Magnesium oxide carbonized foundation solidification soil and its preparation method and application

Abstract

The present invention relates to the technical field of building materials, and in particular to a magnesium oxide carbonized foundation solidification soil and a preparation method and application thereof. The present invention adopts soil as a filler, adopts active magnesium oxide as a cementing material, adds microorganisms that can produce carbonic anhydrase to improve the carbon fixation capacity, and adds a self-developed reinforcing agent to strengthen the solidified soil, synergistically improves the carbon dioxide absorption, and prepares a solidified soil with high mechanical properties and strong carbon fixation capacity, which can be used as a foundation raw material for construction.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a magnesium oxide carbonized foundation solidification soil and a preparation method and application thereof. Background Art

[0002] Active MgO carbonization solidification technology is an innovative technology for treating soft soil with low-carbon mixing proposed in recent years.

[0003] This technology first mixes active magnesium oxide with soil, and then uses CO 2 It is carbonized to achieve the purpose of quickly increasing strength.

[0004] This is a new low-carbon, environmentally friendly and rapid soil solidification method that can quickly reduce soil moisture content, reduce soil porosity and increase soil strength, while absorbing a large amount of CO 2 The gas solidifies it in the soil.

[0005] The reaction process is as follows:

[0006] MgO + H 2 O → Mg(OH) 2

[0007] Mg(OH) 2 + CO 2 + 2H 2 O → MgCO 3 •3H 2 O

[0008] 5Mg(OH) 2 + 4CO 2 + H 2 O → (Mg)5(CO 3 ) 4 (OH) 2 •5H 2 O

[0009] 5Mg(OH) 2 + 4CO 2 → (Mg) 5 (CO 3 ) 4 (OH) 2 •4H 2 O

[0010] Microbial geotechnical technology refers to the technology that uses microbial processes to solve geotechnical engineering problems.

[0011] As a practical technology, microbial geotechnical technology has developed very rapidly in recent years.

[0012] At present, in microbial geotechnical technology, microbial mineralization technology is a hot topic of research. This technology uses microbial processes to produce some crystalline and non-crystalline inorganic compounds. These inorganic compounds play a filling and cementing role in geotechnical materials, and their function is similar to cement. Among them, urea hydrolysis process is the most commonly used microbial process.

[0013] Research on other aspects of microbial geotechnical technology is still in a relatively primitive stage.

[0014] However, the foundation strength prepared by carbonization and solidification of MgO in the prior art is still weak, and the carbon fixation amount is not high. In order to improve the strength of the active MgO carbonization solidified soil, it is mainly through increasing the activity of MgO, increasing the amount of MgO, increasing the CO 2 Pressure, prolonged carbonization time, adding chemical auxiliary materials, etc., which will not only increase the construction cost, but also prolong the construction period, which is time-consuming and labor-intensive. Microbial geotechnical technology mostly uses lime or cement to provide Ca 2+ The curing of MgO-based cementitious materials has not been effectively explored. Summary of the invention

[0015] In order to solve the problems existing in the prior art, the present invention provides a magnesium oxide carbonized foundation solidification soil and a preparation method and application thereof. Specifically, the present invention adopts soil as a filler, adopts active magnesium oxide as a cementing material, adds microorganisms that can produce carbonic anhydrase, and adds a self-developed reinforcing agent to strengthen the solidified soil, synergistically improves the carbon dioxide absorption, and prepares a solidified soil with high mechanical properties and strong carbon fixation ability, which can be used as a foundation raw material for construction.

[0016] Specifically, the magnesium oxide carbonized foundation solidification soil of the present invention is composed of the following raw materials in parts by weight:

[0017] 100 parts of soil, 8-15 parts of active magnesium oxide, 1-5 parts of Bacillus subtilis powder, and 30-50 parts of enhancer.

[0018] Carbonic anhydrase (CA) is a metalloenzyme widely distributed in animals, plants and prokaryotes. It is one of the fastest enzymes known and has the ability to accelerate the conversion of CO 2 Hydration to form HCO 3 - The characteristics of CO (increased by about 107 times) can significantly increase 2 absorption efficiency and absorption rate.

[0019] In view of this, the present invention is inspired by the phenomenon that microorganisms in nature actively participate in the carbon cycle and stimulate carbonization. By utilizing the enzymatic catalysis of carbonic anhydrase secreted by microorganisms, an innovative method is proposed to promote the carbonization of active MgO by incorporating carbonic anhydrase-producing microorganisms, thereby increasing the hydration of active MgO to generate Mg(OH) 2 The carbonization rate is increased to generate more magnesium carbonate, thereby increasing the carbonization degree of MgO after the carbonization reaction.

[0020] Ultimately, the goal of low-cost, pollution-free and high-efficiency improvement of the engineering performance of soil after active MgO solidification is achieved.

[0021] Preferably, the steps of preparing the enhancer are:

[0022] ① According to the mass ratio, mix 100 parts of steel slag powder, 200-300 parts of iron tailings powder, 20-30 parts of alkali slag, 8-11 parts of lignin fiber, and 2-4 parts of SAP particles evenly to obtain dry powder.

[0023] ② Dissolve 3-5 parts of alcoholamine in 60-80 parts of water to form an alcoholamine solution.

[0024] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, sieve the 0.8-2.5mm particles to obtain the enhancer.

[0025] The present invention has found that although the carbonic anhydrase produced by Bacillus mucilaginosus accelerates carbonization and increases the carbonization rate, the activity of magnesium oxide is different from that of lime in the prior art. The early strength of the solidified soil increases rapidly, but the generated magnesium carbonate has poor interface adhesion with the surface of soil particles, and shrinkage cracks occur in the solidified soil for a long time. The present invention prepares a reinforcing agent, which is obtained by granulating steel slag powder, iron tailings powder, alkali slag, wood cellulose, SAP particles, and alcohol amine solution as raw materials. The steel slag powder has a composition similar to cement and contains a high content of free calcium oxide. It has low activity and poor stability, which makes it difficult to use. The alkali slag is rich in alkaline earth metal ions and is strongly alkaline. The iron tailings powder is a mining solid waste and belongs to an inert filler. The present invention uses Steel slag powder, iron tailings powder and alkali slag are used as active powders to granulate with alcohol amine solution. Lignin fiber and SAP particles have good hydrophilic ability, can absorb part of free water and store it, and slowly release it in the later stage. Lignin fiber is linear and SAP particles are spherical. The closed pores formed by SAP particles are interconnected by lignin fiber, absorbing part of alcohol amine solution and bacterial liquid and forming carbon dioxide transmission channels. Free calcium oxide and alkali slag in steel slag powder are also carbonized under the action of Bacillus and carbon dioxide to form a consolidated body. The addition of reinforcing agent can form a good interface bonding relationship with magnesium carbonate and soil, reduce the long-term shrinkage of solidified soil, sustainably absorb carbon dioxide in the air, and the mechanical properties will not shrink in the later stage.

[0026] Preferably, the soil is at least one of sandy soil and silty soil.

[0027] Preferably, in the reinforcing agent preparation step ①, the steel slag powder is obtained by grinding steel slag, and has a particle size of ≤45 μm.

[0028] Although steel slag powder is almost inactive, it can improve the balling effect of the reinforcing agent and increase the density, which helps to disperse the reinforcing agent evenly.

[0029] Preferably, the particle size of the iron tailings powder in the enhancer preparation step ① is 0.1-0.3 mm.

[0030] Preferably, in the reinforcing agent preparation step ①, the length of the lignin fiber is 60-110 μm.

[0031] Lignocellulose has a certain ability to absorb and retain water, and can be combined with an alcohol amine solution to increase viscosity, thereby facilitating the balling and toughening of the reinforcing agent. The length of the lignin fiber of the present invention is moderate. If the length is too short, it cannot form an effective connection, and if the length is too long, it is not conducive to dispersion.

[0032] Preferably, in the reinforcing agent preparation step ①, the particle size of the SAP particles is 80-200 μm.

[0033] Preferably, the alcoholamine in the enhancer preparation step ② is at least one of triisopropanolamine, diethanolamine and triethanolamine.

[0034] The present invention also relates to a method for preparing the magnesium oxide carbonized foundation solidification soil, which specifically comprises the following steps: uniformly mixing the raw materials to obtain.

[0035] The present invention also relates to the application of the above-mentioned magnesium oxide carbonized foundation solidification soil, specifically, the solidified soil is used in foundation construction.

[0036] Preferably, the application includes the following steps: adding a proper amount of water to the solidified soil for paving, and introducing carbon dioxide-containing gas for carbonization.

[0037] More preferably, the carbonization temperature is 20-45°C, and the carbon dioxide-containing gas can be industrial waste gas or pure CO 2 Gas, pressure 50-500kPa.

[0038] The present invention has the following technical advantages:

[0039] 1. The present invention adds Bacillus colloidus to produce carbonic anhydrase, promotes the carbonization of active magnesium oxide, and improves the strength of solidified soil.

[0040] 2. The reinforcing agent prepared by the present invention can strengthen the solidified soil, improve the bonding strength of the raw material interface, reduce shrinkage, and improve the later mechanical properties of the solidified soil.

[0041] 3. The solidified soil of the present invention has low cost and is pollution-free, consumes a large amount of industrial solid waste, has a high carbon fixation capacity, and has good environmental benefits. DETAILED DESCRIPTION

[0042] In order to characterize the technical effect of the present invention, the solidified soil was prepared with a water-binder ratio of 0.5 and then formed. Pure carbon dioxide gas was used for carbonization curing at 25°C and 300kPa for 6 hours, standard curing was performed to 28 days, and it was naturally stored at room temperature to 56 days, and the performance of the samples was tested.

[0043] During the test, sandy soil was used as the soil, the particle size of steel slag powder was ≤45 μm, the particle size of iron tailings powder was 0.1-0.3 mm, the length of lignin fiber was 60-110 μm, and the particle size of SAP particles was 80-200 μm.

[0044] Example 1

[0045] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0046] 100 parts of soil, 13 parts of active magnesium oxide, 5 parts of Bacillus subtilis powder, and 45 parts of enhancer. The steps for preparing the enhancer are as follows:

[0047] ① According to the mass ratio, mix 100 parts of steel slag powder, 230 parts of iron tailings powder, 22 parts of alkali slag, 10 parts of lignin fiber and 3 parts of SAP particles evenly to obtain dry powder.

[0048] ② Dissolve 4 parts of alcoholamine in 75 parts of water to form an alcoholamine solution.

[0049] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, sieve the 0.8-2.5mm particles to obtain the enhancer.

[0050] After testing, the unconfined compressive strength of the cured soil at 28 days was 13.6 MPa, the shrinkage rate was 0.021%, the carbon fixation weight gain rate was 4.4%, the unconfined compressive strength at 56 days was 15.2 MPa, the shrinkage rate was 0.025%, there was no crack, and the carbon fixation weight gain rate was 4.9%.

[0051] Example 2

[0052] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0053] 100 parts of soil, 10 parts of active magnesium oxide, 3 parts of Bacillus subtilis powder, 50 parts of enhancer, the preparation steps of the enhancer are:

[0054] ① According to the mass ratio, mix 100 parts of steel slag powder, 240 parts of iron tailings powder, 25 parts of alkali slag, 9 parts of lignin fiber and 3 parts of SAP particles evenly to obtain dry powder.

[0055] ② Dissolve 4 parts of alcoholamine in 75 parts of water to form an alcoholamine solution.

[0056] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, sieve the 0.8-2.5mm particles to obtain the enhancer.

[0057] After testing, the unconfined compressive strength of the cured soil at 28 days was 12.1 MPa, the shrinkage rate was 0.023%, the carbon fixation weight gain rate was 4.2%, the unconfined compressive strength at 56 days was 14.9 MPa, the shrinkage rate was 0.028%, there were no cracks, and the carbon fixation weight gain rate was 4.6%.

[0058] Comparative Example 1

[0059] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0060] 100 parts of soil, 10 parts of activated magnesium oxide, and 50 parts of steel slag powder.

[0061] After testing, the unconfined compressive strength of the solidified soil at 28 days was 3.3 MPa, the shrinkage rate was 0.037%, the carbon fixation weight gain rate was 1.5%, the unconfined compressive strength at 56 days was 3.6 MPa, the shrinkage rate was 0.063%, there were microcracks, and the carbon fixation weight gain rate was 1.6%.

[0062] Comparative Example 2

[0063] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0064] 100 parts of soil, 10 parts of activated magnesium oxide, 3 parts of Bacillus subtilis powder, and 50 parts of fly ash.

[0065] After testing, the unconfined compressive strength of the cured soil at 28 days was 4.6 MPa, the shrinkage was 0.034%, the carbon fixation weight gain was 2.7%, the unconfined compressive strength at 56 days was 5.1 MPa, the shrinkage was 0.044%, there were microcracks, and the carbon fixation weight gain was 3.0%.

[0066] Comparative Example 3

[0067] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0068] 100 parts of soil, 10 parts of active magnesium oxide, 3 parts of Bacillus subtilis powder, 50 parts of enhancer, the preparation steps of the enhancer are:

[0069] ① According to the mass ratio, 100 parts of fly ash, 240 parts of iron tailings powder, 25 parts of alkali residue, 9 parts of lignin fiber and 3 parts of SAP particles were mixed evenly to obtain dry powder.

[0070] ② Dissolve 4 parts of alcoholamine in 75 parts of water to form an alcoholamine solution.

[0071] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, and sieve the 0.8-2.5mm particles to obtain the enhancer.

[0072] After testing, the unconfined compressive strength of the cured soil at 28 days was 7.8 MPa, the shrinkage rate was 0.031%, the carbon fixation weight gain rate was 3.1%, the unconfined compressive strength at 56 days was 8.5 MPa, the shrinkage rate was 0.040%, there was no crack, and the carbon fixation weight gain rate was 3.7%.

[0073] Comparative Example 4

[0074] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0075] 100 parts of soil, 10 parts of active magnesium oxide, 3 parts of Bacillus subtilis powder, 50 parts of enhancer, the preparation steps of the enhancer are:

[0076] ① According to the mass ratio, mix 240 parts of steel slag powder, 125 parts of alkali slag, 9 parts of lignin fiber and 3 parts of SAP particles evenly to obtain dry powder.

[0077] ② Dissolve 4 parts of alcoholamine in 75 parts of water to form an alcoholamine solution.

[0078] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, sieve the 0.8-2.5mm particles to obtain the enhancer.

[0079] After testing, the unconfined compressive strength of the cured soil at 28 days was 4.2 MPa, the shrinkage rate was 0.035%, the carbon fixation weight gain rate was 3.3%, the unconfined compressive strength at 56 days was 5.4 MPa, the shrinkage rate was 0.053%, there were microcracks, and the carbon fixation weight gain rate was 3.7%.

[0080] Comparative Example 5

[0081] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0082] 100 parts of soil, 10 parts of active magnesium oxide, 3 parts of Bacillus subtilis powder, 50 parts of enhancer, the preparation steps of the enhancer are:

[0083] ① According to the mass ratio, mix 100 parts of steel slag powder, 240 parts of iron tailings powder, and 25 parts of alkali slag evenly to obtain dry powder.

[0084] ② Dissolve 4 parts of alcoholamine in 75 parts of water to form an alcoholamine solution.

[0085] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, and sieve the 0.8-2.5mm particles to obtain the enhancer.

[0086] After testing, the unconfined compressive strength of the cured soil at 28 days was 5.5 MPa, the shrinkage was 0.029%, the carbon fixation weight gain was 3.6%, the unconfined compressive strength at 56 days was 5.8 MPa, the shrinkage was 0.054%, there were microcracks, and the carbon fixation weight gain was 3.8%.

[0087] Comparative Example 6

[0088] Magnesium oxide carbonized foundation solidification soil is composed of the following raw materials in parts by weight:

[0089] 100 parts of soil, 10 parts of active magnesium oxide, 3 parts of Bacillus subtilis powder, 50 parts of enhancer, the preparation steps of the enhancer are:

[0090] ① According to the mass ratio, mix 100 parts of steel slag powder, 240 parts of iron tailings powder, 25 parts of alkali slag, 9 parts of polypropylene fiber and 3 parts of SAP particles evenly to obtain dry powder.

[0091] ② Dissolve 4 parts of alcoholamine in 75 parts of water to form an alcoholamine solution.

[0092] ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, and sieve the 0.8-2.5mm particles to obtain the enhancer.

[0093] After testing, the unconfined compressive strength of the cured soil at 28 days was 6.7 MPa, the shrinkage rate was 0.033%, the carbon fixation weight gain rate was 3.4%, the unconfined compressive strength at 56 days was 7.7 MPa, the shrinkage rate was 0.037%, there were no cracks, and the carbon fixation weight gain rate was 3.9%.

[0094] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A magnesium oxide carbonized foundation stabilization soil, characterized in that: It is composed of the following raw materials in parts by weight: 100 parts of soil, 8-15 parts of active magnesium oxide, 1-5 parts of Bacillus subtilis powder, 30-50 parts of enhancer, The steps of preparing the enhancer are: ① According to the mass ratio, mix 100 parts of steel slag powder, 200-300 parts of iron tailings powder, 20-30 parts of alkali slag, 8-11 parts of lignin fiber, and 2-4 parts of SAP particles evenly to obtain dry powder. ② Dissolve 3-5 parts of alcoholamine in 60-80 parts of water to form an alcoholamine solution. ③Put the dry powder into the disc granulator, spray the alcoholamine solution and roll the granulator, sieve the 0.8-2.5mm particles to obtain the enhancer.

2. The magnesium oxide carbonized foundation stabilization soil according to claim 1, characterized in that: The soil is at least one of sandy soil and silty soil.

3. The magnesium oxide carbonized foundation stabilization soil according to claim 1, characterized in that: In the reinforcing agent preparation step ①, the steel slag powder is obtained by grinding steel slag, and the particle size is ≤45 μm.

4. The magnesium oxide carbonized foundation stabilization soil according to claim 1, characterized in that: In the step ① of preparing the reinforcing agent, the particle size of the iron tailings powder is 0.1-0.3 mm.

5. The magnesium oxide carbonized foundation stabilization soil according to claim 1, characterized in that: In the reinforcing agent preparation step ①, the length of the lignin fiber is 60-110 μm.

6. The magnesium oxide carbonized foundation stabilization soil according to claim 1, characterized in that: In the reinforcing agent preparation step ①, the particle size of the SAP particles is 80-200 μm.

7. The magnesium oxide carbonized foundation stabilization soil according to claim 1, characterized in that: In the enhancer preparation step ②, the alcohol amine is at least one of triisopropanolamine, diethanolamine and triethanolamine.

8. The method for preparing magnesium oxide carbonized foundation stabilization soil according to any one of claims 1 to 7, characterized in that: The method comprises the following steps: mixing the raw materials uniformly to obtain the product.

9. The use of magnesium oxide carbonized foundation stabilization soil according to any one of claims 1 to 7, characterized in that: The stabilized soil is used for foundation construction.

10. The use according to claim 9, characterized in that: The method comprises the following steps: adding a proper amount of water to the solidified soil for paving, and introducing carbon dioxide-containing gas for carbonization.