Carbon sequestration foamed lightweight soil and preparation method thereof

Abstract

The present application belongs to the technical field of civil and architectural engineering materials, and in particular relates to an environmental and low-carbon foamed lightweight soil prepared by using CO.sub.2 and MgO as raw materials. Raw material compositions of the carbon sequestration foamed lightweight soil include, in parts by weight, 10 to 200 parts of MgO, 10 to 100 parts of a filler, 2 to 45 parts of a CO.sub.2 bubble cluster and 20 to 400 parts of water. The present application is made in view of the problems of large carbon emission and serious energy consumption caused by a cement solidification agent used in traditional foamed lightweight soil.

Claims

1. A carbon sequestration foamed lightweight soil, comprising, according to a raw material ratio, 10 to 200 parts of MgO, 10 to 100 parts of a filler, 2 to 45 parts of a CO.sub.2 bubble cluster and 20 to 400 parts of an aqueous solution, wherein the raw material ratio is in parts by weight.

2. The carbon sequestration foamed lightweight soil according to claim 1, wherein the MgO is a mixture or one of light MgO or heavy MgO.

3. The carbon sequestration foamed lightweight soil according to claim 1, wherein the filler comprises a raw material soil, and the raw material soil is an engineering waste soil, a sandy soil, a silt or a clay soil.

4. The carbon sequestration foamed lightweight soil according to claim 1, wherein producing materials of the CO.sub.2 bubble cluster comprise, in parts by weight, 0.33 to 20 parts of a foaming agent, 0.0033 to 2 parts of a foam stabilizer and 0.0033 to 2 parts of an active agent, wherein the foaming agent is one or a mixture of more of a rosin resin foaming agent, a synthetic surface active foaming agent, a protein foaming agent and a composite foaming agent; the foam stabilizer is cellulose ether, lauryl alcohol, triethanolamine or calcium stearate; and the active agent is sodium cocoyl glycinate, potassium cocoyl glycinate, sodium lauroyl glutamate or potassium cocoyl glutamate.

5. A method for preparing the carbon sequestration foamed lightweight soil according to claim 1, comprising the following steps: Step S1 preparation of raw materials, comprising preparing 10 to 100 parts of MgO, 10 to 100 parts of a filler, and 100 to 200 parts of an aqueous solution; Step S2 preparation of a slurry, comprising putting the MgO and the filler prepared in the Step S1 into a stirring device, conducting stirring at a rotation speed of 100 r/min for 1 to 2 minutes so that the MgO and the filler are mixed evenly to obtain a mixture, adding the aqueous solution into the mixture in 2 or 3 portions respectively, conducting stirring for 1 to 2 minutes after one portion of the aqueous solution is added each time, and keeping powder from sinking to the bottom and agglomeration to ensure that the slurry is uniform and free of deposition until the aqueous solution is added completely, so as to obtain the slurry; Step S3 preparation of a CO.sub.2 bubble cluster, comprising preparing the CO.sub.2 bubble cluster with high-pressure CO.sub.2 by using a pre-foaming method, wherein the high-pressure CO.sub.2 is industrial high-purity CO.sub.2 or industrial waste gas purified CO.sub.2; Step S4 mixing under stirring, comprising adding 2 to 45 parts of the CO.sub.2 bubble cluster into the slurry obtained in the Step S2 and conducting stirring at a speed of 600 to 900 r/min for a time of 10 to 12 minutes, and keeping that the CO.sub.2 bubble cluster is evenly distributed in the slurry and the slurry is free of deposition so as to obtain a mixed paste; and Step S5 sample preparation and curing, comprising immediately pouring the mixed paste obtained in the Step S4 into a mold, conducting sealing, and conducting curing in a constant-temperature curing chamber to obtain the foamed lightweight soil.

6. The method according to claim 5, wherein in Step S3, the preparation of the CO.sub.2 bubble cluster comprises the following steps: diluting a foaming agent of the CO.sub.2 bubble cluster according to a dilution multiple of 20 to 60 times, controlling an active agent in a ratio of 1% to 10% of the foaming agent, and conducting mixing to obtain a foaming liquid; connecting the foaming liquid to a CO.sub.2 high-pressure tank through an air pipe, opening a ventilation valve of the CO.sub.2 high-pressure tank and adjusting a pressure to 200 kPa; after an air in a foaming liquid pipeline is exhausted and the foaming liquid completely enters a water pump, closing the ventilation valve after a pressure and a foaming rate of the foaming device are stable; and opening a foaming valve, and controlling a pressure range to be within 0.1 to 0.4 mpa, a specific speed of the water pump to be between 20 and 80 and a corresponding water pump flow to be 1 to 4 L/min so as to discharge fine and stable CO.sub.2 foam; and receiving the CO.sub.2 foam with a container so as to obtain the CO.sub.2 bubble cluster.

7. The method according to claim 5, wherein in the Steps S4 and S5, the sample preparation needs to be completed within a half-life of the foaming agent of the CO.sub.2 bubble cluster to prevent the foam from bursting to cause leakage of CO.sub.2.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a flow diagram of a preparation method of a carbon sequestration foamed lightweight soil in one example of the present application.

(2) FIG. 2 is a schematic diagram of a preparation method of a carbon sequestration foamed lightweight soil in one example of the present application.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(3) In order to make the present application better understood, the content of the present application is further illustrated below in combination with examples, but the present application is not limited to the following examples. It should be understood that the specific examples described herein are only used to explain the present application, but not to limit the present application.

(4) FIG. 1 shows a flow diagram of a preparation method of a carbon sequestration foamed lightweight soil in one example of the present application. The preparation method includes the following steps. S1. Preparation of raw materials, including preparing 10 to 100 parts of MgO, 10 to 100 parts of a filler, 2 to 45 parts of a CO.sub.2 bubble cluster and 100 to 200 parts of an aqueous solution. S2. Preparation of a slurry, including putting the MgO and the filler prepared in the Step S1 into a stirring device, conducting stirring at a rotation speed of 100 r/min for 1 to 2 minutes so that the MgO and the filler are mixed evenly to obtain a mixture, adding the aqueous solution into the mixture in 2 or 3 portions respectively, conducting stirring for 1 to 2 minutes after one portion of the aqueous solution is added each time, and during the stirring, paying attention that powder cannot sink to the bottom or agglomerate to ensure that the slurry is uniform and free of deposition until the aqueous solution is added completely, so as to obtain the slurry. S3. Preparation of the CO.sub.2 bubble cluster, including preparing the CO.sub.2 bubble cluster with high-pressure CO.sub.2 by using a pre-foaming method, wherein the high-pressure CO.sub.2 is industrial high-purity CO.sub.2 or industrial waste gas purified CO.sub.2.

(5) The pre-foaming method in the examples includes the following steps: firstly mixing a base material (a raw material soil), a solidifying material (MgO) and water evenly, conducting mixing to form a raw material soil slurry, and then foaming a foaming agent solution by a foaming device; then, stirring the raw soil slurry and air bubbles evenly to obtain a bubble lightweight soil slurry body; and then, pouring the mixed slurry into a mold and conducting curing forming to form a lightweight soil. S4. Mixing under stirring, including adding 2 to 45 parts of the CO.sub.2 bubble cluster into the slurry obtained in the Step S2 and conducting stirring at a speed of 600 to 900 r/min for a time of 10 to 12 minutes, and ensuring that the CO.sub.2 bubble cluster is evenly distributed in the slurry and the slurry is free of deposition so as to obtain a mixed paste. S5. Sample preparation and curing, including immediately pouring the mixed paste obtained in the Step S4 into a mold, conducting sealing, and conducting curing in a constant-temperature curing chamber to obtain the foamed lightweight soil.

Example 1

(6) A carbon sequestration foamed lightweight soil was provided. Each cubic meter of the carbon sequestration foamed lightweight soil included: 100 parts of reactive MgO powder, 100 parts of a silty clay, 10 parts of a CO.sub.2 bubble cluster and 200 parts of water. The silty clay needed to be air-dried before being ground down to pass through a 2 mm sieve. The water used was tap water, including water used for the CO.sub.2 bubble cluster.

(7) Sodium dodecyl benzene sulfonate was selected as a foaming agent, which was diluted according to a dilution multiple of 40 times. The dosage of sodium cocoyl glycinate was controlled to be 3% of the foaming agent. Mixing was conducted to obtain a foaming liquid, a foaming rate thereof was 20 times, and a half-life thereof was 20 to 40 minutes.

(8) TABLE-US-00001 TABLE 1 Main physical and chemical indexes of silty clay Test items Test values Natural density /(g .Math. cm.sup.3) 1.88 Natural moisture content, w/% 33.3 Maximum dry density/(g .Math. cm.sup.3) 1.72 Optimum moisture content/% 17.4 Liquid limit, w.sub.L (%) 43 Plastic limit, w.sub.p (%) 22.5 Specific gravity, G.sub.s 2.75 pH value 8.30

(9) TABLE-US-00002 TABLE 2 Main chemical compositions of silty clay and MgO Loss on Compositions MgO Al.sub.2O.sub.3 CaO SiO.sub.2 Fe.sub.2O.sub.3 Na.sub.2O ignition Silty clay 2.18 11.9 5.57 62.5 3.3 1.28 10 MgO 95.5 0.24 1.05 1.02 0.18 0.023 1.68

(10) The carbon sequestration foamed lightweight soil was prepared by the following steps: S1. preparation of raw materials: 100 parts of the reactive MgO powder and 100 parts of the silty clay are weighed for standby; S2. slurry preparation: the MgO and the silty clay were put into a stirring device according to a proportion, and stirring was conducted at a rotation speed of 100 r/min for 2 minutes, so that the MgO and the silty clay were mixed evenly; S3. preparation of the CO.sub.2 bubble cluster: the foaming agent was mixed with the water at a dilution multiple of 40 times, the dosage of the sodium cocoyl glycinate active agent was controlled to be in 0.15 part, the dosage of a lauryl alcohol foam stabilizer was controlled to be in 0.05 part, mixing was conducted to obtain a foaming liquid, which was then connected to a CO.sub.2 high-pressure tank through an air pipe, a CO.sub.2 ventilation valve was opened and a pressure was adjusted to 200 kPa, and after an air in a foaming liquid pipeline was exhausted and the foaming liquid completely entered a water pump, the CO.sub.2 ventilation valve was closed after a pressure and a foaming rate of the foaming device were stable. Then, a foaming valve was opened, a pressure of 0.2 mpa, a water pump specific speed of 60 and a water pump flow of 3 L/min were selected, fine and stable CO.sub.2 foam was discharged, and the CO.sub.2 foam was received with a container for standby; S4. mixing under stirring: 10 parts of the CO.sub.2 bubble cluster was added into the slurry and stirred at a speed of 800 r/min for a time of 10 minutes, so as to ensure that the CO.sub.2 bubble cluster was evenly distributed and the slurry was free of deposition, thereby a mixed paste was obtained; and S5. sample preparation and curing: the mixed paste was immediately poured into a mold, and curing was conducted for 7 days in a constant-temperature curing chamber to obtain the foamed lightweight soil. From the Steps S4 to S5, the sample preparation needed to be completed within a half-life of the foaming agent to prevent the foam from bursting to cause leakage of CO.sub.2.

Example 2

(11) A carbon sequestration foamed lightweight soil was provided. Each cubic meter of the carbon sequestration foamed lightweight soil included: 100 parts of reactive MgO powder, 100 parts of a silty clay, 10 parts of a CO.sub.2 bubble cluster and 200 parts of water. The same silty clay, MgO, water and foaming agent were used as in Example 1, and treatment methods for various materials were also kept the same.

(12) A preparation method of the carbon sequestration foamed lightweight soil in Example 2 was the same as that in Example 1, and a curing time thereof was 1 day.

Comparative Example 1

(13) A carbon sequestration foamed lightweight soil was provided. Each cubic meter of the carbon sequestration foamed lightweight soil included: 100 parts of reactive MgO powder, 100 parts of a silty clay, 20 parts of a CO.sub.2 bubble cluster and 200 parts of water. The same silty clay, MgO, water and foaming agent were used as in Example 1, and treatment methods for various materials were also kept the same.

(14) A preparation method of the carbon sequestration foamed lightweight soil in Comparative Example 1 was the same as that in Example 1, and a curing time thereof was 7 days.

Comparative Example 2

(15) A carbon sequestration foamed lightweight soil was provided. Each cubic meter of the carbon sequestration foamed lightweight soil included: 90 parts of reactive MgO powder, 100 parts of a silty clay, 10 parts of a CO.sub.2 bubble cluster and 200 parts of water. The same silty clay, MgO, water and foaming agent were used as in Example 1, and treatment methods for various materials were also kept the same.

(16) A preparation method of the carbon sequestration foamed lightweight soil in Comparative Example 2 was the same as that in Example 1, and a curing time thereof was 7 days.

Comparative Example 3

(17) A carbon sequestration foamed lightweight soil was provided. Each cubic meter of the carbon sequestration foamed lightweight soil included: 100 parts of reactive MgO powder, 100 parts of a silty clay, 10 parts of a CO.sub.2 bubble cluster and 200 parts of water. The same silty clay, MgO, water and foaming agent were used as in Example 1, and treatment methods for various materials were also kept the same.

(18) A preparation method of the carbon sequestration foamed lightweight soil in Comparative Example 3 was the same as that in Example 1, and a curing time thereof was 3 days.

(19) Test Detection

(20) Carbon sequestration foamed lightweight soil samples prepared in Examples 1, 2 and Comparative Examples 1, 2, and 3 were tested for unconfined compressive strength and soil pH values. The test for unconfined compressive strength was carried out in accordance with the specification Test Methods of Soils for Highway Engineering JTG E40-2007 by using a CBR-2 bearing ratio tester. A pH value of a solidified soil was measured according to ASTM Standard Test Method for pH of Soils D4972-13 by using a Shanghai Lei Ci PHS-3C PH meter.

(21) Test Results

(22) TABLE-US-00003 TABLE 3 Properties of carbon sequestration foamed lightweight soil CO.sub.2 Unconfined Soil MgO bubble Curing compressive pH Samples content cluster time strength (KPa) value Example 1 100% 10% 7 d 250.1 10.39 Example 2 100% 10% 1 d 66.2 10.83 Comparative 100% 20% 7 d 172.1 10.22 Example 1 Comparative 90% 10% 7 d 193.2 10.25 Example 2 Comparative 100% 10% 3 d 119.3 10.48 Example 3
Strength Index

(23) It can be seen from Table 3 that: through Example 1 and Comparative Example 1, the increase in the usage amount of the CO.sub.2 bubble cluster will reduce the strength of the carbon sequestration foamed lightweight soil, and when the content of the CO.sub.2 bubble cluster is increased from 10% to 20%, the 7d strength of the carbon sequestration foamed lightweight soil can be reduced by 19.86%.

(24) Through Example 1 and Comparative Example 2, the higher the MgO content, the higher the strength of the carbon sequestration foamed lightweight soil, and when the MgO content is increased from 90% to 100%, the 7d strength of the carbon sequestration foamed lightweight soil is increased by 8.92%.

(25) Through Examples 1, 2 and Comparative Example 3, the 1d strength, 3d strength and 7d strength of the carbon sequestration foamed lightweight soil corresponding to the 100% MgO and 20% CO.sub.2 bubble cluster contents are 66.2 KPa, 119.3 KPa, and 250.1 KPa, respectively, the strength of the carbon sequestration foamed lightweight soil increases with age, and increases most rapidly in the first 3d, and the strength increases relatively rapidly.

(26) Acid-Base Properties

(27) A pH value of the carbon sequestration foamed lightweight soil is about 10.5, which is much lower than that (>11.5) of corresponding cement-solidified soils, will not cause alkali pollution to the environment and has a good ecological effect.

(28) Through Example 1 and Comparative Example 1, the increase in the usage amount of the CO.sub.2 bubble cluster will reduce the pH value of the carbon sequestration foamed lightweight soil, and when the content of the CO.sub.2 bubble cluster is increased from 10% to 20%, the pH value of the carbon sequestration foamed lightweight soil can be reduced from 10.39 to 10.22.

(29) Through Example 1 and Comparative Example 2, it is found that the higher the MgO content, the higher the pH value of the carbon sequestration foamed lightweight soil, and when the MgO content is increased from 90% to 100%, the pH value of the carbon sequestration foamed lightweight soil can be increased from 10.25 to 10.35.

(30) Through Examples 1, 2 and Comparative Example 3, the 1d pH value, 3d pH value and 7d pH value of the carbon sequestration foamed lightweight soil corresponding to the 100% MgO and 10% CO.sub.2 bubble cluster contents are 10.83, 10.48, and 10.39, respectively, and the pH value of the carbon sequestration foamed lightweight soil gradually decreases with age, and has the largest decrease in the first 3d.

(31) Finally, the method of the present application is only a preferred embodiment, and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc., made within the spirit and principle of the present application should be included in the scope of protection of the present application.