Impermeable high-strength concrete and preparation method thereof

Abstract

The invention belongs to the technical field of building materials, and relates to impermeable high-strength concrete and a preparation method thereof. The invention provides impervious high-strength concrete which is prepared from the following components in parts by mass: 150 to 200 parts of cement, 80 to 100 parts of organic and inorganic composite modified bentonite, 900 to 1300 parts of fine aggregate, 230 to 340 parts of coarse aggregate, 2 to 10 parts of additive and 250 to 350 parts of water, the organic and inorganic composite modified bentonite is obtained by modifying bentonite with polyepichlorohydrin dimethyl ammonium and then modifying the modified bentonite with hydroxyl polyaluminum chloride. The invention aims to solve the technical problem that the compressive strength and the elastic modulus of the concrete for the underground diaphragm wall are almost synchronously reduced along with the increase of the use amount of bentonite, so that the compressive strength and the elastic modulus are difficult to consider at the same time.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of building materials, and relates to a kind of anti-permeation high-strength concrete and a preparation method thereof. BACKGROUND

[0002] An underground cutoff wall is a continuous underground anti-seepage structure built in loose water-permeable foundation, which is formed by special equipment to make holes and pour concrete or cement clay mortar. Its core function is to cut off underground seepage and ensure the stability of foundation permeation, and it is widely used in water conservancy and hydropower engineering (such as dams, cofferdams), mine pit, tailings dam and municipal engineering fields. In order to make the cutoff wall have better deformation performance, using plastic concrete cutoff wall is an effective way. The biggest difference between the raw materials of plastic concrete and ordinary concrete is the composition of cementitious materials. In addition to cement, plastic concrete also contains bentonite, clay and other materials. The elastic modulus of plastic concrete can be adjusted by changing the mix proportion of the material. According to the stress-strain curve of the surrounding soil layer, the most suitable mix proportion of plastic concrete is selected, so as to effectively reduce the stress-strain relationship of the cutoff wall under load, reduce the cracks of the wall body, and improve the safety of the cutoff wall. At the same time, due to the reduction of cement content in the wall material, the project investment is effectively reduced. Bentonite is an important raw material in plastic concrete. The compressive strength and elastic modulus of plastic concrete decrease almost synchronously with the increase of bentonite content. At present, the compressive strength or the amount of bentonite is controlled to make the elastic modulus within a certain range, so as to meet the technical requirements of engineering design. SUMMARY

[0003] The present application aims to solve the technical problem that the compressive strength and elastic modulus of the concrete for underground cutoff wall decrease almost synchronously with the increase of bentonite content, making it difficult to balance the compressive strength and elastic modulus. To this end, the present application provides an anti-permeation high-strength concrete and a preparation method thereof to meet the needs in this field. By modifying bentonite with organic-inorganic composite, the compressive strength remains relatively low when increasing the amount of bentonite to reduce the elastic modulus, and finally a concrete for underground cutoff wall with high compressive strength and low elastic modulus is obtained.

[0004] In one aspect, the present application relates to an anti-permeation high-strength concrete, which comprises, by mass fraction: cement 150-200 parts, organic-inorganic composite modified bentonite 80-100 parts, fine aggregate 900-1300 parts, coarse aggregate 230-340 parts, additive 2-10 parts, and water 250-350 parts. The organic-inorganic composite modified bentonite is obtained by modifying bentonite with polyepoxy chloropropane dimethyl ammonium and then modifying it with hydroxyl polyaluminum.

[0005] Preferably, in the anti-permeation high-strength concrete provided by the present application, the concrete comprises, in parts by mass, cement 190 parts, organic-inorganic composite modified bentonite 90 parts, fine aggregate 1200 parts, coarse aggregate 320 parts, additive 3 parts, and water 300 parts.

[0006] Further, in the anti-permeation high-strength concrete provided by the present application, the cement is ordinary Portland cement.

[0007] Optionally, in the anti-permeation high-strength concrete provided by the present application, the cement is at least one of ordinary Portland cement, slag-based polymer cement, alkali-activated slag cement, or sulphoaluminate cement.

[0008] Further, in the anti-permeation high-strength concrete provided by the present application, the bentonite is at least one of sodium-based bentonite, calcium-based bentonite, magnesium-based bentonite, or aluminum-based bentonite.

[0009] Preferably, in the anti-permeation high-strength concrete provided by the present application, the bentonite is sodium-based bentonite.

[0010] Further, in the anti-permeation high-strength concrete provided by the present application, the fine aggregate is prepared by uniformly mixing natural sand and artificial sand, and has a fineness modulus of 2.72.

[0011] Further, in the anti-permeation high-strength concrete provided by the present application, the coarse aggregate is natural cobblestone with a size of 5-20 mm.

[0012] Further, in the anti-permeation high-strength concrete provided by the present application, the additive is a water reducing agent and an air entraining agent.

[0013] Optionally, in the anti-permeation high-strength concrete provided by the present application, the additive is at least one of a water reducing agent, an air entraining agent, a defoaming agent, and an early strength agent.

[0014] Illustratively, in the anti-permeation high-strength concrete provided by the present application, the water reducing agent is a naphthalene-based high-efficiency water reducing agent, a sodium lignin sulfonate water reducing agent, an amino high-efficiency water reducing agent, or a polycarboxylic acid high-efficiency water reducing agent; the air entraining agent is a rosin resin air entraining agent, an alkyl air entraining agent, or a sulfonate acid air entraining agent; the defoaming agent is an organic silicon defoaming agent, a polyether defoaming agent, or a polyether-modified polysiloxane defoaming agent; and the early strength agent is a nitrite, calcium formate, a composite early strength agent, or triethanolamine.

[0015] Further, in the anti-permeation high-strength concrete provided by the present application, in the additive, the mass ratio of the water reducing agent to the air entraining agent is 10:5-10.

[0016] In another aspect, the present application relates to a preparation method of the anti-permeation high-strength concrete, which comprises: configuring a polyepichlorohydrin dimethyl ammonium solution, then adding the bentonite, stirring at a constant temperature of 60-80℃ for 2-3h, drying after water washing by suction filtration, activating at 105-110℃ for 1-2h, and then crushing to pass a 200-mesh sieve to obtain the polyepichlorohydrin dimethyl ammonium modified bentonite; adding the polyepichlorohydrin dimethyl ammonium modified bentonite into a hydroxyl polyaluminum solution, stirring at a constant temperature of 60-80℃ for 2-3h, and then aging for at least 24h, drying after water washing by suction filtration until no chloride ions are present in the filtrate to obtain the organic-inorganic composite modified bentonite; mixing the fine aggregate and the coarse aggregate uniformly, then adding the cement and the organic-inorganic composite modified bentonite, and finally adding water and the additive, and then stirring to obtain the concrete.

[0017] Further, in the preparation method of the anti-permeation high-strength concrete provided by the present application, the mass ratio of the polyepichlorohydrin dimethyl ammonium to the bentonite is 3-5:20. The amount of aluminum in the hydroxyl polyaluminum solution and the polyepichlorohydrin dimethyl ammonium modified bentonite is 8-12mmol / g.

[0018] In another aspect, the present application relates to the use of the anti-permeation high-strength concrete in the preparation of underground anti-permeation walls.

[0019] Compared with the prior art, the technical solution provided by the present application has at least the following beneficial effects or advantages: The technical solution provided by the present application significantly alleviates the problem of rapid decrease in compressive strength caused by the increase in the amount of bentonite by using the organic-inorganic composite modified bentonite (doubly modified by polyepichlorohydrin dimethyl ammonium and hydroxyl polyaluminum), while effectively reducing the elastic modulus. The data of the examples show that the decrease in the compressive strength of the unmodified bentonite group (#1-#4) is 3.11MPa, while the decrease in the compressive strength of the modified bentonite group (#5-#8) is only 1.38MPa, the loss rate of the compressive strength is reduced by 56%, and the elastic modulus is simultaneously reduced, thereby realizing the synergistic optimization of high compressive strength and low elastic modulus. In addition, the modified concrete has excellent workability, self-flowing property and anti-permeation performance, and is suitable for deep wall construction, thereby solving the performance imbalance problem of the traditional plastic concrete caused by the increase in the amount of bentonite. DETAILED DESCRIPTION

[0020] The technical solutions of the present application will be described below in combination with examples, but the present application is not limited to the following examples. The experimental methods and detection methods described in each example are all conventional methods unless otherwise specified; the reagents and materials described are all commercially available unless otherwise specified. The % in the following examples is the mass percentage content unless otherwise specified. The proportions in the following examples are mass ratios unless otherwise specified.

[0021] In the following examples, the cement is ordinary Portland cement, P.O 42.5; the bentonite is sodium-based bentonite, purchased from Henan Yixiang Company, meeting the Grade II bentonite standard; the fine aggregate is prepared by uniformly mixing natural sand and artificial sand, and the fineness modulus is 2.72; the coarse aggregate is natural pebble with a size of 5-20 mm; the admixture is water reducing agent and air entraining agent, the water reducing agent is polycarboxylic acid water reducing agent PC-303 purchased from Wuhan Huaxuan High-tech Co., Ltd., and the air entraining agent is concrete mortar air entraining agent AE-1450 purchased from Nanjing Xinyi Synthetic Technology Co., Ltd.

[0022] Example 1 This example is intended to illustrate the influence of the bentonite addition amount on the compressive strength and elastic modulus of concrete.

[0023] The test raw materials and grouping are shown in Table 1.

[0024] Table 1: Dosage of ordinary plastic concrete (kg)

[0025] In the stirring device, the fine aggregate and the coarse aggregate are put in and stirred for 1 min, then the cement and the bentonite are put in and stirred for 5 min, and finally the water, the water reducing agent and the air entraining agent are put in together, and the concrete is prepared after sufficient stirring.

[0026] The test mainly refers to (DL / T5199-2004) “Hydraulic Concrete Test Procedures” and “Water Conservancy and Hydropower Engineering Concrete Cutoff Wall Construction Specification” (DL / T5150-2001), and refers to the corresponding test methods and related test methods of the Three Gorges Project. Forced mixer is used to mix the concrete, and the test piece is formed by inserting and tamping.

[0027] The compressive strength test uses a 100mm cube specimen. The test uses a liquid universal testing machine with a range of 100kN. The curing to the age of the compressive strength specimen is placed in the middle of the lower platen, and the upper and lower platens should be padded with a pad between the specimen. The pressure surface of the specimen should be perpendicular to the top surface when forming. Start the testing machine, and if there is a significant deviation when the upper pad and the upper platen are about to contact, adjust the ball seat to make the specimen uniform. When loading, attention should be paid to the loading speed, and the loading speed of plastic concrete should be controlled at 0.05~0.15MPa / s, which is equivalent to 0.5~1.5kN / S for a 100mm cube specimen. The average value of the three specimen measurements multiplied by the conversion coefficient (0.95 for a 100mm cube specimen) is taken as the compressive strength test result of the group of specimens.

[0028] The elastic modulus test uses a 150mm×300mm cylindrical specimen, and the deformation test gauge length is the full length of the specimen (300mm). The slope of the elastic deformation section of the stress-strain curve is taken as the elastic modulus of the plastic concrete.

[0029] The test results are shown in Table 2.

[0030] Table 2: Effect of bentonite addition on concrete

[0031] As shown in Table 2, for ordinary plastic concrete, the compressive strength and elastic modulus decrease almost synchronously with the increase of bentonite dosage, and it is difficult to balance high compressive strength and low elastic modulus. Generally, a moderate amount of bentonite (for example, #2 concrete) is selected to meet the technical requirements.

[0032] Example 2 This example provides the preparation of organic-inorganic composite modified bentonite and the effect test of its addition amount on concrete.

[0033] Step 1: Add 50g / L of polyepoxy chloropropane dimethyl ammonium solution to sodium-based bentonite, control the mass ratio of polyepoxy chloropropane dimethyl ammonium and sodium-based bentonite to be 4:20. Stir at 70℃ for 2h, wash with water after suction filtration, dry, activate at 105℃ for 2h, crush through a 200 mesh sieve, and prepare polyepoxy chloropropane dimethyl ammonium modified bentonite.

[0034] Step 2: Keep stirring, slowly add 1mol / L of NaOH solution to 0.5mol / L of AlCl3 solution, stir at 60℃ for 2h, then age at 60℃ for 12h, and prepare a hydroxyl polyaluminum solution.

[0035] Step 3: The polyepoxy chloropropane dimethyl ammonium modified bentonite is added to the hydroxyl polymeric aluminum solution, and the amount of aluminum in the hydroxyl polymeric aluminum solution and the polyepoxy chloropropane dimethyl ammonium modified bentonite is controlled to be 10 mmol / g. After stirring at 80°C for 2h, cross-linking is performed. After aging at 80°C for 24h, the product is dried after water washing by suction filtration until there is no chloride ion in the filtrate, to obtain the organic-inorganic composite modified bentonite.

[0036] The test method and preparation method of the concrete are the same as those in Example 1, and the test raw materials and grouping are shown in Table 3.

[0037] Table 3: Amount of organic-inorganic composite modified bentonite added to plastic concrete (kg)

[0038] The test results are shown in Table 4.

[0039] Table 4: Effect of the amount of organic-inorganic composite modified bentonite on concrete

[0040] As shown in Table 4, the organic-inorganic composite modified bentonite provided by the present application can effectively reduce the adverse effect of the addition amount on the compressive strength, and the change rate of #5~#8 is 1.38 MPa, while the change rate of #1~#4 is 3.11 MPa, thereby preparing plastic concrete with high compressive strength and low elastic modulus. The reasons for the decrease in the strength of the concrete caused by the increase in the amount of bentonite mainly include the influence of the strong water absorption on the workability, the dilution of the cement paste to reduce the strength of the matrix, the expansion to hinder the hydration of cement, the change in the pore structure to weaken the mechanical properties, and the strength decreasing trend supported by experimental data. These factors jointly act to cause the decrease in the strength of the concrete with the increase in the amount of bentonite. In the present application, the organic-inorganic composite modification is used to increase the distance between the layers of the bentonite, introduce organic components into the bentonite, replace the exchangeable cations or structural water between the layers of the bentonite with organic functional groups or organic matters, and then form an organic composite bentonite combined by covalent bond, ionic bond, coupling bond or Van der Waals force; on the other hand, the inorganic modification is to form an inorganic columnar structure between the layers of the bentonite to expand the interlayer distance and improve the specific surface area, form a two-dimensional pore network structure between the layers, and also make the bentonite not collapse in the concrete environment and improve the stability. After the above two functions are comprehensively used, the rate of the decrease in the strength of the concrete caused by the increase in the amount of bentonite is effectively alleviated, and the effect of the decrease in the elastic modulus caused by the increase in the amount of bentonite is not affected.

[0041] Example 3 The present example provides the preparation of the organic-inorganic composite modified bentonite and the performance test results of the concrete.

[0042] The organic-inorganic composite modified bentonite #1 is the same as in Example 2.

[0043] Organic-inorganic composite modified bentonite #2, same as organic-inorganic composite modified bentonite #1, the difference is that the mass ratio of polyepoxy chloropropane dimethyl ammonium and sodium-based bentonite is 3:20, the amount of aluminum in the hydroxyl polymeric aluminum solution and polyepoxy chloropropane dimethyl ammonium modified bentonite is 8mmol / g.

[0044] Organic-inorganic composite modified bentonite #3, same as organic-inorganic composite modified bentonite #1, the difference is that the mass ratio of polyepoxy chloropropane dimethyl ammonium and sodium-based bentonite is 5:20, the amount of aluminum in the hydroxyl polymeric aluminum solution and polyepoxy chloropropane dimethyl ammonium modified bentonite is 12mmol / g.

[0045] Concrete #7, same as group #7 in Example 2.

[0046] Concrete #8, cement 150kg, organic-inorganic composite modified bentonite #2 80kg, fine aggregate 900kg, coarse aggregate 230kg, water reducing agent 1kg, air entraining agent 1kg, water 250kg.

[0047] Concrete #9, cement 200kg, organic-inorganic composite modified bentonite #3 100kg, fine aggregate 1300kg, coarse aggregate 340kg, water reducing agent 5kg, air entraining agent 3kg, water 350kg.

[0048] The performance thereof is measured as shown in Table 5.

[0049] Table 5: Performance of concrete with organic-inorganic composite modified bentonite addition

[0050] As can be seen from Table 5, the concrete provided by the present application has excellent workability, good workability, high compressive strength and low elastic modulus, especially strong self-flowing property, self-diffusion capacity and long retardation time, which is suitable for deep wall construction.

[0051] The above describes the basic principles, main features and advantages of the present application. The above examples and descriptions are only preferred embodiments of the present application, and the present application is not limited by the above examples. Various changes and improvements to the technical solutions of the present application made by those skilled in the art without departing from the spirit and scope of the present application shall fall within the scope of protection of the present application.

Claims

1. A high-strength, impermeable concrete, characterized in that, The concrete comprises, in parts by mass, cement 150-200 parts, organic-inorganic composite modified bentonite 80-100 parts, fine aggregate 900-1300 parts, coarse aggregate 230-340 parts, additive 2-10 parts, and water 250-350 parts. The organic-inorganic composite modified bentonite is obtained by modifying bentonite with polyepoxy chloropropane dimethyl ammonium and then modifying with hydroxyl polymeric aluminum.

2. The anti-osmotic high-strength concrete according to claim 1, characterized in that, The cement is ordinary Portland cement.

3. The anti-osmotic high-strength concrete according to claim 1, characterized in that, The bentonite is at least one of sodium-based bentonite, calcium-based bentonite, magnesium-based bentonite, and aluminum-based bentonite.

4. The anti-permeation high-strength concrete according to claim 1, characterized by, The fine aggregate is obtained by uniformly mixing natural sand and artificial sand, and has a fineness modulus of 2.

72.

5. The anti-osmotic high-strength concrete according to claim 1, characterized in that, The coarse aggregate is natural pebble with a size of 5-20 mm.

6. The anti-permeation high-strength concrete according to claim 1, characterized by, The additive is water reducing agent and air entraining agent.

7. The anti-osmotic high-strength concrete according to claim 6, characterized in that, In the additive, the mass ratio of water reducing agent to air entraining agent is 10:5-10.

8. A method of producing a high-strength concrete resistant to permeation, characterized by, The preparation of the anti-permeation high-strength concrete of any one of claims 1-7 comprises: configuring a polyepoxy chloropropane dimethyl ammonium solution, then adding the bentonite, stirring at a constant temperature of 60-80°C for 2-3 h, washing with water by suction filtration, drying, activating at 105-110°C for 1-2 h, and crushing to pass a 200-mesh sieve to obtain polyepoxy chloropropane dimethyl ammonium modified bentonite; The polyepoxy chloropropane dimethyl ammonium modified bentonite is added to a hydroxyl polymeric aluminum solution, stirred at a constant temperature of 60-80°C for 2-3 h, aged for at least 24 h, washed with water by suction filtration until no chloride ions are present in the filtrate, and dried to obtain the organic-inorganic composite modified bentonite; The fine aggregate and the coarse aggregate are uniformly mixed, the cement and the organic-inorganic composite modified bentonite are added, and finally the water and the additive are added, followed by thorough stirring to obtain the concrete.

9. The method of producing anti-infiltration high-strength concrete according to claim 8, characterized by, The mass ratio of polyepoxy chloropropane dimethyl ammonium to the bentonite is 3-5:

20. The amount of aluminum in the hydroxyl polymeric aluminum solution and the polyepoxy chloropropane dimethyl ammonium modified bentonite is 8-12 mmol / g.

10. Use of the anti-permeation high-strength concrete of any one of claims 1-7 in the preparation of an underground anti-permeation wall.

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