Tough concrete and its preparation method

Abstract

This invention discloses a resilient concrete and its preparation method in the field of tunnel and underground engineering reinforcement technology. The resilient concrete comprises the following components by weight: 350-450 parts cement, 120-150 parts ultrafine slag powder, 50-80 parts silica fume, 750-800 parts manufactured sand, 850-900 parts crushed stone, 6-8 parts ultra-high molecular weight polyethylene fiber, 4-6 parts basalt fiber, 1-2 parts polyacrylonitrile fiber, 38-60 parts ethylene-vinyl acetate copolymer emulsion, 5.5-6.5 parts water-reducing agent, and 120-125 parts water. This application significantly enhances the ductility, energy dissipation capacity, and fatigue resistance of concrete by using macroscopic bridging of ultra-high molecular weight polyethylene fiber, microcrack suppression of basalt fiber, and plasticity control of polyacrylonitrile fiber, combined with the strengthening of fiber-matrix interface bonding by ethylene-vinyl acetate copolymer emulsion and the increase in density by ultrafine slag powder. This enables it to effectively adapt to large deformations of surrounding rock under strong earthquakes and inhibit crack propagation.

Description

Technical Field

[0001] This invention relates to the field of tunnel and underground engineering reinforcement technology, specifically to a tough concrete and its preparation method. Background Technology

[0002] Under high-intensity earthquakes, tunnel structures face severe risks of damage due to the surge in inertial forces caused by strong vibrations, instability of surrounding rock deformation, and fault slippage shearing. Existing reinforcement technologies, such as increasing the thickness of ordinary reinforced concrete linings, using steel fiber reinforced concrete, and adding anchor bolts and steel arches, generally have significant drawbacks: ordinary concrete has poor ductility and is prone to brittle wide cracks or even spalling and collapse during earthquakes; conventional steel fiber reinforced concrete has insufficient energy dissipation capacity under large deformations and requires stringent construction techniques; rigid reinforcement systems have poor coordination with surrounding rock deformation, easily leading to stress concentration and voids. Furthermore, existing construction equipment is not well-suited for high-fiber-content or tough concrete, often resulting in problems such as pipe blockage, rebound, and uneven spraying. Summary of the Invention

[0003] To overcome the problem that existing reinforcement technologies cannot adapt to environments such as high-intensity earthquake zones and active faults, this invention provides a tough concrete and its preparation method.

[0004] The technical solution adopted by this invention to solve its technical problem is:

[0005] The resilient concrete comprises the following components by weight: 350-450 parts cement, 120-150 parts ultrafine slag powder, 50-80 parts silica fume, 750-800 parts manufactured sand, 850-900 parts crushed stone, 6-8 parts ultra-high molecular weight polyethylene fiber, 4-6 parts basalt fiber, 1-2 parts polyacrylonitrile fiber, 38-60 parts ethylene-vinyl acetate copolymer emulsion, 5.5-6.5 parts water-reducing agent, and 120-125 parts water; the ultra-high molecular weight polyethylene fiber is 10-14 mm long and 0.45-0.55 mm in diameter, the basalt fiber is 16-20 mm long and 18-22 μm in diameter, and the polyacrylonitrile fiber is 5-7 mm long and 14-16 μm in diameter.

[0006] This application significantly enhances the ductility, energy dissipation capacity, and fatigue resistance of concrete by using macroscopic bridging of ultra-high molecular weight polyethylene fibers, microcrack suppression of basalt fibers, plasticity control of polyacrylonitrile fibers, and combining ethylene-vinyl acetate copolymer emulsion to strengthen fiber-matrix interface bonding and ultrafine slag powder to improve density. This enables the concrete to effectively adapt to large deformation of surrounding rock under strong earthquakes and suppress crack propagation.

[0007] The present invention also provides a method for preparing the above-mentioned tough concrete, comprising the following steps:

[0008] Step S101: Premix cement, ultrafine slag powder, silica fume, manufactured sand and crushed stone to obtain a mixture;

[0009] Step S102: Add polyacrylonitrile fiber, basalt fiber and ultra-high molecular weight polyethylene fiber;

[0010] Step S103: Inject the premix of water-reducing agent and water, and add ethylene-vinyl acetate copolymer emulsion.

[0011] In some embodiments, step S101: premix cement, ultrafine slag powder and silica fume at 55-65 r / min for 45-75 seconds, add manufactured sand and crushed stone and continue dry mixing for 75-105 seconds, and control the moisture content to <0.5% throughout the process.

[0012] In some embodiments, step S102: the rotation speed is reduced to 42-48 r / min for gradient feeding, first adding polyacrylonitrile fiber and stirring for 25-35 seconds, then adding basalt fiber and stirring for 25-35 seconds, and finally adding ultra-high molecular weight polyethylene fiber and stirring for 55-65 seconds.

[0013] In some embodiments, step S103: the rotation speed is increased to 110-130 r / min, the premixed liquid of water-reducing agent and water is injected and stirred for 50-70 seconds, and the ethylene-vinyl acetate copolymer emulsion is added and stirred for ≤120 seconds before stopping.

[0014] The beneficial effects of this invention are:

[0015] By using macroscopic bridging of ultra-high molecular weight polyethylene fibers, microcrack suppression of basalt fibers, and plasticity control of polyacrylonitrile fibers, combined with ethylene-vinyl acetate copolymer emulsion to strengthen fiber-matrix interface bonding and ultrafine slag powder to improve density, the ductility, energy dissipation capacity and fatigue resistance of concrete are significantly enhanced, enabling it to effectively adapt to large deformation of surrounding rock under strong earthquakes and suppress crack propagation. Attached Figure Description

[0016] Figure 1 This is a schematic flowchart of the method for preparing tough concrete provided by the present invention. Detailed Implementation

[0017] The invention will be further described below with reference to the accompanying drawings.

[0018] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0019] like Figure 1As shown, in view of the shortcomings of the prior art, the present invention provides a tough concrete with high ductility, strong energy dissipation capacity, and the ability to effectively adapt to the deformation of surrounding rock and resist the effects of high-intensity earthquakes (including fault displacement), as well as a method for preparing the concrete.

[0020] The resilient concrete comprises the following components by weight: 350-450 parts cement, 120-150 parts ultrafine slag powder, 50-80 parts silica fume, 750-800 parts manufactured sand, 850-900 parts crushed stone, 6-8 parts ultra-high molecular weight polyethylene fiber, 4-6 parts basalt fiber, 1-2 parts polyacrylonitrile fiber, 38-60 parts ethylene-vinyl acetate copolymer emulsion, 5.5-6.5 parts water-reducing agent, and 120-125 parts water.

[0021] This application significantly enhances the ductility, energy dissipation capacity, and fatigue resistance of concrete by using macroscopic bridging of ultra-high molecular weight polyethylene fibers, microcrack suppression of basalt fibers, plasticity control of polyacrylonitrile fibers, and combining ethylene-vinyl acetate copolymer emulsion to strengthen fiber-matrix interface bonding and ultrafine slag powder to improve density. This enables the concrete to effectively adapt to large deformation of surrounding rock under strong earthquakes and suppress crack propagation.

[0022] As a preferred option, ultra-high molecular weight polyethylene fibers are 10-14 mm long and 0.45-0.55 mm in diameter, mainly used to control macroscopic crack bridging and provide high elongation at break.

[0023] Preferably, the basalt fibers are 16-20 mm long and 18-22 μm in diameter, and are mainly used to suppress the development of microcracks and improve fatigue resistance.

[0024] Preferably, the polyacrylonitrile fibers are 5-7 mm long and 14-16 μm in diameter, which are used to reduce plastic shrinkage cracks and optimize construction and workability.

[0025] Preferably, the ultrafine slag powder has a specific surface area of ​​≥800m² / kg, which is used to fill concrete pores, activate the pozzolanic effect, and improve the density of tough concrete.

[0026] Preferably, the ethylene-vinyl acetate copolymer emulsion has a solid content of 50% and is used to cover the fiber-matrix interface after film formation, thereby enhancing adhesion and improving energy dissipation capacity.

[0027] Preferably, the manufactured sand has a particle size of 0-3 mm, and the crushed stone has a particle size of 5-10 mm.

[0028] Example 1

[0029] A type of tough concrete, by weight, is made from the following raw materials: 380 parts cement, 120 parts ultrafine slag powder, 50 parts silica fume, 800 parts manufactured sand, 900 parts crushed stone, 8 parts ultra-high molecular weight polyethylene fiber, 4 parts basalt fiber, 1 part polyacrylonitrile fiber, 38 parts ethylene-vinyl acetate copolymer emulsion, 5.5 parts polycarboxylate superplasticizer, and 120 parts water.

[0030] Example 2

[0031] A type of tough concrete, by weight, is made from the following raw materials: 400 parts cement, 150 parts ultrafine slag powder, 80 parts silica fume, 750 parts manufactured sand, 850 parts crushed stone, 6 parts ultra-high molecular weight polyethylene fiber, 6 parts basalt fiber, 2 parts polyacrylonitrile fiber, 60 parts ethylene-vinyl acetate copolymer emulsion, 6.0 parts polycarboxylate superplasticizer, and 125 parts water.

[0032] Example 3

[0033] A type of tough concrete, by weight, is made from the following raw materials: 390 parts cement, 130 parts ultrafine slag powder, 60 parts silica fume, 780 parts manufactured sand, 880 parts crushed stone, 7 parts ultra-high molecular weight polyethylene fiber, 5 parts basalt fiber, 1 part polyacrylonitrile fiber, 50 parts ethylene-vinyl acetate copolymer emulsion, 6.0 parts polycarboxylate superplasticizer, and 120 parts water.

[0034] Comparative Example 1

[0035] A type of resilient concrete, by weight, is made from the following raw materials: 380 parts cement, 120 parts ultrafine slag powder, 50 parts silica fume, 800 parts manufactured sand, 900 parts crushed stone, 13 parts ultra-high molecular weight polyethylene fiber (equal volume replacement for basalt fiber and polyacrylonitrile fiber), 38 parts ethylene-vinyl acetate copolymer emulsion, 5.7 parts polycarboxylate superplasticizer, and 120 parts water. Only ultra-high molecular weight polyethylene fiber is used; basalt fiber and polyacrylonitrile fiber are omitted.

[0036] Comparative Example 2

[0037] A type of resilient concrete, by weight, is made from the following raw materials: 400 parts cement, 150 parts ultrafine slag powder, 80 parts silica fume, 750 parts manufactured sand, 850 parts crushed stone, 6 parts ultra-high molecular weight polyethylene fiber, 6 parts basalt fiber, 1.5 parts polyacrylonitrile fiber, 6.5 parts polycarboxylate superplasticizer, and 125 parts water. The contribution of interface modification to energy dissipation capacity was investigated by eliminating the ethylene-vinyl acetate copolymer emulsion.

[0038] Performance tests were conducted on the tough concrete in each embodiment and comparative example according to relevant national and industry standards, and the results are shown in Table 1.

[0039] Table 1 Mechanical properties of tough concrete in Examples 1-3 and Comparative Examples 1-2

[0040]

[0041] Note: Data are based on 28-day standard curing specimens with a loading rate of 2 mm / min; energy absorption value is the cumulative energy consumed by cyclic compression to 80% of peak strain.

[0042] As shown in Table 1, the ultimate tensile strain of Comparative Example 1 using a single ultra-high molecular weight polyethylene fiber was 1.80%, significantly lower than that of Example 1 (2.50%), confirming the core role of basalt fiber in inhibiting microcracks and polyacrylonitrile fiber in controlling plastic shrinkage. In addition, the energy absorption value of Comparative Example 2, which did not use ethylene-vinyl acetate copolymer emulsion, was 88 kJ / m³, a decrease of 29% compared to 124 kJ / m³ in Example 2. This demonstrates that the ethylene-vinyl acetate copolymer emulsion enhances energy dissipation capacity by forming a film covering the fiber interface, and the synergistic effect with the ultrafine slag powder filling the pores can increase the compressive strength by 4-6 MPa.

[0043] The above results show that this tough concrete is suitable for high-intensity earthquake zones. Addressing the shortcomings of existing tough concrete for tunnels in high-intensity earthquake zones in terms of self-healing capability, this application provides a tough concrete suitable for high-intensity earthquake zones. This tough concrete, by adjusting its mix proportions, is suitable for different tunnel geological conditions. Furthermore, this tough concrete features high ductility, energy dissipation capacity, and strong fatigue resistance, effectively adapting to large deformations of the surrounding rock under strong earthquakes and inhibiting crack propagation.

[0044] To more accurately explain the preparation method of the above-mentioned tough concrete, such as Figure 1 As shown in the figure, this application provides a flowchart of a method for preparing the above-mentioned tough concrete, and the specific steps are as follows:

[0045] In step S101, when the dry materials are premixed, a forced mixer is used with the speed adjusted to 60 r / min. First, cement, ultrafine slag powder and silica fume are added and dry-mixed for 60 seconds until they are uniformly mixed. Then, manufactured sand and crushed stone are added and dry-mixed for another 90 seconds. During this process, the moisture content is strictly controlled to be <0.5% to prevent fiber clumping.

[0046] Preferably, in step S101, premix cement, ultrafine slag powder and silica fume at 55-65 r / min for 45-75 seconds, add manufactured sand and crushed stone and continue dry mixing for 75-105 seconds, and control the moisture content to <0.5% throughout the process.

[0047] In step S102, after the dry materials are premixed, the fibers are fed in a gradient to achieve layered dispersion. Specifically, the mixer speed is reduced to 45 r / min, polyacrylonitrile fibers are added first and stirred for 30 seconds, then basalt fibers are added and stirred for another 30 seconds; finally, ultra-high molecular weight polyethylene fibers are added and stirred for 60 seconds.

[0048] Preferably, in step S102, the rotation speed is reduced to 42-48 r / min for gradient feeding. First, polyacrylonitrile fiber is added and stirred for 25-35 seconds, then basalt fiber is added and stirred for 25-35 seconds, and finally ultra-high molecular weight polyethylene fiber is added and stirred for 55-65 seconds.

[0049] Step S103: After the fiber is stirred, the liquid component is incorporated. The speed of the mixer is increased to 120 r / min. The water-reducing agent is premixed with water for 30 seconds and then injected into the mixer and stirred for 60 seconds until the fluidity meets the standard. Then, the ethylene-vinyl acetate copolymer emulsion is slowly added and stirred for another 120 seconds.

[0050] Preferably, in step S103, the rotation speed is increased to 110-130 r / min, the premix of water-reducing agent and water is injected and stirred for 50-70 seconds until the fluidity meets the standard, the ethylene-vinyl acetate copolymer emulsion is slowly added and stirring is stopped immediately after ≤120 seconds to avoid demulsification failure.

[0051] It should be noted that in step S101, the moisture content of the dry material needs to be controlled to be <0.5% to avoid premature clumping of the fibers added later; in step S103, after the ethylene-vinyl acetate copolymer emulsion is added, the stirring time should be strictly controlled to be <120s to avoid demulsification failure.

[0052] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A ductile concrete, characterized in that, The cement 350-450 parts by weight, superfine slag powder 120-150 parts by weight, silica fume 50-80 parts by weight, machine-made sand 750-800 parts by weight, gravel 850-900 parts by weight, ultra-high molecular weight polyethylene fiber 6-8 parts by weight, basalt fiber 4-6 parts by weight, polyacrylonitrile fiber 1-2 parts by weight, ethylene-vinyl acetate copolymer emulsion 38-60 parts by weight, water reducing agent 5.5-6.5 parts by weight, and water 120-125 parts by weight are contained. The ultra-high molecular weight polyethylene fiber is 10-14 mm long and 0.45-0.55 mm in diameter, the basalt fiber is 16-20 mm long and 18-22 μm in diameter, the polyacrylonitrile fiber is 5-7 mm long and 14-16 μm in diameter, and the superfine slag powder has a specific surface area of ≥800 m² / kg.

2. The method of making ductile concrete according to claim 1, wherein, The method comprises the following steps, Step S101: premixing cement, superfine slag powder, silica fume, machine-made sand and gravel to obtain a mixture; Step S102: reduce the rotation speed to 42-48 r / min, first add the polyacrylonitrile fiber and stir for 25-35 seconds, then add the basalt fiber and stir for 25-35 seconds, and finally add the ultra-high molecular weight polyethylene fiber and stir for 55-65 seconds; Step S103: inject the premixed solution of water reducing agent and water, and add the ethylene-vinyl acetate copolymer emulsion.

3. The production method according to claim 2, characterized by, Step S101: premix the cement, superfine slag powder and silica fume at 55-65 r / min for 45-75 seconds, add the machine-made sand and gravel and continue to dry mix for 75-105 seconds, and control the water content to be <0.5% throughout the process.

4. The method of any one of claims 2-3, wherein, Step S103: increase the rotation speed to 110-130 r / min, inject the premixed solution of water reducing agent and water and stir for 50-70 seconds, and after adding the ethylene-vinyl acetate copolymer emulsion, stir for ≤120 seconds and stop.

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