Steam-cured high-performance concrete for prestressed steel cylinder concrete jacking pipe as well as mix proportion design method and preparation method of steam-cured high-performance concrete

Abstract

The invention discloses steam-cured high-performance concrete for a prestressed steel cylinder concrete jacking pipe as well as a mix proportion design method and a preparation method of the steam-cured high-performance concrete, and belongs to the technical field of high-performance concrete. Based on the MAA model considering the particle size of the coarse aggregate and the least square method, the volume mixing amount of the coarse aggregate can be obtained, and then based on the set volume ratio of the cement to the auxiliary cementing material in the cementing material and the set volume ratio of the cementing material to the fine aggregate, the mixing ratio of the cement to the auxiliary cementing material to the fine aggregate to the coarse aggregate is obtained. According to the mix proportion design method, reference can be provided for the formula design of the existing steam-curing type high-performance concrete for the prestressed steel cylinder concrete jacking pipe, the experimental process is simplified, the obtained concrete has excellent mechanical property and durability, the 28d compressive strength can reach 120 MPa or above, the 28d breaking strength can reach 10 MPa or above, and the impermeability grade is larger than P12.

Description

Technical Field

[0001] The present invention relates to the technical field of high-performance concrete, and particularly to a steam-cured high-performance concrete for prestressed concrete cylinder pipes for jacking, and a mix ratio design method and a preparation method thereof. Background Art

[0002] The information disclosed in the background art of the present invention is only intended to increase the understanding of the overall background of the present invention, and is not necessarily regarded as an admission or an indication in any form that this information constitutes the prior art that has become well-known to those skilled in the art.

[0003] As a key component of modern water conveyance and regulation projects, Jacking Prestressed Concrete Cylinder Pipe (J-PCCP for short) is widely used in fields such as municipal water supply and drainage, and long-distance water conveyance projects. With the increasing complexity of the engineering environment, J-PCCP not only needs to bear complex mechanical loads such as axial jacking force and internal water pressure, but also has to withstand the adverse environmental effects such as freeze-thaw cycles, chemical erosion, and uneven settlement of the foundation, which puts forward higher performance requirements for the core concrete material.

[0004] The traditional J-PCCP core usually uses ordinary C50 concrete, and has the following technical defects: (1) Insufficient mechanical properties, it is difficult to meet the strength requirements under the conditions of large diameter and deep overburden, and the strength is difficult to meet the requirements of long-distance continuous jacking construction; (2) Poor durability, the impermeability grade can usually only reach P8-P10, the frost resistance grade is between F150-F200, and the chloride ion diffusion coefficient ≥ 5×10 -12 m 2 / s, it is difficult to meet the working performance under harsh environments; (3) Poor volume stability, temperature cracks are easily generated under steam curing conditions; (4) Poor bulk density, there are holes in the core and the protective layer, affecting the appearance of the pipeline.

[0005] Mix proportion design is a key link to ensure that high-performance concrete (HPC) achieves the expected performance. At present, there are not many studies on the mix proportion design of high-performance concrete for J-PCCP. The mix proportion design of concrete still mainly relies on experiments and experience, which may lead to the inefficient utilization of various materials in high-performance concrete (HPC). In addition, the existing mix proportion design often only considers the particle size of cementitious materials and fine aggregates, without considering the particle size of coarse aggregates, which will result in: (1) Aggravation of the weak interface area: Microcrack-rich ITZ is easily formed on the surface of large-sized coarse aggregates, reducing the impermeability and crack resistance of concrete; (2) Insufficient packing density: The large particle size of coarse aggregates leads to an increase in the void ratio between particles, and additional paste needs to be added for filling, affecting economy; (3) Poor workability: The poor matching between the particle size of coarse aggregates and the viscosity of mortar is likely to cause segregation or an increase in pumping resistance.

[0006] Therefore, it is an urgent problem to provide a mix proportion design method for steam-cured high-performance concrete considering the most compact packing theory of coarse aggregate particle size, and to provide a steam-cured high-performance concrete for prestressed concrete cylinder pipe jacking with good mechanical properties, durability and economy. Summary of the Invention

[0007] In view of this, the present invention provides a steam-cured high-performance concrete for prestressed concrete cylinder pipe jacking, its mix proportion design method and preparation method. The mix proportion design method provided by the present invention can quickly obtain the appropriate proportions of each component, and at the same time, the provided steam-cured high-performance concrete has good mechanical properties and durability, and high economy.

[0008] In the first aspect, the present invention provides a mix proportion design method for steam-cured high-performance concrete for prestressed concrete cylinder pipe jacking, including the following steps:

[0009] (1) Determine the particle size distributions of cementitious materials, fine aggregates and coarse aggregates, wherein the particle size of the coarse aggregates is 5-10 mm; the cementitious materials include cement and supplementary cementitious materials;

[0010] (2) According to the maximum particle size and minimum particle size of the particles determined in step (1), obtain the cumulative passing percentage P(D) under each set sieve pore based on formula ①, and obtain the target packing curve based on the MAA model;

[0011]

[0012] wherein, D is the particle size; P(D) represents the cumulative percentage of particles smaller than the particle size D; D max and D min are the maximum particle size and minimum particle size respectively; q is the particle size distribution modulus, and q takes 0.20-0.25;

[0013] (3) Based on the particle size distributions of the cementitious material, fine aggregate, and coarse aggregate determined in step (1), using the least squares method, a computer software is employed to fit the mixture packing curve, obtaining the volume ratios of the cementitious material, fine aggregate, and coarse aggregate, and further obtaining the volume admixture of the coarse aggregate.

[0014] The calculation formula of the least squares method is as shown in formula ②:

[0015]

[0016] where s s is the sum of squared residuals, P mix and P MAA respectively refer to the mixture packing curve and the target packing curve, and n is the number of calculation points of the packing curve.

[0017] (4) Set the volume ratio of cement to supplementary cementitious material in the cementitious material to (55 - 65):(35 - 45), and set the volume ratio of the cementitious material to the fine aggregate to 0.5 - 0.6; according to the volume admixture of the coarse aggregate calculated in step (3), calculate the mix proportion of cement, supplementary cementitious material, fine aggregate, and coarse aggregate.

[0018] In the second aspect, the present invention provides a steam-cured high-performance concrete for prestressed concrete cylinder pipe (PCCP) obtained based on the above mix proportion design method, the raw materials of which include cement, supplementary cementitious material, fine aggregate, coarse aggregate, water reducer, and water. Among them, the volume ratio of cement, supplementary cementitious material, fine aggregate, and coarse aggregate is (15 - 18):(10 - 12):(45 - 55):(20 - 25), the water-binder ratio is 0.18 - 0.22, and the mass of the water reducer is 1.0 - 1.5 wt% of the total mass of cement and supplementary cementitious material.

[0019] In the third aspect, the present invention provides a preparation method of the above steam-cured high-performance concrete for prestressed concrete cylinder pipe (PCCP), including the following steps:

[0020] Pour the weighed coarse aggregate and fine aggregate into a mixer for dry mixing, and then add cement and supplementary cementitious material and continue dry mixing to obtain a dry mixture.

[0021] Mix the water reducer and water evenly and add them to the dry mixture, and obtain a mixed material after mixing.

[0022] Pour the mixed material into a mold, and then cover the molded specimen with a film and perform steam curing for 3 - 6 h, and the temperature of steam curing is 50 - 80 °C, thus obtaining the steam-cured high-performance concrete for prestressed concrete cylinder pipe (PCCP).

[0023] Compared with the prior art, the present invention has achieved the following beneficial effects:

[0024] (1) The present invention incorporates the particle size range of coarse aggregate (5 - 10 mm continuous grading) into the target packing curve for constructing the MAA model. Through the particle size distribution modulus q, the contribution degree of the coarse aggregate particle size range to dense packing is quantified. This method can consider the influence of the coarse aggregate particle size range, and the dosage of coarse aggregate calculated by the most dense packing theory can be directly used as the volume admixture ratio of the steam-cured high-performance concrete finally used for prestressed concrete cylinder pipe jacking. The present invention has verified through experiments that the volume admixture of coarse aggregate obtained by this method is beneficial to obtaining high-performance concrete with optimal mechanical properties and durability, and can provide reference for the formula design of the existing steam-cured high-performance concrete used for prestressed concrete cylinder pipe jacking, simplifying the test process.

[0025] (2) The present invention limits the cement dosage to avoid the problem that the performance of the steam-cured high-performance concrete is poor due to too low cement content in the obtained theoretical mix ratio. The steam-cured high-performance concrete used for prestressed concrete cylinder pipe jacking obtained according to the provided mix ratio design method has excellent mechanical properties and durability. The 28-day compressive strength can reach above 120 MPa, the 28-day flexural strength can reach above 10 MPa, the impermeability grade is greater than P12, and at the same time, the cost is low, having good economy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The accompanying drawings forming a part of this invention are used to provide a further understanding of the present invention. The schematic embodiments and descriptions thereof of the present invention are used to explain the present invention and do not constitute an improper limitation to the present invention. Obviously, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0027] Figure 1 is the particle size distribution diagram of each substance in the embodiment of the present invention;

[0028] Figure 2 is the target packing curve, mixture packing curve, and actual packing curve of Embodiment 1 and Comparative Examples 2 - 4 of the present invention;

[0029] Figure 3 is the target packing curve and actual packing curve of Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0030] It should be noted that the following detailed descriptions are all exemplary and are intended to provide further explanations of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0031] The present invention provides a method for designing the mix proportion of steam-cured high-performance concrete for prestressed concrete cylinder pipe jacking, comprising the following steps:

[0032] (1) Determine the particle size distribution of the cementitious material, fine aggregate and coarse aggregate, wherein the particle size of the coarse aggregate is 5 - 10 mm (continuous grading); the cementitious material includes cement and supplementary cementitious material;

[0033] (2) According to the maximum and minimum particle sizes of the particles determined in step (1), obtain the cumulative passing percentage P(D) under each set sieve pore based on formula ①, and obtain the target packing curve based on the MAA model;

[0034]

[0035] wherein, D is the particle size; P(D) is the cumulative percentage representing particles smaller than the particle size D; D max and D min are the maximum particle size and minimum particle size respectively; q is the particle size distribution modulus, and q takes 0.20 - 0.25;

[0036] (3) According to the particle size distribution of the cementitious material, fine aggregate and coarse aggregate determined in step (1), based on the least squares method, use computer software to fit the mixture packing curve, obtain the volume ratio of the cementitious material, fine aggregate and coarse aggregate, and further obtain the volume content of the coarse aggregate;

[0037] The calculation formula of the least squares method is as shown in formula ②:

[0038]

[0039] wherein, S s is the sum of squared residuals, P mix and P MAA refer to the mixture packing curve and the target packing curve respectively, and n is the number of calculation points of the packing curve;

[0040] (4) Set the volume ratio of cement to supplementary cementitious material in the cementitious material to (55 - 65):(35 - 45), and set the volume ratio of the cementitious material to the fine aggregate to 0.5 - 0.6; according to the volume content of the coarse aggregate calculated in step (3), calculate the mix proportion of cement, supplementary cementitious material, fine aggregate and coarse aggregate.

[0041] The present invention first uses the MAA model (Modified Andreasen and Andersen model) to accurately calculate the target packing curve in the state of the densest packing. In this process, the present invention takes into account the influence of coarse aggregate on the packing density and establishes the theory of the densest packing of its continuous gradation. The prior art generally only considers the particle sizes of the cementitious material and fine aggregate, and there is no report on the influence of the values obtained by considering the particle size of the coarse aggregate on the actual mix design and concrete performance. The present invention discovers that when the particle size of the coarse aggregate is considered, the dosage of the coarse aggregate in the mix ratio calculated by the least squares method has the optimal performance in the actual concrete design. In the present invention, the particle size range of the coarse aggregate is 5 - 10 mm. If the particle size of the coarse aggregate is too large, it will lead to the aggravation of the weak interface zone, insufficient packing density and poor construction performance. Therefore, the present invention sets its particle size to 5 - 10 mm.

[0042] In addition, the present invention discovers that in the calculated mix ratio, the volume dosage of cement is significantly low and cannot exhibit good performance in actual application. Therefore, the present invention sets the volume ratio of cement to the supplementary cementitious material to (55 - 65):(35 - 45), and sets the volume ratio of the cementitious material to the fine aggregate to 0.5 - 0.6. With the volume dosage of the coarse aggregate fixed, the final mix ratio is calculated. The present invention discovers that the actual packing curve of this mix ratio is close to the target packing curve, indicating a relatively dense packing state.

[0043] In the present invention, q takes 0.23.

[0044] The present invention places no special restrictions on the computer software used in the fitting process, and preferably uses MATLAB software.

[0045] In the present invention, the cement is ordinary Portland cement, and the type can be P.O.42.5 or P.O.52.5.

[0046] In the present invention, the fine aggregate is river sand, with a medium sand particle size and a fineness modulus of 2.3 - 3.0.

[0047] The present invention also provides steam-cured high-performance concrete for prestressed concrete cylinder pipe jacking obtained based on the above mix design method. Its raw materials include cement, supplementary cementitious material, fine aggregate, coarse aggregate, water reducer and water. Among them, the volume ratio of cement, supplementary cementitious material, fine aggregate and coarse aggregate is (15 - 18):(10 - 12):(45 - 55):(20 - 25), the water-binder ratio is 0.18 - 0.22, and the mass of the water reducer is 1.0 - 1.5 wt% of the total mass of cement and supplementary cementitious material.

[0048] In the present invention, the water-cement ratio refers to the mass ratio of water to the cementitious materials (cement + supplementary cementitious materials), and the mass of the cementitious materials can be obtained by calculation based on the densities and volume dosages of the components of the cementitious materials.

[0049] In the present invention, the supplementary cementitious materials include fly ash, slag powder, and silica fume, and the volume ratio of the fly ash, slag powder, and silica fume is (30 - 35):(24 - 28):(38 - 43). The present invention does not impose special restrictions on the above materials, and commonly used fly ash, slag powder, and silica fume in the art can be adopted.

[0050] The present invention does not impose special restrictions on the types of water reducers. For example, naphthalene-based water reducers or polycarboxylate-based water reducers can be adopted.

[0051] The steam-cured high-performance concrete for prestressed concrete cylinder pipe in the present invention comprises the following components in parts by mass: 460 - 530 parts of cement, 72 - 85 parts of slag powder, 70 - 83 parts of fly ash, 115 - 125 parts of silica fume, 800 - 900 parts of fine aggregate, 550 - 610 parts of coarse aggregate, 140 - 170 parts of water, and 8 - 12 parts of water reducer.

[0052] The present invention also provides a preparation method for the above-mentioned steam-cured high-performance concrete for prestressed concrete cylinder pipe, comprising the following steps:

[0053] Pour the weighed coarse aggregate and fine aggregate into a mixer for dry mixing, and then add the cement and supplementary cementitious materials and continue dry mixing to obtain a dry mixture;

[0054] Mix the water reducer and water evenly and add them to the dry mixture, and obtain a mixed material after mixing;

[0055] Pour the mixed material into a mold, and then cover the molded specimen with a film and perform steam curing for 3 - 6 h at a steam curing temperature of 50 - 80 °C, thus obtaining the steam-cured high-performance concrete for prestressed concrete cylinder pipe.

[0056] The present invention does not impose special restrictions on the above mixing method and time, as long as a uniformly mixed material can be obtained.

[0057] The technical solution of the present invention will be further elaborated below in conjunction with specific embodiments. In the following embodiments, the densities of cement, fly ash, slag powder, silica fume, river sand, and crushed stone are approximately 3000 kg / m 3 、2100 kg / m 3 、2800 kg / m 3 、2700 kg / m 3 、1700 kg / m 3 and 2650 kg / m 3 ; the particle size distributions of the various substances are asFigure 1 As shown in the figure. Ordinary Portland cement P.O.42.5 is used for cement, medium sand is used for river sand, and the fineness modulus is 2.3 - 3.0.

[0058] Example 1

[0059] (1) Use a laser particle size distribution analyzer to measure the particle size distributions of cement, fly ash, ground granulated blast - furnace slag, silica fume, river sand and crushed stone. The particle size of the crushed stone is 5 - 10 mm;

[0060] (2) According to the maximum and minimum particle sizes of the particles determined in step (1), based on formula ①, obtain the cumulative passing percentage P(D) under each set sieve aperture, and obtain the target packing curve based on the MAA model; as shown by "Target curve - HPC" in Figure 2 ;

[0061]

[0062] Among them, D is the particle size; P(D) is the cumulative percentage representing particles smaller than the particle size D; D max and D min are the maximum particle size and the minimum particle size respectively; q is the particle size distribution modulus, and q takes 0.23;

[0063] (3) According to the particle size distributions of cement, fly ash, ground granulated blast - furnace slag, silica fume, river sand and crushed stone determined in step (1), based on the least - squares method, use MATLAB to fit and obtain the mixture packing curve, as shown by "Calculated curve - HPC" in Figure 2 ; obtain the volume ratio of cement, fly ash, ground granulated blast - furnace slag, silica fume, river sand and crushed stone as 0.05:0.15:0.06:0.09:0.42:0.22, and further obtain the volume content of coarse aggregate as 22%;

[0064] The calculation formula of the least - squares method is as shown in formula ②:

[0065]

[0066] Among them, S s is the sum of squared residuals, P mix and P MAA refer to the mixture packing curve and the target packing curve respectively, and n is the number of calculation points of the packing curve;

[0067] (4) Set the volume ratio of cement, fly ash, slag powder, and silica fume to 61:13:10:16, and set the volume ratio of the cementitious materials (cement, fly ash, slag powder, and silica fume) to river sand to 0.55. According to the coarse aggregate volume content (0.22) in step (3), calculate the volume ratio of cement, fly ash, slag powder, silica fume, river sand, and crushed stone to be 0.169:0.028:0.036:0.044:0.503:0.220. Draw the actual accumulation curve, as Figure 2 shown. It can be seen that the actual accumulation curve of this embodiment is close to the target curve - HPC and the calculated curve - HPC.

[0068] (5) According to the results of step (4), in the raw materials of the designed concrete, by mass fraction, it includes: 506.4 parts of cement, 77.6 parts of fly ash, 75.6 parts of slag powder, 119.6 parts of silica fume, 855.4 parts of river sand, 583.0 parts of crushed stone, 155.8 parts of water, and 9.4 parts of water reducer.

[0069] (6) First, pour the weighed crushed stone and river sand into the mixer and dry mix for 90 s to fully mix the aggregates and achieve uniform distribution. Subsequently, add the cementitious materials (including cement, fly ash, slag powder, and silica fume) and continue to mix for 90 s to ensure full mixing of the cementitious materials and the aggregates. During the mixing process, pour the water reducer into the pre-weighed water and stir evenly to form a water reducer solution. After the mixing of the cementitious materials and the aggregates is completed, slowly pour the water reducer solution into the mixer and continue to mix for 120 s to ensure the uniformity of the mixture. After the mixing is completed, pour the concrete mixture into the pre-prepared mold and vibrate and compact it on a vertical vibrating table to eliminate the air bubbles in the mixture and ensure the density and uniformity of the specimen. Cover the surface of the mold with the formed specimen with plastic wrap to prevent water evaporation and surface cracking. Finally, cure it in steam at 60 °C for 4 h to enhance the early strength.

[0070] Example 2

[0071] The difference between this embodiment and Example 1 is that steps (4) and (5) are different, specifically as follows:

[0072] (4) Set the volume ratio of cement, fly ash, slag powder, and silica fume to 58:14:11:17, and set the volume ratio of the cementitious materials (cement, fly ash, slag powder, and silica fume) to river sand to 0.53. According to the coarse aggregate volume content in step (3), calculate the volume ratio of cement, fly ash, slag powder, silica fume, river sand, and crushed stone to be 0.157:0.038:0.030:0.046:0.509:0.220.

[0073] (5) Based on the results of step (4), in the raw materials of the concrete, by volume parts, there are 471 parts of cement, 80.8 parts of fly ash, 84 parts of slag powder, 124.2 parts of silica fume, 865.3 parts of river sand, 583 parts of crushed stone, 152 parts of water, and 9.1 parts of water reducing agent.

[0074] Comparative Example 1

[0075] This comparative example uses the C50 ordinary concrete (QL-NC) currently used by Ningxia Qinglong Pipeline Co., Ltd. The raw materials are as follows: 405 parts of cement, 40 parts of slag powder, 710 parts of river sand, 480 parts of 5-10mm crushed stone, 641 parts of 10-20mm crushed stone, 133.5 parts of water (water-binder ratio is 0.3), and 5.3 parts of water reducing agent.

[0076] The target packing curve and the actual packing curve of QL-NC are as Figure 3 shown. It can be seen that there are significant differences between the target packing curve and the actual packing curve of QL-NC, indicating that its packing density is relatively low and it fails to reach the state of the densest packing.

[0077] Comparative Example 2

[0078] Compared with Example 1, in this comparative example, the volume ratio of the cementitious material to the river sand is kept unchanged, and the volume ratio of the cement to other auxiliary cementitious materials (fly ash, slag powder, and silica fume) is kept unchanged. The volume content of the crushed stone is adjusted to 12%, and the missing part is supplemented by other materials; that is, by mass parts, there are 571.5 parts of cement, 85.2 parts of fly ash, 87.4 parts of slag powder, 135 parts of silica fume, 965 parts of river sand, 318 parts of crushed stone, 175.8 parts of water, and 10.5 parts of water reducing agent. The actual packing curve of Comparative Example 2 is as Figure 2 shown. It can be seen that when the volume content of the coarse aggregate is further reduced to 12%, the packing density of the high-performance concrete begins to deviate from the target curve, indicating that too low a volume content of the coarse aggregate weakens the framework effect of the coarse aggregate and reduces the packing density.

[0079] Comparative Example 3

[0080] Compared with Example 1, in this comparative example, the volume ratio of the cementitious material to the river sand is kept unchanged, and the volume ratio of the cement to other auxiliary cementitious materials (fly ash, slag powder, and silica fume) is kept unchanged. The volume content of the crushed stone is adjusted to 32%, and the missing part is supplemented by other materials; that is, by mass parts, there are 441.3 parts of cement, 65.7 parts of fly ash, 67.5 parts of slag powder, 104 parts of silica fume, 746.3 parts of river sand, 848 parts of crushed stone, 135.7 parts of water, and 8.1 parts of water reducing agent. The actual packing curve of Comparative Example 3 is as Figure 2 shown. It can be seen that as the volume content of the coarse aggregate increases, the packing density of the high-performance concrete shows a trend of moving away from the target curve.

[0081] Comparative Example 4

[0082] Compared with Example 1, in this comparative example, the volume ratio of the gelling material and river sand is kept unchanged, and the volume ratio of cement and other auxiliary gelling materials (fly ash, slag powder, and silica fume) is also kept unchanged. The volume content of crushed stone is adjusted to 42%, and the missing part is supplemented with other materials; that is, by mass, 376.2 parts of cement, 56 parts of fly ash, 57.7 parts of slag powder, 88.8 parts of silica fume, 636.5 parts of river sand, 1113 parts of crushed stone, 115.8 parts of water, and 6.9 parts of water reducing agent. The actual accumulation curve of Comparative Example 4 is as shown in Figure 2 shown. It can be seen that as the content of coarse aggregate increases, the bulk density of the high-performance concrete shows a trend of moving away from the target curve.

[0083] Comparative Example 5

[0084] Compared with Example 1, in this comparative example, the volume ratio obtained in step (3) is adopted, that is, the volume ratio of cement, fly ash, slag powder, silica fume, river sand, and crushed stone is 0.05:0.15:0.06:0.09:0.42:0.22. That is, by mass, 150 parts of cement, 315 parts of fly ash, 168 parts of slag powder, 243 parts of silica fume, 714 parts of river sand, 583 parts of crushed stone, 175.2 parts of water, and 10.5 parts of water reducing agent.

[0085] The formulations of the high-performance concrete in Examples 1-2 and Comparative Examples 1-5 are shown in Table 1.

[0086] Table 1 Formulations of the high-performance concrete in Examples 1-2 and Comparative Examples 1-5 (unit: mass parts)

[0087]

[0088] Test Example

[0089] The specimens of Examples 1-2 and Comparative Examples 1-5 after steam curing at 60°C for 4 h were subjected to 28-day standard curing, and then their mechanical properties and durability were tested, as shown in Table 2.

[0090] Table 2 Test results of mechanical properties and durability

[0091] Mix ratio Compressive strength (MPa) Flexural strength (MPa) Impermeability <![CDATA[Chloride ion erosion resistance (m 2 / s)]]> Example 1 121.5 11.4 ＞P12 <![CDATA[0.05×10 -12 > Example 2 120.1 11.2 ＞P12 <![CDATA[0.06×10 -12 > Comparative example 1 70.3 5.6 P8 - P10 <![CDATA[5.2×10 -12 > Comparative example 2 110.8 9.5 ＞P12 <![CDATA[0.20×10 -12 > Comparative example 3 115.1 9.9 ＞P12 <![CDATA[0.07×10 -12 > Comparative example 4 111.2 9.6 ＞P12 <![CDATA[0.17×10 -12 > Comparative example 5 102.0 8.2 ＞P12 <![CDATA[0.37×10 -12 >

[0092] As can be seen from Table 2, the high-performance concrete in Examples 1-2 exhibits the optimal mechanical properties and durability. The 28-day compressive strength can reach over 120 MPa, the 28-day flexural strength can reach over 10 MPa, the impermeability grade is greater than P12, and the chloride ion erosion resistance is less than 0.1×10 -12 m 2 / s, far superior to the performance of ordinary C50 concrete. In addition, it can be seen from the comparison between Example 1 and Comparative Examples 1-4 that the mechanical properties and durability of high-performance concrete show a trend of first increasing and then decreasing as the volume content of crushed stone decreases from 42% to 12%, and reach the optimal value when the volume content of coarse aggregate is 22%. In Comparative Example 5, the cement content is relatively low, so the compressive strength and flexural strength of the finally prepared concrete are both relatively low.

[0093] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A mix design method for steam-cured high-performance concrete for prestressed steel cylinder concrete jacking pipe, characterized in that: The steps include: (1) determining the particle size distribution of cementitious materials, fine aggregates and coarse aggregates, wherein the particle size of the coarse aggregate is 5 to 10 mm; the cementitious materials include cement and auxiliary cementitious materials; and the fine aggregate is sand; (2) according to the maximum and minimum particle sizes of the particles determined in step (1), the cumulative passing percentage P(D) at each set sieve aperture is obtained based on formula ①, and the target stacking curve is obtained based on the MAA model; Where D is the particle size; P(D) is the cumulative percentage of particles smaller than D; D max and D min are the maximum and minimum particle sizes, respectively; q is the particle size distribution modulus, q is 0.20-0.25; (3) according to the particle size distribution of the cementitious material, fine aggregate and coarse aggregate determined in step (1), a mixture packing curve is obtained by fitting using computer software based on the least square method, and the volume ratio of the cementitious material, fine aggregate and coarse aggregate is obtained, thereby obtaining the volume content of the coarse aggregate; The calculation formula of the least squares method is shown in formula ②: Among them, S s is the residual sum of squares, P mix and P MAA They refer to the mixture stacking curve and the target stacking curve, respectively, and n is the number of calculation points of the stacking curve; (4) The volume ratio of cement to auxiliary cementitious material in the cementitious material is set to (55-65):(35-45), and the volume ratio of cementitious material to fine aggregate is set to 0.5-0.6; according to the volume content of coarse aggregate calculated in step (3), the mix ratio of cement, auxiliary cementitious material, fine aggregate and coarse aggregate is calculated.

2. The mix design method according to claim 1, characterized in that: q is taken as 0.

23.

3. The mix design method according to claim 1, characterized in that: The coarse aggregate is crushed stone.

4. The mix design method according to claim 1, characterized in that: The cement is ordinary Portland cement.

5. The mix design method according to claim 1, characterized in that: The fine aggregate is river sand with a particle size of medium sand and a fineness modulus of 2.3 to 3.

0.

6. The steam-cured high performance concrete for prestressed steel cylinder concrete jacking pipe obtained by the mix design method according to any one of claims 1 to 5, characterized in that: Its raw materials include cement, auxiliary cementitious materials, fine aggregate, coarse aggregate, water reducing agent and water, wherein the volume ratio of cement, auxiliary cementitious materials, fine aggregate and coarse aggregate is (15-18):(10-12):(45-55):(20-25), the water-cement ratio is 0.18-0.22, and the mass of the water reducing agent is 1.0-1.5wt% of the total mass of cement and auxiliary cementitious materials.

7. The steam-cured high performance concrete for prestressed concrete cylinder jacking pipe according to claim 6, characterized in that: The auxiliary cementitious materials include fly ash, mineral powder and silica fume.

8. The steam-cured high performance concrete for prestressed concrete cylinder jacking pipe according to claim 7, characterized in that: The volume ratio of the fly ash, mineral powder and silica fume is (30-35):(24-28):(38-43).

9. The steam-cured high performance concrete for prestressed concrete cylinder jacking pipe according to claim 8, characterized in that: The raw materials of the steam-cured high-performance concrete for prestressed steel cylinder concrete jacking pipe include the following components in parts by mass: 460-530 parts of cement, 72-85 parts of mineral powder, 70-83 parts of fly ash, 115-125 parts of silica fume, 800-900 parts of fine aggregate, 550-610 parts of coarse aggregate, 140-170 parts of water, and 8-12 parts of water reducer.

10. The method for preparing steam-cured high performance concrete for prestressed steel cylinder concrete jacking pipe according to any one of claims 6 to 9, characterized in that: The steps include: Pour the weighed coarse aggregate and fine aggregate into a mixer and dry mix them, then add cement and auxiliary cementitious materials and continue dry mixing to obtain a dry mix; Mixing the water reducer and water and adding the mixture to the dry mix to obtain a mixture; The mixture is cast into shape, and then the formed test piece is covered with a film and steam-cured for 3 to 6 hours at a steam-curing temperature of 50 to 80° C., thereby obtaining steam-cured high-performance concrete for prestressed steel cylinder concrete jacking pipe.

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