Ultra-high performance concrete for spraying, its preparation method and usage method

Abstract

The present invention discloses a shotcrete ultra-high performance concrete, its preparation method and usage method, relating to the technical field of concrete. The present invention uses water, Portland cement, rapid hardening sulphoaluminate cement, silica fume, fly ash, sand, retarder, water reducer, defoamer, accelerator, basalt fiber, and steel fiber as raw materials to make the shotcrete ultra-high performance concrete. The concrete of the present invention has excellent properties such as early strength, high strength, high fluidity, and strong crack resistance, and can solve the problems of large shrinkage and easy cracking of ultra-high performance concrete after being hardened by shotcrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, and particularly to a super high performance concrete for spraying, its preparation method and usage method. Background Art

[0002] Ultra-high performance concrete (UHPC) has high durability, high workability and high strength, and is called the concrete of the 21st century. With the advancement and development of green concrete engineering materials, ultra-high performance concrete has attracted great attention in aspects such as environmental improvement, economic benefit enhancement, and solution of difficult problems in engineering.

[0003] In the existing building construction process, the concrete material is often used by spraying method. However, the building materials formed by spraying traditional concrete often have low strength and are prone to cracking. Therefore, how to adjust the composition of ultra-high performance concrete so that this type of concrete can be used for spraying and obtain building materials with strong mechanical properties is a research hotspot in this industry. Summary of the Invention

[0004] Based on this, the object of the present invention is to provide a super high performance concrete for spraying, its preparation method and usage method. The present invention studies the influence laws of different water-binder ratios, different maximum aggregate sizes and fiber dosages on the workability and mechanical properties such as compressive strength and splitting tensile strength of ultra-high performance sprayed concrete. Aiming at the problems that the ultra-high performance concrete mixture does not meet the requirements of the spraying process and the ultra-high performance concrete has large shrinkage and is prone to cracking after hardening, the present invention studies the modification measures of ultra-high performance concrete from the perspectives of improving sprayability and shrinkage, and studies the components and ratios of suitable ultra-high performance concrete for spraying.

[0005] The present invention is realized by adopting the following technical solutions:

[0006] A super high performance concrete for spraying, characterized in that it is composed of the following components in parts by weight:

[0007] Water 7 - 10 parts,

[0008] Portland cement 20 - 30 parts,

[0009] Quick-setting sulphoaluminate cement 5 - 20 parts,

[0010] Silica fume 1 - 5 parts,

[0011] Fly ash 5 - 10 parts,

[0012] Sand 30 - 50 parts,

[0013] Retarder 0.2 - 0.7 part,

[0014] Water reducing agent 0.8 - 1.1 parts,

[0015] Defoamer: 0 - 0.1 part

[0016] Accelerator: 0.2 - 0.7 part

[0017] Basalt fiber: 0 - 1 part

[0018] Steel fiber: 0 - 1 part

[0019] Preferably, the sand is composed of quartz stones with particle sizes of 0.15 - 0.3 mm, 0.3 - 0.6 mm, 0.6 - 1.18 mm, and river sand with a particle size of 1.18 - 2.36 mm, mixed in a mass ratio of 38:27:20:15.

[0020] Preferably, the water - reducing agent is a polycarboxylate water - reducing agent; the defoamer is a silicone defoamer, and the Portland cement is PO52.5 Portland cement.

[0021] Preferably, the retarder is borax; the accelerator is an alkali - free accelerating agent. The liquid alkali - free accelerating agent used in this invention is produced by Kunming Guandu District Baiqiang Building Materials Factory in Yunnan, and the product model is BY - 2710 alkali - free accelerating agent.

[0022] Preferably, the steel fiber is cold - drawn copper - plated steel fiber.

[0023] This invention also provides a preparation method for the spray - used ultra - high - performance concrete, including the following steps:

[0024] Weigh Portland cement, rapid - hardening sulphoaluminate cement, silica fume, fly ash, sand, water - reducing agent, defoamer, and accelerator proportionally, mix and stir for 15 - 30 s, then add water and retarder proportionally and stir for 200 - 300 s; finally, add basalt fiber and steel fiber proportionally and stir for 30 - 50 s to prepare the spray - used ultra - high - performance concrete.

[0025] This invention also provides a usage method for the spray - used ultra - high - performance concrete. Add water to the ultra - high - performance concrete to make a mixed material with a water - binder ratio of 0.18, and spray it under a pressure of 0.7 MPa - 1 Mpa.

[0026] Compared with the prior art, the following technical effects are disclosed in this invention:

[0027] This invention provides a spray - used ultra - high - performance concrete, which has excellent properties such as early strength, high strength, high fluidity, and strong crack - resistance ability, and can solve the problems of large shrinkage and easy cracking after the ultra - high - performance concrete is spray - hardened. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1This is the maintenance effect diagram of the 1# specimen prepared in Example 5 of the present invention after 28 days of maintenance;

[0029] Figure 2 This is the splitting tensile test diagram of the 2# specimen prepared in Example 5 of the present invention after 28 days of maintenance. Specific implementation manners

[0030] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0031] To make the above objects, features, and advantages of the present invention more obvious and understandable, the present invention will be further described in detail below in conjunction with specific implementation manners.

[0032] Example 1

[0033] The specific preparation steps of a kind of ultra-high performance concrete for spraying are as follows:

[0034] First, weigh 27 parts by weight of portland cement, 6.5 parts by weight of rapid hardening sulphoaluminate cement, 3 parts by weight of silica fume, 8 parts by weight of fly ash, 48 parts by weight of sand, 0.1 part by weight of water reducing agent, 0.004 part of defoaming agent, 0.2 part by weight of coagulant (BY-2710 type alkali-free rapid setting agent), mix and stir for 20 s, then add 8 parts by weight of water and 0.1 part of retarder and stir for 240 s; finally, add 0.1 part by weight of basalt fiber and 2.7 parts by weight of cold drawn copper-plated steel fiber, and stir for 40 s to obtain the ultra-high performance concrete for spraying. The sand is composed of quartz sand with a particle size of 0.15 - 0.3 mm, quartz sand with a particle size of 0.3 - 0.6 mm, quartz sand with a particle size of 0.6 - 1.18 mm, and river sand with a particle size of 1.18 - 2.36 mm, and they are mixed in a mass ratio of 38:27:20:15.

[0035] Example 2

[0036] The specific preparation steps of a kind of ultra-high performance concrete for spraying are as follows:

[0037] First, weigh 24.5 parts by weight of Portland cement, 9 parts by weight of rapid hardening sulphoaluminate cement, 3 parts by weight of silica fume, 8 parts by weight of fly ash, 48 parts by weight of sand, 0.1 part by weight of water reducing agent, 0.004 part of defoaming agent, 0.2 part by weight of accelerating agent (non-alkali rapid setting agent of BY-2710 type), mix and stir for 20 s, then add 8 parts by weight of water and 0.1 part of retarder, and stir for 240 s; finally, add 0.1 part by weight of basalt fiber and 2.7 parts by weight of cold drawn copper-plated steel fiber, and stir for 40 s to prepare ultra-high performance concrete for spraying. The sand is composed of quartz sand with particle size of 0.15 - 0.3 mm, quartz sand with particle size of 0.3 - 0.6 mm, quartz sand with particle size of 0.6 - 1.18 mm, and river sand with particle size of 1.18 - 2.36 mm, which are mixed in a mass ratio of 38:27:20:15.

[0038] Example 3

[0039] The specific preparation steps of ultra-high performance concrete for spraying are as follows:

[0040] First, weigh 22 parts by weight of Portland cement, 11.5 parts by weight of rapid hardening sulphoaluminate cement, 3 parts by weight of silica fume, 8 parts by weight of fly ash, 48 parts by weight of sand, 0.1 part by weight of water reducing agent, 0.004 part of defoaming agent, 0.2 part by weight of accelerating agent (non-alkali rapid setting agent of BY-2710 type), mix and stir for 20 s, then add 8 parts by weight of water and 0.1 part of retarder, and stir for 240 s; finally, add 0.1 part by weight of basalt fiber and 2.7 parts by weight of cold drawn copper-plated steel fiber, and stir for 40 s to prepare ultra-high performance concrete for spraying. The sand is composed of quartz sand with particle size of 0.15 - 0.3 mm, quartz sand with particle size of 0.3 - 0.6 mm, quartz sand with particle size of 0.6 - 1.18 mm, and river sand with particle size of 1.18 - 2.36 mm, which are mixed in a mass ratio of 38:27:20:15.

[0041] Example 4

[0042] The specific preparation steps of ultra-high performance concrete for spraying are as follows:

[0043] First, weigh 20 parts by weight of Portland cement, 13.5 parts by weight of rapid hardening sulphoaluminate cement, 3 parts by weight of silica fume, 8 parts by weight of fly ash, 48 parts by weight of sand, 0.1 part by weight of water reducing agent, 0.004 part of defoaming agent, 0.2 part by weight of accelerating agent (non-alkali rapid setting agent of BY-2710 type), mix and stir for 20 s, then add 8 parts by weight of water and 0.1 part of retarder, and stir for 240 s; finally, add 0.1 part by weight of basalt fiber and 2.7 parts by weight of cold drawn copper-plated steel fiber, and stir for 40 s to prepare ultra-high performance concrete for spraying. The sand is composed of quartz sand with particle size of 0.15 - 0.3 mm, quartz sand with particle size of 0.3 - 0.6 mm, quartz sand with particle size of 0.6 - 1.18 mm, and river sand with particle size of 1.18 - 2.36 mm, which are mixed in a mass ratio of 38:27:20:15.

[0044] Example 5

[0045] Water is added to the concrete made in Example 1, where the water-to-cement ratio is 0.18 for all. After thorough mixing, it is sprayed into molds of 100mm×100mm×100mm and 150mm×150mm×150mm respectively under a pressure of 1 Mpa, to make Specimen No. 1 of 100mm×100mm×100mm and Specimen No. 2 of 150mm×150mm×150mm.

[0046] Specimen No. 1 is maintained for 28 days. The maintenance method is in accordance with the requirements of "Reactive Powder Concrete" (GBT31387). After pouring and leveling, it is covered with cotton quilts and maintained under moisturizing conditions for 28 days, with the maintenance temperature above 20°C. As Figure 1 shown, and the compressive strengths of Specimen No. 1 at 3 days, 7 days, 21 days, and 28 days of maintenance are detected (the detection method of compressive strength refers to "Test Regulations for Cement and Cement Concrete in Highway Engineering" (JTG 3420—2020)).

[0047] Specimen No. 2 is maintained according to the above method, and the splitting tensile strengths of Specimen No. 2 at 3 days, 7 days, 21 days, and 28 days of maintenance are detected (the test method of splitting tensile strength refers to "Test Regulations for Cement and Cement Concrete in Highway Engineering" (JTG 3420—2020)). The splitting tensile effect of Specimen No. 2 after 28 days of maintenance is as Figure 2 shown.

[0048] Example 6

[0049] The concrete made in Examples 2 - 4 is tested according to the method of Example 5. The specific test results are shown in Table 1. In Table 1, sagging refers to the phenomenon that the concrete sprayed on the column has traces of flowing downward. The concrete sprayed on the column in all four examples has no traces of flowing downward. Sagging can be detected according to the test method of the national standard GB / T9264-88 "Determination of Sagging of Paint".

[0050] Table 1

[0051]

[0052] The ultra-high performance concrete for spraying of the present invention has excellent characteristics such as early strength, high strength, high fluidity, and strong crack resistance. For complex construction conditions, such as various diseases existing in existing bridge piers, such as exposed and corroded steel bars, scoured and hollowed concrete, pile necking, and exposed steel reinforcement cages, after the high-performance concrete is sprayed, it can quickly coagulate and harden, avoid flowing, and has a short construction period and high efficiency.

[0053] In the present specification, the various embodiments are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same or similar parts among the various embodiments, reference may be made to each other. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple. For the relevant parts, reference may be made to the description in the method section.

[0054] In this article, specific examples are used to elaborate on the principles and implementation manners of the present invention. The descriptions of the above embodiments are only used to help understand the method of the present invention and its core idea. At the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

Claims

1. A method for using ultra-high performance concrete for spraying, characterized in that: Ultra-high performance concrete for spraying is composed of the following components in parts by weight: 7-10 parts water, 20-30 parts of Portland cement, 5-20 parts of fast-hardening sulphoaluminate cement, 1-5 parts of silica fume, 5-10 parts fly ash, 30-50 parts of sand, Retarder 0.2-0.7 parts, 0.8-1.1 parts of water reducing agent, Defoaming agent 0-0.1 parts, 0.2-0.7 parts of coagulant, Basalt fiber 0-1 part, 1-3 parts of steel fiber; The sand is made by mixing quartz stone with a particle size of 0.15 to 0.3 mm, quartz stone with a particle size of 0.3 to 0.6 mm, quartz stone with a particle size of 0.6 to 1.18 mm, and river sand with a particle size of 1.18 to 2.36 mm in a mass ratio of 38:27:20:15; The method for preparing the ultra-high performance concrete for spraying comprises the following steps: Portland cement, rapid-hardening sulfoaluminate cement, silica fume, fly ash, sand, water reducer, defoamer, and setting accelerator are weighed in proportion, mixed and stirred for 15 to 30 seconds, and then water and retarder are added in proportion and stirred for 200 to 300 seconds; finally, basalt fiber and steel fiber are added in proportion and stirred for 30 to 50 seconds to prepare ultra-high performance concrete for spraying; Water is added to the ultra-high performance concrete to prepare a mixed material with a water-binder ratio of 0.18, and the mixed material is sprayed under a pressure of 0.7 MPa to 1 MPa.

2. The method for using the ultra-high performance concrete for spraying according to claim 1, characterized in that: The water reducer is a polycarboxylic acid water reducer; the defoamer is an organosilicon defoamer; and the silicate cement is PO52.5 silicate cement.

3. The method for using the sprayed ultra-high performance concrete according to claim 1, characterized in that: The retarder is borax, and the accelerator is an alkali-free quick-setting agent.

4. The method for using the sprayed ultra-high performance concrete according to claim 1, characterized in that: The steel fiber is a cold-drawn copper-plated steel fiber.

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