Cement material composition and cement mixing pile construction method

Abstract

The invention provides a cement material composition and a cement mixing pile construction method, and belongs to the technical field of pile foundation construction. The cement material composition comprises cement, an additive and a polymer emulsion, the additives are bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder and latex powder; the polymer emulsion is styrene-butadiene emulsion and acrylic emulsion. The cement material composition is applied to cement mixing pile construction and is good in anti-seepage effect and high in compressive strength.

Description

Technical Field

[0001] This invention provides a cement material composition and a cement mixing pile construction method, belonging to the field of pile foundation construction technology. Background Technology

[0002] Cement-soil mixing piles use cement as the main solidifying agent. During drilling, a specialized mixing machine injects grout or atomized powder into the soft soil, forcibly mixing the solidifying agent and soft soil in situ deep within the foundation. Through a series of physical and chemical reactions, a cement-reinforced soil pile column with strength far exceeding that of natural soil is formed. This column possesses excellent properties such as integrity and water stability. These reinforced soil pile columns and the soil between the piles together constitute a high-bearing-capacity composite foundation, significantly reducing building settlement and improving slope stability. However, with the continuous development of geotechnical engineering, traditional pure cement-soil materials, due to insufficient strength and impermeability, are gradually becoming unable to meet the requirements of modern construction.

[0003] Chinese patent CN106088009A discloses a method for improving the strength of cement-soil mixing piles, which includes the following steps: 1) Take a certain mass of undisturbed soil and determine the amount of cement to be added based on the mass of the undisturbed soil; 2) Determine the amount of fly ash based on the amount of cement added, and add a certain amount of sodium bentonite. Then, mix the cement, fly ash and sodium bentonite to form a cement slurry for reinforcing materials. 3) Cement grout is injected into the undisturbed soil using a mixing pile machine and pressurizing equipment, and the undisturbed soil and cement grout are mixed evenly and poured into a mold for compressive and shear tests to form a cement-soil mixing pile with a certain strength.

[0004] The invention uses fly ash and bentonite as a mixture to improve the strength of cement soil, but its 28-day compressive strength is only 7 MPa, which is insufficient.

[0005] A master's thesis from Zhejiang University of Technology, "Experimental Study on Mechanical Properties and Permeability Characteristics of Composite Cement Soil" (Xie Jiawen, June 2020), published on this topic, revealed that adding admixtures (triethanolamine and lignin) and mineral fly ash to cement, respectively, improved the strength of cement-soil. The strength of cement-soil with added fly ash generally increased by about 10% compared to that without fly ash. However, its 28-day strength was only a maximum of 2 MPa, which was insufficient. Summary of the Invention

[0006] The purpose of this invention is to provide a cement material composition and a method for constructing cement mixing piles, as well as related technologies, to solve the technical problem of improving the seepage prevention effect and mechanical strength of cement mixing piles.

[0007] In a first aspect, the present invention provides a cement material composition comprising cement, additives, and a polymer emulsion; wherein the additives are bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder, and latex powder; and the polymer emulsion is styrene-butadiene emulsion and acrylic emulsion.

[0008] Specifically, the mass of the additive is 10-20% of the mass of the cement.

[0009] Preferably, the mass of the additive is 15-20% of the mass of the cement.

[0010] Specifically, the mass ratio of bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder and latex powder is (5-9):(0.5-2):(0.5-1):(1-5):(1-4):(1-2).

[0011] Preferably, the mass ratio of bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder and latex powder is (5-9):(1-2):(0.5-1):(2-4.5):(2-4):(1-2).

[0012] Furthermore, the asphalt is at least one of natural asphalt, petroleum asphalt, and coal tar pitch.

[0013] Further, the bentonite is at least one of sodium-based bentonite, calcium-based bentonite, lithium-based bentonite, hydrogen-based bentonite, and organo-bentonite.

[0014] Further, the latex powder is at least one of the following: vinyl acetate and ethylene copolymer powder (Vac / E), ethylene, vinyl chloride and vinyl silicate terpolymer powder (E / Vc / VL), vinyl acetate, ethylene and higher fatty acid vinyl ester terpolymer powder (Vac / E / VeoVa), vinyl acetate and higher fatty acid vinyl ester copolymer powder (Vac / VeoVa), acrylate and styrene copolymer powder (A / S), vinyl acetate, acrylate and higher fatty acid vinyl ester terpolymer powder (Vac / A / VeoVa), vinyl acetate homopolymer powder (PVac), and styrene and butadiene copolymer powder (SBR).

[0015] Specifically, the polymer emulsion has a mass of 5-15% of the cement mass.

[0016] Preferably, the polymer emulsion has a mass of 5-10% of the cement mass.

[0017] Specifically, the mass ratio of the styrene-butadiene emulsion to the acrylic emulsion is (1-8):(2-12).

[0018] Preferably, the mass ratio of the styrene-butadiene emulsion to the acrylic emulsion is (1-8):(2-4).

[0019] Secondly, the present invention provides a construction method for cement mixing piles, comprising the following steps: (1) Mix the cement material composition and water evenly to make cement slurry; (2) Mix the cement slurry and soil evenly.

[0020] Specifically, the mass ratio of the water and cement material composition is (1-2):1.

[0021] Preferably, the mass ratio of the water and cement material composition is (1.5-2):1.

[0022] Specifically, the mass of the cement slurry is 15-20% of the soil.

[0023] Preferably, the mass of the cement slurry is 18-20% of the soil.

[0024] Furthermore, the soil is at least one of loam, sandy soil, silt, clay, and silty sand.

[0025] The beneficial effects of this invention are: This invention significantly improves the unconfined compressive strength and structural density of materials through the synergistic formulation of cement, additives and polymer emulsion, effectively reduces the permeability coefficient, and has excellent load-bearing capacity and water-stopping performance. Moreover, the formula is reasonable and highly adaptable, which can meet the high-strength and low-permeability requirements of projects such as cement mixing piles. Detailed Implementation

[0026] The following non-limiting embodiments are intended to enable those skilled in the art to gain a more comprehensive understanding of the present invention, but do not limit the invention in any way. The following content is merely an exemplary description of the scope of protection claimed by the present invention, and those skilled in the art can make various changes and modifications to the present invention based on the disclosed content, and such changes should also fall within the scope of protection claimed by the present invention.

[0027] The present invention will be further described below by way of specific embodiments. Unless otherwise specified, all instruments, devices, equipment, reagents, products, etc., used in the embodiments of the present invention are obtained through conventional commercial means.

[0028] The cement of this invention is PO42.5 cement, and the asphalt conforms to the relevant provisions of AH-90 asphalt in GB / T 15180-2025 "Petroleum Asphalt for Heavy Traffic Roads". The mineral admixtures (steel slag powder and fly ash) of this invention conform to the provisions of GB / T 51003-2014 "Technical Specification for Application of Mineral Admixtures" and GB / T 1596-2017 "Fly Ash for Cement and Concrete". The bentonite of this invention is sodium-based bentonite, and its quality conforms to the provisions of high-viscosity bentonite in the current national standard GB / T20973 "Bentonite". The latex powder of this invention conforms to the standard of JC / T 2189-2024 "Redispersible Latex Powder for Dry-Mixed Mortar".

[0029] This invention can be achieved with styrene-butadiene emulsions having a solid content of 45-50%, pH = 7-10, and viscosity (25°C) of 40-150 mPa·s, and acrylic emulsions (acrylate copolymer emulsions) having a solid content of 40-50 wt%, pH = 8 ± 1.0, and viscosity (25°C) of 50-1000 mPa·s. In the embodiments and comparative examples of this invention, the styrene-butadiene emulsions used had a solid content of 49.8%, pH = 8, and viscosity (25°C) of 100-120 mPa·s. In the embodiments and comparative examples of this invention, the acrylic emulsions used had a solid content of 50.3 wt%, pH = 8, and viscosity (25°C) of 750-800 mPa·s.

[0030] I. Examples and Comparative Examples: A Cement Material Composition The bill of materials for Examples 1-3 and Comparative Examples 1-6 is shown in Table 1.

[0031] Table 1 (Unit: parts by weight)

[0032] Note: The latex powder used in Examples 1-3 and Comparative Examples 1-6 was VAC / E. VAC / E had a bulk density of 500 g / L, an ash content of 10 wt%, and a minimum film-forming temperature of 0°C. The asphalt used in Examples 1-3 and Comparative Examples 1-6 was petroleum asphalt AH-70.

[0033] Table 2

[0034] Comparative Example 7: A cement material composition It is composed of the following parts by weight: 100 parts cement, 5 parts bentonite, and 20 parts fly ash.

[0035] Preparation method: Mix and stir all the materials in the cement material composition until they are homogeneous.

[0036] II. Effect Experiment Cement material compositions from Examples 1-3 and Comparative Examples 1-7 were prepared into cement-soil cube specimens according to the method of Shandong Provincial Engineering Construction Standard DB37 / T 5255-2023 "Technical Standard for Cement-Soil Testing". Specific parameters are shown in Table 3.

[0037] Table 3

[0038] Note: The parameters of Comparative Examples 1-7 are the same as those of Example 3.

[0039] According to the unconfined compressive strength test (28d) and indoor permeability test (28d) methods recorded in Shandong Provincial Engineering Construction Standard DB37 / T 5255-2023 "Technical Standard for Cement and Soil Testing", cement and soil cube specimens of Examples 1-3 and Comparative Examples 1-7 of this invention were prepared and tested. The experimental results are shown in Table 4.

[0040] The soil sample used was silty sand.

[0041] Table 4

[0042] The cement compositions of Examples 1-3 of the present invention have high unconfined compressive strength and low permeability coefficient, forming a high-strength, low-permeability structure, which effectively improves water-stopping performance and load-bearing capacity.

[0043] Comparative Example 1, by varying the amounts of additives and polymer emulsions, showed a decrease in lateral compressive strength and an increase in permeability coefficient.

[0044] Comparative Examples 2-3 changed the type and amount of additives, resulting in a decrease in unconfined compressive strength and an increase in permeability coefficient.

[0045] Comparative Examples 4-6 varied the type and amount of polymer emulsion, resulting in a decrease in unconfined compressive strength and an increase in permeability coefficient.

[0046] III. Construction Method Based on the Langxi County Changxi River Basin Comprehensive Management and Southern Area Rural Revitalization (EOD) construction project, the soil was found to be mainly silty loam, silt, and silty sand, with a permeability coefficient of 8.7 × 10⁻⁶. -5 (cm / s), and the cement composition of Example 3 of the present invention is used for construction. The specific steps are as follows: (1) The cement composition of Example 3 was mixed with water (as shown in Table 3) to make cement slurry.

[0047] (2) Start the mixer and make the mixer cut the soil downward along the guide frame. At the same time, turn on the grout pump to spray cement grout into the soil. Simultaneously, cut and mix the soil in both the forward and reverse directions. The mixer continues to sink, and the sinking speed shall not exceed 0.8m / min until the designed depth of the pile body is reached. Continuously spray grout and mix at the pile end for more than 10 seconds.

[0048] (3) Turn off the grout pump, change the rotation direction of the inner and outer drill rods, and stir the two sets of blades in the forward and reverse directions at the same time. Lift the drill rod, and the lifting speed shall not exceed 1m / min until it reaches 40cm above the designed pile top elevation.

[0049] After construction, following the methods described in JGJ340-2015 "Technical Specification for Testing of Building Foundations", core samples were taken from 0.5% of the total number of piles. The unconfined compressive strength of the core samples was found to be 9.8 MPa, and the permeability coefficient was 1.01 × 10⁻⁶. -8 cm / s.

[0050] The cementitious material composition of this invention can form a high-strength, low-permeability structure. The core lies in the enhanced hydration reaction, densified microstructure, and optimized interfacial bonding resulting from the synergistic effect of each component. Cement, as a cementitious material, generates CSH gel and Ca(OH)2 through hydration, forming the basic strength framework. Among the additives, bentonite expands upon contact with water, filling pores and simultaneously adsorbing free water to slow down the cement hydration rate, resulting in a more uniform structure. Asphalt and latex powder form a flexible film that encapsulates cement particles and fills microcracks, enhancing interfacial adhesion. Sodium carbonate, as an early-strength agent, accelerates the cement hydration process and promotes early strength development. Zeolite powder, with its porous structure, adsorbs water and ions, participating in secondary hydration reactions to generate more gel substances, further densifying the structure. Steel slag powder, as an active admixture, reacts with cement hydration products to generate an additional cementitious phase, enhancing the framework strength. During hydration, the styrene-butadiene emulsion and acrylic emulsion in the polymer emulsion form a continuous polymer network that intertwines with cement hydration products. This network enhances the material's flexibility to resist shrinkage stress and reduces pore connectivity through the barrier effect of the polymer film. Simultaneously, the interfacial bonding between the polymer and the cement gel reduces defects in the transition zone, resulting in a denser overall structure. These combined effects contribute to increased unconfined compressive strength and reduced permeability, ultimately achieving a synergistic improvement in both waterproofing performance and load-bearing capacity.

[0051] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, and is not intended to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions made by those skilled in the art to the technical solution of the present invention do not depart from the essence and scope of the technical solution of the present invention.

Claims

1. A cement material composition, characterized in that, It includes cement, additives, and polymer emulsions; the additives are bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder, and latex powder; the polymer emulsions are styrene-butadiene emulsion and acrylic emulsion.

2. The cement material composition according to claim 1, characterized in that, The mass of the additive is 10-20% of the mass of the cement.

3. The cement material composition according to claim 1, characterized in that, The mass ratio of bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder and latex powder is (5-9):(0.5-2):(0.5-1):(1-5):(1-4):(1-2).

4. The cementitious material composition according to claim 3, characterized in that, The mass ratio of bentonite, asphalt, sodium carbonate, zeolite powder, steel slag powder and latex powder is (5-9):(1-2):(0.5-1):(2-4.5):(2-4):(1-2).

5. The cement material composition according to claim 1, characterized in that, The polymer emulsion has a mass of 5-15% of the cement mass.

6. The cement material composition according to claim 1, characterized in that, The mass ratio of the styrene-butadiene emulsion to the acrylic emulsion is (1-8):(2-12).

7. The cementitious material composition according to claim 6, characterized in that, The mass ratio of the styrene-butadiene emulsion to the acrylic emulsion is (1-8):(2-4).

8. A construction method for cement mixing piles, characterized in that, Includes the following steps: (1) The cement material composition according to any one of claims 1-7 is mixed with water to form a cement slurry; (2) Mix the cement slurry and soil evenly.

9. The construction method according to claim 8, characterized in that, The mass ratio of the water and cement material composition is (1-2):

1.

10. The construction method according to claim 8, characterized in that, The mass of the cement slurry is 15-20% of the soil.

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