Sprayed concrete tackifier for tunnel engineering as well as preparation method and application of sprayed concrete tackifier

Abstract

The invention belongs to the field of building materials, and particularly relates to a shotcrete tackifier for tunnel engineering and a preparation method and application thereof, and the shotcrete tackifier is prepared from the following raw materials in parts by weight: 30-40 parts of modified polyacrylamide, 53-60 parts of accelerant and 1-2 parts of calcium carbonate. The prepared tackifier is high in viscosity, and concrete is small in rebound resilience and high in early strength.

Description

Technical Field

[0001] The invention belongs to the field of building materials, and in particular relates to a shotcrete viscosity enhancer for tunnel engineering, a preparation method and an application thereof. Background Art

[0002] Shotcrete is a kind of concrete formed by spraying concrete mixture on the sprayed surface through high-speed spraying equipment, which quickly solidifies and hardens. It is widely used in tunnels, water conservancy projects, mines, underground projects and other fields. It has the characteristics of fast construction speed, simple process and convenient operation. There are two main construction methods of shotcrete: dry mixing method is to mix cement, sand and stone evenly in a dry state, send it and the accelerator to the nozzle with compressed air and mix it with pressurized water for spraying; wet mixing method is to send the mixed concrete to the nozzle through a grouting pump, and then spray it with compressed air. Although the dry mixing method can improve the strength of concrete and has good adhesion, due to the high spraying speed, dust pollution and rebound are serious. The spraying speed of the wet mixing method is lower, and the rebound is improved, but the early strength of the concrete is lower. Therefore, admixtures used to increase the strength of concrete and reduce the rebound rate have become the key research direction of personnel in this field.

[0003] Patent CN106082766B discloses a water-retaining and viscosity-increasing admixture for wet spraying concrete, which includes the following components: sodium polyacrylate, organic polymer binder, and polyvinyl alcohol. By adding a viscosity-increasing agent, the adhesion and water retention are increased, the rebound rate of wet spraying concrete is reduced, the spraying quality is more stable, and the waste of materials is avoided; on the other hand, the dispersion and fluidity of the concrete slurry can be improved, and then the uniformity of wet spraying concrete can be improved, the porosity can be reduced, and finally the mechanical properties of wet spraying concrete can be improved. However, the invention contains a large amount of water-absorbing substances, which may solidify slowly and affect the early compressive strength of concrete.

[0004] Patent CN117567068A discloses a water-resistant rebound-inhibiting thickener, preparation and use methods and applications, wherein the thickener comprises the following components: a water-resistant component, a water-retaining thickening component, a fiber thickening component, a rheological enhancement component, an early strength component, and a nano-enhancing additive. The invention can effectively improve the cohesion between shotcrete and wet rock surface, water scouring resistance, and the cohesion of shotcrete itself, and improve the early strength of shotcrete without reducing the fluidity of shotcrete or prolonging the setting time. The rebound rate of shotcrete is greatly reduced, but the early strength component of the invention is preferably sulphoaluminate cement, which is relatively expensive.

[0005] Therefore, there is an urgent need on the market for a concrete viscosity enhancer with high compressive strength and reduced usage of sulphoaluminate cement. Summary of the invention

[0006] In order to overcome the deficiencies of the above-mentioned prior art, the present invention provides a tunnel shotcrete thickener and a preparation method and application thereof. The thickener prepared by the present invention has high viscosity, can effectively reduce the resilience of concrete, and increase the early compressive strength.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The first aspect of the present invention provides a tunnel shotcrete viscosity enhancer, which comprises the following raw materials in parts by weight: 30-40 parts of modified polyacrylamide, 53-60 parts of accelerator, and 1-2 parts of calcium carbonate.

[0009] In some embodiments, the method for preparing the modified polyacrylamide comprises the following steps:

[0010] (1) adding pentaerythritol diacrylate to DMF, stirring at 0-5° C. for 20-30 min, then adding anhydrous potassium carbonate, stirring for 3-6 min, then adding cis-4-chloro-2-butenamine hydrochloride, continuing to stir for 25-35 min, then heating to 30-35° C., reacting for 47-49 h, extracting, washing, and drying to obtain multifunctional pentaerythritol diacrylate;

[0011] (2) adding the multifunctional pentaerythritol diacrylate, acrylamide, 1-dodecanethiol and azobisisobutyronitrile obtained in step (1) to toluene, degassing the solution, and reacting at 70-80° C. for 12-15 hours under a nitrogen atmosphere to obtain modified polyacrylamide.

[0012] The present invention preferably uses pentaerythritol diacrylate with multiple double bonds and multiple hydroxyl groups, and then reacts the chlorine atom on the alkane chain segment of cis-4-chloro-2-butenylamine hydrochloride with the hydroxyl group of pentaerythritol diacrylate to obtain a multifunctional pentaerythritol diacrylate containing four double bonds, which is then polymerized with acrylamide to obtain a modified polyacrylamide, which is used in a tackifier for shotcrete and can effectively reduce the resilience and early strength of concrete. The possible reason is that the modified polyacrylamide has a hyperbranched structure that can "entangle and cross" the concrete to increase the bonding effect, and has multiple amino groups that can It coordinates with metal ions such as calcium and aluminum in concrete, so that it can be evenly mixed with the viscosity enhancer to form a suspended state, reducing the problem of concrete falling off easily or having high porosity due to gravity sedimentation, requiring multiple constructions and increasing costs; in addition, modified polyacrylamide contains chloride, which can react with calcium hydroxide generated by concrete hydration, mainly chloride, to form calcium chlorate that is not easily soluble in water, increasing the volume of the solid phase in the concrete, which is conducive to the formation of stable CSH and CASH gels, thereby accelerating the hardening rate of the concrete mixture and improving the early strength of the concrete.

[0013] In some embodiments, the mass ratio of pentaerythritol diacrylate to cis-4-chloro-2-butenamine hydrochloride is 1:(0.6-0.8).

[0014] In some embodiments, the mass ratio of the multifunctional pentaerythritol diacrylate to acrylamide in step (2) is 1:(5.5-6).

[0015] The invention limits the mass ratio of pentaerythritol diacrylate to cis-4-chloro-2-butenamine hydrochloride so that the hydroxyl group of pentaerythritol diacrylate can fully react, which is beneficial to the formation of multifunctional pentaerythritol diacrylate. The mass ratio of multifunctional pentaerythritol diacrylate to acrylamide is further limited so that the modified polyacrylamide has good bonding force with concrete. The possible reason is that the change of the ratio of the two will lead to the change of the acting force between the modified polyacrylamide and the concrete, resulting in uneven dispersion of the concrete, reduced bonding and reduced resilience.

[0016] In some embodiments, the weight average molecular weight of the modified polyacrylamide is 130,000-150,000.

[0017] The invention limits the weight average molecular weight of the modified polyacrylamide so that the modified polyacrylamide can be easily dispersed in water, has strong wettability to concrete admixture, and has increased adhesion.

[0018] In some embodiments, the promoter is modified xanthan gum and polyvinyl alcohol, and the mass ratio of the two is (5-7):1.

[0019] In some embodiments, the method for preparing the modified xanthan gum comprises the following steps: adding xanthan gum, gallic acid and KH550 to ethanol, stirring at 60-70° C. for 7-8 hours, and rotary evaporating to obtain the modified xanthan gum.

[0020] Although xanthan gum has certain viscosity, it has poor stability and is easy to stick together and form lumps. In the present invention, gallic acid is loaded on xanthan gum by using a silane coupling agent so that it can be evenly dispersed, and its viscosity with other substances can be increased while avoiding self-adhesion, thereby increasing the bonding force. The possible reason is that gallic acid has hydroxyl and carboxyl groups that have an adsorption effect on concrete, so that negative charges are formed on the surface of concrete particles, generating repulsion, and increasing the dispersibility of the concrete while increasing its own dispersibility. Due to the increased dispersibility of the concrete, water contained in the concrete can be released, the setting time is shortened, and the collapse loss is reduced. In addition, the amino group of the preferred silane coupling agent KH550 and the hydroxyl group of the gallic acid can weaken the oxidation of the double bond of the modified polyacrylamide, prevent the brittleness of the tackifier from becoming larger, and prevent the concrete from being easy to crack.

[0021] In some embodiments, the mass ratio of xanthan gum to gallic acid is 1:(0.7-1).

[0022] The invention increases the dispersibility of xanthan gum by limiting the mass ratio of xanthan gum to gallic acid, thereby avoiding the problems of excessive gallic acid causing increased interaction with water, prolonged concrete drying time, and easy water seepage after drying.

[0023] The second aspect of the present invention provides a method for preparing a tunnel shotcrete viscosity enhancer, comprising the following steps: stirring modified polyacrylamide, an accelerator and calcium carbonate at 50-60° C. for 60-80 min to obtain the obtained product.

[0024] A third aspect of the present invention provides an application of a shotcrete viscosity enhancer for tunnel engineering, wherein the viscosity enhancer is 15-30wt% of cement in concrete.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] 1. The present invention obtains a tunnel shotcrete thickener by modifying polyacrylamide and compounding an accelerator and calcium carbonate. The shotcrete thickener has good viscosity and low rebound rate and can improve the early strength of concrete.

[0027] 2. The present invention preferably uses pentaerythritol diacrylate having multiple double bonds and multiple hydroxyl groups, and then reacts the chlorine atom on the alkane chain segment of cis-4-chloro-2-butenamine hydrochloride with the hydroxyl group of pentaerythritol diacrylate to obtain a multifunctional pentaerythritol diacrylate containing four double bonds, which is then polymerized with acrylamide to obtain modified polyacrylamide, which is used in the viscosity enhancer of shotcrete and can effectively reduce the resilience and early strength of concrete.

[0028] 3. The present invention uses a silane coupling agent to load gallic acid on xanthan gum. Gallic acid has hydroxyl and carboxyl groups that have an adsorption effect on concrete, so that a negative charge is formed on the surface of concrete particles, generating repulsion, thereby increasing the dispersibility of the concrete while increasing the dispersibility of the concrete. Due to the increased dispersibility of the concrete, the water contained in the concrete can be released, the setting time is shortened, and the collapse loss is reduced. In addition, the amino group of the preferred silane coupling agent KH550 and the hydroxyl group of the gallic acid can weaken the oxidation of the double bond of the modified polyacrylamide, prevent the brittleness of the tackifier from becoming larger, and prevent the concrete from cracking easily. DETAILED DESCRIPTION

[0029] The present invention will be described below in conjunction with specific embodiments. It should be noted that the following examples and comparative examples are only used to illustrate the present invention and are not intended to limit the present invention. Other combinations and various modifications within the concept of the present invention may be performed without departing from the spirit or scope of the present invention.

[0030] In order to facilitate those skilled in the art to implement the present invention, some raw materials and manufacturers of the embodiments and comparative examples are described as follows:

[0031] The compounds and related reagents used in the following examples and comparative examples can all be purchased from the market, wherein polyvinyl alcohol was purchased from Shanghai E-En Chemical Technology Co., Ltd., Mw=90,000.

[0032] Preparation Example 1

[0033] The preparation method of modified polyacrylamide-1 comprises the following steps:

[0034] (1) 10 g of pentaerythritol diacrylate was added to 100 ml of DMF, and the mixture was stirred at 2° C. for 25 min. Then, 2 g of anhydrous potassium carbonate was added, and the mixture was stirred for 5 min. Then, 7 g of cis-4-chloro-2-butenamine hydrochloride was added, and the mixture was stirred for 30 min. Then, the mixture was heated to 33° C., reacted for 48 h, extracted, washed, and dried to obtain multifunctional pentaerythritol diacrylate;

[0035] (2) 10 g of the multifunctional pentaerythritol diacrylate obtained in step (1), 58 g of acrylamide, 1 g of 1-dodecanethiol and 0.7 g of azobisisobutyronitrile were added to 200 ml of toluene, the solution was degassed, and reacted at 75° C. for 13 h under a nitrogen atmosphere to obtain modified polyacrylamide-1.

[0036] Preparation Example 2

[0037] The preparation method of modified polyacrylamide-2 is the same as that of Preparation Example 1, except that the amount of cis-4-chloro-2-butenamine hydrochloride added is 10 g.

[0038] Preparation Example 3

[0039] The preparation method of modified polyacrylamide-3 is the same as that of Preparation Example 1, except that the amount of acrylamide added is 50 g.

[0040] Preparation Example 4

[0041] The preparation method of modified xanthan gum-1 comprises the following steps: adding 10g xanthan gum, 8g gallic acid and 5g KH550 into 100ml anhydrous ethanol, stirring at 65°C for 7.5h, and rotary evaporating to obtain modified xanthan gum-1.

[0042] Preparation Example 5

[0043] The preparation method of modified xanthan gum-2 is the same as that of Preparation Example 4, except that the amount of gallic acid added is 12 g.

[0044] Preparation Example 6

[0045] The preparation method of polyacrylamide comprises the following steps: adding 50g acrylamide and 0.5g azobisisobutyronitrile into 200ml toluene, degassing the solution, and reacting at 75°C for 13h under a nitrogen atmosphere to obtain polyacrylamide.

[0046] Example 1

[0047] A tunnel shotcrete viscosity enhancer comprises the following raw materials, measured in parts by weight: 135 parts of modified polyacrylamide, 56 parts of accelerator, and 1.5 parts of calcium carbonate. The accelerator is modified xanthan gum-1 and polyvinyl alcohol, and the mass ratio of the two is 6:1.

[0048] The preparation method of the tunnel shotcrete viscosity enhancer in this embodiment comprises the following steps: stirring modified polyacrylamide-1, an accelerator and calcium carbonate at 55° C. for 70 minutes to obtain the solution.

[0049] Example 2

[0050] A tunnel shotcrete viscosity enhancer comprises the following raw materials, measured in parts by weight: 130 parts of modified polyacrylamide, 53 parts of accelerator, and 1 part of calcium carbonate. The accelerator is modified xanthan gum-1 and polyvinyl alcohol, and the mass ratio of the two is 5:1.

[0051] The preparation method of the tunnel shotcrete viscosity enhancer in this embodiment comprises the following steps: stirring modified polyacrylamide-1, an accelerator and calcium carbonate at 50° C. for 80 minutes to obtain the obtained solution.

[0052] Example 3

[0053] A tunnel shotcrete thickener comprises the following raw materials, measured in parts by weight: 140 parts of modified polyacrylamide, 60 parts of accelerator, and 2 parts of calcium carbonate. The accelerator is modified xanthan gum-1 and polyvinyl alcohol, and the mass ratio of the two is 7:1.

[0054] The preparation method of the tunnel shotcrete viscosity enhancer in this embodiment comprises the following steps: stirring modified polyacrylamide-1, an accelerator and calcium carbonate at 60° C. for 60 minutes to obtain the solution.

[0055] Example 4

[0056] A tunnel shotcrete viscosity enhancer and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified polyacrylamide-1 is replaced by modified polyacrylamide-2.

[0057] Example 5

[0058] A tunnel shotcrete viscosity enhancer and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified polyacrylamide-1 is replaced by modified polyacrylamide-3.

[0059] Example 6

[0060] A tunnel shotcrete viscosity enhancer and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified xanthan gum-1 is replaced by modified xanthan gum-2.

[0061] Example 7

[0062] A tunnel shotcrete viscosity enhancer and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified xanthan gum-1 is replaced by xanthan gum.

[0063] Comparative Example 1

[0064] A tunnel shotcrete viscosity enhancer and a preparation method thereof. The specific implementation method is the same as that of Example 1, except that an equal amount of modified polyacrylamide-1 is replaced by polyacrylamide.

[0065] Performance Testing

[0066] The viscosity enhancers obtained in the examples and comparative examples were added to concrete at 23 wt % of the cement in the concrete, and the following tests were performed.

[0067] 1. Compressive strength

[0068] Refer to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete".

[0069] 2. Rebound rate

[0070] The rebound rate refers to JGJ / T 372-2016 "Technical Code for Application of Shotcrete".

[0071] The test results are shown in Table 1.

[0072] Table 1

[0073]

[0074] By comparing the experimental data of Examples 1-3 in Table 1, it can be seen that the tackifier has good adhesion, can improve the early compressive strength of concrete, and has a lower rebound rate; by comparing Examples 4 and 5 with Example 1, it can be seen that the ratio of pentaerythritol diacrylate to cis-4-chloro-2-butenamine hydrochloride and the ratio of multifunctional pentaerythritol diacrylate to acrylamide may change the force between the tackifier and the concrete, resulting in a decrease in the compressive strength and resilience of the concrete; by comparing Example 6 with Example 1, it can be seen that the change in the ratio of xanthan gum to gallic acid may increase the water absorption of the tackifier, and the compressive strength and resilience of the concrete are both reduced; by comparing Example 7 with Example 1, it can be seen that directly using xanthan gum may be easy to adhere to itself, and the compressive strength and resilience are both reduced; by comparing Comparative Example 1 with Example 1, it can be seen that directly using polyacrylamide reduces the compressive strength and resilience of the concrete.

[0075] The above description is only a preferred embodiment of the present invention and does not limit the present invention in any form. Although the present invention has been disclosed as a preferred embodiment as above, it is not used to limit the present invention. Any technician familiar with this profession can make some changes or modifications to equivalent embodiments of equivalent changes using the technical contents disclosed above without departing from the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A shotcrete thickener for tunnel engineering, characterized in that: The invention comprises the following raw materials in parts by weight: 30-40 parts of modified polyacrylamide, 53-60 parts of accelerator and 1-2 parts of calcium carbonate.

2. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 1, characterized in that: The preparation method of the modified polyacrylamide comprises the following steps: (1) adding pentaerythritol diacrylate to DMF, stirring at 0-5° C. for 20-30 min, then adding anhydrous potassium carbonate, stirring for 3-6 min, then adding cis-4-chloro-2-butenamine hydrochloride, continuing to stir for 25-35 min, then heating to 30-35° C., reacting for 47-49 h, extracting, washing, and drying to obtain multifunctional pentaerythritol diacrylate; (2) adding the multifunctional pentaerythritol diacrylate, acrylamide, 1-dodecanethiol and azobisisobutyronitrile obtained in step (1) to toluene, degassing the solution, and reacting at 70-80° C. for 12-15 hours under a nitrogen atmosphere to obtain modified polyacrylamide.

3. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 2, characterized in that: The mass ratio of the pentaerythritol diacrylate to cis-4-chloro-2-butenamine hydrochloride is 1:(0.6-0.8).

4. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 2, characterized in that: The mass ratio of the multifunctional pentaerythritol diacrylate to acrylamide in step (2) is 1:(5.5-6).

5. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 2, characterized in that: The weight average molecular weight of the modified polyacrylamide is 130,000-150,000.

6. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 1, characterized in that: The accelerators are modified xanthan gum and polyvinyl alcohol, and the mass ratio of the two is (5-7):

1.

7. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 6, characterized in that: The preparation method of the modified xanthan gum comprises the following steps: adding xanthan gum, gallic acid and KH550 into ethanol, stirring at 60-70° C. for 7-8 hours, and rotary evaporating to obtain the modified xanthan gum.

8. The sprayed concrete viscosity enhancer for tunnel engineering according to claim 7, characterized in that: The mass ratio of xanthan gum to gallic acid is 1:(0.7-1).

9. A method for preparing a sprayed concrete viscosity enhancer for tunnel engineering according to any one of claims 1 to 8, characterized in that: The method comprises the following steps: stirring the modified polyacrylamide, the accelerator and the calcium carbonate at 50-60° C. for 60-80 minutes to obtain the product.

10. Use of the sprayed concrete tackifier for tunnel engineering according to any one of claims 1 to 8 or the sprayed concrete tackifier obtained by the preparation method according to claim 9, characterized in that: The viscosity enhancer accounts for 15-30 wt% of the cement in the concrete.

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