High-performance long-distance pumping concrete and preparation method thereof

Abstract

The invention belongs to the technical field of building material production, and discloses high-performance long-distance pumping concrete and a preparation method thereof. According to the ratio calculated according to the specification, the concrete components are obtained through orthogonal regression calculation. The concrete components comprise 290 to 360 parts of cement, 690 to 730 parts of sand, 1000 to 1050 parts of broken stone, 140 to 210 parts of mineral admixture, 4.3 to 5.5 parts of water reducing agent and 152 to 163 parts of water. A compound admixture prepared from sodium gluconate, cane sugar, sodium hexametaphosphate, boric acid, sodium fluosilicate and glycerol is added into concrete, so that the concrete has excellent flowability, slump retaining property and mechanical property, the long-distance pumping performance is remarkably improved, and the problem of pipe blockage is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building material production, in particular to a high-performance long-distance pumping concrete and a preparation method thereof. BACKGROUND

[0002] In building construction, concrete pumping construction technology as one of the important construction technologies, its construction process and technical requirements are increasingly high. The commercial concrete is transported to the pumping construction site by the concrete tank truck, and then the concrete is transported to the specified pouring height and pouring site along the pumping pipeline through pumping, the concrete pumping technology greatly improves the construction efficiency of concrete pouring, therefore the concrete must have good fluidity, high cohesiveness, slump retention, and the ability to resist segregation and bleeding. High-performance concrete, as a new building material, has the characteristics of high compressive strength, high stiffness, high density and low porosity, and is widely used in high-rise buildings, large-span bridges and some high-demand special buildings.

[0003] Concrete is widely used as a structural material in bridge and building structures, and pumping concrete is one of the most important key technologies in building structure construction. In actual concrete pumping construction, high-pressure, long-distance and long-time concrete pouring is required using a concrete pumping system. Since concrete is a non-homogeneous, multi-phase composite material, under the action of pumping, the pumping changes the rheological properties of the pumped concrete and the spatial position of the aggregate, which changes the rheological properties and fluidity of the concrete in the pipe, easily leading to pipe blockage, which directly affects the construction quality and construction progress, and the durability and strength of the bridge and building structure are relatively high, so high-performance concrete needs to be used to meet the requirements.

[0004] The incorporation of admixtures can greatly increase the fluidity of concrete, and can also delay the hydration reaction inside the concrete, so that the pumped concrete has good slump retention. However, the admixture content and the slump retention of the concrete show a nonlinear relationship, and the performance cannot reach the effect if the content is insufficient, and the content is too large not only delays the demolding time, but also hinders the early hydration of cement, resulting in a decrease of more than 30% in 7-day strength, and if the retardation exceeds 72 hours, it may also cause permanent strength loss. Therefore, the admixture needs to be improved by re-doping, taking into account the mechanical properties and working properties.

[0005] The existing high-performance concrete strength has met the demand, but it is still difficult to consider its pumpability and fluidity, so now a new design method for pumped concrete is needed, and the admixture is mixed by re-doping to adapt to the high-performance concrete, so that the high-performance concrete not only has good working properties and mechanical properties, but also prevents the phenomenon of pipe blockage during pumping, ensures that the mechanical properties and durability of the poured structure meet the design requirements, and at the same time takes into account the economic benefits and reduces the production cost. SUMMARY

[0006] In view of the defects of the prior art, the present application provides a high-performance long-distance pumping concrete and a preparation method thereof, through reasonable design, the concrete has good fluidity, slump retention and anti-segregation performance, and the compressive strength can also reach the design strength, so that the concrete is easy to pump and meets the use requirements.

[0007] The technical scheme adopted by the present application to solve the above problems is:

[0008] The present application provides a high-performance long-distance pumping concrete, comprising the following components in parts by weight:

[0009] Cement: 290-360 parts;

[0010] Sand: 690-730 parts;

[0011] Gravel: 1000-1050 parts;

[0012] Mineral admixture: 140-210 parts;

[0013] Water reducing agent: 4.3-5.5 parts;

[0014] Compound admixture: 0.265-0.298 parts;

[0015] Water: 152-163 parts;

[0016] The components of the compound admixture include sodium gluconate, sucrose, sodium hexametaphosphate, boric acid, sodium fluorosilicate and glycerol; the mass ratio of the sodium gluconate, sucrose, sodium hexametaphosphate, boric acid, sodium fluorosilicate and glycerol is 15:18:22:4:1.8:6; the organic substances are adsorbed on the surface of cement particles in the form of a hydration film through (sodium gluconate, sucrose, glycerol), and can also form unstable complexes with calcium ions to delay the reaction of and at the initial stage of hydration, and sodium hexametaphosphate can greatly promote the dispersion of the slurry, so that the viscosity of the slurry is reduced, and sodium fluorosilicate can stimulate , so as to compensate for the early strength. The combination of these can make the high-performance concrete maintain good fluidity for a long time, greatly improve the slump retention, and will not affect the early strength.

[0017] The mineral admixture comprises the following components in parts by weight: 70-100 parts of mineral powder, 10-20 parts of silica fume, 50-80 parts of fly ash, and 0-40 parts of microbeads. The fly ash, mineral powder and silica fume can be used to replace the cement for mixing concrete. Since the size and performance of the three components are different, the hydration reaction rates are different, and thus the early strength of the concrete is different. The microbeads are mixed into the above three mineral admixtures by replacing the cement in the same volume. When the four components are used together, the particle size distribution in the concrete can be improved, the particle packing of the whole concrete is more compact and reasonable, the workability of the concrete mixture and the structure of the hardened concrete are improved, the concrete has good fluidity and high mechanical properties, and the loss during pumping is reduced.

[0018] Further, the water reducing agent is a polycarboxylic acid water reducing agent.

[0019] Further, the preparation method of the complex admixture includes the following steps:

[0020] (1) The sodium fluosilicate, sodium gluconate, sucrose and boric acid are pretreated to make the particle size of each component meet the requirements, and the glycerol is preheated to 40 DEG C;

[0021] (2) Step-by-step premixing, the sodium fluosilicate is added into the glycerol and ultrasonically dispersed at 40 DEG C for 15 min to obtain A liquid; the sodium hexametaphosphate and sodium molybdate are dissolved in water at 40 DEG C to obtain B liquid; the glycerol and defoaming agent are high-speed emulsified for 5 min to obtain C liquid;

[0022] (3) In a double-cone mixer, the sodium gluconate, sucrose and boric acid are first stirred for 15 min, then the C liquid is added and mixed for 8 min, then the B liquid is added and mixed for 10 min, finally the atomized mixed liquid A liquid is added and stirred and mixed for 15 min to obtain the finished product, and the material temperature is kept ≤ 35 DEG C throughout the process;

[0023] (4) Finally, nitrogen is flushed and sealed, and stored in the dark at 10-25 DEG C.

[0024] Further, the defoaming agent in step (2) is a polyether defoaming agent.

[0025] The application also provides a preparation method of the high-performance long-distance pumping concrete, which comprises the following steps:

[0026] Step one, the cement, sand and gravel are weighed and put into a mixer and stirred for 1 min;

[0027] Step two, the mineral powder, silica fume, fly ash and microbeads are added and continue to stir for 2 min;

[0028] Step three, after mixing water, water reducing agent and complex admixture evenly, add half into the mixer and stir for 1 min;

[0029] Step four, add the remaining mixture of step three into the mixer and stir for 1.5 min, to obtain a high-performance long-distance pumping concrete.

[0030] The present application has the following beneficial effects:

[0031] 1. A reference mix ratio is obtained by standard calculation, and the data obtained by orthogonal regression analysis is used to reasonably design the reasonable amount of each material in the concrete, so that the performance of each material is fully utilized, the mixed and stirred concrete has good flow performance, excellent mechanical properties and durability, can meet the pumping demand on site, and also meets the design requirements of the building.

[0032] 2. The present application adjusts a special admixture, which not only has the effect of water reducing, but also can improve the slump retention of high-performance long-distance pumping concrete, so that it maintains good fluidity for a long time, and the sensitivity of the admixture content to the performance of the concrete is reduced, and through the synergistic effect of organic and inorganic functional additives, the early strength loss of the concrete caused by retardation is compensated, so that the controllability of the working performance of the concrete is guaranteed, the pipe blocking phenomenon of long-distance pumping concrete is largely avoided, and the initial setting strength of the concrete is not affected. DETAILED DESCRIPTION

[0033] The preparation method of the complex admixture used in the following examples is as follows:

[0034] (1) The sodium fluorosilicate, sodium gluconate, sucrose and boric acid are pretreated to meet the required particle size, the glycerol is preheated to 40℃, the sodium fluorosilicate is crushed through a 325 mesh sieve, and the sodium gluconate, sucrose and boric acid are crushed through a 200 mesh sieve.

[0035] (2) Step 1: preparation of sodium fluorosilicate safety premix solution (premix solution A)

[0036] Take 0.90 kg of glycerol and then add 0.90 kg of sodium fluorosilicate, ultrasonic dispersion at a frequency of 40 kHz, 40℃ water bath, dispersion for 15 min, end point: no visible particles, white homogeneous liquid, total weight 1.80 kg of premix solution A.

[0037] Step 2: preparation of sodium hexametaphosphate stabilizing solution (solution B)

[0038] Sodium hexametaphosphate 11.00 kg and sodium molybdate 0.75 kg were poured into 40 °C deionized water 5.00 L, the magnetic stirring speed was 800 rpm, the temperature was maintained at 40 °C, the time was 30 min, the end point: the solution was transparent without precipitation, pH = 6.0-6.5. The total weight of solution B was 16.75 kg.

[0039] Step 3: Preparation of defoaming glycerol (liquid C)

[0040] Take glycerol 2.10 kg, add polyether defoamer 1.50 kg, then high-speed shear emulsification in a high-shear emulsifier at a speed of 10,000 rpm for 5 min, the end point: foam disappears, the liquid is light yellow and homogeneous, the total weight of liquid C is 3.60 kg.

[0041] (3) Main mixing process, in a 50 L stainless steel double-cone mixer,

[0042] The specific operation is as follows:

[0043] 1. Dry powder mixing stage (15 min)

[0044] Feed: sodium gluconate 7.50 kg + sucrose 9.00 kg + boric acid 2.00 kg

[0045] Parameters: speed 15 rpm, jacket water temperature ≤ 25 °C

[0046] End point: uniform color of powder (gray-white)

[0047] 2. Wet mixing stage (8 min)

[0048] Spray liquid C (3.60 kg)

[0049] Parameters: speed 30 rpm, spraying rate 200 g / min

[0050] End point: no dry powder agglomeration, wet granular

[0051] Solution mixing stage (10 min)

[0052] Pump in solution B (16.75 kg)

[0053] Parameters: speed 45 rpm, jacket cooling water (material temperature ≤ 35 °C)

[0054] End point: material is a sticky paste

[0055] Final mixing stage (15 min)

[0056] Atomized spray into premix A (1.80 kg)

[0057] Parameters: rotation speed 20 rpm, atomization pressure 0.3 MPa

[0058] End point: paste turns into loose particles (light yellow)

[0059] (4) Finally, the finished product is sealed and packaged in an iron drum and stored in the dark at 10-25°C.

[0060] Uniformity test and solubility verification are carried out. Five samples are taken to measure the sodium gluconate content, and the relative standard deviation (RSD) is ≤3%. 1 g of the mixture is added to 100 ml of water, stirred for 3 min, and then observed for no precipitation. The prepared sample is qualified;

[0061] Test the difference in setting time:

[0062] Reference concrete: P·O 42.5 cement 400 g, water 180 g, ISO standard sand 1350 g

[0063] Test group: reference concrete + 0.03% retarder (based on the mass of the glue material)

[0064] Initial setting time difference: +3.0-6.0 h (actual measurement: +4.5 h)

[0065] Final setting time difference: +4.0-8.0 h (actual measurement: +6.2 h)

[0066] 3d strength loss rate: ≤10% (actual measurement: -6.3%)

[0067] The ideal range is an initial setting time extension of 2-6 h and a final setting time extension of 3-8 h.

[0068] The prepared sample meets the use requirements.

[0069] The following examples use cement: Portland cement 52.5; sand: river sand, particle size 0.15-4.75 mm, graded II zone medium sand; crushed stone: particle size 5-10 mm and 10-20 mm diabase; polycarboxylic acid water reducer: HLX (standard type) polycarboxylic acid high-performance water reducer, color: transparent or light yellow.

[0070] The sample specifications used in each example are shown in Table 3.

[0071] Example 1: The preparation steps of a high-performance long-distance pumping concrete are as follows:

[0072] Step one, weigh 320 kg of cement, 710 kg of river sand, and 1030 kg of crushed stone as shown in Table 3, and put them into a mixer and stir for 1 min;

[0073] Step two, add 85 kg of mineral powder, 60 kg of fly ash, 20 kg of microbeads with a particle size of 2 μm, 15 kg of silica fume, and continue stirring for 2 min;

[0074] Step three, mix 158 kg of water, 5.2 kg of polycarboxylate superplasticizer, and 0.282 kg of complex admixture evenly, then add half of the mixture into the mixer and stir for 1 min;

[0075] Step four, add the remaining half of the mixture into the mixer and stir for 1.5 min to obtain a high-performance long-distance pumping concrete.

[0076] Example 2: Preparation of a high-performance long-distance pumping concrete, which is different from Example 1 in terms of component composition and content, as shown in Table 3.

[0077] Example 3: Preparation of a high-performance long-distance pumping concrete, which is different from Example 1 in terms of component composition and content, mainly the content of microbeads is 40 kg / m³, and the content of complex admixture is also increased, and other components are shown in Table 3.

[0078] Example 4: Preparation of a high-performance long-distance pumping concrete, which is different from Example 1 in terms of component composition and content, mainly the content of fly ash is 65 kg / m³, and other components are shown in Table 3.

[0079] Example 5: Preparation of a high-performance long-distance pumping concrete, which is different from Example 1 in terms of component composition and content, mainly the content of microbeads is 15 kg / m³, and other components are shown in Table 3.

[0080] Table 3: Components and their weight fractions of high-performance long-distance pumping concrete in Examples 1-5

[0081]

[0082] Comparative Example

[0083] Comparative Example 1: A concrete, which is different from Example 1 in terms of, as shown in Table 4.

[0084] Comparative Example 2: A concrete, which is different from Example 2 in terms of, as shown in Table 4.

[0085] Comparative Example 3: A concrete, which is different from Example 3 in terms of, as shown in Table 4.

[0086] Comparative Example 4: A concrete, which is different from Example 4 in terms of, as shown in Table 4.

[0087] Comparative Example 5: A concrete, which is different from Example 5 in terms of, as shown in Table 4.

[0088] Table 4: Components of the concrete in Comparative Examples 1-5 and their weight fractions.

[0089]

[0090] The performance of the concrete in Examples 1-5 and Comparative Examples 1-5 was tested, and the results are shown in Tables 5 and 6. The testing methods used for the concrete prepared in each of the above examples and comparative examples are as follows:

[0091] Test 1: Slump and T500 test

[0092] Test method: The slump of the high performance long distance pumping concrete prepared in Examples 1-5 and Comparative Examples 1-5 when it comes out of the machine and the time required for the development of the slump to 500 mm were measured according to the specifications in GB / T 50080 “Standard Test Methods for Testing Performance of Ordinary Concrete Mixtures”.

[0093] Test 2: Compressive strength test

[0094] Test method: The concrete mixtures in Examples 1-5 and Comparative Examples 1-5 were made into concrete test blocks, and the 3d and 28d compressive strengths (MPa) of the concrete were detected according to the compressive strength test in GB / T 50081-2002 “Standard Test Methods for Mechanical Properties of Ordinary Concrete”.

[0095] Test instrument: Universal testing machine

[0096] Table 5: Performance test results of the high performance long distance pumping concrete in Examples 1-5

[0097]

[0098] Table 6: Performance test results of the concrete in Comparative Examples 1-5

[0099]

[0100] Comparing the test results of the examples and comparative examples in Tables 5 and 6, the comparative examples showed a 12%-19% decrease in strength, a 10%-18% decrease in workability, and a maximum deviation of over 300% in the setting time of mechanical properties. Without microspheres, the ball-bearing effect of the microspheres was lost, resulting in a 210% increase in slurry viscosity, an increase in the pouring time from 8 seconds to 22 seconds, and an increased risk of pipe blockage. The absence of fly ash increased the internal pore connectivity of the concrete, leading to a collapse in its chloride resistance. Increased cement content resulted in accelerated hydration and earlier initial setting. The absence of mineral powder meant the interfacial transition zone (ITZ) was not strengthened, the secondary hydration effect disappeared, and early strength was halved. The absence of sucrose reduced the slurry cohesion from 4.8 Pa to 1.2 Pa, causing uncontrolled aggregate settlement. Insufficient microspheres implicitly increased the actual water-cement ratio by 0.03, increased cement hydration by 17%, and caused the temperature peak to exceed the safety threshold. Any change in components resulted in a strength loss >10%, leading to engineering risks. The 3-hour slump loss in the examples was <6%, making them suitable for long-distance pumping, while the loss rate in the comparative examples exceeded 38%.

[0101] The compound admixture of this invention achieves long-lasting slump retention, no strength loss, and optimized pumping at extremely low dosages (0.265~0.298 parts) through the synergistic effect of organic retarder components (sodium gluconate, sucrose, glycerol) and inorganic functional components (sodium hexametaphosphate, boric acid, sodium fluorosilicate). The organic components adsorb cement particles to form a hydration film, delaying the slump. Hydration ensures that the slump retention rate of concrete is >94% after 3 hours; sodium fluorosilicate activation... Hydration compensates for early strength, and sodium hexametaphosphate dispersion reduces viscosity, enabling a 3-day compressive strength of over 45 MPa. The compound system reduces concrete sensitivity, significantly improves the smoothness of long-distance pumping, and eliminates the risk of pipe blockage. The "retardation-strengthening-viscosity reduction" three-in-one mechanism overcomes the technical contradiction of the incompatibility between "slump retention, early strength, and fluidity" in pumped concrete.

[0102] The mix design and orthogonal test yielded a high-performance long-distance pumpable concrete mix ratio. Then, admixtures were added to synergistically complement the concrete's performance, taking into account both workability and mechanical properties. The mechanical properties met the design requirements, and the workability also met the requirements for smooth pumping.

[0103] In this invention, the admixture is prepared from sodium gluconate, sucrose, sodium hexametaphosphate, boric acid, sodium fluorosilicate, and glycerol. Its main function is to improve the fluidity and slump retention of concrete, allowing it to maintain a flowing state for a longer period during pumping and preventing pipe blockage caused by excessively rapid setting. Simultaneously, the admixture also enhances the mechanical properties of the concrete, ensuring it maintains good strength and durability during long-distance transportation, greatly improving the operability and stability of long-distance concrete pumping and significantly reducing the risk of pipe blockage.

Claims

1. A high performance long distance pumping concrete, characterized in that, The components include the following weight parts: Cement: 290-360 parts; Sand: 690-730 parts; Gravel: 1000-1050 parts; Mineral admixture: 140-210 parts; Water reducing agent: 4.3-5.5 parts; Compound admixture: 0.265-0.298 parts; Water: 152-163 parts; The components of the compound admixture include sodium gluconate, sucrose, sodium hexametaphosphate, boric acid, sodium fluorosilicate and glycerol; the mass ratio of the sodium gluconate, sucrose, sodium hexametaphosphate, boric acid, sodium fluorosilicate and glycerol is 15:18:22:4:1.8:6; The mineral admixture includes the following components by weight: mineral powder 70-100 parts, silica fume 10-20 parts, fly ash 50-80 parts, microbeads 0-40 parts.

2. A high performance long distance pumping concrete according to claim 1, characterized in that, The water reducing agent is a polycarboxylic acid water reducing agent.

3. A high performance long distance pumping concrete according to claim 1, wherein The preparation method of the compound admixture includes the following steps: (1) first pretreat sodium fluorosilicate, sodium gluconate, sucrose and boric acid so that the particle size of each component meets the requirements, and preheat glycerol to 40℃; (2) stepwise premixing, adding sodium fluorosilicate into glycerol, ultrasonic dispersing at 40℃ for 15 min to obtain A liquid; dissolving sodium hexametaphosphate and sodium molybdate in 40℃ water to obtain B liquid; high-speed emulsifying glycerol and defoaming agent for 5 min to obtain C liquid; (3) in a double-cone mixer, first add sodium gluconate, sucrose and boric acid to stir for 15 min, then add C liquid to mix for 8 min, then add B liquid to mix for 10 min, finally add atomized mixing liquid A to stir and mix for 15 min to obtain the finished product, and the material temperature is kept ≤35℃ throughout the process; (4) finally, flush with nitrogen, seal and store in the dark at 10-25℃.

4. A high performance long distance pumping concrete according to claim 3, wherein The defoaming agent in step (2) is a polyether defoaming agent.

5. A high performance long distance pumping concrete according to claim 1, wherein The preparation method includes the following steps: Step one, weigh the cement, sand and gravel and put them into the mixer to stir for 1 min; Step two, add mineral powder, silica fume, fly ash and microbeads and continue to stir for 2 min; Step three, mix water, water reducing agent and compound admixture uniformly, then add half of them into the mixer to stir for 1 min; Step four, add the remaining mixture of step three into the mixer to stir for 1.5 min to obtain a high-performance long-distance pumping concrete.

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