Baking-free brick prepared by solidifying shield muck through industrial solid waste and preparation process of baking-free brick

Abstract

The invention provides a baking-free brick prepared by solidifying shield muck through industrial solid waste. The baking-free brick is prepared from low-heat energy-saving micro-expansive cement, the industrial solid waste, shield sand, shield slurry, an alkali activator, a plasticizer and water. The low-heat energy-saving micro-expansive cement has relatively high later strength increasing capacity, can solve the problem of strength shrinkage of geopolymers, and compensates chemical shrinkage and drying shrinkage of the geopolymers to a certain extent; the industrial solid wastes comprise granite stone powder, fly ash and steel slag powder, and the granite stone powder has good effects of reducing shrinkage and inhibiting carbonization. Compared with the prior art, the method has the following advantages that shrinkage is remarkably reduced, carbonization is inhibited, the shrinkage cracking risk is reduced, and the problem of potential environmental pollution caused by the high leaching characteristic is also solved; the problem of geopolymer strength shrinkage is solved, and the long-term durability of the baking-free brick is improved; the plasticizer ensures that the fresh mixture is plasticized for more than or equal to 2 hours, and construction production is ensured.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to a non-fired brick for solidifying shield muck by using industrial solid waste and a preparation process thereof. Background Art

[0002] At present, there are few studies on the green discharge and resource recovery and utilization of shield muck, and the application cases are relatively scarce. The application of additives such as bentonite, foaming agent, and polymer has caused different adverse effects on water quality, soil, environment, traffic, etc. during the stacking and transportation of shield muck. There are still many problems in the treatment methods of shield muck waste slurry, including the requirement of pollution-free transportation process, the need for a large area of site, controlling the pollution caused by the foaming agent to the environment, and the difficulty of separation after consolidation. These problems have led to the situation that in many places, people would rather make the stacking permanent than carry out subsequent treatment on the stacked muck, which directly harms or wastes the national land and environmental resources, highlighting the conflict between construction and development, and also indicating the necessity and urgency of muck recycling technology.

[0003] At present, there are mainly two types of bricks circulating in the market. One is the traditional sintered red brick; the other is the non-fired compressed brick, which is made by adding cement and water to concrete waste and pressing it. Such bricks have good quality, but the cost is relatively high, and they cannot be mixed with soil materials. If shield muck can be used to make bricks, especially non-fired compressed bricks, it can not only reduce the manufacturing cost of non-fired compressed bricks, but also realize the resource utilization of shield muck, which has important economic and environmental benefits.

[0004] Compared with the traditional Portland cement solidification method, the geopolymer solidification technology has many advantages such as replacing cement and reducing carbon emissions, high mechanical properties and high durability. However, it also has many defects at the same time: 1) The shrinkage of geopolymers is large and the carbonation resistance is poor. During the shield construction process, additives such as water, bentonite, foaming agent, polymer, and thickening agent are usually added to the soil bin. The high leaching characteristics of shrinkage cracking will cause potential pollution problems to the environment; 2) The strength reversion problem of geopolymers is serious, and the long-term mechanical properties cannot be guaranteed; 3) The plasticizing time of geopolymers is very short. To meet the construction production requirements, it is necessary to extend the plasticizing time as much as possible. Therefore, the problems of large shrinkage, poor carbonation resistance, strength reversion, and short plasticizing time are difficult problems that need to be solved urgently in this field.

[0005] Patent CN115353336A discloses a recycled mortar for alkali-activated non-fired waste soil bricks, its preparation method and application. The raw materials used are basically all solid wastes from the construction industry and industry, including shield muck, recycled sand, recycled powder, slag powder and fly ash. Through alkali activation, these solid wastes are recycled. On the one hand, a large amount of different types of solid wastes are disposed of, and on the other hand, the dependence on natural resources is reduced, which conforms to the idea of circular economy. In addition, this recycled mortar has better adaptability to the blocks of the alkali-activated non-fired brick masonry structure, making the final masonry structure more integral, and the mortar has the advantages of early strength, strong adhesion, no need for wet curing, and higher durability.

[0006] Patent CN108046669A discloses a geopolymer, its preparation method and application, which is prepared from fly ash, shield muck with high mud content and an alkaline activator. The main component of the shield muck with high mud content is clay, which is used as fine aggregate after drying. Fly ash is a pozzolanic material. The preparation raw materials do not include any traditional cementitious materials such as cement and lime, avoiding large carbon emissions, with low cost, and realizing the resource utilization of shield muck with high mud content; the above geopolymer has an extremely low porosity and a very small permeability coefficient, high strength and good water resistance; the geopolymer is an oxide network structure system, will not oxidize and decompose, has good durability, and can be used for building materials products, as well as underwater buildings, acid-resistant, alkali-resistant, high-temperature-resistant buildings, etc. Summary of the Invention

[0007] Aiming at the problems of large shrinkage, poor carbonation resistance, strength reversion and short plasticization time existing in the process of preparing non-fired bricks in the prior art, the present invention provides a non-fired brick using industrial solid wastes to solidify shield muck and its preparation process. The obtained non-fired brick not only has excellent long-term durability properties such as mechanical properties, crack resistance and water stability, but also involves low cost and simple preparation method. Compared with the prior art, it can replace cement-based materials for solidification and has the potential advantage of low-carbon environmental protection.

[0008] A non-fired brick using industrial solid wastes to solidify shield muck, comprising the following raw materials: low-heat energy-saving micro-expansion cement, industrial solid wastes, shield sand, shield mud, alkali activator, plasticizer, water;

[0009] Taking shield sand (SS) and shield mud (SM) as inert aggregates (A), and the ratio between the two is (3-4):(1-2);

[0010] Low-heat energy-saving micro-expansion cement (C) and industrial solid wastes (IW) are used as cementitious materials (B), accounting for 5-9% and 35%-50% of the mass of the inert aggregates respectively;

[0011] The mass of the alkali activator (JF) is 30-40% of the industrial solid waste;

[0012] The mass of the plasticizer (PC) is 1-1.8% of the industrial solid waste;

[0013] The water consumption is 32-45% of the solid mass;

[0014] The above low-heat energy-saving micro-expansive cement is prepared by using waste coal gangue or lime slag as the Ca source, papermaking sludge or aluminum tailings slag as the Al source and mixing fly ash, MgO, BaCO3, and phosphogypsum;

[0015] Among them, the raw materials and their mass percentages are: waste coal gangue 75-87% or lime slag 80-87%, papermaking sludge 4-12% or aluminum tailings slag 5-13%, fly ash 4-11%, MgO 0.5-1.5%, BaCO3 1.0-1.5%;

[0016] The dosage ratio of phosphogypsum to the total mass of the above raw materials is (0.03-0.05):1.

[0017] The above low-heat energy-saving micro-expansive cement is prepared through the following steps: (1) The Ca source, Al source, fly ash, MgO (expansion component), and BaCO3 (activator) are ball-milled and mixed evenly; (2) 2%-4% of the water by mass of the mixture obtained by ball-milling in step (1) is added, and after continuous mixing evenly, it is pressed to obtain a green compact; (3) The obtained green compact is heated to 1150-1200°C, the sintering range is 100°C, and the temperature is maintained for 40-50 min, then taken out and quenched in air, and then ground to less than 0.075 mm to obtain the ground clinker; (4) The ground clinker is mixed evenly with industrial phosphogypsum and then ground to less than 0.045 mm (with a mass percentage of more than 95%), and the low-heat energy-saving micro-expansive cement is obtained.

[0018] The low-heat energy-saving micro-expansive cement has a strong ability to increase the later strength, can solve the problem of strength retrogradation of geopolymers, and can make up for the autogenous chemical shrinkage and drying shrinkage of geopolymers to a certain extent. The dosage of the low-heat energy-saving micro-expansive cement is limited to 5-9% of the mass of the inert aggregate because too little dosage will affect the improvement of the later strength, and too much dosage will increase the risk of expansion and cracking.

[0019] The lime slag in the above Ca source is derived from acetylene industrial waste and is obtained through dehydration treatment;

[0020] The above industrial solid waste includes granite powder, fly ash, and steel slag powder, among which the mass percentage of granite powder is 15-30%; the dosage of granite powder exceeding this range will not have a particularly good effect on the shrinkage and carbonation resistance performance, and even play a negative role.

[0021] The above-mentioned granite powder is a by-product of stone processing, which can be simply treated by fine grinding and screening, and the particle size can be below 200 mesh; there is a relatively high proportion of (sodium, potassium) feldspar in the granite powder, up to 60-70%, and (sodium, potassium) feldspar can promote the hydration process of alkali-activated slag and the formation of C-A-S-H gel, thereby significantly improving the carbonation resistance and shrinkage resistance of geopolymers.

[0022] The fly ash is grade III or above, with a loss on ignition ≤ 15% and a vitreous content ≥ 60%; in the preparation process of steel slag powder, water spraying treatment and natural cooling are omitted, and then it is mechanically crushed and ground. The specific surface area is above 380 m 2 / kg, and it is required that the particle size and composition of the steel slag are uniform, and the f-CaO content is less than 3%.

[0023] Industrial solid waste mainly contains components such as Al2O3, CaO, and SiO2, and has the characteristics similar to auxiliary cementitious materials such as fly ash and blast furnace slag, and can undergo geopolymerization reactions under alkaline conditions and exposure to water.

[0024] The above-mentioned alkali activator is an aqueous solution of sodium silicate and NaOH. The molar ratio of SiO2 / Na2O in sodium silicate is 1.5-2.4, the concentration of NaOH solution is 6M-8M, and the ratio of Na2O·nSiO2 / NaOH is 0.5-0.7. For solid waste with low activity, it is not easily activated by a single Na2SiO3 solution, and strong alkali hydroxides are needed to partially dissolve the waste particles to trigger the formation of aluminosilicate gel. Regardless of the alkali content, the optimal ratio range of Na2SiO3 / NaOH is 0.5-0.7, and a high percentage of NaOH is required to improve the compressive strength because the solubility of Si and Al in the milled slag depends on NaOH. When the temperature is below 65°C, it is not sufficient to react the waste particles with the NaOH solution, and silicate minerals such as muscovite and clay in the muck cannot be effectively activated, and a higher temperature is required to release more free silicon and aluminum ions for reaction.

[0025] The above-mentioned plasticizer is an aqueous solution of K2HPO4 or H3PO4 compounded with calcium lignosulfonate. The concentrations of K2HPO4 or H3PO4 are 30-50 g / L and 40-70 g / L respectively, and the concentration of calcium lignosulfonate is 100-200 g / L, which can inhibit the early hardening effect of alkali activation and extend the plasticizing time; phosphates act as retarders to coordinate the plasticizing effect.

[0026] The above-mentioned shield sand is obtained by washing, screening and hydrocyclone treatment of shield muck. The particle size of the shield sand is 20 μm - 0.6 mm, and the water content is less than 15%; the above-mentioned shield mud is shield muck after secondary hydrocyclone, and then through adding 5% mass fraction of lime in the mud as a filter aid and squeezing and dewatering treatment, it is a silty clay shield mud with a water content less than 25%.

[0027] Further, the shield muck is obtained by the construction of the slurry shield technology in the river-crossing tunnel project.

[0028] A preparation process of non-fired bricks using industrial solid waste to solidify shield muck includes the following steps:

[0029] (a) Mix and stir industrial solid waste, low-heat energy-saving micro-expansion cement, shield sand, and shield slurry for 2 - 4 min, then continue to add an alkali activator, a plasticizer, and water, and continuously stir for not less than 5 min;

[0030] (b) Load the mixture from step (a) into a mold, vibrate for 5 - 8 s, the vibration equipment frequency is 50 ± 2 Hz, the vertical amplitude of the table is 0.5 mm ± 0.02 mm, and vibrate to form;

[0031] (c) Place the non-fired bricks formed in step (b) in an environment with a relative humidity of 90% and a temperature of 50 °C for curing for 48 h, and then cure at a high temperature of 155 °C for 12 h or at 85 °C for 24 h, and finally place it under natural conditions.

[0032] The present invention has the following advantages compared with the prior art:

[0033] 1) Significantly reduce shrinkage, inhibit carbonation, reduce the risk of shrinkage cracking, and solve the potential pollution problem caused by the high leaching characteristics to the environment;

[0034] 2) Solve the problem of the strength retrogression of geopolymers and improve the long-term durability of non-fired bricks;

[0035] 3) The plasticizer ensures a plasticizing time of ≥2 h for the freshly mixed mixture and ensures construction production. Description of the Drawings

[0036] Figure 1 It is a figure of non-fired bricks obtained from the ratio of Example 1 of this application. Detailed Embodiments

[0037] The following will combine the embodiments of the present invention to clearly and completely describe the technical solutions of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0038] In the following embodiments, the industrial solid waste used in the embodiments is a composite of granite powder, steel slag powder, and waste fly ash, and each embodiment has different proportional combinations.

[0039] Among them, the granite powder is provided by a certain stone processing factory in Ezhou, Hubei, and the particle size is below 200 mesh;

[0040] The steel slag powder is treated by exemption from water spraying, then mechanically crushed and ground, with a specific surface area of 390 m 2 / kg, f-CaO content of 2.8%, produced by Maanshan Iron and Steel Group;

[0041] Fly ash produced by a certain power plant in Nantong is used, grade III and above, with a vitreous content of 63%, specific surface area of 354 m 2 / kg, water demand ratio of 109%, loss on ignition of 9.62%, 28-day activity index of 62%;

[0042] The shield sand used is the shield muck after being washed, screened and treated by hydrocyclone, with a particle size range of 20μm - 0.6mm and an air-dried moisture content of 10.5%;

[0043] The shield mud used is the shield muck after being treated by secondary hydrocyclone, filter aid and pressing dehydration, which is a silty clay type shield mud with its moisture content controlled at 23.2%;

[0044] The plasticizer is lignosulfonate calcium (200g / L) compounded with K2HPO4 (50g / L). The plasticizer formula in Comparative Example 2 is lignosulfonate calcium (200g / L);

[0045] The alkali activator used is a composite solution of water glass and NaOH. The molar ratio of SiO2 / Na2O in water glass is 2.31, the concentration of NaOH solution is 8M, and the mass ratio of Na2O·nSiO2 / NaOH is 0.7;

[0046] The low-heat energy-saving micro-expansion cement used has an apparent density of 3.05 g / cm 3 and a specific surface area of 325 m 2 / Kg, average particle size of 12.6μm. The specific preparation method includes the following steps:

[0047] (1) Using lime slag as the Ca source, papermaking sludge as the Al source, and furnace ash, MgO (expansion component) and BaCO3 (activator) as the main raw materials, after weighing each raw material according to the ratio (lime slag 80.0%, papermaking sludge 15.0%, furnace ash 4.0%, analytical pure MgO 1.0%, BaCO3 1.0%), ball mill and mix evenly;

[0048] (2) Add 3% of the moisture content of the raw material mass to the mixture obtained by ball milling in step (1), continue to mix evenly, and then press to obtain a raw material tablet;

[0049] (3) Heat the obtained raw material tablet to 1200°C, maintain the temperature for 50 min, then take it out and quickly cool it in the air, and then grind it to less than 0.075 mm to obtain the ground clinker;

[0050] (4) Mix the ground clinker and industrial phosphogypsum evenly at a mass ratio of 1:0.03, and then grind it to less than 0.045 mm (96.5% by mass) to obtain low-heat energy-saving slightly expanded cement.

[0051] The preparation process of the non-fired brick specifically includes the following steps:

[0052] 1) Material preparation: Store the granite powder, steel slag powder and waste fly ash in the form of pre-intermixed materials;

[0053] 2) Prepare the alkali activator: The molar ratio of SiO2 / Na2O in water glass is 2.31, the concentration of NaOH solution is 8M, and the mass ratio of Na2O·nSiO2 / NaOH is 0.7. Stir evenly and let it stand for more than 18h for full reaction;

[0054] 3) Prepare the mixture: Put the pre-intermixed materials prepared in 1), as well as the low-heat energy-saving slightly expanded cement, shield sand and shield mud into the mixer in sequence, stir for 3 min, then continue to add the plasticizer, alkali activator and water, and continue to stir for 5 min;

[0055] 4) Vibration molding: Put the plastic mixture obtained in 3) into the non-fired brick mold and vibrate it into shape. The vibration equipment frequency is 50, and the vertical amplitude of the table is 0.5 mm;

[0056] 5) Curing: Place the non-fired brick in an environment with a relative humidity of 90% and a temperature of 50 °C for 48 h, and then cure it at a high temperature of 155 °C for 12 h, and finally place it under natural conditions.

[0057] Test Example 1:

[0058] The test method follows GB / T 4111-2013 "Test Methods for Concrete Blocks and Bricks".

[0059] The ratios of Examples 1-13 are shown in Table 1. The non-fired brick specimens of Examples 1-11 are cured in a conventional environment, and those of Examples 12-14 are placed in a carbonation box for curing. The performance test results of the prepared non-fired brick specimens are shown in Tables 2 and 3.

[0060] Table 1 Composition of non-fired brick ratio / %

[0061]

[0062]

[0063] Table 2 Characterization of basic properties of non-fired bricks

[0064]

[0065] Table 3 Characterization of properties of non-fired bricks

[0066]

[0067]

[0068] Comparing Example 1# and Example 6#, when adding 30% granite stone powder by proportion, the drying shrinkage decreased by 53.57%. At the same time, Comparative Examples 3# - 5# showed that in a carbonation environment, adding granite stone powder reduced the impact of carbonation curing on the compressive strength, and the addition of (sodium, potassium) feldspar could mitigate the negative impact of CO2 on the strength of alkali-activated slag; comparing Example 1#, Example 8#, and Comparative Example 1#, the low-heat energy-saving slightly expansive cement solved the problem of the reverse shrinkage of the compressive strength of the non-fired brick at 28 days, and the compressive strength at 90 days also increased to a certain extent; Example 1#, Example 9#, and Comparative Example 2# showed that the addition of a plasticizer improved the fluidity performance at 15 minutes and extended the plasticization time to 2 hours. Without adding or only adding lignosulfonic acid component could not achieve the effect of extending the plasticization time. The non-fired brick obtained by the present invention has a 28-day hardened density ≥ 1.9 g / cm 3 , a saturated water absorption rate ≤ 3.3%, a 28-day compressive strength ≥ 18.3 MPa, a softening coefficient ≥ 83%, a dry shrinkage rate ≤ 0.0013, having excellent mechanical compressive properties, water resistance stability, long-term durability, and better environmental benefits.

[0069] Although the embodiments of the present invention have been shown and described, for those of ordinary skill in the art, it can be understood that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A non-fired brick for solidifying shield muck by using industrial solid waste, characterized in that, It includes the following raw materials: Low-heat energy-saving slightly expanding cement, industrial solid waste, shield sand, shield mud, alkali activator, plasticizer, water; Using shield sand and shield mud as inert aggregates, and the ratio between them is (3 - 4):(1 - 2); Low-heat energy-saving slightly expanding cement and industrial solid waste are used as cementitious materials, accounting for 5 - 9% and 35% - 50% of the mass of the inert aggregates respectively; The mass of the alkali activator is 30 - 40% of that of the industrial solid waste; The mass of the plasticizer is 1 - 1.8% of that of the industrial solid waste; The water consumption is 32 - 45% of the solid mass; The low-heat energy-saving slightly expanding cement is prepared by using waste coal gangue or lime slag as the Ca source, papermaking sludge or aluminum tailings slag as the Al source and mixing fly ash, MgO, BaCO3, and phosphogypsum; Among them, the mass percentages of each raw material are: 75 - 87% of waste coal gangue or 80 - 87% of lime slag, 4 - 12% of papermaking sludge or 5 - 13% of aluminum tailings slag, 4 - 11% of fly ash, 0.5 - 1.5% of MgO, 1.0 - 1.5% of BaCO3; The dosage ratio of phosphogypsum to the total mass of the above raw materials is (0.03 - 0.05):1; The industrial solid waste includes granite powder, fly ash, and steel slag powder, and the mass proportion of granite powder is 15 - 30%; 2. The non-fired brick for solidifying shield muck by using industrial solid waste according to claim 1, characterized in that, The low-heat energy-saving slightly expanding cement is prepared through the following steps: (1) Ball-mill and mix the Ca source, Al source, fly ash, MgO, and BaCO3 evenly; (2) Add 2% - 4% of the mass of water to the mixture obtained by ball-milling in step (1), continue to mix evenly and then press to obtain a raw material tablet; (3) Heat the obtained raw material tablet to 1150 - 1200°C, with a sintering range of 100°C, maintain the temperature for 40 - 50 min, then take it out and cool it rapidly in the air, and then grind it to less than 0.075 mm to obtain a ground clinker; (4) Mix the ground clinker with industrial phosphogypsum evenly, and then grind it to less than 0.045 mm to obtain the low-heat energy-saving slightly expanding cement.

3. The non-fired brick for solidifying shield muck by using industrial solid waste according to claim 1, wherein: The particle size of the granite powder is below 200 mesh; the fly ash is of grade III or above, with a loss on ignition ≤ 15% and a vitreous content ≥ 60%; the specific surface area of the steel slag powder is above 380 m 2 / kg, and the f-CaO content is less than 3%.

4. The unfired brick for solidifying shield muck by using industrial solid waste according to claim 1, characterized in that: The alkali activator is a composite solution of water glass and NaOH, the molar ratio of SiO2 / Na2O in water glass is 1.5 - 2.4, the concentration of the NaOH solution is 6M - 8M, and the ratio of Na2O·nSiO2 / NaOH is 0.5 - 0.

7.

5. The unfired brick for solidifying shield muck by using industrial solid waste according to claim 1, characterized in that: The plasticizer is an aqueous solution of K2HPO4 or H3PO4 and calcium lignosulfonate, the concentrations of K2HPO4 or H3PO4 are 30 - 50 g / L and 40 - 70 g / L respectively, and the concentration of calcium lignosulfonate is 100 - 200 g / L.

6. The unfired brick for solidifying shield muck by using industrial solid waste according to claim 1, wherein: The shield sand is obtained by washing, screening, and hydrocyclone treatment of shield muck, the particle size of the shield sand is 20 μm - 0.6 mm, and the water content is less than 15%.

7. The unfired brick for solidifying shield muck by using industrial solid waste according to claim 1, characterized in that: The shield mud is a silty clay-like shield mud obtained by secondary hydrocyclone treatment of shield muck, and then adding 5% by mass of lime as a filter aid and performing press dewatering treatment, and its water content is less than 25%.

8. The preparation process of a non-fired brick using industrial solid waste to solidify shield muck according to any one of claims 1-7, characterized in that, It includes the following steps: (a) Mix and stir the industrial solid waste, low-heat energy-saving slightly expanding cement, shield sand, and shield mud for 2 - 4 min, then continue to add the alkali activator, plasticizer, and water, and continuously stir for no less than 5 min; (b) Load the mixture in step (a) into a mold, vibrate for 5 - 8 s, the vibration equipment frequency is 50 ± 2 Hz, the vertical amplitude of the table is 0.5 mm ± 0.02 mm, and vibrate to form. (c) Place the non - fired bricks formed in step (b) in an environment with a relative humidity of 90% and a temperature of 50 °C for 48 h, and then cure at a high temperature of 155 °C for 12 h or at 85 °C for 24 h, and finally place it under natural conditions.

Images