Iron tailing-incorporated non-sintered artificial aggregate ultra-high performance concrete and preparation method thereof

Abstract

The application provides a kind of super high performance concrete of sintering-free artificial aggregate with iron tailings and a preparation method thereof.The concrete comprises the following components: cement, silica fume, quartz sand, sintering-free artificial aggregate with iron tailings, steel fiber, nano-silicon dioxide, polyacrylamide, silane coupling agent, air entraining agent, retarder, water reducing agent and water;the mass ratio of quartz sand to sintering-free artificial aggregate with iron tailings is (10-15):1;the sintering-free artificial aggregate with iron tailings needs to be treated with composite activator and carbonization;the composite activator comprises water glass, NaOH, sulfate activator and triethanolamine.The concrete uses sintering-free artificial aggregate with iron tailings to replace part of natural aggregate, which not only effectively solves the problems of iron tailings storage and environmental pollution, realizes the resource utilization of industrial solid waste, but also reduces the exploitation of natural sand and stone resources, reduces the damage to the ecological environment, and has significant environmental and social benefits.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of concrete production, and particularly relates to a kind of mixed iron tailings sinter-free artificial aggregate ultra-high performance concrete and a preparation method thereof. BACKGROUND

[0002] Iron tailings are industrial waste discharged after extracting iron concentrate from raw ore through crushing, grinding and magnetic separation processes. With the rapid economic development, people's demand for steel products is also growing, and the iron tailings generated in the corresponding mineral processing process are also increasing. A large amount of iron tailings fine mud is stored in the tailings dam, which not only occupies a large amount of land resources, but also causes soil and groundwater pollution due to the heavy metals in the iron tailings flowing into the ground with rainwater. In addition, the dam collapse accident of the tailings dam may also cause great threat to life and property safety. Therefore, the resource utilization of iron tailings has attracted widespread attention.

[0003] Studies have shown that the performance of iron tailings fine mud is similar to that of building materials. At present, iron tailings are mainly used to prepare blocks, bricks, ceramics and microcrystalline glass, etc. However, the amount of iron tailings used is small, which is not enough to absorb a large amount of iron tailings fine mud, and has little effect on solving the environmental and social problems caused by the storage of iron tailings fine mud. SUMMARY

[0004] In view of this, the present application aims to provide a kind of mixed iron tailings sinter-free artificial aggregate ultra-high performance concrete and a preparation method thereof. The use of iron tailings sinter-free artificial aggregate to replace part of the natural aggregate not only effectively solves the problem of storage and environmental pollution of iron tailings, realizes the resource utilization of industrial solid waste, but also reduces the exploitation of natural sandstone resources and the damage to the ecological environment, which has significant environmental and social benefits.

[0005] To achieve the above purpose, the technical scheme of the present application is as follows:

[0006] A kind of mixed iron tailings sinter-free artificial aggregate ultra-high performance concrete, the concrete includes the following components by weight fraction: 600-700 parts of cement, 150-200 parts of silica fume, 1000-1200 parts of quartz sand, 50-150 parts of iron tailings sinter-free artificial aggregate, 100-200 parts of steel fiber, 3-9 parts of nano silicon dioxide, 0.6-1.8 parts of polyacrylamide, 1-3 parts of silane coupling agent, 0.06-0.3 parts of air entraining agent, 0.6-1.8 parts of retarder, 10-40 parts of water reducing agent, 160-220 parts of water; wherein the mass ratio of quartz sand to iron tailings sinter-free artificial aggregate is (10-15):1, and the iron tailings sinter-free artificial aggregate also needs to be treated with a composite activator and carbonized. The composite activator includes water glass, NaOH, sulfate activator and triethanolamine.

[0007] In the formula, cement, silica fume and nano-silica are cementitious materials, and quartz sand and iron tailings sinter-free artificial aggregate are aggregates. Cement is the matrix, silica fume fills the gap between cement particles, and nano-silica fills the micropores of silica fume and cement, so that the compactness of the cementitious system is improved.

[0008] Quartz sand provides a high-strength skeleton, and the treated iron tailings aggregate has the dual functions of inert filling and active participation. The CaCO3 layer on the surface of the iron tailings aggregate reacts with the cement paste to generate C-S-H, realizing chemical bonding at the "aggregate-cementitious" interface and avoiding the "weak interface" problem of traditional aggregates.

[0009] Further, the iron tailings sinter-free artificial aggregate is prepared from raw materials including the following weight percentages: iron tailings powder 50%-80%, activator 5%-25%, inert filler 1%-15%, and auxiliary cementing agent 5%-30%. The auxiliary cementing agent is cement, fly ash, mineral powder and silica fume, and the activator is calcium hydroxide and water glass. The iron tailings sinter-free artificial aggregate uses the iron tailings-based artificial high-strength fine aggregate proposed in the application number CN202311054552.6.

[0010] Further, the cement is Portland cement, and the strength grade of the cement is 42.5 or 52.5. The Portland cement should meet the requirements of the national standard GB 175-2007 to ensure its quality stability and compatibility with the concrete system of the present application.

[0011] The strength grade of the silica fume is 95 or 92, and the particle size distribution range of the silica fume is 0.1-1.0 μm, of which the proportion of particles with a particle size less than 0.5 μm is not less than 80%. This more accurately controls the microstructure of the silica fume, thereby better exerting its pozzolanic effect in the concrete.

[0012] The particle size distribution range of the nano-silica should be 10-100 nm to better exert its filling and reinforcing effects in the concrete, the specific surface area should be greater than 100 m 2 / g to improve its dispersibility and activity in the concrete, and the purity should be not less than 99% to ensure its quality stability and effect in the concrete.

[0013] Further, the particle size range of the quartz sand is 0.315-2.50 mm, and the shape of the quartz sand is spherical or near-spherical particles with good particle shape to reduce the frictional resistance between particles and improve the fluidity of the concrete. The clay content in the quartz sand is not more than 0.5%, and the mica content is not more than 0.3% to ensure the workability and durability of the concrete.

[0014] The non-sintered artificial aggregate made from iron tailings is in the form of spherical particles with a particle size range of 1.25-2.50 mm. The chemical composition of the non-sintered artificial aggregate made from iron tailings contains no less than 40% SiO2, no less than 10% Al2O3, and no more than 15% Fe2O3 to ensure good chemical stability and compatibility with cementitious matrix. Before use, the non-sintered artificial aggregate made from iron tailings is surface-cleaned with anionic surfactants to remove surface dust and impurities, thereby improving its bonding strength with cementitious matrix.

[0015] Due to its porous structure, this artificial aggregate can provide internal curing, and its uniform spherical shape can optimize the rheological properties of the mixture and improve the uniformity and orientation of fiber distribution in the matrix.

[0016] Furthermore, the specific treatment method for non-sintering artificial aggregates from iron tailings is as follows:

[0017] S1, Composite Activator Treatment

[0018] Spray the non-sintering artificial aggregate made from iron tailings with a composite activator solution containing water glass, NaOH, sulfate activator, and triethanolamine for 3-4 hours at a temperature of 20-40℃; the water glass content is 5-8wt%, the NaOH content is 2-4wt%, the sulfate activator content is 1-2wt%, and the triethanolamine content is 1-2wt%.

[0019] S2, carbonization treatment

[0020] The non-sintering artificial aggregate of iron tailings treated with composite activator is placed in a CO2 environment at a temperature of 50-60°C, a humidity of 80-95%, and a pressure of 2-4MPa for 4-8 hours for carbonization.

[0021] In the composite activator treatment, water glass and NaOH form a highly alkaline environment, which directionally breaks the Si-O bonds in the aluminosilicate glass in iron tailings, thereby increasing the dissolution of active SiO2; the sulfate activator introduces SO4. 2- , with Ca 2+ The reaction produces ettringite, which fills the pores on the surface of the aggregate; triethanolamine accelerates cement hydration through complexation; the three synergistically increase the active sites on the aggregate surface, providing sufficient Ca for subsequent carbonation reactions. 2+ source.

[0022] The "densification finishing touch" of carbonization: CO2 rapidly penetrates into the aggregate, reacting with Ca(OH)2 and Ca in CSH generated after activation. 2+ The reaction generates CaCO3 crystals, forming a triple-filled structure of "ettringite-CSH-calcium carbonate". This process reduces the porosity of the aggregate, increases its surface hardness, and improves the interfacial bonding strength with the cement paste.

[0023] Further, the steel fiber is a stainless steel fiber or a high-strength carbon steel fiber with good corrosion resistance, a length of 10-30 mm, a diameter of 0.2-0.5 mm, and a tensile strength not less than 600 MPa, so as to enhance the crack resistance and toughness of the concrete, and the surface of the steel fiber can be further plated with copper or coated with an epoxy coating to prevent rusting during the mixing of the concrete and affecting the performance of the concrete.

[0024] Further, the molecular weight of the polyacrylamide is 10-20 million to ensure that it has good thickening and dispersion performance, improves the fluidity and workability of the concrete, and the ionicity is 10-30% to adjust the adsorption and dispersion effect in the concrete.

[0025] Further, the silane coupling agent is one or more of KH550, KH560 and KH570; the specific type should be selected according to the performance requirements of the concrete and the properties of the raw materials, the purity should be not less than 98% to ensure the quality stability and the effect in the concrete, and the active group content should be not less than 10% to improve the chemical bonding ability with the quartz sand, the sintering-free artificial aggregate and the cement matrix, and enhance the interfacial strength of the concrete.

[0026] The air entraining agent is one or more of rosin hot polymer air entraining agent, alkyl benzene sulfonate air entraining agent or synthetic air entraining agent; the foaming capacity should be not less than 50% (volume increase rate), the introduced air bubbles in the concrete should have good stability, the air bubble half-life should be not less than 60 minutes, and the air entraining agent should have good compatibility with cement, silica fume, nano silicon dioxide and other components without chemical reaction or negative effect;

[0027] The retarder is one or more of sugar retarder (such as sucrose, sodium gluconate), lignin sulfonate retarder or polycarboxylate retarder; the retarder can prolong the initial setting time of the concrete to not less than 4 hours and the final setting time to not less than 6 hours, the retarder should have a certain water reducing function with a water reducing rate not less than 10%, and the retarder should have good compatibility with cement, silica fume, nano silicon dioxide and other components without chemical reaction or negative effect;

[0028] The water reducing agent is a polycarboxylic acid high-efficiency water reducing agent, which is a light yellow viscous liquid with a water reducing rate of 35% and a solid content of 40%.

[0029] The application also provides a preparation method of the super high performance concrete mixed with the sintering-free artificial aggregate of iron tailings, which comprises the following steps:

[0030] I. The sintering-free artificial aggregate of iron tailings is first treated with a composite activator and carbonized;

[0031] II. Quartz sand, iron tailings unsintered artificial aggregate, cement, silica fume, nano-silica, polyacrylamide, silane coupling agent are simultaneously poured into the concrete mixer for stirring;

[0032] III. Air entraining agent, retarder, water reducing agent are pre-mixed with water, and then poured into the concrete mixer for stirring;

[0033] IV. Steel fiber is slowly poured into the concrete mixer, the adding speed of steel fiber is controlled at 0.5-1.0 kg / min, and low-speed stirring of the mixer is maintained during the adding process, the stirring speed is 20-30 r / min, so as to prevent the steel fiber from being bunched and ensure the uniform distribution of the steel fiber in the concrete mixture, after the steel fiber is completely poured, the stirring is continued for 2-5 min, so as to ensure the uniform distribution of the steel fiber in the mixture;

[0034] V. The uniformly stirred concrete is loaded into a test mold, the test mold is vibrated on a vibration table for vibration molding, and the test piece is cured.

[0035] Further, in step II, the stirring speed is 30-50 r / min, the stirring time is 4-10 min, and the temperature during the stirring process is 10-30℃, so as to prevent the performance of the concrete from being affected due to excessively high or low temperature; in step III, the stirring speed is 40-60 r / min, and the stirring time is 3-8 min.

[0036] Further, in step III, the pre-mixing time is not less than 2 min, and a high-speed stirrer is used for sufficient stirring, so as to ensure the uniform dispersion of the water reducing agent in water and improve the dispersion effect of the water reducing agent and the working performance of the concrete.

[0037] Further, in step V, the vibration molding time is 10-30 s, the vibration frequency is 30-50 Hz, and the amplitude is 0.5-1.0 mm, so as to ensure the compactness and molding quality of the concrete test piece; the test mold should be a standard size concrete test mold, and the inner wall of the test mold should be coated with a thin layer of release agent, so as to facilitate the demolding of the test piece and ensure the appearance quality of the test piece;

[0038] The curing is steam curing or / and standard curing;

[0039] The iron tailings unsintered artificial aggregate treated in step I is subjected to surface cleaning treatment with an anionic surfactant.

[0040] Further, in the steam curing, the test piece is demolded after being placed in a constant temperature and humidity condition for 24 h, and immediately put into a curing box, cured at 45℃ for 2 h in the curing box, then the temperature is increased to 60℃ for curing for 2 h, and finally the temperature is increased to 75℃ for curing for 68 h, the humidity in the curing box should be maintained at 90%-95% during the steam curing, so as to prevent dry shrinkage cracks from appearing on the surface of the concrete, and then standard curing can be carried out.

[0041] Further, during standard curing, the curing temperature is 20±1℃, and the humidity RH≥95%, during the standard curing process, the surface of the test piece in the curing chamber should be sprayed regularly to ensure that the surface of the test piece is always kept in a wet state.

[0042] Compared with the prior art, the sintering-free artificial aggregate ultra-high performance concrete mixed with iron tailings has the following advantages:

[0043] (1) The sintering-free artificial aggregate ultra-high performance concrete mixed with iron tailings replaces part of the quartz sand with sintering-free artificial aggregate of iron tailings, which can play a good internal curing role in the concrete, and the strengthening effect of the transition zone of the matrix-aggregate interface and the pozzolanic activity of the artificial aggregate itself can also densify the microstructure of the ultra-high performance concrete, thereby improving the mechanical properties and durability of the concrete, and the spherical particle shape of the artificial aggregate can also optimize the rheological properties of the concrete mixture, such as yield stress, plastic viscosity, etc., thereby improving the uniformity and orientation of the fiber distribution in the concrete, and thereby improving the crack resistance of the concrete. Replacing part of the quartz sand with sintering-free artificial aggregate of iron tailings reduces the consumption of quartz sand and the production cost of ultra-high performance concrete, making the prepared ultra-high performance concrete more economical.

[0044] (2) The sintering-free artificial aggregate ultra-high performance concrete prepared by replacing quartz sand with sintering-free artificial aggregate of iron tailings can reduce the preparation cost of ultra-high performance concrete, reduce the amount of quartz sand and thereby reduce the mining of mineral resources, and protect natural resources; on the other hand, the sintering-free artificial aggregate of iron tailings is made of iron tailings fine mud, and there is no sintering process in the preparation of artificial aggregate, which saves a lot of energy consumption, at the same time, absorbs a large amount of iron tailings fine mud, solves the dam collapse, land resource occupation, soil and groundwater pollution and other threats to the natural environment caused by the storage of iron tailings, compared with other treatment methods, the sintering-free artificial aggregate of iron tailings is made of iron tailings fine mud and then applied to ultra-high performance concrete, which is more safe and reliable and has a large amount of absorption, and can also play the material advantages of artificial aggregate itself. The process adopted in the present application is simple, easy to operate and has wide application range.

[0045] (3) The sintering-free artificial aggregate ultra-high performance concrete prepared by replacing quartz sand with sintering-free artificial aggregate of iron tailings has good mechanical properties, the prepared concrete test piece has a 3-day compressive strength of >60MPa, a 7-day compressive strength of >80MPa, and a 28-day compressive strength of >130MPa, the microstructure of the concrete matrix mixed with artificial aggregate of iron tailings is more compact, the pore structure is more refined, and the interface transition zone is more compact, the prepared ultra-high performance concrete has excellent performance and is green and environmentally friendly, and has the advantages of environment and economy, and has wide application prospect. BRIEF DESCRIPTION OF DRAWINGS

[0046] The accompanying drawings, which form a part of the present application, are included to provide a further understanding of the application, and are incorporated in and constitute a part of this specification. The illustrations are shown schematically in the drawings of the preferred embodiments of the application, and the illustrations are used to explain the application and are not intended to limit the application in any way.

[0047] Figure 1 Relative humidity comparison of the concrete prepared for Example 1-2 and Comparative Example;

[0048] Figure 2 Micro-morphology of the concrete test piece prepared for Example 1;

[0049] Figure 3 Micro-morphology of the concrete test piece prepared for Example 2;

[0050] Figure 4 Micro-morphology of the concrete test piece prepared for Comparative Example 1. DETAILED DESCRIPTION

[0051] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict.

[0052] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the present application.

[0053] Example 1

[0054] An iron tailing-incorporated non-sintered artificial aggregate super-high performance concrete comprises the following components: gel material: 600 parts of ordinary Portland cement, 160 parts of silica fume and 4 parts of nano silicon dioxide;

[0055] Aggregate: 1000 parts of quartz sand, 75 parts of iron tailing-incorporated non-sintered artificial aggregate;

[0056] Steel fiber: 100 parts;

[0057] Polyacrylamide: 0.9 parts;

[0058] Silane coupling agent: 1 part;

[0059] Air entraining agent: 0.1 part;

[0060] Retarder: 0.6 parts;

[0061] Water reducing agent: 15 parts, polycarboxylic acid-based high efficiency water reducing agent;

[0062] Water: 170 parts.

[0063] The strength grade of the ordinary portland cement is PO 42.5, the strength grade of the silica fume is 95, the particle size distribution range of the silica fume is 0.1-1.0 μm, and the proportion of particles with a particle size less than 0.5 μm is not less than 80%; the particle size distribution range of the nano-silicon dioxide should be 20-30 nm, the specific surface area is greater than 100 m 2 / g, and the purity is not less than 99%.

[0064] The particle size range of the quartz sand is 1.25-2.50 mm, the shape of the quartz sand is spherical or near-spherical particles with good particle shape, the clay content in the quartz sand is not more than 0.5%, and the mica content is not more than 0.3%;

[0065] The sinter-free artificial aggregate of iron tailings is prepared from raw materials including the following weight percentages: iron tailings powder 50%-80%, activator 5%-25%, inert filler 1%-15%, and auxiliary cementing agent 5%-30%; wherein the auxiliary cementing agent is cement, fly ash, mineral powder and silica fume, and the activator is calcium hydroxide and water glass.

[0066] The sinter-free artificial aggregate of iron tailings is spherical particles with a particle size range of 1.25-2.50 mm, the SiO2 content in the chemical composition of the sinter-free artificial aggregate of iron tailings is not less than 40%, the Al2O3 content is not less than 10%, and the Fe2O3 content is not more than 15%; before use, the sinter-free artificial aggregate of iron tailings is subjected to surface cleaning treatment using an anionic surfactant sodium dodecyl benzene sulfonate (0.8% concentration) to remove surface dust and impurities.

[0067] The steel fiber is a stainless steel fiber with a length of 10 mm and a diameter of 0.2 mm, and a tensile strength of not less than 600 MPa.

[0068] The molecular weight of the polyacrylamide is 12 million, and the ionicity is 15%.

[0069] The silane coupling agent is KH550, the air entraining agent is a rosin hot polymer air entraining agent, and the retarder is a sugar retarder sodium gluconate.

[0070] The preparation method of the above-mentioned super high performance concrete mixed with the sinter-free artificial aggregate of iron tailings is as follows:

[0071] (1) Pretreatment of sinter-free artificial aggregate of iron tailings

[0072] (1-1) Composite activator treatment

[0073] The sintering-free artificial aggregate of iron tailings is sprayed with a composite activator solution containing 5wt% water glass, 2wt% NaOH, 1wt% sulfate activator Na2SO4 and 1wt% triethanolamine for 3h at a temperature of 25°C;

[0074] (1-2) Carbonization treatment

[0075] The sintering-free artificial aggregate of iron tailings treated with the composite activator is placed in a CO2 environment at a temperature of 50°C, a humidity of 80% and a pressure of 2MPa for 4.5 hours of carbonization;

[0076] (1-3) Surface treatment

[0077] Surface cleaning treatment is performed using an anionic surfactant sodium dodecyl benzene sulfonate (0.8% concentration) to remove floating dust and impurities on the surface;

[0078] (2) The quartz sand, sintering-free artificial aggregate of iron tailings, ordinary portland cement, silica fume, nano-silicon dioxide, polyacrylamide and silane coupling agent are simultaneously poured into a concrete mixer, and stirred at 30r / min for 4min, with a temperature of 25°C during stirring;

[0079] (3) The water, polycarboxylate superplasticizer, air entraining agent and retarder are pre-mixed for 2min, and then poured into the concrete mixer and stirred at 60r / min for 8min;

[0080] (4) The steel fibers are slowly poured into the concrete mixer, with an addition speed controlled at 0.5kg / min, and low-speed stirring is maintained during the addition process to prevent the steel fibers from clumping and ensure uniform distribution in the concrete mixture. After the steel fibers are completely poured in, stirring is continued for 2min to ensure uniform distribution of the steel fibers in the mixture;

[0081] (5) The concrete mixture is loaded into a test mold, and the test mold is vibrated on a vibration table for vibration molding. The vibration molding time is 20s, the vibration frequency is 35Hz, and the amplitude is 0.5mm;

[0082] (6) The curing method of the test piece is standard curing. The test piece is removed from the mold after being placed in a constant temperature and humidity environment for 24h, and then standard curing is performed until each age. The curing temperature is 20±1°C, and the humidity RH≥95%.

[0083] The prepared super high performance concrete structure is dense, the slump of the concrete is 240 mm, the slump spread is 540 mm, the 3-day compressive strength of the concrete sample is 67 MPa, the 7-day compressive strength is 85 MPa, the 28-day compressive strength is 136 MPa, the 28-day flexural strength is 21 MPa, the 28-day tensile strength is 6.5 MPa, the 28-day elastic modulus is 44 MPa, the chloride ion diffusion coefficient is 0.12*10 -12 m 2 / s, and the drying shrinkage is 210*10 -6 -6. The performance, mechanical properties and durability of the mixture meet the relevant requirements of national standards and industry standards.

[0084] Example 2

[0085] A super high performance concrete mixed with iron tailings and sintered artificial aggregate includes the following components: gel material: 700 parts of ordinary Portland cement, 200 parts of silica fume and 7 parts of nano silicon dioxide;

[0086] Aggregate: 1200 parts of quartz sand, 120 parts of iron tailings and sintered artificial aggregate;

[0087] Steel fiber: 180 parts;

[0088] Polyacrylamide: 1.5 parts;

[0089] Silane coupling agent: 3 parts;

[0090] Air entraining agent: 0.25 parts;

[0091] Retarder: 1.7 parts;

[0092] Water reducing agent: 30 parts, polycarboxylate high efficiency water reducing agent;

[0093] Water: 210 parts.

[0094] The strength grade of the ordinary Portland cement is PO 42.5, the strength grade of the silica fume is 95, the particle size distribution range of the silica fume is 0.1-1.0 μm, and the proportion of particles with a particle size less than 0.5 μm is not less than 80%; the particle size distribution range of the nano silicon dioxide should be 30-40 nm, the specific surface area is greater than 100 m 2 / g, and the purity is not less than 99%.

[0095] The particle size range of the quartz sand is 1.25-2.50 mm, the shape of the quartz sand is spherical or near-spherical particles with good particle shape, the clay content in the quartz sand is not more than 0.5%, and the mica content is not more than 0.3%;

[0096] The sinter-free artificial aggregate of iron tailings adopts the iron tailings-based artificial high-strength fine aggregate proposed in the application number CN202311054552.6. The sinter-free artificial aggregate of iron tailings is a spherical particle with a particle size range of 1.25-2.50 mm. The content of SiO2 in the chemical composition of the sinter-free artificial aggregate of iron tailings is not less than 40%, the content of Al2O3 is not less than 10%, and the content of Fe2O3 is not more than 15%. The sinter-free artificial aggregate of iron tailings is subjected to surface cleaning treatment using an anionic surfactant sodium dodecyl benzene sulfonate (0.8% concentration) before use to remove floating dust and impurities on the surface.

[0097] The steel fiber is a carbon steel fiber with a length of 15 mm and a diameter of 0.3 mm, and a tensile strength of not less than 600 MPa.

[0098] The molecular weight of the polyacrylamide is 15 million, and the ionicity is 20%.

[0099] The silane coupling agent is KH560, the air entraining agent is an alkyl benzene sulfonate air entraining agent, and the retarder is a lignin sulfonate retarder.

[0100] The preparation method of the above-mentioned super high performance concrete mixed with the sinter-free artificial aggregate of iron tailings is as follows:

[0101] (1) Pretreatment of sinter-free artificial aggregate of iron tailings

[0102] (1-1) Composite activator treatment

[0103] The sinter-free artificial aggregate of iron tailings is sprayed with a composite activator solution containing 8wt% water glass, 4wt% NaOH, 2wt% sulfate activator Na2SO4 and 1.5wt% triethanolamine for 4h at a temperature of 38°C;

[0104] (1-2) Carbonization treatment

[0105] The sinter-free artificial aggregate of iron tailings treated with the composite activator is placed in a CO2 environment at a temperature of 60°C, a humidity of 92% and a pressure of 4MPa for 7 hours of carbonization;

[0106] (1-3) Surface treatment

[0107] Surface cleaning treatment is performed using an anionic surfactant sodium dodecyl benzene sulfonate (0.8% concentration) to remove floating dust and impurities on the surface;

[0108] (2) The quartz sand, sinter-free artificial aggregate of iron tailings, ordinary Portland cement, silica fume, nano silicon dioxide, polyacrylamide and silane coupling agent are simultaneously poured into a concrete mixer, and stirred at 30r / min for 4min, with a temperature of 25°C during the stirring process;

[0109] (3) Pre-mixing water, polycarboxylate superplasticizer, air entraining agent and retarder for 2 minutes, then pouring into the concrete mixer and stirring at 60 r / min for 8 minutes;

[0110] (4) Slowly pouring the steel fiber into the concrete mixer, and controlling the adding speed of the steel fiber at 0.9 kg / min, and keeping the low-speed stirring of the mixer during the adding process to prevent the steel fiber from agglomerating and ensure the uniform distribution of the steel fiber in the concrete mixture, and stirring for 2 minutes after the steel fiber is completely poured to ensure the uniform distribution of the steel fiber in the mixture;

[0111] (5) Pouring the concrete mixture into the test mold, and performing vibration molding on the vibration table; the vibration molding time is 20 seconds, the vibration frequency is 40 Hz, and the vibration amplitude is 1.0 mm;

[0112] (6) The curing method of the test piece is first steam curing: placing the test piece in a constant temperature and humidity environment for 24 hours, then removing the mold and immediately placing it in a curing box, curing at 45°C for 2 hours, then increasing the temperature to 60°C for 2 hours, and finally increasing the temperature to 75°C for 68 hours, and the humidity in the curing box should be maintained at 90-95% during the steam curing process to prevent dry shrinkage cracks on the surface of the concrete, and then standard curing can be performed.

[0113] During standard curing, the curing temperature is 20±1°C and the humidity RH≥95%, and during the standard curing process, the test piece surface in the curing room should be sprayed regularly to ensure that the test piece surface is always kept wet.

[0114] The prepared ultra-high performance concrete structure is dense, the slump of the concrete is 250 mm, the slump spread is 550 mm, the 3-day compressive strength of the concrete test piece is 64 MPa, the 7-day compressive strength is 81 MPa, the 28-day compressive strength is 134 MPa, the 28-day flexural strength is 23 MPa, the 28-day tensile strength is 6.1 MPa, the 28-day elastic modulus is 41 MPa, and the chloride ion diffusion coefficient is 0.13×10 -12 m 2 / s, and the dry shrinkage is 220×10 -6 . The performance, mechanical properties and durability of the mixture meet the relevant requirements of national standards and industry standards.

[0115] Comparative Example 1: No iron tailings sinter-free artificial aggregate is added

[0116] An ultra-high performance concrete mixed with iron tailings sinter-free artificial aggregate, comprising the following components: gel material: 600 parts of ordinary Portland cement, 160 parts of silica fume and 4 parts of nano silicon dioxide;

[0117] Aggregate: 1075 parts of quartz sand;

[0118] Steel fiber: 100 parts;

[0119] Polyacrylamide: 0.9 parts;

[0120] Silane coupling agent: 1 part;

[0121] Air entraining agent: 0.1 part;

[0122] Retarder: 0.6 parts;

[0123] Water reducing agent: 15 parts, polycarboxylic acid high efficiency water reducing agent;

[0124] Water: 170 parts.

[0125] Preparation is the same as Example 1.

[0126] The relative humidity change curve in the super high performance concrete test piece of Example 1-2 and Comparative Example 1 is shown in Figure 1 It can be seen that the addition of the sinter-free artificial aggregate of iron tailings can effectively delay the decrease of the relative humidity in the concrete matrix, and can play a good internal curing effect.

[0127] The micro-morphology of the concrete test piece of Example 1, Example 2 and Comparative Example 1 is shown in Figures 2-4 It can be seen from the figure that the addition of the sinter-free artificial aggregate of iron tailings does not affect the compactness of the concrete matrix, and the microstructure of the concrete matrix with the addition of the sinter-free artificial aggregate of iron tailings is more compact, the pore structure is more refined, and the interface transition zone is more compact.

[0128] Comparative Example 2

[0129] The difference from the above Example 1 is that the amount of the sinter-free artificial aggregate of iron tailings is different, which is 50 parts, the mass ratio of quartz sand to sinter-free artificial aggregate of iron tailings is 20:1, and the others are the same as Example 1.

[0130] Comparative Example 3

[0131] The difference from the above Example 1 is that the amount of the sinter-free artificial aggregate of iron tailings is different, which is 150 parts, the mass ratio of quartz sand to sinter-free artificial aggregate of iron tailings is 6.7:1, and the others are the same as Example 1.

[0132] Comparative Example 4

[0133] The difference from the above Example 1 is that the amount of the sinter-free artificial aggregate of iron tailings is different, which is 300 parts, and the others are the same as Example 1.

[0134] Comparative Example 5

[0135] The difference from the above Example 1 is that the sinter-free artificial aggregate of iron tailings is not subjected to any pretreatment (i.e. not subjected to composite activator treatment and carbonization treatment), and the others are the same as Example 1.

[0136] Comparative Example 6

[0137] The difference from Example 1 is that the pretreatment of the sinter-free artificial aggregate of iron tailings removes the carbonization treatment, and the others are the same as Example 1.

[0138] Comparative Example 7

[0139] The difference from Example 1 is that the pretreatment of the sinter-free artificial aggregate of iron tailings removes the composite activator treatment, and the others are the same as Example 1.

[0140] Comparative Example 8

[0141] The difference from Example 1 is that the pretreatment step of the sinter-free artificial aggregate of iron tailings is different, first carbonization treatment, then composite activator treatment, and the others are the same as Example 1.

[0142] Table 1 Performance comparison of each example and comparative example

[0143]

[0144] By comparing Example 1 with Comparative Example 1, it can be seen that adding an appropriate amount of sinter-free artificial aggregate of iron tailings can improve the mechanical properties and durability of ultra-high performance concrete, because the sinter-free artificial aggregate of iron tailings can play an internal curing role in concrete, and the water release of the sinter-free artificial aggregate of iron tailings can make the concrete matrix undergo secondary hydration during the curing process of the concrete specimen, thereby densifying the concrete matrix, making the concrete matrix more dense, and thus improving the mechanical properties and durability of the concrete.

[0145] By comparing Example 1 with Comparative Examples 2-4, it can be seen that only an appropriate amount of sinter-free artificial aggregate of iron tailings can obtain concrete with better performance, and excessive or insufficient sinter-free artificial aggregate of iron tailings will reduce the mechanical properties and durability of ultra-high performance concrete; because the cylinder compressive strength of the sinter-free artificial aggregate of iron tailings is lower than that of quartz sand, when excessive sinter-free artificial aggregate of iron tailings is added, the negative effect of the low strength of the artificial aggregate will be greater than the positive effect of the self-curing of the artificial aggregate, thus reducing the mechanical properties of the ultra-high performance concrete, because the artificial aggregate has a porous structure, thus excessive addition will reduce the overall density of the concrete, thus excessive addition of the artificial aggregate will reduce the durability of the concrete.

[0146] By comparing example 1 with comparative examples 5-8, it can be seen that the pretreatment can improve the performance of the iron tailings artificial aggregate, and thus the mechanical properties and durability of the prepared ultra-high performance concrete can be improved. The lack of either one of the composite activator treatment and the carbonation treatment, or the lack of both, will affect the performance of the concrete to varying degrees, because the surface activity of the artificial aggregate is improved after pretreatment, the interfacial bonding strength with the cement paste is enhanced, the interfacial transition zone pores are reduced, and the interfacial density and impermeability are improved.

[0147] The above merely describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. An ultra high performance concrete incorporating iron ore tailings unsintered artificial aggregate, characterized in that: The concrete comprises the following components in parts by weight: 600-700 parts of cement, 150-200 parts of silica ash, 1000-1200 parts of quartz sand, 50-150 parts of iron tailings non-sintered artificial aggregate, 100-200 parts of steel fiber, 3-9 parts of nano silicon dioxide, 0.6-1.8 parts of polyacrylamide, 1-3 parts of silane coupling agent, 0.06-0.3 parts of air entraining agent, 0.6-1.8 parts of retarder, 10-40 parts of water reducing agent, and 160-220 parts of water; wherein the mass ratio of quartz sand to iron tailings non-sintered artificial aggregate is (10-15):1, the iron tailings non-sintered artificial aggregate further needs to be treated with a composite activator and carbonized, and the composite activator comprises water glass, NaOH, sulfate activator and triethanolamine; The iron tailings non-sintered artificial aggregate is prepared from raw materials comprising the following weight percentages: 50%-80% of iron tailings powder, 5%-25% of activator, 1%-15% of inert filler, and 5%-30% of auxiliary cementing agent; wherein the auxiliary cementing agent is cement, fly ash, mineral powder and silica ash, and the activator is calcium hydroxide and water glass; The particle size of the quartz sand ranges from 0.315 mm to 2.50 mm, and the particle size of the iron tailings non-sintered artificial aggregate ranges from 1.25 mm to 2.50 mm.

2. The sintering-free artificial aggregate ultra high performance concrete incorporating iron ore tailings as claimed in claim 1, wherein: The cement is Portland cement, and the strength grade of the cement is 42.5 or 52.5; The strength grade of the silica ash is 95 or 92, and the particle size distribution range of the silica ash is 0.1-1.0 μm, wherein the proportion of particles with a particle size less than 0.5 μm is not less than 80%; The particle size distribution range of the nano-silica should be 10-100 nm, and the specific surface area should be greater than 100 m 2 / g, and the purity should be not less than 99%.

3. The sintering-free artificial aggregate ultra high performance concrete incorporating iron ore tailings as claimed in claim 1, wherein: The shape of the quartz sand is spherical or near-spherical particles with good particle shape, the clay content in the quartz sand is not more than 0.5%, and the mica content is not more than 0.3%; The iron tailings non-sintered artificial aggregate is spherical, the chemical composition of the iron tailings non-sintered artificial aggregate contains not less than 40% of SiO2, not less than 10% of Al2O3, and not more than 15% of Fe2O3; and the iron tailings non-sintered artificial aggregate is surface cleaned by using an anionic surfactant before use to remove surface dust and impurities.

4. The sintering-free artificial aggregate ultra high performance concrete incorporating iron ore tailings as claimed in claim 1, wherein: The specific treatment method of the iron tailings non-sintered artificial aggregate is as follows: S1, composite activator treatment Spray the iron tailings non-sintered artificial aggregate with a composite activator solution containing water glass, NaOH, sulfate activator and triethanolamine for 3-4 hours at a temperature of 20-40°C; the content of water glass is 5-8 wt%, the content of NaOH is 2-4 wt%, the content of sulfate activator is 1-2 wt%, and the content of triethanolamine is 1-2 wt%; S2, carbonization treatment Place the iron tailings non-sintered artificial aggregate treated with the composite activator in a CO2 environment at a temperature of 50-60°C, a humidity of 80-95%, and a pressure of 2-4 MPa for carbonization for 4-8 hours.

5. The sintering-free artificial aggregate ultra high performance concrete incorporating iron ore tailings as claimed in claim 1, wherein: The steel fiber is stainless steel fiber or carbon steel fiber, with a length of 10-30 mm, a diameter of 0.2-0.5 mm, and a tensile strength of not less than 600 MPa.

6. The sintering-free artificial aggregate ultra high performance concrete incorporating iron ore tailings as claimed in claim 1, wherein: The molecular weight of the polyacrylamide is 10-20 million, and the ionicity is 10%-30%. The silane coupling agent is one or more of KH550, KH560 and KH570; The air entraining agent is one or more of rosin hot polymer air entraining agent, alkyl benzene sulfonate air entraining agent and synthetic air entraining agent; the foaming capacity of the air entraining agent should be not less than 50%, and the bubble half-life period is not less than 60 min; The retarder is one or more of sugar retarder, lignin sulfonate retarder and polycarboxylate retarder; The water reducing agent is polycarboxylate high efficiency water reducing agent, which is a light yellow viscous liquid, the water reducing rate is 35%, and the solid content is 40%.

7. A method of manufacturing sintering-free artificial aggregate ultra-high performance concrete admixed with iron tailings as claimed in any one of claims 1 to 6, characterized in that: The method comprises the following steps: I. First, the sinter-free artificial aggregate of iron tailings is treated with a composite activator and carbonized; II. The quartz sand, sinter-free artificial aggregate of iron tailings, cement, silica fume, nano silicon dioxide, polyacrylamide and silane coupling agent are simultaneously poured into a concrete mixer for stirring; III. The air entraining agent, the retarder and the water reducing agent are pre-mixed with water, and then poured into the concrete mixer for uniform stirring; IV. The steel fiber is slowly poured into the concrete mixer, the addition speed of the steel fiber is controlled at 0.5-1.0 kg / min, and the low-speed stirring of the mixer is maintained during the addition process, the stirring speed is 20-30 r / min, and the steel fiber is stirred for 2-5 min after being completely poured; V. The uniformly stirred concrete is loaded into a test mold, the test mold is vibrated on a vibration table to form, and the test piece is cured.

8. The method of producing sintering-free artificial aggregate ultra-high performance concrete by incorporating iron tailings as claimed in claim 7, wherein: In step II, the stirring speed is 30-50 r / min, the stirring time is 4-10 min, and the temperature during the stirring process is 10-30℃; in step III, the stirring speed is 40-60 r / min, and the stirring time is 3-8 min.

9. The method of manufacturing sintering-free artificial aggregate ultra high performance concrete incorporating iron ore tailings as claimed in claim 7, wherein: In step V, the vibration forming time is 10-30 s, the vibration frequency is 30-50 Hz, and the amplitude is 0.5-1.0 mm; The curing is steam curing or / and standard curing; The sinter-free artificial aggregate of iron tailings treated in step I is subjected to surface cleaning treatment with an anionic surfactant.

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