Self-compacting micro-expansion high-volume-weight concrete and preparation method thereof

Abstract

The invention relates to self-compacting micro-expansive high-volume-weight concrete and a preparation method thereof, and the self-compacting micro-expansive high-volume-weight concrete comprises the following components in parts by weight: 240-400 parts of cement, 80-150 parts of fly ash, 30-100 parts of silica fume, 20-60 parts of a rheology modified material, 20-60 parts of an expanding agent, 50-150 parts of an internal curing agent, 600-900 parts of fine aggregate, 800-1200 parts of coarse aggregate, 140-260 parts of water and 5-12 parts of an additive, the rheology modified material comprises glass beads, cellulose ether and polycarboxylic acid ether, and the mass ratio of the glass beads to the cellulose ether to the polycarboxylic acid ether is 1: (0.1-0.3): (0.001-0.01); the expanding agent comprises calcium oxide and active magnesium oxide; the internal curing agent comprises natural zeolite and zeolite powder; the fine aggregate comprises river sand and iron tailings; the coarse aggregate comprises broken stones and iron tailings. The problem of restriction among the volume weight, the volume stability and the working performance of the concrete in related technologies can be solved, so that the self-compaction, micro-expansion and high volume weight functions of the concrete are realized.

Description

Technical Field

[0001] The present application relates to the field of bridge technology, and in particular to a self-compacting micro-expansion high bulk density concrete and a preparation method thereof. Background Art

[0002] As a new type of bridge structure system, the ultra-short side span concrete composite slab-truss composite beam structure has the characteristics of shorter side span, convenient construction and high economy. However, in order to balance the load of the middle span main beam, the side span chord needs to be filled with concrete, and the concrete density is required to be greater than 2500kg / m 3 , in order to achieve the weight-bearing function; it has a micro-expansion function to avoid air loss and debonding; it meets the self-compacting requirements and is easy to construct.

[0003] Usually, adding heavy aggregates such as iron sand to concrete can meet the bulk density requirements, but it will cause segregation and affect the working performance. Adding expansion agents can reduce shrinkage to a certain extent, but it is difficult to achieve the micro-expansion function, and it will lead to a decrease in bulk density and a decrease in working performance. Increasing the sand ratio and the amount of glue can improve the working performance, but it will reduce the bulk density and increase shrinkage. Therefore, the bulk density, volume stability and working performance of concrete affect and restrict each other, and the concrete provided by the prior art is difficult to meet the requirements of bulk density, micro-expansion and self-compacting at the same time. Summary of the invention

[0004] The embodiments of the present application provide a self-compacting, slightly expansive, high bulk density concrete and a preparation method thereof, so as to solve the restriction problem between the bulk density, volume stability and working performance of concrete in the related art, thereby realizing the self-compacting, slightly expansive and high bulk density functions of concrete.

[0005] In a first aspect, a self-compacting slightly expansive high bulk density concrete is provided, which comprises, by weight: 240-400 parts of cement, 80-150 parts of fly ash, 30-100 parts of silica fume, 20-60 parts of rheology modifier, 20-60 parts of expansion agent, 50-150 parts of internal curing agent, 600-900 parts of fine aggregate, 800-1200 parts of coarse aggregate, 140-260 parts of water and 5-12 parts of admixture;

[0006] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, wherein the mass ratio of the glass microspheres, the cellulose ether and the polycarboxylate ether is 1:(0.1-0.3):(0.001-0.01);

[0007] The expansion agent includes calcium oxide and active magnesium oxide;

[0008] The internal curing agent includes natural zeolite and zeolite powder;

[0009] The fine aggregate includes river sand and iron tailings;

[0010] The coarse aggregate includes crushed stone and iron tailings.

[0011] In some embodiments, the median particle size D50 of the glass microspheres is 5 to 12 μm, the viscosity of the cellulose ether is 100,000 to 200,000, and the hydroxyl value of the polycarboxylate ether is 20 to 30 mgKOH / g.

[0012] In some embodiments, the mass ratio of calcium oxide to active magnesium oxide is 1:(0.5-2).

[0013] In some embodiments, the purity of the calcium oxide is above 90%, and the specific surface area is ≥300m 2 / kg;

[0014] The purity of the active magnesium oxide is above 95%, and the citric acid value is 150-200s.

[0015] In some embodiments, the mass ratio of the natural zeolite to the zeolite powder is 1:(1-2).

[0016] In some embodiments, the particle size of the natural zeolite is 0.15 to 3 mm, and the porosity is ≥ 50%;

[0017] The particle size of the zeolite powder is 150-300 meshes, and the porosity is ≥50%.

[0018] In some embodiments, the mass fraction of the iron tailings in the fine aggregate is 30% to 100%;

[0019] The river sand has a particle size of 0.075-4.75 mm, a fineness modulus of 2.5-2.9, and an apparent density of 2400-2600 kg / m 3 ;

[0020] The iron tailings are crushed from iron tailings, with a particle size of 0.075-4.75 mm and an apparent density of 3200-3300 kg / m 3 .

[0021] In some embodiments, the mass fraction of the iron tailings in the coarse aggregate is 40% to 100%;

[0022] The crushed stone is a continuously graded crushed stone with a diameter of 5 to 15 mm and an apparent density of 2500 to 2800 kg / m 3 ;

[0023] The iron tailings are crushed from iron tailings, with a particle size of 5 to 15 mm and an apparent density of 3300 to 3500 kg / m 3 .

[0024] In some embodiments, the cement is silicate cement or ordinary silicate cement;

[0025] The fly ash is Class F Grade I or Grade II fly ash;

[0026] The silica fume is grade 90 silica fume or grade 85 silica fume;

[0027] The admixture is a polycarboxylic acid water reducer, and the water reduction rate is ≥25%.

[0028] In a second aspect, a method for preparing the self-compacting slightly expansive high bulk density concrete as described above is provided, comprising:

[0029] Mixing glass microspheres, cellulose ether and polycarboxylate ether to obtain a rheology-modified material;

[0030] Mixing calcium oxide and active magnesium oxide to obtain a swelling agent;

[0031] Putting natural zeolite and zeolite powder into a container, adding a certain amount of water to pre-wet, and obtaining a pre-wet internal curing agent;

[0032] Mixing cement, fly ash, silica fume, rheology modifier, expansion agent and fine aggregate to obtain a first mixture;

[0033] Pour the pre-wetted internal curing agent, the remaining water and the admixture into the first mixture, and continue stirring to obtain a second mixture;

[0034] Pour the coarse aggregate into the second mixture and continue mixing to obtain fresh concrete;

[0035] The freshly mixed concrete is compacted, formed and cured to obtain self-compacting, slightly expansive, high bulk density concrete.

[0036] The beneficial effects of the technical solution provided by this application include:

[0037] The present application successfully prepared self-compacting, slightly expansive, high bulk density concrete by adding rheology modifiers, expansion agents, internal curing agents and iron tailings gravel into concrete, achieving the coordinated unification of concrete working performance, volume stability and bulk density.

[0038] The rheology modifier proposed in the present application is composed of glass microspheres, cellulose ether and polycarboxylate ether. By synergizing the ball lubrication effect of the glass microspheres, the thickening effect of the cellulose ether and the water reduction effect of the polycarboxylate ether, the fresh concrete is achieved to have a large flow state, high consistency, high homogeneity and good stability, and effectively solves the segregation and bleeding of the self-compacting concrete.

[0039] The expansion agent proposed in this application is composed of calcium oxide and low-activity active magnesium oxide. The expansion reaction of calcium oxide mainly occurs in the early stage of hydration, while the expansion reaction of low-activity active magnesium oxide mainly occurs in the late stage of hydration. Therefore, the expansion agent can continue to expand during the entire cycle of concrete hydration reaction, completely compensate for the shrinkage of concrete and achieve a micro-expansion effect.

[0040] The internal curing agent proposed in this application is composed of natural zeolite and zeolite powder. The natural zeolite and zeolite powder after absorbing water are added to the concrete. As the concrete hydration reaction proceeds, the free water absorbed by the natural zeolite and zeolite powder is gradually released, further promoting cement hydration and expansion agent reaction. At the same time, the pore sizes of natural zeolite and zeolite powder are different. Natural zeolite mainly provides reaction water for the initial stage of cement hydration and calcium oxide, while zeolite powder mainly provides reaction water for the final stage of cement hydration and low-activity active magnesium oxide, thereby achieving a gradient internal curing effect and ensuring the complete hydration of cement and the full reaction of the expansion agent.

[0041] This application uses iron tailings and iron tailings with high apparent density to replace part of traditional river sand and crushed stone to achieve a high bulk density index of concrete. Furthermore, by processing iron tailings into iron tailings and iron tailings, not only the use of natural sand and gravel is significantly reduced, but also the abandoned iron tailings are efficiently utilized, and the efficient value-added utilization of iron tailings resources is achieved, which has green environmental protection significance and meets the requirements of the concept of sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0043] Figure 1 A flow chart of the method for preparing the self-compacting slightly expansive high bulk density concrete provided in an embodiment of the present application. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0045] The embodiment of the present application provides a self-compacting slightly expansive high bulk density concrete, which includes, by weight: 240-400 parts of cement, 80-150 parts of fly ash, 30-100 parts of silica fume, 20-60 parts of rheology modifier, 20-60 parts of expansion agent, 50-150 parts of internal curing agent, 600-900 parts of fine aggregate, 800-1200 parts of coarse aggregate, 140-260 parts of water and 5-12 parts of admixture.

[0046] Among them, cement, fly ash, silica fume and admixtures are commonly used materials. For example, as an example, the cement can be selected from silicate cement or ordinary silicate cement, the fly ash can be selected from Class F Grade I or Grade II fly ash, the silica ash can be selected from Grade 90 silica ash or Grade 85 silica ash, and the admixture can be selected from polycarboxylic acid water reducer with a water reduction rate ≥25%.

[0047] Wherein, the rheology modifier includes glass beads, cellulose ether and polycarboxylate ether, and the mass ratio of glass beads, cellulose ether and polycarboxylate ether is 1: (0.1-0.3): (0.001-0.01); within this range, the concrete can have large fluidity, high homogeneity and low viscosity characteristics, thereby realizing the self-compacting function. If there are too many glass beads, the expansion of the concrete becomes larger, but phenomena such as segregation and bleeding may occur; if there are too few, the viscosity is too high, which is not conducive to construction. If there are too many cellulose ethers, the concrete is too viscous and construction is inconvenient; if there are too few, the concrete has poor homogeneity and is easy to separate and bleed. If there are too many polycarboxylate ethers, the concrete has more floating slurry and is easy to stratify; if there are too few, the fluidity is poor and the self-compacting function cannot be achieved.

[0048] The applicant has found through research that if the median particle size D50 of the glass microspheres is too low, the rolling effect is not obvious and the improvement on the fluidity of the concrete is small. If the median particle size D50 of the glass microspheres is too high, the pores inside the concrete will become larger, affecting the later strength and durability. In order to achieve the self-compacting micro-expansion high bulk density of the concrete, the median particle size D50 of the glass microspheres is 5 to 12 μm,

[0049] The applicant has found through research that if the viscosity of the cellulose ether is too low, the improvement of the slurry consistency is not obvious; if it is too high, the slurry consistency will increase significantly, resulting in poor concrete performance. In order to achieve the self-compacting micro-expansion high bulk density of concrete, the viscosity of the cellulose ether is 100,000 to 200,000.

[0050] The applicant has found through research that if the hydroxyl value of the polycarboxylate ether is too low, the intermolecular stability is poor and the water reduction effect is poor; if it is too high, the synthesis process becomes more difficult and uneconomical. In order to achieve the self-compacting micro-expansion high bulk density of concrete, the hydroxyl value of the polycarboxylate ether is 20-30 mgKOH / g.

[0051] The rheology modifier is composed of glass microspheres, cellulose ether and polycarboxylate ether. The glass microspheres are smooth spherical and can exert a ball effect to reduce the frictional resistance between the slurry; the cellulose ether can increase the anti-dispersion ability and homogeneity of the cement slurry, improve the stability of the concrete, and prevent stratification, segregation and water bleeding; the surface adsorption and steric hindrance of the polycarboxylate ether can make the cement particles disperse evenly and reduce the water consumption.

[0052] The expansion agent includes calcium oxide and active magnesium oxide; the mass ratio of the calcium oxide to the active magnesium oxide is 1: (0.5-2), the purity of the calcium oxide is above 90%, and the specific surface area is ≥300m 2 / kg; the purity of the active magnesium oxide is above 95%, and the citric acid value is 150-200s.

[0053] The expansive agent is composed of calcium oxide and active magnesium oxide with lower activity. Calcium oxide can generate calcium hydroxide in the early stage of cement hydration. The volume of calcium hydroxide is twice that of calcium oxide, so it can cause volume expansion. The low-activity active magnesium oxide begins to generate magnesium hydroxide in the later stage of cement hydration. With the continuous growth of magnesium hydroxide, the crystals contact each other and squeeze the pore walls, thereby causing volume expansion.

[0054] Calcium oxide and active magnesium oxide are mixed to form an expansion agent. Due to the high activity of calcium oxide, calcium oxide reacts first, and after the reaction of calcium oxide is completed, the low-activity magnesium oxide reacts, thereby achieving long-term expansion of concrete and continuously compensating for the shrinkage of concrete caused by hydration.

[0055] The high purity of calcium oxide and active magnesium oxide is to ensure good expansion effect in concrete. If the purity is too low, the expansion effect is not significant. The specific surface area is to ensure the high activity of calcium oxide, which is less than 300m 2 / kg, the reaction is delayed and the early expansion is not obvious. The citric acid value is to ensure the low activity of magnesium oxide. If it is less than 150s, the activity is too high and the later expansion is insufficient. If it is greater than 200s, the activity is too low and the reaction is too slow. At the same time, there is the possibility of later expansion and cracking.

[0056] The internal curing agent includes natural zeolite and zeolite powder; the mass ratio of the natural zeolite to the zeolite powder is 1: (1-2). After the natural zeolite and zeolite powder are mixed and saturated with water, they can be added to the concrete in this ratio to achieve gradient water release, that is, the natural zeolite releases water first, and the zeolite powder releases water after the water release is completed. The entire water release process corresponds to the reaction of cement and expansion agent, achieving a full-cycle internal curing effect. If it is higher than this ratio, there is more natural zeolite, and the internal curing agent may release water in advance and fail to achieve the internal curing effect in the later stage, resulting in insufficient hydration of cement and insufficient reaction of active magnesium oxide. If it is lower than this ratio, there is more zeolite powder, and the internal curing agent does not release enough water in the early stage, resulting in insufficient reaction of calcium oxide and unclear expansion effect of concrete in the early stage.

[0057] The particle size of the natural zeolite is 0.15-3 mm, and the porosity is ≥50%; the particle size of the zeolite powder is 150-300 meshes, and the porosity is ≥50%.

[0058] According to the preliminary test data, the applicant found that the natural zeolite particle size in the range of 0.15-0.3 and the zeolite powder particle size of 150-300 mesh can absorb the most water and have the least impact on the mechanical properties of concrete. If the particle size is too small, the water absorption is too small, and if the particle size is too large, the mechanical properties of concrete will be seriously reduced. At the same time, the porosity is set to ≥50% to ensure that sufficient water can be absorbed to avoid insufficient water absorption.

[0059] Internal curing agent is composed of natural zeolite and zeolite powder. Natural zeolite and zeolite powder have high porosity. They can provide free water for the reaction of cement and expansion agent by saturating concrete with water in advance. At the same time, natural zeolite has a larger pore size and mainly provides free water in the early stage of hydration; while zeolite powder has a smaller pore size and mainly provides free water in the late stage of hydration.

[0060] The fine aggregate includes river sand and iron tailings; the mass fraction of the iron tailings in the fine aggregate is 30% to 100%; the particle size of the river sand is 0.075 to 4.75 mm, the fineness modulus is 2.5 to 2.9, and the apparent density is 2400 to 2600 kg / m 3 The iron tailings are crushed from iron tailings, with a particle size of 0.075-4.75 mm and an apparent density of 3200-3300 kg / m 3 .

[0061] According to the test results, when the replacement rate of iron tailings is less than 30%, the concrete density cannot meet 2500kg / m 3 .

[0062] The coarse aggregate includes crushed stone and iron tailings. The iron tailings account for 40% to 100% of the mass fraction of the coarse aggregate; the crushed stone is a continuous graded crushed stone with a diameter of 5 to 15 mm and an apparent density of 2500 to 2800 kg / m3 The iron tailings are crushed from iron tailings, with a particle size of 5 to 15 mm and an apparent density of 3300 to 3500 kg / m 3 .

[0063] According to the test results, when the iron tailings replacement rate is less than 40%, the concrete density cannot meet 2500kg / m 3 .

[0064] In order to meet the engineering requirements, the concrete density must be at least 2500kg / m 3 However, the concrete bulk density prepared by simply using river sand and conventional crushed stone cannot meet the requirements. Therefore, this application proposes to use iron tailings to replace part or all of the river sand, and use iron tailings to replace part or all of the crushed stone to prepare concrete, so as to achieve the high bulk density target. At the same time, it not only provides a new way for the resource processing of iron tailings, but also reduces the use of natural sand and stone, which is in line with the concept of green environmental protection.

[0065] See also Figure 1 As shown, the embodiment of the present application also provides a method for preparing a self-compacting micro-expansion high bulk density concrete, which comprises the following steps:

[0066] 101: Mix glass microspheres, cellulose ether and polycarboxylate ether to obtain a rheology-modified material.

[0067] During the actual mixing in step 101 , the mixing can be performed at a rotation speed of 400 to 500 rpm and for a time of 20 to 24 hours.

[0068] 102: Calcium oxide and activated magnesium oxide are mixed to obtain a swelling agent.

[0069] During the actual mixing in step 102, the mixing can be performed at a rotation speed of 200 to 300 rpm and for a time of 20 to 24 hours.

[0070] 103: Put natural zeolite and zeolite powder into a container, add a certain amount of water to pre-wet, and obtain a pre-wet internal curing agent.

[0071] The amount of water added in step 102 can be determined as needed. For example, the amount of water added accounts for 20% of the 140 to 260 parts of water. After the water is added, the seal is sealed and allowed to stand for 20 to 24 hours.

[0072] 104: Mix cement, fly ash, silica fume, rheology modifier, expansion agent and fine aggregate to obtain a first mixture.

[0073] The stirring time in step 104 can be set according to actual needs, such as stirring for 60±5s.

[0074] 105: Pour the pre-wetted internal curing agent, the remaining water and the admixture into the first mixture, continue stirring, and obtain the second mixture.

[0075] The stirring time in step 105 can be set according to actual needs, such as stirring for 60±5s.

[0076] 106: Pour the coarse aggregate into the second mixture and continue mixing to obtain fresh concrete.

[0077] The stirring time in step 106 can be set according to actual needs, such as stirring for 120±5s.

[0078] 107: The freshly mixed concrete is compacted, formed and cured to obtain self-compacting, slightly expansive, high bulk density concrete.

[0079] The present application is described below through some embodiments and comparative examples.

[0080] Example 1

[0081] A self-compacting slightly expansive high bulk density concrete, comprising, by weight: 300 parts of cement, 100 parts of fly ash, 80 parts of silica fume, 50 parts of rheology modifier, 50 parts of expansion agent, 100 parts of internal curing agent, 800 parts of fine aggregate, 1000 parts of coarse aggregate, 200 parts of water and 9 parts of admixture;

[0082] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.2:0.005.

[0083] The expansion agent includes calcium oxide and active magnesium oxide; the mass ratio of the calcium oxide to the active magnesium oxide is 1:1.

[0084] The internal curing agent comprises natural zeolite and zeolite powder; the mass ratio of the natural zeolite to the zeolite powder is 1:1.5.

[0085] Wherein, the cement is P·Ⅱ52.2 silicate cement, the fly ash is Class F Grade I fly ash, and the silica fume is Grade 90 silica fume.

[0086] The median particle size D50 of the glass microspheres is 9.5 μm, the viscosity of the cellulose ether is 180,000, and the hydroxyl value of the polycarboxylic acid ether is 23 mgKOH / g.

[0087] The purity of the calcium oxide is 95% and the specific surface area is 360m 2 / kg; the purity of the active magnesium oxide is 99%, and the citric acid value is 180s.

[0088] The particle size of the natural zeolite is 0.15-3 mm, and the porosity is ≥50%; the particle size of the zeolite powder is 150-300 meshes, and the porosity is ≥50%.

[0089] The fine aggregate includes river sand and iron tailings; the mass fraction of the iron tailings in the fine aggregate is 60%; the particle size of the river sand is in the range of 0.075 to 4.75 mm, the fineness modulus is 2.6, and the apparent density is 2600 kg / m 3 The iron tailings are crushed from iron tailings, with a particle size ranging from 0.075 to 4.75 mm and an apparent density of 3250 kg / m 3 .

[0090] The coarse aggregate includes crushed stone and iron tailings. The iron tailings account for 60% of the mass fraction of the coarse aggregate; the crushed stone is a continuous graded crushed stone with a diameter of 5 to 15 mm and an apparent density of 2700 kg / m 3 The iron tailings are crushed from iron tailings, with a particle size of 5 to 15 mm and an apparent density of 3400 kg / m 3 .

[0091] The admixture is a polycarboxylic acid high-efficiency water reducing agent with a water reducing rate of 30%.

[0092] Example 2

[0093] The difference from Example 1 is:

[0094] A self-compacting slightly expansive high bulk density concrete comprises, by weight, 400 parts of cement, 150 parts of fly ash, 100 parts of silica fume, 60 parts of rheology modifier, 60 parts of expansion agent, 150 parts of internal curing agent, 900 parts of fine aggregate, 1200 parts of coarse aggregate, 260 parts of water and 12 parts of admixture.

[0095] Example 3

[0096] The difference from Example 1 is:

[0097] A self-compacting slightly expansive high bulk density concrete comprises, by weight, 240 parts of cement, 80 parts of fly ash, 30 parts of silica fume, 20 parts of rheology modifier, 20 parts of expansion agent, 50 parts of internal curing agent, 600 parts of fine aggregate, 800 parts of coarse aggregate, 140 parts of water and 5 parts of admixture.

[0098] Example 4

[0099] The difference from Example 1 is:

[0100] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.1:0.005.

[0101] Example 5

[0102] The difference from Example 1 is:

[0103] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.3:0.005.

[0104] Example 6

[0105] The difference from Example 1 is:

[0106] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.2:0.001.

[0107] Example 7

[0108] The difference from Example 1 is:

[0109] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.2:0.01.

[0110] Example 8

[0111] The difference from Example 1 is:

[0112] The mass ratio of the calcium oxide to the active magnesium oxide is 1:0.5.

[0113] Example 9

[0114] The difference from Example 1 is:

[0115] The mass ratio of the calcium oxide to the active magnesium oxide is 1:2.

[0116] Example 10

[0117] The difference from Example 1 is:

[0118] The mass ratio of the natural zeolite to the zeolite powder is 1:1.

[0119] Embodiment 11

[0120] The difference from Example 1 is:

[0121] The mass ratio of the natural zeolite to the zeolite powder is 1:2.

[0122] Example 12

[0123] The difference from Example 1 is:

[0124] The mass fraction of iron tailings in the fine aggregate is 30%; the mass fraction of iron tailings in the coarse aggregate is 40%.

[0125] Embodiment 13

[0126] The difference from Example 1 is:

[0127] The mass fraction of iron tailings in the fine aggregate is 100%; the mass fraction of iron tailings in the coarse aggregate is 100%.

[0128] Comparative Example 1

[0129] The difference from Example 1 is:

[0130] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 2:0.2:0.005.

[0131] Comparative Example 2

[0132] The difference from Example 1 is:

[0133] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 0.5:0.2:0.005.

[0134] Comparative Example 3

[0135] The difference from Example 1 is:

[0136] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.4:0.005.

[0137] Comparative Example 4

[0138] The difference from Example 1 is:

[0139] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.05:0.005.

[0140] Comparative Example 5

[0141] The difference from Example 1 is:

[0142] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.2:0.02.

[0143] Comparative Example 6

[0144] The difference from Example 1 is:

[0145] The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, and the mass ratio of the glass microspheres, cellulose ether and polycarboxylate ether is 1:0.2:0.0005.

[0146] Comparative Example 7

[0147] The difference from Example 1 is:

[0148] The mass ratio of the calcium oxide to the active magnesium oxide is 1:0.2.

[0149] Comparative Example 8

[0150] The difference from Example 1 is:

[0151] The mass ratio of the calcium oxide to the active magnesium oxide is 1:3.

[0152] Comparative Example 9

[0153] The difference from Example 1 is:

[0154] The mass ratio of the natural zeolite to the zeolite powder is 1:0.5.

[0155] Comparative Example 10

[0156] The difference from Example 1 is:

[0157] The mass ratio of the natural zeolite to the zeolite powder is 1:3.

[0158] Comparative Example 11

[0159] The difference from Example 1 is:

[0160] The fine aggregate does not contain iron tailings, and the coarse aggregate does not contain iron tailings.

[0161] The above examples and comparative examples were tested for expansion, T500, bulk density, compressive strength and expansion performance.

[0162] The expansion degree and T500 shall comply with the Technical Code for Application of Self-compacting Concrete (JGJT 283-2012).

[0163] The bulk density is based on the Standard Test Method for Performance of Ordinary Concrete Mixtures (GB / T50080-2016).

[0164] The compressive strength adopts the "Standard for Test Methods for Physical and Mechanical Properties of Concrete" (GB / T50081-2019), and the age is 28d.

[0165] The expansion performance adopts the concrete autogenous volume deformation test method in the "Test Code for Hydraulic Concrete" (SLT 352-2020).

[0166] The test results are shown in Table 1:

[0167] Table 1 Concrete performance test results of the embodiments and comparative examples

[0168]

[0169]

[0170] According to the data in Table 1, it can be seen that the freshly mixed state of the concrete in all the examples is good, with expansion ≥ 600 mm, T500 ≤ 8 s, and self-compacting function; the expansion value 7d ≥ 75 × 10 -6 , 28d≥45×10 -6 、90d≥20×10 -6 , with micro-expansion function; bulk density>2500kg / m 3 . It meets the high bulk density target value. Overall, the self-compacting, micro-expansion and high bulk density function of concrete is achieved.

[0171] Combining the test results of Examples 1, 2, 3, 4, 5, 6 and Comparative Examples 1, 2, 3, 4, 5, 6, it can be seen that the concrete of Examples 1, 2, 3, 4, 5, 6 has low viscosity and high consistency, and has good working performance such as water retention, cohesion, and homogeneity. At the same time, the expansion degree is ≥ 605 mm, and T500 is ≤ 7s, which meets the performance index of self-compacting concrete. However, the concrete of Comparative Examples 1, 2, 3, 4, 5, 6 will have phenomena such as segregation and bleeding, poor water retention, poor cohesion, and poor homogeneity. At the same time, the expansion degree and T500 index do not meet the performance index of self-compacting concrete. This shows that when the mass ratio of glass microspheres, cellulose ethers and polycarboxylic acid ethers in the rheology modifier is not within the range of 1: (0.1-0.3): (0.001-0.01), the working performance of the concrete will deteriorate and the self-compacting function cannot be achieved.

[0172] Combining the test results of Examples 1, 8, 9 and Comparative Examples 7 and 8, it can be seen that the concrete expansion value 7d of Examples 1, 8, and 9 is ≥75×10 -6 ,28d≥46×10 -6 、90d≥20×10 -6 , with micro-expansion function. This shows that when the mass ratio of calcium oxide to active magnesium oxide in the expansion agent is kept in the range of 1: (0.5-2), the concrete can maintain good volume stability. In contrast, the calcium oxide content of the expansion agent in Comparative Example 7 is high, and the 7d expansion value of the concrete reaches 93×10 -6 However, the expansion performance is insufficient in the later stage, and the expansion value at 28 days is reduced to 25×10 -6The 90d expansion value is even less than 0, showing volume shrinkage. In Comparative Example 8, the active magnesium oxide content of the expansion agent is too high, and the 7d expansion value of the concrete is only 43×10 -6 Due to insufficient expansion in the early stage, expansion in the later stage was difficult, and the expansion value at 90 days was -18×10 -6 , showing a shrinking trend.

[0173] Combining the test results of Examples 1, 10, 11 and Comparative Examples 9 and 10, it can be seen that the concrete of Examples 1, 10, 11 has good micro-expansion function and compressive strength> 60MPa. This shows that when the mass ratio of natural zeolite to zeolite powder in the internal curing agent is kept in the range of 1: (1-2), the volume stability and mechanical properties of the concrete are good. In contrast, the natural zeolite content of the internal curing agent in Comparative Example 9 is relatively high, and the 7d expansion value of the concrete is as high as 91×10 -6 However, the expansion performance in the later stage is obviously insufficient, and the expansion value at 28 days is only 13×10 -6 , shrinkage occurred after 90 days, and the compressive strength was only 48.6MPa, and the mechanical properties were seriously reduced. In Comparative Example 10, the zeolite powder content of the internal curing agent was too high, and the initial expansion of the concrete was insufficient, only 26×10 -6 , and it also shows a shrinkage trend in the later period, and the working performance of concrete is poor.

[0174] Compared with the comparative example 11, the concrete bulk density of the examples 1, 12 and 13 is significantly increased. When the iron tailings sand and gravel content is 100%, the concrete bulk density can reach 2640kg / m 3 Without iron tailings and gravel, the concrete density is only 2410kg / m 3 , does not meet the bulk density ≥ 2500kg / m 3 This shows that increasing the amount of iron tailings sand and gravel can significantly increase the bulk density of concrete.

[0175] The above description is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest range consistent with the principles and novel features applied for herein.

Claims

1. A self-compacting slightly expansive high bulk density concrete, characterized in that: According to weight, it includes: 240-400 parts of cement, 80-150 parts of fly ash, 30-100 parts of silica fume, 20-60 parts of rheology modifier, 20-60 parts of expansion agent, 50-150 parts of internal curing agent, 600-900 parts of fine aggregate, 800-1200 parts of coarse aggregate, 140-260 parts of water and 5-12 parts of admixture; The rheology modifier comprises glass microspheres, cellulose ether and polycarboxylate ether, wherein the mass ratio of the glass microspheres, the cellulose ether and the polycarboxylate ether is 1:(0.1-0.3):(0.001-0.01); The expansion agent includes calcium oxide and active magnesium oxide; The internal curing agent includes natural zeolite and zeolite powder; The fine aggregate includes river sand and iron tailings; The coarse aggregate includes crushed stone and iron tailings.

2. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The median particle size D50 of the glass microspheres is 5 to 12 μm, the viscosity of the cellulose ether is 100,000 to 200,000, and the hydroxyl value of the polycarboxylic acid ether is 20 to 30 mgKOH / g.

3. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The mass ratio of the calcium oxide to the active magnesium oxide is 1:(0.5-2).

4. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The purity of the calcium oxide is above 90%, and the specific surface area is ≥300m 2 / kg; The purity of the active magnesium oxide is above 95%, and the citric acid value is 150-200s.

5. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The mass ratio of the natural zeolite to the zeolite powder is 1:(1-2).

6. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The particle size of the natural zeolite is 0.15-3 mm, and the porosity is ≥50%; The particle size of the zeolite powder is 150-300 meshes, and the porosity is ≥50%.

7. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The mass fraction of the iron tailings in the fine aggregate is 30% to 100%; The river sand has a particle size of 0.075-4.75 mm, a fineness modulus of 2.5-2.9, and an apparent density of 2400-2600 kg / m 3 ; The iron tailings are crushed from iron tailings, with a particle size of 0.075-4.75 mm and an apparent density of 3200-3300 kg / m 3 .

8. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The mass fraction of the iron tailings in the coarse aggregate is 40% to 100%; The crushed stone is a continuously graded crushed stone with a diameter of 5 to 15 mm and an apparent density of 2500 to 2800 kg / m 3 ; The iron tailings are crushed from iron tailings, with a particle size of 5 to 15 mm and an apparent density of 3300 to 3500 kg / m 3 .

9. The self-compacting slightly expansive high bulk density concrete according to claim 1, characterized in that: The cement is silicate cement or ordinary silicate cement; The fly ash is Class F Grade I or Grade II fly ash; The silica fume is grade 90 silica fume or grade 85 silica fume; The admixture is a polycarboxylic acid water reducer, and the water reduction rate is ≥25%.

10. A method for preparing the self-compacting slightly expansive high bulk density concrete according to any one of claims 1 to 9, characterized in that: It includes: Mixing glass microspheres, cellulose ether and polycarboxylate ether to obtain a rheology-modified material; Mixing calcium oxide and active magnesium oxide to obtain a swelling agent; Putting natural zeolite and zeolite powder into a container, adding a certain amount of water to pre-wet, and obtaining a pre-wet internal curing agent; Mixing cement, fly ash, silica fume, rheology modifier, expansion agent and fine aggregate to obtain a first mixture; Pour the pre-wetted internal curing agent, the remaining water and the admixture into the first mixture, and continue stirring to obtain a second mixture; Pour the coarse aggregate into the second mixture and continue mixing to obtain fresh concrete; The freshly mixed concrete is compacted, formed and cured to obtain self-compacting, slightly expansive, high bulk density concrete.

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