Mud for wharf cast-in-place pile and preparation method thereof

Abstract

The invention belongs to the technical field of constructional engineering, and particularly relates to slurry for a wharf cast-in-place pile, which is prepared from the following raw materials: 60 to 80 parts of modified bentonite, 0.5 to 3 parts of defoaming agent, 1 to 5 parts of sodium carbonate, 0.5 to 2 parts of thickening agent, 5 to 10 parts of modified polyacrylamide composite flocculant and 100 to 150 parts of water. By adopting the specific modified bentonite and modified polyacrylamide composite flocculant, the viscosity of the slurry and the thickness of the slurry cake can be remarkably improved, and the sand content and the water loss rate of the slurry are reduced, so that the excellent slurry wall protection effect and the excellent hole cleaning effect in the construction process are ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction engineering, and particularly relates to a slurry for wharf cast-in-place piles and a preparation method thereof. Background Art

[0002] In recent years, with the rapid development of China's infrastructure construction, cast-in-place piles have been widely used in the construction of wharves, highways, railways, high-rise buildings, long-span bridges, etc. In particular, during the construction process of wharf cast-in-place piles, special strata are likely to cause problems such as construction hole collapse, necking, and thick sediment. To avoid the above problems, the circulating slurry has the functions of stabilizing the water level in the hole and carrying drill cuttings, and can form a mud cake with a uniform thickness on the hole wall, which can protect the hole wall and prevent collapse. Therefore, whether in the hole-forming stage or the pouring stage, the quality of the slurry has an important impact on the quality of wharf cast-in-place piles, and thus has a greater impact on the bearing capacity of the pile foundation.

[0003] Chinese invention patent with the publication number CN117342826 A discloses a slurry for bored cast-in-place piles and a preparation method thereof. The raw materials include: mixing water, bentonite, soda ash, mineral materials, weighting agents, solidifying agents, anti-seepage auxiliary materials, etc. However, the auxiliary materials included in the above slurry are relatively complex, and the related properties of the slurry need to be improved.

[0004] Chinese invention patent with the publication number CN117658543 A discloses a method for preparing a slurry for cast-in-place piles under deep silt geological conditions. By selecting bentonite as the cohesive soil and adding a thickening agent to improve the overall viscosity of the slurry and enhance the adhesion of the slurry; using biodegradable polymer polylactic acid grafted modified polyacrylamide as an aqueous slurry to be added, not only makes the gas wrapped in the slurry easy to discharge, but also reduces the sand content rate of the slurry while increasing the specific gravity and viscosity of the slurry. However, the above slurry has a relatively high sand content rate and causes certain wear to the machine.

[0005] Based on this, there is an urgent need to develop a slurry for wharf cast-in-place piles with high viscosity, low water loss, and low sand content rate. Summary of the Invention

[0006] Aiming at the deficiencies in the prior art, the present invention aims to provide a slurry for wharf cast-in-place piles with excellent performance and a preparation method thereof. To achieve the above object, the present invention adopts the following technical solutions: A slurry for wharf cast-in-place piles, calculated by weight, the raw materials thereof include: Modified bentonite 60 - 80 parts Defoamer 0.5 - 3 parts Sodium carbonate 1 - 5 parts Thickening agent 0.5 - 2 parts Modified polyacrylamide composite flocculant 5 - 10 parts 100 - 150 parts of water Among them, the preparation method of the modified bentonite includes: Treating bentonite with concentrated hydrochloric acid to obtain acidified bentonite; then using a modifier To modify the acidified bentonite to obtain modified bentonite; The preparation method of the modified polyacrylamide composite flocculant includes: Adding sodium silicate into a reactor, diluting with water, adjusting the pH of the solution to 6 - 9 with hydrochloric acid, and adding a silane coupling agent to obtain silica sol; adding starch, NaOH and water into a reactor, adding hydrochloric acid to adjust the pH of the solution to 6 - 9 to obtain a starch solution; adding the silica sol into the starch solution, introducing N2, and then successively adding acrylamide and potassium persulfate to react to obtain the modified polyacrylamide composite flocculant.

[0007] In some embodiments, the silane coupling agent is selected from one or more of KH 550, KH 560, KH 570, KH 792, KH 791.

[0008] In some embodiments, the mass ratio of bentonite to the modifier is (3 - 6):1; the particle size of bentonite is 200 - 300 mesh.

[0009] In some embodiments, the mass ratio of sodium silicate to the silane coupling agent is 1:(0.1 - 0.5); the mass ratio of sodium silicate to starch is 1:(2 - 10); the mass ratio of sodium silicate to acrylamide is 1:(5 - 10).

[0010] In some embodiments, the defoaming agent is selected from one or more of tributyl phosphate, emulsifying silicone oil, high - carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropylene amine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, polydimethylsiloxane.

[0011] In some embodiments, the thickener is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose and carboxymethyl cellulose.

[0012] In some embodiments, by weight, its raw materials include: 80 parts of modified bentonite 1 part of tributyl phosphate 3 parts of sodium carbonate 0.5 part of carboxymethyl cellulose 10 parts of modified polyacrylamide composite flocculant 120 parts of water.

[0013] The present invention also provides a preparation method of the slurry for the wharf cast - in - place pile, including the following steps: Weigh each raw material according to the ratio; first, add modified bentonite to water and stir for 5 - 10 min; then add defoamer, sodium carbonate, thickener, and modified polyacrylamide composite flocculant, and continue to stir for 10 - 30 min at a stirring speed of 50 - 100 r / min until evenly stirred without lumps to obtain the slurry for wharf cast-in-place piles. Compared with the prior art, the beneficial effects of the present invention are as follows: 1) The present invention uses specific modified bentonite and modified polyacrylamide composite flocculant, which can significantly improve the viscosity and mud cake thickness of the slurry, as well as reduce the sand content rate and water loss rate of the slurry, thereby ensuring excellent slurry wall protection effect and hole cleaning effect during construction; 2) The present invention introduces SiO2 and starch structures into the traditional polyacrylamide flocculant. The modified polyacrylamide flocculant contains active groups such as amide groups and hydroxyl groups, which can have an affinity and adsorption effect with the flocculated substances to form hydrogen bonds or form a physical cross-linked state, thus greatly improving the flocculation performance. It can remove drill cuttings during slurry circulation and improve the relevant properties of the slurry; 3) The present invention modifies bentonite by using specific modifiers and introduces multiple NH2 active groups. It improves the fluidity between clays through hydrogen bond action and increases the viscosity of the slurry. In addition, the modified bentonite can also improve its bonding strength with the surrounding soil mass and reduce the water loss amount and mud cake thickness by increasing the compactness of the mud cake. Specific Embodiments

[0014] The following non-limiting examples can enable those of ordinary skill in the art to more comprehensively understand the present invention, but do not limit the present invention in any way. The following content is only an exemplary illustration of the scope claimed by the present invention. Those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and they should also fall within the scope claimed by the present invention.

[0015] When the examples give numerical ranges, it should be understood that unless otherwise specified in the present invention, any value between the two endpoints of each numerical range and either endpoint can be selected. Unless otherwise defined, all technical and scientific terms used in the present invention have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention belongs.

[0016] The present invention will be further described below by way of specific examples. All chemical reagents used in the examples of the present invention are obtained through conventional commercial channels unless otherwise specified.

[0017] Preparation Example 1 Preparation of Modified Bentonite Weigh bentonite (10.0 g) (water content 1.5 wt%, sand content 0.12 wt%, particle size 200 mesh, density 2.40 g / cm 3 ) and disperse it in concentrated hydrochloric acid (1 mol / L, 200 mL). Stir evenly at 60 °C for 12 h. After the reaction, filter by suction, wash with deionized water until the filtrate is neutral, then dry in vacuum at 60 °C for 24 h, and grind with a mortar to obtain acidified bentonite.

[0018] Add ethanol solution with a mass fraction of 60% (200 mL) to a three-necked flask, and then add a modifier (2.0 g), heat up to 70 °C and stir for 10 min, then add the above acidified bentonite, continue to stir and react for 12 h. After the reaction, filter by suction, wash with toluene 3 times, then dry in vacuum at 60 °C for 24 h, and finally grind with a mortar to obtain modified bentonite for standby.

[0019] Preparation Example 2 Preparation of Modified Polyacrylamide Composite Flocculant Add sodium silicate (0.5 g) to a three-necked flask, dilute with water to 30 mL, slowly adjust the pH of the solution to 7 with hydrochloric acid (0.1 g·mL –1 ), then stir at 70 °C for 3 h, then add silane coupling agent KH570 (0.01 g), and continue to stir to obtain silica sol for standby.

[0020] Add starch (1.5 g), NaOH (0.2 g) and water (30 mL) to the reactor, heat up to 80 °C and stir for 1 h, then cool to room temperature, add hydrochloric acid (0.1 g·mL –1 ) to adjust the pH of the solution to 7 to obtain a starch solution. Add the prepared silica sol to the starch solution, and pass N2 to remove oxygen for 30 min. Then add acrylamide (4.5 g) and potassium persulfate (0.01 g) in sequence, heat up to 70 °C and stir and react for 5 h. After the reaction, precipitate the polymer from the obtained viscous liquid with ethanol, then wash with acetone, dry in vacuum at 60 °C to obtain the crude product. Finally, use a mixed solution of ethanol and glacial acetic acid with a volume ratio of 4:6 to extract in a Soxhlet extractor for 24 h to remove unreacted monomers and impurities in the crude product, and dry in vacuum to obtain the modified polyacrylamide composite flocculant for standby.

[0021] Example 1 A kind of slurry for wharf cast-in-place piles, by weight, its raw materials include: Modified bentonite (obtained from Preparation Example 1) 80 parts Defoamer: tributyl phosphate 1 part Sodium carbonate 3 parts Thickener: carboxymethyl cellulose 0.5 part Modified polyacrylamide composite flocculant (obtained from Preparation Example 2) 10 parts Water 120 parts The preparation method of the slurry for the wharf cast-in-place pile includes the following steps: Weigh each raw material according to the ratio. First, add modified bentonite to water and stir for 10 min; then add defoamer, sodium carbonate, thickener, modified polyacrylamide composite flocculant, and continue to stir for 30 min at a stirring speed of 100 r / min until evenly stirred without lumps to obtain the slurry for the cast-in-place pile.

[0022] Example 2 A slurry for the wharf cast-in-place pile, by weight, its raw materials include: Modified bentonite (obtained from Preparation Example 1) 70 parts Defoamer: Emulsifying silicone oil 2 parts Sodium carbonate 5 parts Thickener: Hydroxyethyl cellulose 1.0 part Modified polyacrylamide composite flocculant (obtained from Preparation Example 2) 10 parts Water 120 parts The preparation method of the slurry for the wharf cast-in-place pile includes the following steps: Weigh each raw material according to the ratio. First, add modified bentonite to water and stir for 10 min; then add defoamer, sodium carbonate, thickener, modified polyacrylamide composite flocculant, and continue to stir for 30 min at a stirring speed of 100 r / min until evenly stirred without lumps to obtain the slurry for the cast-in-place pile.

[0023] Example 3 A slurry for the wharf cast-in-place pile, by weight, its raw materials include: Modified bentonite (obtained from Preparation Example 1) 80 parts Defoamer: Emulsifying silicone oil 3 parts Sodium carbonate 5 parts Thickener: Hydroxypropyl cellulose 0.5 part Modified polyacrylamide composite flocculant (obtained from Preparation Example 2) 8 parts Water 120 parts The preparation method of the slurry for the wharf cast-in-place pile includes the following steps: Weigh each raw material according to the ratio. First, add modified bentonite to water and stir for 10 min; then add defoamer, sodium carbonate, thickener, modified polyacrylamide composite flocculant, and continue to stir for 30 min at a stirring speed of 100 r / min until evenly stirred without lumps to obtain the slurry for the cast-in-place pile.

[0024] Comparative Example 1 On the basis of Example 1, the modified bentonite was replaced with unmodified bentonite, and other conditions were the same as those in Example 1.

[0025] Comparative Example 2 On the basis of Example 1, the modified polyacrylamide composite flocculant was replaced with a polyacrylamide flocculant, and other conditions were the same as those in Example 1.

[0026] Comparative Example 3 On the basis of Preparation Example 1, the modifier was replaced with (KH560), and other conditions were the same as those in Preparation Example 1 to prepare modified bentonite A.

[0027] On the basis of Example 1, the modified bentonite was replaced with the above-mentioned modified bentonite A, and other conditions were the same as those in Example 1.

[0028] Performance Test Relevant performance tests were carried out on the cast-in-place pile mud prepared in Examples 1-3 and Comparative Examples 1-3. The test methods are as follows: Viscosity: The viscosity (S) of the mud was measured using a 1006-type standard funnel viscometer. The steps were as follows: Use open-ended cups at both ends to measure 200 mL and 500 mL of the mud respectively, filter out sand grains with a particle size exceeding 4 mm using a sieve, and then pour the mud into the funnel. The time required for the mud to flow out of the funnel and fill the 500 mL measuring cup is the viscosity (s) of the mud.

[0029] Water loss and mud cake thickness: A ZNS-type water loss instrument was used to measure the water loss of the mud. Generally, under a specified pressure of 0.7 MPa, the liquid leakage volume of the mud after 30 minutes was measured as the water loss of the mud. When the time for measuring the water loss has arrived, immediately remove the measuring cylinder and hanging rack, remove the mud cup, take out the filter paper, wash the floating slurry on the mud cake, and at the same time measure the thickness of the mud cake formed on the filter paper, which is the mud cake thickness.

[0030] Sand content: It was measured using a sand content meter. During the measurement, 100 ml of the mud was filled into a measuring cup, the mud was diluted with clear water, the diluted mud was poured into the filter cylinder sieve for filtration, and then washed with water. Finally, the remaining sand grains were poured into a clean sand content measuring cup and allowed to stand vertically for one minute. Record the milliliter number of the sediment volume. The milliliter number of the sediment volume divided by 100 is the sand content of the mud.

[0031] The results are shown in Table 1.

[0032] Table 1 Performance Test Results of Cast-in-Place Pile Mud As can be seen from Table 1, the specific modified bentonite and modified polyacrylamide composite flocculant used in the present invention can significantly increase the viscosity and mud cake thickness of the mud, as well as reduce the sand content and water loss rate of the mud, thereby ensuring excellent mud wall protection effect and hole cleaning effect during the construction process. The main reasons may be as follows: 1) In the present invention, SiO2 and starch structures are introduced into the traditional polyacrylamide flocculant. The modified polyacrylamide flocculant contains active groups such as amide groups and hydroxyl groups, which can have an affinity and adsorption effect with many flocculated substances to form hydrogen bonds or form a physical cross-linked state, thus greatly improving the flocculation performance. It can remove drill cuttings during mud circulation and improve the relevant properties of the mud; 2) In the present invention, bentonite is modified by using a specific modifier and multiple NH2 active groups are introduced. It improves the fluidity between clays through hydrogen bond action and increases the viscosity of the mud. In addition, the modified bentonite can also improve its bonding strength with the surrounding soil mass and reduce the water loss and mud cake thickness by increasing the compactness of the mud cake.

[0033] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement methods and are all included in the protection scope of the present invention.

Claims

1. A slurry for pier cast-in-place piles, the raw materials of which include, by weight: Modified bentonite 60~80 parts Defoaming agent 0.5~3 parts 1~5 parts of sodium carbonate Thickener 0.5~2 parts Modified polyacrylamide composite flocculant 5~10 parts 100~150 parts water Wherein, the preparation method of the modified bentonite comprises: The bentonite is treated with concentrated hydrochloric acid to obtain acidified bentonite; then a modifier is used to Modifying the acidified bentonite to obtain modified bentonite; The preparation method of the modified polyacrylamide composite flocculant comprises: Add water glass to the reactor, dilute with water, adjust the pH value of the solution to 6-9 with hydrochloric acid, and add a silane coupling agent to obtain silica colloidal solid; add starch, NaOH and water to the reactor, add hydrochloric acid to adjust the pH value of the solution to 6-9 to obtain starch solution; add silica colloidal solid to the starch solution, pass N2, and then add acrylamide and potassium persulfate in sequence to react to obtain a modified polyacrylamide composite flocculant.

2. The mud for pier bored piles according to claim 1, characterized in that: The silane coupling agent is selected from one or more of KH550, KH 560, KH 570, KH 792 and KH 791.

3. The mud for pier bored piles according to claim 1, characterized in that: The mass ratio of bentonite to modifier is (3~6):1; the particle size of bentonite is 200~300 mesh.

4. The mud for pier bored piles according to claim 1, characterized in that: The mass ratio of water glass to silane coupling agent is 1: (0.1~0.5); the mass ratio of water glass to starch is 1: (2~10); the mass ratio of water glass to acrylamide is 1: (5~10).

5. The mud for pier bored piles according to claim 1, characterized in that: The defoaming agent is selected from one or more of tributyl phosphate, emulsified silicone oil, high carbon alcohol fatty acid ester complex, polyoxyethylene polyoxypropylene pentaerythritol ether, polyoxyethylene polyoxypropanolamine ether, polyoxypropylene glycerol ether, polyoxypropylene polyoxyethylene glycerol ether, and polydimethylsiloxane.

6. The mud for pier bored piles according to claim 1, characterized in that: The thickener is selected from one or more of hydroxyethyl cellulose, hydroxypropyl cellulose and carboxymethyl cellulose.

7. The mud for pier bored piles according to claim 1, characterized in that: By weight, the raw materials include: 80 parts of modified bentonite Tributyl phosphate 1 part 3 parts sodium carbonate 0.5 parts of carboxymethyl cellulose Modified polyacrylamide composite flocculant 10 parts 120 parts of water.

8. A method for preparing the mud for the wharf bored piles according to any one of claims 1 to 6, comprising the following steps: Weigh the raw materials according to the ratio; first add modified bentonite into water and stir for 5-10 min; then add defoamer, sodium carbonate, thickener, modified polyacrylamide composite flocculant, continue stirring for 10-30 min, stirring speed 50-100r / min, stir evenly until there are no lumps, and obtain mud for dock bored piles.

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