A flow aid for preparing highly fluid solidified loess, its preparation method and uses

Abstract

The flow aid for preparing highly fluid solidified loess provided by the present invention is mainly made of polyphosphate, polyquaternary ammonium salt and its derivatives, sodium metabisulfite, water retaining agent and water. It is characterized in that the mass percentage ratio of the polyphosphate, polyquaternary ammonium salt and its derivatives, water retaining agent, sodium metabisulfite and water is (2-5)%:(0.2-1)%:(0.2-0.8)%:(10-15)%:(75-85)%. The flow aid provided by the present invention effectively improves the comprehensive performance of the highly fluid solidified soil, obtains highly fluid solidified loess that meets the fluidity requirements, and ensures the quality of backfilling and filling projects.

Description

Technical Field

[0001] The present invention belongs to the field of backfill / fill soil for construction projects, and particularly relates to a flow aid for preparing highly fluid solidified loess, a preparation method thereof, and uses thereof. Background Art

[0002] Loess is mainly distributed in the warm climate zones of the mid-latitudes. Such regions are characterized by aridity, semi-aridity, warm and less rainfall, and strong seasonal variations, among which the loess in Asia is the most widely distributed. It is estimated that about 9.3% of the earth's land area is covered by loess.

[0003] Loess is composed of yellowish-gray or yellowish-brown dust and fine particles, and is also widely distributed in the loess plateau regions of Gansu, Ningxia, Shaanxi, and Shanxi in China. Although China has rich loess resources, defects such as the collapsibility of loess limit its effective utilization in engineering construction. Collapsible loess refers to loess that, when wetted by water under a certain pressure, the soil structure is rapidly damaged and significant additional settlement occurs. The main characteristics of collapsible loess include: (1) Porosity: large porosity and loose soil structure; (2) Collapsibility: after being wetted by water, the soil structure is rapidly damaged, and significant additional settlement occurs, its strength and permeability are rapidly reduced, and even an impermeable layer is generated. Therefore, loess needs to be properly treated in engineering construction.

[0004] Due to its strong viscosity, existing studies have shown that when using loess to prepare fluid solidified soil, a relatively high dosage of water reducing agent is required, which is quite uneconomical; moreover, when only using a water reducing agent as the flow improvement component of loess, the fluidity and flow uniformity of the prepared fluid solidified soil are poor, and the fluidity loss is relatively fast, which does not meet the long-term construction requirements; furthermore, when the dosage of the water reducing agent in loess is too high, water bleeding will occur on the surface of the prepared loess-based fluid solidified soil, deteriorating the overall performance of the solidified soil and affecting the construction quality.

[0005] Currently, there are no relevant reports on the research of flow aids in the process of preparing highly fluid solidified soil specifically targeting these characteristics of loess, and it is necessary to fill the gap in engineering practice in this field. Summary of the Invention

[0006] Aiming at the deficiencies of the existing technology, the present invention provides a flow aid for preparing highly fluid solidified loess, a preparation method thereof, and uses thereof. By designing a flow aid to improve the fluidity of loess to make highly fluid solidified soil for backfill / fill projects, the highly fluid solidified loess has good strength, and can greatly improve the fluidity while ensuring a relatively low dosage of the water reducing component and ensure good flow uniformity, and will not lose too fast, effectively improving the comprehensive performance of the highly fluid solidified soil, obtaining highly fluid solidified loess that meets the fluidity requirements, and ensuring the quality of backfill and fill projects in practical applications.

[0007] To achieve the technical object of the invention, the technical solution of the present invention is realized as follows:

[0008] The flow aid for preparing highly fluid solidified loess provided by the present invention is mainly made of inorganic polyphosphate, polyquaternary ammonium salt and its derivatives, sodium metabisulfite, water retaining agent and water. It is characterized in that the mass percentage ratio of the polyphosphate, polyquaternary ammonium salt and its derivatives, water retaining agent, sodium metabisulfite and water is (2-5)%:(0.2-1)%:(0.2-0.8)%:(10-15)%:(75-85)%, and the sum of the percentages of each component is 100%.

[0009] Preferably, for the flow aid for preparing highly fluid solidified loess provided by the present invention, wherein the inorganic polyphosphate includes one or several of sodium tripolyphosphate, sodium hexametaphosphate, sodium polyphosphate.

[0010] More preferably, for the flow aid for preparing highly fluid solidified loess provided by the present invention, wherein the polyphosphate is sodium hexametaphosphate.

[0011] The inventors found that when improving the performance of highly fluid solidified loess, polyphosphates such as sodium hexametaphosphate can form stable complexes with loess particles. The formed complexes can weaken the adsorption of polycarboxylate superplasticizer by high-valent metal ions in loess, such as calcium ions, aluminum ions, magnesium ions, etc., release polycarboxylic acid molecules, and retain more polycarboxylic acid molecules.

[0012] Preferably, for the flow aid for preparing highly fluid solidified loess provided by the present invention, wherein the polyquaternary ammonium salt and its derivatives are selected from one or several of alkyl dimethyl benzyl ammonium chloride, dimethyl diallyl ammonium chloride, benzyl trimethyl ammonium chloride, tetramethyl ammonium chloride.

[0013] The inventors found that when improving the performance of highly fluid solidified loess, on the one hand, since the overall surface of loess mineral particles is negatively charged, the polyquaternary ammonium salt and its derivatives, as a cationic surfactant, will adsorb on the surface of loess mineral particles; at the same time, on the other hand, due to the characteristics of its small molecular structure, it can preferentially adsorb on the surface of loess mineral particles, thus reducing the number of loess particles in contact with polycarboxylic acid molecules and retaining more polycarboxylic acid molecules.

[0014] Preferably, for the flow aid for preparing highly fluid solidified loess provided by the present invention, wherein the water retaining agent is acrylamide-acrylate copolymer crosslinking polymer, selected from one or several of polyacrylamide, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate.

[0015] More preferably, for the flow aid for preparing highly fluid solidified loess provided by the present invention, wherein the water retaining agent is polyacrylamide.

[0016] The inventors found that when improving the properties of highly fluid solidified loess, water retention agents such as polyacrylamide have suitable water retention properties, making the highly fluid loess not prone to chromatography and dispersion. The specific mechanism is that polyacrylamide hydrolyzes to produce carboxyl groups, and the molecular chain carries negative charges, which can adsorb the positive charges in the highly fluid loess system and consolidate its water retention performance.

[0017] The inventors also found that when improving the properties of highly fluid solidified loess, sodium metabisulfite can adsorb loess, release the free water wrapped by loess aggregates through its adsorption-dispersion effect, and form a diffusion double layer after adsorbing loess, which can further hinder the adsorption of loess and polycarboxylic acid molecules, reduce the consumption of polycarboxylic acid molecules, and the existence of this formed double layer also plays a lubricating role, thus increasing the fluidity of the mixed slurry.

[0018] The inventors found that when improving the properties of highly fluid solidified loess, the above components of the flow aid synergistically act to overcome problems such as the large consumption of loess water reducer and the stability of soil structure. Macroscopically, the solidified loess exhibits advantages such as good fluidity, good flow uniformity, small loss of fluidity in a long time period, and increased strength.

[0019] The present invention also provides a preparation method of the flow aid for preparing highly fluid solidified loess, comprising the following steps:

[0020] (1) Weigh each raw material component according to the mass ratio;

[0021] (2) Add each raw material component into a stirring container and stir at a rotation speed of 60 - 120 revolutions per minute for 8 - 10 minutes to make it uniformly mixed;

[0022] (3) Then add water and stir for 8 - 10 minutes to make it uniformly mixed to obtain the flow aid product.

[0023] Preferably, in the preparation method of the flow aid for preparing highly fluid solidified loess provided by the present invention, in step (3), the total mass concentration of the highly fluid loess flow aid solution is controlled at 10% - 40%.

[0024] The present invention also provides the use of the flow aid for preparing highly fluid solidified loess, and the usage method is as follows:

[0025] (1) Using loess as the basic raw material, stir and uniformly mix the flow aid provided by the invention with loess, curing agent, water reducer, and industrial water. The mass ratio is curing agent / dry soil = 5 - 20%, water / dry soil = 35 - 45%, water reducer / curing agent = 1 - 3%, flow aid / curing agent = 0.5 - 2% to obtain highly fluid solidified loess;

[0026] (2) The uses of the above highly fluid solidified loess include backfilling and filling projects.

[0027] Preferably, for the use of the flow aid for preparing highly fluid solidified loess provided by the present invention, the liquid limit of the loess is 22% - 32%, and the plastic limit is 12% - 18%; the components and mass percentages of the solidifying agent are (42 - 48)% cement, (27 - 33)% fly ash, (8 - 12)% mineral powder, (7 - 8)% gypsum, and (7 - 9)% quicklime.

[0028] The present invention has achieved good effects:

[0029] (1) By hindering the adsorption of clay and polycarboxylate superplasticizer, the present invention reduces the consumption of polycarboxylate superplasticizer. Compared with the prior art, the cost of highly fluid solidified loess is reduced; when the dosage of polycarboxylate superplasticizer is as low as 1% of the dosage of the solidifying agent, it can still ensure that the highly fluid solidified loess has advantages such as good fluidity, good flow uniformity, small loss of fluidity during a long time period, and improvement of 7-day strength and 28-day strength.

[0030] (2) The present invention uses loess to prepare highly fluid solidified soil, effectively realizing the utilization of loess resources and promoting the development of raw material resources for construction projects.

[0031] (3) The flow aid prepared by the present invention for highly fluid solidified loess has advantages such as good fluidity, good flow uniformity, small loss of fluidity during a long time period, and good strength, and has excellent engineering construction performance, specifically manifested as:

[0032] Good fluidity, no need for manual paving, good appearance of the solidified body, and the solidified soil mixture still maintains good fluidity and flow uniformity within 1 hour, which is conducive to construction organization and has excellent construction performance. The fluidity at 0 min is as high as >290 mm, the fluidity at 30 min is 285 mm, and the fluidity at 1 h is 275 mm. It can be seen that the fluidity only decreases by 10 mm within 30 min.

[0033] It can improve the compressive strength. Comparing Example 1 with Comparative Example 1, the strength of Example 1 with 1% flow aid is increased by 23% for the 7-day strength and 16% for the 28-day strength compared to Comparative Example 1 without adding.

[0034] For the highly fluid solidified loess samples without implementing the technical solution of the present invention, when the dosage of the superplasticizer is low, the fluidity and flow uniformity are poor, and the fluidity at 0 min is only 86 mm and it cannot flow after 30 min and above; when the dosage of the superplasticizer is high, water bleeding occurs during waiting for construction, the flow uniformity is poor, and the fluidity loss is very fast, resulting in great construction difficulty and high economic cost. It is impossible to simultaneously meet the requirements of soil fluidity and strength in an overall consideration. Specific Embodiments

[0035] The following will further describe the present invention in detail in conjunction with embodiments, but the scope of the present invention is not limited to these embodiments.

[0036] Example 1

[0037] 1. Preparation of glidant:

[0038] (1) Weigh each raw material component according to the following mass numbers: 5 kg of sodium hexametaphosphate, 0.3 kg of alkyldimethylbenzylammonium chloride, 13 kg of sodium metabisulfite, 0.5 kg of polyacrylamide, and 81.2 kg of water;

[0039] (2) Add the above raw material components (excluding water) to a stirring container, with a rotation speed of 60 - 120 revolutions per minute and a stirring time of 8 - 10 minutes to make them evenly mixed;

[0040] (3) Then add water and stir for 8 - 10 minutes to make them evenly mixed, obtaining the glidant product.

[0041] 2. Preparation of highly fluid solidified loess

[0042] Take loess as the basic raw material, with the liquid limit of the loess being 27% and the plastic limit being 15%.

[0043] The solidifying agent used, its composition and mass percentage are: 45% cement, 30% fly ash, 10% mineral powder, 7.5% gypsum, 7.5% quicklime.

[0044] Fully stir the loess, solidifying agent, and industrial water, add polycarboxylate water - reducing agent, and then add the glidant obtained in step (3) above, and continue to stir evenly to form a uniformly mixed fluid solidified soil. The mass ratio is solidifying agent / dry soil = 15:100, water / dry soil = 35:100, polycarboxylate water - reducing agent / solidifying agent = 1:100, glidant / solidifying agent = 1:100. Obtain highly fluid solidified loess.

[0045] Test the fluidity of the above - mentioned highly fluid solidified loess at the upper, middle, and lower parts at three time periods of 0 min, 30 min, and 1 h; test the strength of the solidified soil specimen.

[0046] 3. Use the above - mentioned highly fluid solidified loess for backfilling / filling projects to examine whether it can meet the requirements of perfusion fluidity.

[0047] Example 2

[0048] 1. Preparation of glidant:

[0049] (1) Weigh each raw material component according to the following mass numbers: 5 kg of sodium hexametaphosphate, 0.5 kg of alkyldimethylbenzylammonium chloride, 14 kg of sodium metabisulfite, 0.8 kg of polyacrylamide, and 79.7 kg of water;

[0050] (2) Add the above raw material components (excluding water) to a stirring container, stir at a speed of 60 - 120 revolutions per minute for 8 - 10 minutes to make the mixture uniform;

[0051] (3) Then add water and stir for 8 - 10 minutes to make the mixture uniform, obtaining a flow aid product.

[0052] 2. Prepare highly fluid solidified loess

[0053] Use loess as the basic raw material, with the liquid limit of the loess being 27% and the plastic limit being 15%.

[0054] The curing agent used has the following composition and mass percentage: 45% cement, 30% fly ash, 10% mineral powder, 7.5% gypsum, 7.5% quicklime.

[0055] Fully stir the loess, curing agent, and industrial water, add a polycarboxylate water reducer, and then add the flow aid obtained in step (3) above, and continue to stir evenly to form a uniformly mixed fluidized solidified soil. The mass ratio is curing agent / dry soil = 15:100, water / dry soil = 35:100, polycarboxylate water reducer / curing agent = 1:100, flow aid / curing agent = 1:100. Obtain highly fluid solidified loess.

[0056] Test the fluidity of the above highly fluid solidified loess at the upper, middle, and lower parts at three time periods of 0 min, 30 min, and 1 h; test the strength of the solidified soil specimen.

[0057] 3. Use the above highly fluid solidified loess for backfilling / filling projects to investigate whether it can meet the requirements of perfusion fluidity.

[0058] Comparative Example 1

[0059] 1. Prepare highly fluid solidified loess

[0060] Use loess as the basic raw material, with the liquid limit of the loess being 27% and the plastic limit being 15%.

[0061] The curing agent used has the following composition and mass percentage: 45% cement, 30% fly ash, 10% mineral powder, 7.5% gypsum, 7.5% quicklime.

[0062] Fully stir the loess, curing agent, and industrial water, add a polycarboxylate water reducer, and continue to stir evenly to form a uniformly mixed fluidized solidified soil. The mass ratio is curing agent / dry soil = 15:100, water / dry soil = 35:100, polycarboxylate water reducer / curing agent = 1:100. Obtain highly fluid solidified loess.

[0063] Test the fluidity of the above highly fluid solidified loess at the upper, middle, and lower parts at three time periods of 0 min, 30 min, and 1 h; test the strength of the solidified soil specimen.

[0064] 2. Use the above high-fluidity solidified loess for backfilling / filling projects to examine whether it can meet the requirements of perfusion fluidity.

[0065] Comparative Example 2

[0066] 1. Prepare high-fluidity solidified loess

[0067] Use loess as the basic raw material. The liquid limit of the loess is 27%, and the plastic limit is 15%.

[0068] The solidifying agent used has the following components and mass percentages: 45% cement, 30% fly ash, 10% mineral powder, 7.5% gypsum, and 7.5% quicklime.

[0069] Thoroughly stir the loess, solidifying agent, and industrial water, add polycarboxylate water reducer, and continue to stir evenly to form a uniformly mixed fluidized solidified soil. The mass ratio is solidifying agent / dry soil = 15:100, water / dry soil = 35:100, and polycarboxylate water reducer / solidifying agent = 11:100. Obtain high-fluidity solidified loess.

[0070] Test the fluidity of the above high-fluidity solidified loess at the upper, middle, and lower parts at three time periods of 0 min, 30 min, and 1 h; test the strength of the solidified soil specimens.

[0071] 2. Use the above high-fluidity solidified loess for backfilling / filling projects to examine whether it can meet the requirements of perfusion fluidity.

[0072] The following further illustrates the beneficial effects of the present invention through experimental test data:

[0073] Testing method:

[0074] 1. Compressive strength test

[0075] The compressive strength uses an unconfined compressive specimen prepared with a mold with a height of 80 mm, an inner diameter of 39 mm, and an outer diameter of 45 mm.

[0076] The fluidized soil sample to be measured does not need to be compacted. The vibrated soil flows like a fluid and self-balances. After the fluidized soil is loaded into the above mold, it is placed in a curing box at a constant temperature of 20°C and a constant humidity (relative humidity 65%) for 1 day, and then demolded; after demolding, the specimen is wrapped with plastic wrap and placed in a constant temperature and humidity box for curing for 7 days and 28 days, and its strength is tested respectively to obtain the 7-day compressive strength and 28-day compressive strength.

[0077] Unconfined Compressive Strength Test: The unconfined compressive strength test was carried out using the YZM-IIC multi-functional pavement material strength testing machine produced by Beijing Aerospace Keyu Testing Instrument Co., Ltd., Beijing, China. The loading rate was 1 mm / min. The testing machine was equipped with a pressure sensor (resolution 0.01 kN) and a displacement sensor (resolution 0.001 mm), and the equipment terminal could collect pressure data and displacement data in real time.

[0078] 2. Flowability Measurement Method:

[0079] The flowability was measured using a cylindrical bucket with a height of 80 mm, an inner diameter of 80 mm, and an outer diameter of 90 mm. The specific steps were as follows: at an ambient temperature of 20 - 25 °C, the cylindrical bucket was filled with the mixture to be measured and leveled. Then, the cylindrical bucket was lifted, and after one minute, the maximum and minimum diameters of the slump were measured with a ruler, and the average value was taken as the flowability. It was determined according to the engineering requirements, and the following classification could be made according to the flowability: the general flowability mixture was preferably 160 - 220 mm; the high flowability mixture was preferably > 220 mm; when the flowability was greater than 290 mm, the mixture was as fluid as water and the flowability could not be measured, and it was uniformly represented by > 290 mm.

[0080] The index detection data of each example and comparative example are shown in Table 1 below:

[0081] Table 1 Index Detection Data of Each Example and Comparative Example

[0082]

[0083]

[0084] It can be seen from the data in the above table that:

[0085] The high-fluidity solidified loess prepared using the flow aid provided by the present invention has good comprehensive performance and excellent engineering construction performance, specifically manifested as:

[0086] Good flowability, the flowability at 0 min is as high as 270 mm - > 290 mm, the flowability at 30 min is as high as 260 mm - 285 mm, and the flowability at 60 min still remains at 239 mm - 275 mm. The solidified soil shows high fluidity, and there is no water separation phenomenon within 60 min. The uniformity of the example is good, and the difference in flowability between the upper and lower parts is 4 - 10 mm, while the uniformity of the comparative example is very poor, and the difference in flowability between the upper and lower parts is 30 - 50 mm. The strength of the high-fluidity solidified loess with the added flow aid not only does not decrease but also slightly increases, and the construction performance is good.

[0087] It can improve the compressive strength. Comparing Example 1 with Comparative Example 1, the strength of Example 1 with 1% flow aid added is 23% higher than that of Comparative Example 1 without addition at 7 days, and 16% higher at 28 days.

[0088] For the highly fluid solidified loess samples without implementing the technical solution of the present invention, when the water reducer dosage is low, the fluidity is poor, and the fluidity at 0 min is only 86 mm, and it cannot flow after 30 min and above; when the water reducer dosage is high, bleeding occurs during waiting for construction, the fluidity is relatively poor, the fluidity difference between the upper and lower parts is 30 - 50 mm, and the fluidity loss is very fast, resulting in great construction difficulty and high economic cost; neither can comprehensively solve the problems of the fluidity of backfill soil, the uniformity of fluid soil, the retention of fluidity, and the economy, and neither can meet the requirements of backfill / filling construction for highly fluid backfill soil.

[0089] The above are only the preferred embodiments of the present invention, and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A flow aid for preparing highly fluid solidified loess, mainly composed of inorganic polyphosphate, polyquaternary ammonium salt and its derivatives, sodium metabisulfite, a water retaining agent and water, It is characterized in that The mass percentage ratios of the inorganic polyphosphate, polyquaternary ammonium salt and its derivatives, water retaining agent, sodium metabisulfite and water are (2-5)%: (0.2-1)%: (0.2-0.8)%: (10-15)%: (79.7-85)%, and the sum of the percentages of each component is 100%; wherein the polyquaternary ammonium salt and its derivatives are selected from one or more of alkyl dimethyl benzyl ammonium chloride, dimethyl diallyl ammonium chloride, benzyl trimethyl ammonium chloride and tetramethyl ammonium chloride.

2. A flow aid for preparing highly fluid solidified loess according to claim 1, It is characterized in that The inorganic polyphosphate includes one or more of sodium tripolyphosphate, sodium hexametaphosphate and sodium polyphosphate.

3. A flow aid for preparing highly fluid solidified loess according to claim 1 or 2, It is characterized in that The inorganic polyphosphate is sodium hexametaphosphate.

4. A flow aid for preparing highly fluid solidified loess according to claim 1 or 2, It is characterized in that The water retaining agent is an acrylamide-acrylate copolymer cross-linked product, selected from one or more of polyacrylamide, sodium polyacrylate, potassium polyacrylate, and ammonium polyacrylate.

5. A flow aid for preparing highly fluid solidified loess according to claim 4, It is characterized in that The water retaining agent is polyacrylamide.

6. The method for preparing a flow aid for preparing highly fluid solidified loess according to any one of claims 1 to 5, It is characterized in that The steps include: (1) Weigh each raw material component according to mass ratio; (2) adding each raw material component into a stirring container and stirring at a speed of 60 to 120 rpm for 8 to 10 minutes to ensure uniform mixing; (3) Add water and stir for 8 to 10 minutes to mix evenly to obtain a flow aid product.

7. The method for preparing a flow aid for preparing highly fluid solidified loess according to claim 6, It is characterized in that Step (3) controls the overall mass concentration of the high-fluidity loess flow aid solution to be between 10% and 40%.

8. Use of the flow aid for preparing highly fluid solidified loess according to any one of claims 1 to 5, It is characterized in that Here’s how to use it: (1) Stir loess, curing agent and industrial water thoroughly, and add polycarboxylate water reducer; (2) adding the flow aid and continuing to stir evenly to form a uniformly mixed fluidized solidified soil; the mass ratio is solidifying agent / dry soil = 15: 100, water / dry soil = 35: 100, polycarboxylic acid water reducer / solidifying agent = 1: 100, flow aid / solidifying agent = 1: 100, and highly fluid solidified loess is obtained; (3) The high-fluidity solidified loess mentioned above is used for high-fluidity solidified soil that meets the injection fluidity requirements, including: backfill and filling soil.

9. The use of the flow aid for preparing highly fluid solidified loess according to claim 8, It is characterized in that The liquid limit of the loess is 22% to 32%, and the plastic limit is 12% to 18%; the components and mass percentages of the solidifying agent are (42 to 48)% cement, (27 to 33)% fly ash, (8 to 12)% mineral powder, (7 to 8)% gypsum, and (7 to 9)% quicklime.

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