Low-self-shrinkage ultra-high performance concrete containing solid waste

Abstract

The invention discloses low-self-shrinkage ultra-high performance concrete containing solid waste, and belongs to the technical field of civil engineering. The ultra-high performance concrete material comprises the following components: 410 kg / m < 3 > of cement, 210 kg / m < 3 > of silica fume, 90 kg / m < 3 > of fly ash, 1100 kg / m < 3 > of quartz sand, 145 kg / m < 3 > of copper-plated steel fiber, 200 kg / m < 3 > of water, 25-30 kg / m < 3 > of a water reducing agent, 200-300 kg / m < 3 > of lithium slag and 50-100 kg / m < 3 > of red mud. The lithium slag and the red mud are used as main cementing materials, so that the utilization rate of the lithium slag and the red mud is increased, the environmental pollution is reduced, the self-constriction of the ultra-high performance concrete is reduced, and the development of early strength and later strength of the ultra-high performance concrete is considered.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a low-autoclaved solid waste-containing ultra-high performance concrete. BACKGROUND

[0002] Compared with ordinary concrete, ultra-high performance concrete (UHPC) has the characteristics of high compressive strength, high tensile strength, tensile strain hardening behavior and extremely low permeability. Due to its excellent performance, UHPC has been widely applied in the fields of bridges, fabricated buildings, architectural decoration and the like in recent years, and has a broad application prospect.

[0003] However, the content of cement in UHPC is high and the water-cement ratio is low, so that the hydration rate of cement in UHPC is only 30-40%, and a large amount of cement only plays a filling role as micro aggregate, resulting in a large waste of energy and resources. In addition, the high cement content also leads to a large self-shrinkage of UHPC, and the cracks caused by shrinkage may cause harm to the strength and durability of the UHPC structure, which restricts the application of UHPC in repair and reinforcement and post-pouring belt engineering.

[0004] Therefore, it is of great significance to use solid waste capable of compensating shrinkage to replace part of the cement to prepare low-autoclaved UHPC. SUMMARY

[0005] The application provides a low-autoclaved solid waste-containing ultra-high performance concrete, part of cement is replaced by lithium slag and red mud, the sulfate salt in the lithium slag can react with the aluminum salt in the red mud and the tricalcium aluminate in the cement to generate needle-bar-shaped ettringite to compensate the self-shrinkage of UHPC, and the hydraulic mineral contained in the lithium slag and the red mud is helpful to the strength development of UHPC; in addition, the reduction of the cement content in UHPC will greatly reduce the hydration heat, reduce the shrinkage cracks, improve the utilization rate of cement, realize the low-autoclaved UHPC target, and promote the application process of UHPC.

[0006] To solve the above technical problems, the application comprises the following technical scheme:

[0007] In a first aspect, the application provides a low-autoclaved solid waste-containing ultra-high performance concrete, 1m 3 The concrete raw material is used in an amount of 1m 3 , silica fume: 210kg / m 3 , fly ash: 90kg / m 3 , quartz sand: 1100kg / m 3 , steel fiber: 145kg / m 3 , water: 200kg / m 3Water reducing agent: 25-30 kg / m 3 Lithium residue: 200-300 kg / m 3 Red mud: 50-100 kg / m 3 .

[0008] The following is a preferred technical solution of the present application, but not as a limitation of the technical solutions provided by the present application, through the following technical solutions, the technical purpose and beneficial effects of the present application can be better achieved and realized.

[0009] As a preferred technical solution of the present application, the lithium residue is an acid leaching residue produced after lithium extraction from spodumene, the remaining lithium content after extraction is less than 0.1%, the sulfate content is higher than 13%, the lithium residue is dried and ground, the specific surface area is 1100 m 2 / kg, and the main mineral composition is calcite, silicate mineral, quartz and gypsum.

[0010] As a preferred technical solution of the present application, the cement is P.Ⅱ52.5 Portland cement, and the apparent density is 3084.83 kg / m 3 .

[0011] As a preferred technical solution of the present application, the fly ash is grade II fly ash specified in the national standard GB / T 1596-2017 "Fly Ash for Use in Cement and Concrete", the apparent density is 2113.45 kg / m 3 , the specific surface area is 423.7 m 2 / kg, and the particle size is 0.3-112.5 μm.

[0012] As a preferred technical solution of the present application, the SiO2 content in silica ash is ≥94%, the apparent density is 2296.39 kg / m 3 , and the particle size is 0.3-112.5 μm.

[0013] As a preferred technical solution of the present application, the red mud is an industrial solid waste produced by Bayer process for extracting alumina, the apparent density is 2800-3000 kg / m 3 , and the particle size distribution satisfies D90≤75 μm and D10≥5 μm.

[0014] As a preferred technical solution of the present application, the quartz sand is composed of three gradations of 26-40 mesh, 40-70 mesh and 70-120 mesh, the 26-40 mesh quartz sand accounts for 29.8% of the total amount, the 40-70 mesh accounts for 27.1%, and the 70-120 mesh accounts for 43.1%.

[0015] As a preferred technical scheme of the present application, the steel fiber has a low-carbon steel (C≤0.15%) as a matrix, a copper layer with a thickness of 1-5 μm on the surface, and is realized by an electroplating process, has an average length of 14 mm and a diameter of 0.2 mm, and has a tensile strength of >2800 MPa after being tested according to the GB / T 228.1-2021 "Metallic Materials-Tensile Testing" standard.

[0016] As a preferred technical scheme of the present application, the water reducing agent is a polycarboxylate-based water reducing agent with a solid content of 35%, is added at 2.8-3% of the mass of cementitious materials, and has a water-reducing rate of ≥40% after being tested according to the GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures" standard.

[0017] Meanwhile, the preparation method of the low-autoclaved super high performance concrete containing solid waste in the present application comprises the following steps:

[0018] Step S1: placing a mixture of cement, silica fume, fly ash, lithium slag, red mud and three-stage quartz sand into a stirrer, stirring at a speed of 50 r / min for 1.5 min to form a uniform mixture;

[0019] Step S2: pouring 80% of the total amount of water into the stirrer, stirring at a speed of 50 r / min for 2 min to make the surface of the materials appear wet;

[0020] Step S3: pouring the water reducing agent into the remaining 20% of water, stirring and dissolving in the water, and then pouring into the stirrer, stirring at a speed of 50 r / min for 5 min to make the mixture appear in a uniform fluid state;

[0021] Step S4: uniformly scattering the steel fiber mixture into the stirrer, stirring at a speed of 120 r / min for 3 min to make the steel fibers uniformly distributed, so that the low-autoclaved super high performance concrete containing solid waste is prepared.

[0022] As a preferred technical scheme of the present application, the curing temperature is 20±1℃, and the relative humidity is ≥95%.

[0023] Compared with the prior art, the present application has the beneficial technical effects that:

[0024] 1. The present application provides a new method for resource utilization of lithium slag industrial solid waste, applies lithium slag in the preparation of super high performance concrete, fully utilizes the sulfate and volcanic ash activity in lithium slag, helps to reduce the early self-shrinkage of UHPC, and further improves the strength of super high performance concrete when used with red mud, effectively alleviates the social and environmental impact of large amounts of lithium slag accumulation, and reduces the environmental pollution of lithium slag; in addition to lithium slag, the raw materials of the present application also include red mud, silica fume, fly ash and other solid waste materials, further reducing the environmental pollution of solid waste and turning waste into treasure.

[0025] 2、The application is simple to operate and easy to maintain in preparing the super high performance concrete.

[0026] 3、The application can improve the utilization rate of cement by using lithium slag and red mud to replace part of the cement to prepare the super high performance concrete, and can improve the hydration degree of cement from about 30% to about 50%.

[0027] 4、The mechanical properties of the super high performance concrete material prepared by the application meet the requirements of T / CBMF 37-2018T / CCPA7-2018 “Basic Performance and Test Method of Super High Performance Concrete” for bearing structure, and the 28d compressive strength can be above 150Mpa, and the flexural strength can be above 40Mpa. DETAILED DESCRIPTION

[0028] The low shrinkage super high performance concrete containing solid waste provided by the application is further described in detail in combination with specific examples. According to the following description, the advantages and characteristics of the application will be more apparent.

[0029] The reagents used in the examples of the application are commercially available reagents in the art. The main chemical components of the cement, lithium slag, fly ash, red mud and silica ash used in the examples of the application are analyzed by X-ray fluorescence spectroscopy, and the results are shown in Table 1. The cement is P·Ⅱ52.5 Portland cement:

[0030] Table 1 Chemical composition of raw materials

[0031]

[0032] Example 1

[0033] Table 2 is the mixing ratio of the first group of low shrinkage super high performance concrete containing solid waste. The quartz sand is composed of three gradations of 26-40 mesh, 40-70 mesh and 70-120 mesh, and the 26-40 mesh quartz sand accounts for 29.8% of the total amount, the 40-70 mesh accounts for 27.1%, and the 70-120 mesh accounts for 43.1%. Among them, unit: kg / m 3 , kg / m 3 represents the amount of raw materials in 1m 3 concrete.

[0034] Table 2 UHPC mixing ratio design of Example 1

[0035] Cement Fly ash Silica fume Lithium slag Red mud Quartz sand Water Steel fiber Water reducing agent 410 90 210 225 75 1100 200 145 29

[0036] The preparation method of the low shrinkage super high performance concrete containing solid waste provided in this example is as follows:

[0037] Step S1: Put the mixed material composed of cement, silica fume, fly ash, lithium slag, red mud and tertiary graded quartz sand into a stirrer, stir at a speed of 50 r / min for 1.5 min to form a uniform mixture;

[0038] Step S2: Pour 80% of the total amount of water into the stirrer, stir at a speed of 50 r / min for 2 min to make the surface of the mixed material appear wet;

[0039] Step S3: Pour the water reducing agent into the remaining 20% water, stir and dissolve in the water, then pour into the stirrer, stir at a speed of 50 r / min for 5 min to make the mixture appear uniform fluid state;

[0040] Step S4: Sprinkle the steel fiber mixture evenly into the stirrer, stir at a speed of 120 r / min for 3 min to make the steel fibers uniformly distributed, thereby obtaining the low self-shrinkage ultra-high performance concrete containing solid waste.

[0041] The curing temperature is 20±1℃, the relative humidity is ≥95%, and the curing time is 28d.

[0042] The compressive strength, flexural strength, 3d self-shrinkage and cement hydration degree results are shown in Table 7.

[0043] Example 2

[0044] Table 3 is the mixing proportion of the second group of low shrinkage ultra-high performance concrete containing solid waste, unit: kg / m 3 , kg / m 3 represents the amount of raw materials in 1m 3 of concrete.

[0045] Table 3 UHPC mix design of Example 2

[0046] Cement Fly ash Silica fume Lithium slag Red mud Quartz sand Water Steel fiber Water reducing agent 410 90 210 275 80 1100 200 145 29

[0047] The preparation method of the low shrinkage ultra-high performance concrete containing solid waste provided in this embodiment is the same as that of Example 1.

[0048] The quartz sand is composed of three gradations of 26-40 mesh, 40-70 mesh and 70-120 mesh, the 26-40 mesh quartz sand accounts for 29.8% of the total amount, the 40-70 mesh accounts for 27.1%, and the 70-120 mesh accounts for 43.1%, wherein, unit: kg / m 3 , kg / m 3 represents the amount of raw materials in 1m 3 of concrete.

[0049] Table 4 UHPC mix design of Comparative Example 1

[0050] Cement Fly ash Silica fume Quartz sand Water Steel fiber Water reducing agent 710 90 210 1100 200 145 28

[0051] The preparation method of the solid waste-containing low-shrinkage ultra-high performance concrete provided in the present comparative example is as follows:

[0052] Step S1: the mixed materials composed of cement, silica fume, fly ash and three-grade quartz sand are placed into a stirrer, stirred at a speed of 50 r / min for 1.5 min to form a uniform mixture;

[0053] Step S2: 80% of the total amount of water used is poured into the stirrer, stirred at a speed of 50 r / min for 2 min to make the surface of the materials appear wet;

[0054] Step S3: the water reducing agent is poured into the remaining 20% of water, and after being fully stirred and dissolved in the water, it is poured into the stirrer, stirred at a speed of 50 r / min for 5 min to make the mixture appear in a uniform fluid state;

[0055] Step S4: the steel fiber mixture is uniformly scattered into the stirrer, stirred at a speed of 120 r / min for 3 min to make the steel fibers uniformly distributed, and the solid waste-containing low-autogenous shrinkage ultra-high performance concrete is prepared.

[0056] The curing temperature is 20±1℃, the relative humidity is ≥95%, and the curing time is 28 d.

[0057] The compressive strength, flexural strength, 3d autogenous shrinkage and cement hydration degree results are shown in Table 7.

[0058] Comparative Example 2

[0059] Table 5 is the mix proportion of the ultra-high performance concrete of Comparative Example 2. Compared with Example 1, no red mud is added in this comparative example, and the quartz sand is composed of three grades of 26-40 mesh, 40-70 mesh and 70-120 mesh, with 26-40 mesh quartz sand accounting for 29.8% of the total amount, 40-70 mesh accounting for 27.1%, and 70-120 mesh accounting for 43.1%. Among them, the unit is kg / m 3 , kg / m 3 represents the amount of raw materials in 1 m 3 of concrete.

[0060] Table 5 is the mix proportion design of UHPC of Comparative Example 2

[0061] Cement Fly ash Silica fume Lithium slag Red mud Quartz sand Water Steel fiber Water reducing agent 410 90 210 300 0 1100 200 145 28

[0062] The preparation method of the solid waste-containing low-shrinkage ultra-high performance concrete provided in the present comparative example is as follows:

[0063] Step S1: the mixed materials composed of cement, silica fume, fly ash, lithium slag and three-grade quartz sand are placed into a stirrer, stirred at a speed of 50 r / min for 1.5 min to form a uniform mixture;

[0064] Step S2: 80% of the total amount of water was poured into the stirrer, and stirred at a speed of 50 r / min for 2 min to make the material surface appear wet;

[0065] Step S3: The water reducing agent was poured into the remaining 20% water, and after fully stirring and dissolving in the water, it was poured into the stirrer, and stirred at a speed of 50 r / min for 5 min to make the mixture appear uniform fluid state;

[0066] Step S4: The steel fiber mixture was evenly scattered into the stirrer, and stirred at a speed of 120 r / min for 3 min to make the steel fiber evenly distributed, and the low shrinkage super high performance concrete containing solid waste was prepared.

[0067] The curing temperature was 20±1℃, the relative humidity was ≥95%, and the curing time was 28d.

[0068] The compressive strength, flexural strength, 3d autogenous shrinkage and cement hydration degree results are shown in Table 7.

[0069] Comparative Example 3

[0070] Table 6 is the mix proportion of the super high performance concrete of Comparative Example 3. Compared with Example 1, no lithium slag is added in this comparative example, and the quartz sand is composed of three gradations of 26-40 mesh, 40-70 mesh and 70-120 mesh, with 26-40 mesh quartz sand accounting for 29.8% of the total amount, 40-70 mesh accounting for 27.1%, and 70-120 mesh accounting for 43.1%. Among them, unit: kg / m 3 , kg / m 3 represents the amount of raw materials in 1m 3 of concrete.

[0071] Table 6 UHPC mix proportion design of Comparative Example 3

[0072] Group 28d compressive strength / MPa 28d flexural strength / MPa 3d autogenous shrinkage / με Cement hydration degree / % Example 1 Example 2 Comparative Example 1 Comparative Example 2 410 90 210 0 300 1100 200 145 28

[0073] The preparation method of the low shrinkage super high performance concrete containing solid waste provided in the present example is as follows:

[0074] Step S1: The mixed materials composed of cement, silica fume, fly ash, red mud and three-grade quartz sand were placed into the stirrer, and stirred at a speed of 50 r / min for 1.5 min to form a uniform mixture;

[0075] Step S2: 80% of the total amount of water was poured into the stirrer, and stirred at a speed of 50 r / min for 2 min to make the material surface appear wet;

[0076] Step S3: The water reducing agent was poured into the remaining 20% water, and after fully stirring and dissolving in the water, it was poured into the stirrer, and stirred at a speed of 50 r / min for 5 min to make the mixture appear uniform fluid state;

[0077] Step S4: evenly spread the steel fiber mixture into the stirrer, stir at a speed of 120 r / min for 3 min to make the steel fibers evenly distributed, and the low self-shrinkage ultra-high performance concrete containing solid waste is prepared.

[0078] The curing temperature is 20±1℃, the relative humidity is ≥95%, and the curing time is 28d.

[0079] The compressive strength, flexural strength, 3d self-shrinkage and cement hydration degree are shown in Table 7.

[0080] Table 7: UHPC performance test results

[0081] Comparative Example 3 ​ ​ ​ ​ ​ 182.2 45.9 1249.2 53.56 ​ 173.6 39.58 1141.6 55.78 ​ 152.7 36.2 2912.56 35.67 ​ 152.4 34.32 1048.5 45.78 ​ 143.67 30.62 2157.9 40.36

[0082] As can be seen from the UHPC performance test results and cost analysis results in Table 7, compared with Example 1, 2 and Comparative Example 1, the mechanical properties (28d compressive strength, 28d flexural strength) are more excellent, and the self-shrinkage of Example 1, 2 is less than that of Comparative Example 1, and the cement hydration degree is significantly improved. It can be seen that the lithium slag and red mud involved in the present application can significantly optimize the self-shrinkage and mechanical properties of the concrete. Compared with Comparative Example 2, Example 1 has better mechanical properties, indicating that red mud can stimulate the activity of lithium slag to a certain extent, further improving the mechanical properties of UHPC. Compared with Comparative Example 3, Example 2 has smaller self-shrinkage, indicating that the sulfate in lithium slag can compensate for the self-shrinkage of UHPC. It can be seen that the use of lithium slag and red mud in the present application can effectively improve the strength of UHPC, reduce the self-shrinkage of UHPC, and reduce the production cost of concrete. Therefore, the technical product of the present application has broad market application prospect.

[0083] The above examples are preferred embodiments of the present application, but the embodiments of the present application are not limited to the above examples. The above examples only express several embodiments of the present application, and the description is more specific and detailed, but it cannot be understood as limiting the scope of the patent. It should be noted that for ordinary skilled in the art, without departing from the concept of the present application, several modifications and improvements can be made, which are within the scope of the present application. Therefore, the scope of protection of the present application patent should be subject to the appended claims.

Claims

1. A low autogenous shrinkage ultra-high performance concrete containing solid waste, characterized in that: 1m 3 Concrete raw material consumption meter, including the following raw materials: Portland cement, silica fume, fly ash, lithium slag, red mud, quartz sand, steel fiber, polycarboxylate water reducer and water, of which cement: 410kg / m 3 , silica fume: 210kg / m 3 , fly ash: 90kg / m 3 , quartz sand: 1100kg / m 3 , steel fiber: 145kg / m 3 , water: 200kg / m 3 , water reducing agent: 25-30kg / m 3 , lithium slag: 200-300kg / m 3 , red mud: 50-100kg / m 3 .

2. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: Lithium slag is the acid leaching residue produced after lithium extraction from spodumene. The residual lithium content after extraction is less than 0.1%.

3. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The cement is P.II52.5 silicate cement.

4. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The fly ash is Class II fly ash specified in the national standard GB / T 1596-2017 "Fly ash used in cement and concrete".

5. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The SiO2 content in the silica fume is ≥94%.

6. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The red mud is industrial solid waste generated by the Bayer process for extracting alumina.

7. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The quartz sand is composed of three gradations: 26-40 mesh, 40-70 mesh, and 70-120 mesh. The quartz sand of 26-40 mesh accounts for 29.8% of the total amount, the quartz sand of 40-70 mesh accounts for 27.1%, and the quartz sand of 70-120 mesh accounts for 43.1%.

8. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The steel fiber has a matrix of low-carbon steel, that is, carbon content is less than or equal to 0.15%, and a surface copper layer with a thickness of 1 to 5 μm.

9. The low autogenous shrinkage ultra-high performance concrete containing solid waste according to claim 1, characterized in that: The water reducer is a polycarboxylic acid-based water reducer, which is added at 2.8-3% of the mass of the cementitious material. The water reduction rate is ≥40% according to the test standard GB / T 8077-2012 "Test method for homogeneity of concrete admixtures".

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