Slag-fly ash composite curing agent for curing loess and preparation method thereof

Abstract

The invention belongs to the field of civil engineering materials, and particularly relates to a slag-fly ash composite curing agent for curing loess and a preparation method thereof.The preparation method of the curing agent comprises the following steps that 1, slag powder, fly ash and loess are mixed and added into a stirrer according to the required amount, and the mixture is fully stirred to be uniform; a slag-fly ash-loess mixture is obtained; step 2, adding a required amount of NaOH particles into the water glass; adjusting the modulus of the water glass to 1.5-3.3, stirring, adding a required amount of water, and fully and uniformly stirring to obtain a mixed solution; and step 3, uniformly and slowly adding the mixed solution obtained in the step 2 into the slag-fly ash-loess mixture, and uniformly mixing to obtain the slag-fly ash solidified soil. According to the slag-fly ash composite curing agent, iron-making byproducts in the iron and steel industry are adopted as raw materials, the fly ash is flue gas generated after coal combustion, the raw materials are easy to obtain, waste resource utilization is achieved, environmental pollution and resource waste are effectively reduced, the production cost is reduced, and certain economic benefits are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of loess solidification, and particularly relates to a slag-fly ash composite solidifying agent for solidifying loess and a preparation method thereof. Background Art

[0002] Loess, widely distributed in northwest my country, has engineering drawbacks such as large porosity, high compressibility, and strong collapsibility. Unconsolidated loess rapidly deteriorates upon contact with water, easily causing collapsible deformation and directly impacting life and property. Therefore, loess reinforcement is necessary to improve its strength and water stability to meet engineering construction requirements.

[0003] At present, the soil solidifiers used in engineering projects are mainly cement, lime, etc. However, cement consumes a large amount of non-renewable resources and energy during the calcination process and produces a large amount of carbon dioxide gas. In order to achieve environmental protection and sustainable development goals, it is urgent to develop a new environmentally friendly solidifier suitable for loess. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention proposes a slag-fly ash composite curing agent for solidifying loess and a preparation method thereof. The raw materials of the slag-fly ash composite curing agent are easily available, and it has higher strength and better durability than cement. Its application in the field of soil solidification can not only make full use of solid waste and save a large amount of resources, but also reduce production costs and have certain economic benefits.

[0005] To achieve the above object, the present invention adopts the following technical solutions:

[0006] The invention provides a slag-fly ash composite solidifying agent for solidifying loess, comprising slag powder, fly ash and an alkali activator.

[0007] Preferably, the mass of the slag powder is 25% of the mass of the loess, and the mass of the fly ash is 12.5% ​​of the mass of the loess.

[0008] Preferably, the slag powder is S105 granulated blast furnace slag powder.

[0009] Preferably, the slag powder contains 34.5 wt% SiO2, 35.3 wt% CaO and 16.7 wt% Al2O3 by mass, and the fly ash contains 48.46 wt% SiO2, 1.7 wt% CaO and 41.29 wt% Al2O3 by mass.

[0010] Preferably, the alkaline activator is sodium water glass.

[0011] Preferably, the modulus of the base activator is 1.5-3.3.

[0012] Preferably, the alkali content of the alkali activator is 0.5%-1.5%, wherein the alkali content is the mass ratio of Na2O to the slag-fly ash-loess mixture.

[0013] The present invention also provides a method for preparing a slag-fly ash-loess composite curing agent for solidifying loess, comprising the following steps:

[0014] Step 1: Mix loess with slag powder and fly ash, and stir thoroughly to obtain a slag-fly ash-loess mixture;

[0015] Step 2: After adjusting the modulus of the alkaline activator, add water to the alkaline activator and stir thoroughly to obtain a mixed solution;

[0016] Step 3: The mixed solution obtained in step 2 is evenly and slowly added to the slag-fly ash-loess mixture, and mixed evenly to obtain a solidified soil sample.

[0017] Preferably, the modulus of the alkaline activator is adjusted by NaOH particles.

[0018] Preferably, the NaOH particles are of analytical grade.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] (1) The present invention compounds slag powder, fly ash and alkali activator, and optimizes the slag powder, fly ash dosage, alkali activator modulus and alkali dosage, so that the soil solidified by the slag-fly ash composite curing agent has high strength and good durability.

[0021] (2) The slag powder of the present invention is blast furnace slag powder, which is a by-product of iron smelting in the steel industry. Fly ash is the flue gas after coal combustion and is usually regarded as waste. Therefore, the raw materials of the present invention are easy to obtain, and the resource utilization of waste can be realized, solid waste can be utilized separately, and the pollution of waste to the environment can be reduced, thereby achieving the purpose of "treating waste with waste", meeting the overall requirements of high-quality green development of my country's engineering industry, and having low cost and good economic benefits.

[0022] (3) The preparation method of the slag-fly ash composite solidifying agent of the present invention is simple, the operation and control are convenient, and it is conducive to industrial production. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a flow chart for preparing the curing agent of the present invention; DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0025] Example 1

[0026] A slag-fly ash composite solidifying agent for solidifying loess, comprising the following mass components:

[0027] 2.3 parts of sodium silicate, 0.3 parts of sodium hydroxide, 12.7 parts of water, 15.4 parts of slag powder, 7.7 parts of fly ash and 61.6 parts of loess;

[0028] In this embodiment, the sodium silicate alkali content is 0.5%, and the water glass modulus is 1.5;

[0029] refer to Figure 1 The specific preparation steps of the slag-fly ash composite curing agent in this embodiment are:

[0030] Step 1: Dry loess, crush it, and pass it through a 2 mm sieve to obtain dry loess. Mix 61.6 parts of dry loess, 15.4 parts of slag powder, and 7.7 parts of fly ash, and stir them thoroughly to obtain a slag-fly ash-loess mixture;

[0031] Step 2: Add 0.3 parts of sodium hydroxide particles to 2.3 parts of sodium water glass, stir to obtain sodium water glass with a modulus of 1.5, then add 12.7 parts of water to the sodium water glass, stir thoroughly to obtain a mixed solution;

[0032] Step 3: The mixed solution obtained in step 2 is evenly and slowly added to the slag-fly ash-loess mixture, and mixed evenly to obtain a solidified soil sample.

[0033] Example 2

[0034] A slag-fly ash composite solidifying agent for solidifying loess, comprising the following mass components:

[0035] 6.7 parts of sodium silicate, 0.8 parts of sodium hydroxide, 10.1 parts of water, 15 parts of slag powder, 7.5 parts of fly ash and 59.9 parts of loess;

[0036] In this embodiment, the sodium silicate alkali content is 1.5%, and the water glass modulus is 1.5;

[0037] The specific preparation steps of the slag-fly ash composite curing agent in this embodiment are:

[0038] Step 1: Dry loess, crush it, and pass it through a 2 mm sieve to obtain dry loess. Mix 59.9 parts of dry loess, 16.2 parts of slag powder, and 7.5 parts of fly ash, and stir them thoroughly to obtain a slag-fly ash-loess mixture;

[0039] Step 2: Add 0.8 parts of sodium hydroxide particles to 6.7 parts of sodium water glass, stir to obtain sodium water glass with a modulus of 1.5, then add 10.1 parts of water to the sodium water glass, stir thoroughly to obtain a mixed solution;

[0040] Step 3: The mixed solution obtained in step 2 is evenly and slowly added to the slag-fly ash-loess mixture, and mixed evenly to obtain a solidified soil sample.

[0041] Example 3

[0042] A slag-fly ash composite solidifying agent for solidifying loess, comprising the following mass components:

[0043] 13 parts of sodium silicate, 5.9 parts of water, 14.8 parts of slag powder, 7.4 parts of fly ash and 58.9 parts of loess;

[0044] In this embodiment, the dosage of sodium silicate is 1.5%, and the modulus of water glass is 3.3;

[0045] The specific preparation steps of the slag-fly ash composite curing agent in this embodiment are:

[0046] Step 1: Dry loess, crush it, and pass it through a 2 mm sieve to obtain dry loess. Mix 58.9 parts of dry loess, 15.93 parts of slag powder, and 7.4 parts of fly ash, and stir them thoroughly to obtain a slag-fly ash-loess mixture;

[0047] Step 2: Add 5.9 parts of water to 13 parts of sodium water glass, stir thoroughly, and obtain a mixed solution; the sodium water glass modulus required in this embodiment is 3.3, and there is no need to add sodium hydroxide particles for preparation.

[0048] Step 3: The mixed solution obtained in step 2 is evenly and slowly added to the slag-fly ash-loess mixture, and mixed evenly to obtain a solidified soil sample.

[0049] Example 4

[0050] A slag-fly ash composite solidifying agent for solidifying loess, comprising the following mass components:

[0051] 6.7 parts of sodium silicate, 0.3 parts of sodium hydroxide, 10 parts of water, 15.2 parts of slag powder, 7.6 parts of fly ash and 60.2 parts of loess;

[0052] In this embodiment, the sodium silicate alkali content is 1%, and the water glass modulus is 2.4;

[0053] The specific preparation steps of the slag-fly ash composite curing agent in this embodiment are:

[0054] Step 1: Dry loess, crush it, and pass it through a 2 mm sieve to obtain dry loess. Mix 60.2 parts of dry loess, 15.2 parts of slag powder, and 7.6 parts of fly ash, and stir them thoroughly to obtain a slag-fly ash-loess mixture;

[0055] Step 2: Add 0.3 parts of sodium hydroxide particles to 6.7 parts of sodium water glass, stir to obtain sodium water glass with a modulus of 2.4, then add 10 parts of water to the sodium water glass, stir thoroughly to obtain a mixed solution;

[0056] Step 3: The mixed solution obtained in step 2 is evenly and slowly added to the slag-fly ash-loess mixture, and mixed evenly to obtain a solidified soil sample.

[0057] Comparative Example 1

[0058] Plain loess, as the control group of solidified loess, consists of the following mass components:

[0059] 87.4 parts loess and 12.6 parts water;

[0060] In this comparative example, no slag powder, fly ash or cement was added, and the specific preparation steps of plain loess were as follows:

[0061] The loess was dried, crushed, and passed through a 2 mm sieve to obtain dry loess. 87.4 parts of the dry loess was mixed with 12.6 parts of water and mixed thoroughly to obtain a solidified soil sample.

[0062] Comparative Example 2

[0063] A control group for solidifying loess with a slag-fly ash composite solidifying agent is composed of the following mass components:

[0064] 76.3 parts loess, 10.9 parts cement and 12.8 parts water;

[0065] In this comparative example, the mass ratio of cement to loess is 1:7, and the cement used is PO 32.5 cement;

[0066] The specific preparation steps of cement-solidified loess in this comparative example are:

[0067] Step 1: Dry loess, grind it, and pass it through a 2 mm sieve to obtain dry loess. Mix 76.3 parts of dry loess with 10.9 parts of cement and stir thoroughly to obtain a cement-loess mixture.

[0068] Step 2: Slowly and evenly add 12.8 parts of water to the cement-loess mixture and mix well to obtain a solidified soil sample;

[0069] Comparative Example 3

[0070] A control group for solidifying loess with a slag-fly ash composite solidifying agent is composed of the following mass components:

[0071] 64.3 parts of loess, 16 parts of slag powder, 8 parts of fly ash and 11.7 parts of water;

[0072] In this comparative example, the mass ratio of slag powder to loess is 1:4, the mass ratio of fly ash to slag powder is 1:2, and the slag powder is commercially available S105 granulated blast furnace slag powder;

[0073] The specific preparation steps of slag-fly ash single-mixed solidified loess in this comparative example are:

[0074] Step 1: Dry loess, crush it, and pass it through a 2 mm sieve to obtain dry loess. Mix 64.3 parts of dry loess, 16 parts of slag powder, and 8 parts of fly ash, and stir them thoroughly to obtain a slag-fly ash-loess mixture;

[0075] Step 2: This comparative example is the solidification of loess by adding only slag-fly ash, without adding sodium water glass and sodium hydroxide particles. That is, 11.7 parts of water are evenly and slowly added to the slag-fly ash-loess mixture, and mixed evenly to obtain a solidified soil sample.

[0076] In the above embodiments, the slag powder is composed of 34.5% SiO2, 35.3% CaO, 16.7% Al2O3 and 13.5% of the remaining components by mass percentage, and the fly ash is composed of 48.46% SiO2, 1.7% CaO, 41.29% Al2O3 and 8.55% of the remaining components by mass percentage.

[0077] To better understand the superior performance of the present invention, the solidified soil samples obtained in Examples 1-4 and Comparative Examples 1-3 were placed in unconfined compression test molds. Standard cylindrical specimens with a diameter of 50 mm and a height of 50 mm were prepared using a compression method and demolded using a jack. The prepared specimens were wrapped with plastic wrap to prevent water loss and placed in a constant temperature and humidity curing chamber (temperature 20±2°C, humidity 95%±1%) for 7, 14, and 28 days. Compression tests were then conducted in accordance with the requirements of JTGE51-2009, "Testing Procedure for Stabilized Materials with Inorganic Binders for Highway Engineering." The test results are shown in Table 1.

[0078] Table 1 is the unconfined compressive strength test results

[0079]

[0080] The specific embodiments of the present invention are provided to enable those skilled in the art to understand or implement the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention.

[0081] It should be understood that the present invention is not limited to the above description and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A slag-fly ash composite solidifying agent for solidifying loess, characterized in that: Including slag powder, fly ash and alkali activator.

2. The slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The mass of the slag powder is 25% of the mass of the loess, and the mass of the fly ash is 12.5% ​​of the mass of the loess.

3. The slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The slag powder is S105 granulated blast furnace slag powder.

4. The slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The slag powder contains 34.5wt% SiO2, 35.3wt% CaO and 16.7wt% Al2O3 by mass percentage, and the fly ash contains 48.46wt% SiO2, 1.7wt% CaO and 41.29wt% Al2O3 by mass percentage.

5. The slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The alkaline activator is sodium water glass.

6. The slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The modulus of the base activator is 1.5-3.

3.

7. The slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The alkali content of the alkali activator is 0.5%-1.5%, wherein the alkali content is the mass ratio of Na2O to the slag-fly ash-loess mixture.

8. The method for preparing a slag-fly ash composite curing agent for curing loess according to claim 1, characterized in that: The following steps are involved: Step 1: Mix loess with slag powder and fly ash, and stir them thoroughly to obtain a slag-fly ash-loess mixture; Step 2: After adjusting the modulus of the alkaline activator, add water to the alkaline activator and stir well to obtain a mixed solution; Step 3: Add the mixed solution obtained in step 2 evenly and slowly into the slag-fly ash-loess mixture and mix evenly.

9. The method for preparing a slag-fly ash composite curing agent for solidifying loess according to claim 8, characterized in that: The modulus of the alkaline activator is adjusted by NaOH particles.

10. The method for preparing a slag-fly ash composite curing agent for solidifying loess according to claim 9, characterized in that: The NaOH particles were of analytical grade.

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