concrete admixture appropriate amount (especially when the temperature is much higher than usual). (5) to prevent excessive evaporation of water, the bubble spilled too fast. (6) the choice of slag cement or pozzolanic cement. (7) to improve the water truck, cooling device. 5 reasons for the pump concrete plugging tube and solution 5. 1 reasons (1) poor workability of concrete, segregation, concrete scattered. (2) Concrete mixture slump small (dry sticky). (3) Concrete mix to grasp the bottom, plate knot. (4) The use of single-gravel, stone size is too large, pumping pipe diameter is small. (5) Stone needle-shaped and more. (6) pump pressure is not enough, or the pipeline seal is not tight. (7) less cementitious material, low sand rate. (8) Too many bends. (9) Foreign body tube is not removed. (10) When mixing concrete, uneven, cement is not loose into a grout. (11) The first pump without concrete mortar before the pump wall. 5.2 solution (1) check the tightness of concrete pipelines and pump performance, make it in good working condition. (2) Check the piping layout to minimize elbows, especially elbows ≤90 °. (3) Before pumping concrete, be sure to lubricate the pipe with mortar. (4) Check the stone size, grain shape is in line with norms, pumping requirements. (5) check the workability of the concrete mixture into the pump, the sand rate is suitable, with or without large cement block, the mixture is bleeding, catching the bottom or plate knot phenomenon, if so, to take appropriate measures See concrete bleeding, segregation problems). (6) check the pump into the concrete slump, cohesive enough, if the slump enough, then increase the amount of concrete admixture, or into the pump at the appropriate amount of superplasticizer, if the concrete Insufficient cohesion, then increase the amount of sand or appropriate amount of grade â…¡ mixed fly ash. (7) Check whether the concrete initial slump ≥ 20cm, if the concrete slump loss caused by concrete blocking pumping phenomenon, you should first solve the problem of concrete loss (see slump loss problem).