An anti-cracking agent for concrete in high-wind and dry areas, its preparation method and application

Abstract

The present invention discloses an anti-cracking agent for concrete in high-wind and dry areas, its preparation method and application, which relates to the technical field of building materials. The anti-cracking agent comprises the following components in parts by weight: 40-65 parts of chopped basalt fibers, 24-38 parts of vitrified microspheres, 2-5 parts of superfine water-absorbing resin, and 4-8 parts of polyvinyl alcohol. By placing the water-retaining material into the cavity of the vitrified microspheres, the present invention controls the water release rate to ensure the content of free water inside the concrete in the early stage of curing. At the same time, through the action of chopped fibers to increase the tensile strength, the present invention effectively avoids the cracking phenomenon of concrete in high-wind and dry areas. The present invention mainly solves the problem of concrete cracking in high-wind and dry areas due to excessive water volatilization. By adding the anti-cracking agent, the present invention effectively reduces the crack defects of concrete and improves the durability of building structures.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and particularly relates to an anti-cracking agent for concrete in a high-wind and dry area, a preparation method thereof, and an application thereof. Background Art

[0002] In the western region of China, it is arid, with large temperature differences, strong winds, gobi deserts, saline-alkali frozen soil, and frequent geological disasters. Compared with the central and eastern regions, the engineering geological conditions are special and the infrastructure construction is more difficult. According to the infrastructure construction situation in the western region in recent years, ordinary specifications and standards are not fully applicable to the harsh climate conditions and geological conditions in the western region. During the construction process, the construction of highway structures in the western region not only has a high cost, but also causes great damage to the ecological environment, resulting in serious soil erosion. The harsh climate environmental characteristics are extremely likely to cause the cracking of concrete, especially newly poured concrete. During the construction period, strong wind weather and dry climate conditions lead to serious loss of surface moisture of the concrete. Coupled with the large local temperature difference, in such an environment, the concrete is very prone to various cracking phenomena such as cracks, fissures, and crevices. Cracks are a kind of discontinuous phenomenon in concrete materials. Concrete cracks not only affect the aesthetics of its structure, but also become a channel for corrosive media to invade the interior of the concrete, ultimately affecting the safety and durability of the concrete structure. In addition, for the repair of later cracks, it is not only time-consuming and laborious, but also the repair cost will be a huge expenditure.

[0003] The phenomenon of volume reduction occurring during the initial setting period of concrete is called concrete shrinkage. The strength of concrete is relatively small in the initial setting stage, and it is accompanied by shrinkage deformation. When the concrete is restricted, tensile stress will be generated inside it. When the tensile strength cannot withstand the internal tensile stress, it will cause the concrete to crack. In a high-wind and dry area, the main factors causing concrete shrinkage are plastic shrinkage, drying shrinkage, and autogenous shrinkage. (1) Plastic shrinkage refers to the shrinkage phenomenon that occurs when the evaporation rate of the secreted water is greater than the internal bleeding rate during a period of time after the concrete is poured, due to the settlement of aggregates and the appearance of bleeding on the concrete surface. Excessive cement dosage, water-binder ratio, high-temperature environment, etc. will cause the concrete to crack within 3 - 12 hours; (2) When the concrete is in unsaturated air, the continuous evaporation and loss of internal water, capillary water in the hardened cement paste, and surface adsorbed water, resulting in drying from the inside to the outside, is called drying shrinkage; (3) Autogenous shrinkage refers to the shrinkage deformation caused by the self-drying of fresh concrete due to water shortage under the condition of constant temperature and absolute humidity with the outside world during the cement hydration process. Autogenous shrinkage is the shrinkage phenomenon caused by the consumption of internal water during cement hydration, thereby causing capillary tension. Summary of the Invention

[0004] To solve the above technical problems, the object of the present invention is to provide an anti-cracking agent for concrete in high-wind and dry areas, its preparation method and application, so as to solve the problem of concrete cracking caused by excessive water evaporation in concrete in high-wind and dry areas in the prior art.

[0005] The technical solution of the present invention to solve the above technical problems is as follows: Provide an anti-cracking agent for concrete in high-wind and dry areas, which includes the following components in parts by weight: 40-65 parts of chopped basalt fiber, 24-38 parts of vitrified microspheres, 2-5 parts of superfine water-absorbing resin, and 4-8 parts of polyvinyl alcohol.

[0006] On the basis of the above technical solution, the present invention can also be improved as follows:

[0007] Further, the anti-cracking agent for concrete in high-wind and dry areas includes the following components in parts by weight: 65 parts of chopped basalt fiber, 29 parts of vitrified microspheres, 2 parts of superfine water-absorbing resin, and 4 parts of polyvinyl alcohol.

[0008] Further, the length of the chopped basalt fiber is 3-6 mm, and the diameter is 8-14 μm.

[0009] Further, the true density of the vitrified microspheres is 0.4-0.6 g / cm 3 , and the diameter is 50-250 μm.

[0010] Further, the water absorption rate of the superfine water-absorbing resin > 200, and the particle size is 200-400 mesh.

[0011] Further, the molecular weight of the polyvinyl alcohol is 170,000-220,000, and the degree of alcoholysis is 85-89%.

[0012] The present invention also provides a preparation method of the above anti-cracking agent for concrete in high-wind and dry areas, which successively includes the following steps:

[0013] (1) Dissolve the superfine water-absorbing resin and polyvinyl alcohol in water, add the vitrified microspheres, and stir evenly;

[0014] (2) Pressurize to 8-12 MPa, and keep the pressure for 3-6 min, release the pressure and filter to obtain the fractured vitrified microspheres, dry them, add the chopped basalt fiber, and mix evenly to obtain the anti-cracking agent for concrete in high-wind and dry areas.

[0015] Further, in step (1), the weight ratio of the superfine water-absorbing resin to water is 1:350-450.

[0016] Further, in step (1), the weight ratio of the superfine water-absorbing resin to water is 1:400.

[0017] Further, in step (2), dry at 60-80 °C for 10-30 min.

[0018] Further, in step (2), it is dried at 80°C for 10 minutes.

[0019] Further, in step (2), the pressure is increased to 10 MPa.

[0020] Further, the manufacturer of the superfine water-absorbing resin is Shandong Nuoer Biotechnology Co., Ltd.

[0021] The present invention also provides the application of the crack-resistant agent for concrete in windy and dry areas in the preparation of concrete.

[0022] The present invention has the following beneficial effects:

[0023] 1. It does not affect the workability of concrete: Most of the water adsorbed by the superfine water-absorbing resin enters the cavity inside the vitrified microspheres. During the concrete mixing, it does not contact the water and admixtures in the concrete, and will not cause the problem of reduced fluidity of the concrete due to the water absorption of the water-absorbing resin.

[0024] 2. It does not affect the mechanical properties of concrete: The vitrified microspheres have an approximately spherical structure, forming a regular structure with good mechanical stability. And the vitrified microspheres are amorphous mainly composed of SiO 2 and have good interfacial bonding ability with the hydration products. Adding the crack-resistant agent will not reduce the mechanical properties of the concrete.

[0025] 3. The water release rate is slow and the crack resistance is good: Under high pressure conditions, the vitrified microspheres are pressured at the weak part of the shell layer to form an internal and external circulation channel. The water-absorbing resin and polyvinyl alcohol solution enter the cavity inside the vitrified microspheres through the channel under the action of hydraulic pressure. Due to the narrow channel, the loss rate of internal water is effectively controlled. Even if the free water inside the concrete loses quickly, it will not affect the water diffusion rate in the crack-resistant agent. The water diffuses into the concrete at a constant speed, effectively improving the anti-drying shrinkage cracking performance of the concrete.

[0026] 4. The present invention controls the water release rate by putting the water-retaining material into the cavity of the vitrified microspheres to ensure the content of free water inside the concrete in the early stage of curing. At the same time, by the short-cut fibers to increase the tensile strength, it effectively avoids the cracking phenomenon of concrete in windy and dry areas. The present invention mainly solves the problem of concrete cracking in windy and dry areas due to the too fast water evaporation. By adding the crack-resistant agent, it effectively reduces the crack defects of the concrete and improves the durability of the building structure. Description of the Drawings

[0027] Figure 1 It is the microscopic structure diagram of the vitrified microspheres after fracturing. Detailed Embodiments

[0028] The principles and features of the present invention will be described below in conjunction with the accompanying drawings. The examples given are only for explaining the present invention and are not intended to limit the scope of the present invention. For those conditions not specified in the examples, they shall be carried out according to conventional conditions or conditions recommended by the manufacturer. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0029] The chopped basalt fibers used in the following examples were provided by Sichuan Errun Basalt Fiber Technology Co., Ltd.; the vitrified microspheres were products of Henan Xinhua Vitrified Microspheres Co., Ltd.; the superfine water-absorbing resin was a product of Shandong Nuoer Biotechnology Co., Ltd.; and the polyvinyl alcohol was a product of Shanghai Chenqi Chemical Technology Co., Ltd.

[0030] Example 1:

[0031] An anti-cracking agent for concrete in high-wind and dry areas, comprising the following components in parts by weight: 65 parts of chopped basalt fibers, 29 parts of vitrified microspheres, 2 parts of superfine water-absorbing resin, and 4 parts of polyvinyl alcohol. Among them, the length of the chopped basalt fibers is 5 mm, and the diameter is 10 μm; the true density of the vitrified microspheres is 0.5 g / cm 3 , the diameter is 100 μm; the water absorption rate of the superfine water-absorbing resin is 300, and the particle size is 300 mesh; the molecular weight of the polyvinyl alcohol is 200,000, and the degree of alcoholysis is 86%.

[0032] A preparation method of an anti-cracking agent for concrete in high-wind and dry areas successively comprises the following steps:

[0033] (1) Dissolve the superfine water-absorbing resin and polyvinyl alcohol in water, add the vitrified microspheres, and stir evenly; among them, the weight ratio of the superfine water-absorbing resin to water is 1:400;

[0034] (2) After dissolving and dispersing evenly, pour it into an autoclave, pressurize to 10 MPa, and keep the pressure for 5 min, relieve the pressure and filter to obtain the fractured vitrified microspheres, dry them at 80 °C for 10 min, add the chopped basalt fibers, and mix evenly to obtain the anti-cracking agent for concrete in high-wind and dry areas.

[0035] Example 2:

[0036] An anti-cracking agent for concrete in high-wind and dry areas, comprising the following components in parts by weight: 65 parts of chopped basalt fibers, 24 parts of vitrified microspheres, 4 parts of superfine water-absorbing resin, and 7 parts of polyvinyl alcohol; the rest is the same as in Example 1.

[0037] A preparation method of an anti-cracking agent for concrete in high-wind and dry areas successively comprises the following steps:

[0038] The rest is the same as in Example 1.

[0039] Example 3:

[0040] An anti-cracking agent for concrete in high-wind and dry areas, comprising the following components in parts by weight: 52 parts of chopped basalt fiber, 38 parts of vitrified microspheres, 5 parts of superfine water-absorbing resin, and 5 parts of polyvinyl alcohol; the rest is the same as in Example 1.

[0041] A preparation method of an anti-cracking agent for concrete in high-wind and dry areas, successively comprising the following steps:

[0042] The same as in Example 1.

[0043] Example 4:

[0044] An anti-cracking agent for concrete in high-wind and dry areas, comprising the following components in parts by weight: 50 parts of chopped basalt fiber, 37 parts of vitrified microspheres, 5 parts of superfine water-absorbing resin, and 8 parts of polyvinyl alcohol; the rest is the same as in Example 1.

[0045] A preparation method of an anti-cracking agent for concrete in high-wind and dry areas, successively comprising the following steps:

[0046] The same as in Example 1.

[0047] Example 5:

[0048] An anti-cracking agent for concrete in high-wind and dry areas, comprising the following components in parts by weight: 40 parts of chopped basalt fiber, 24 parts of vitrified microspheres, 2 parts of superfine water-absorbing resin, and 4 parts of polyvinyl alcohol. Among them, the length of the chopped basalt fiber is 3 mm and the diameter is 8 μm; the true density of the vitrified microspheres is 0.4 g / cm 3 , the diameter is 50 μm; the water absorption rate of the superfine water-absorbing resin is 250, and the particle size is 200 mesh; the molecular weight of the polyvinyl alcohol is 170,000 and the alcoholysis degree is 85%.

[0049] A preparation method of an anti-cracking agent for concrete in high-wind and dry areas, successively comprising the following steps:

[0050] (1) Dissolve the superfine water-absorbing resin and polyvinyl alcohol in water, add the vitrified microspheres, and stir evenly; among them, the weight ratio of the superfine water-absorbing resin to water is 1:350;

[0051] (2) After dissolving and dispersing evenly, pour it into an autoclave, pressurize to 8 MPa, and keep the pressure for 6 min, relieve the pressure and filter to obtain the vitrified microspheres after fracturing, dry them at 60 °C for 30 min, add the chopped basalt fiber, and mix evenly to obtain the anti-cracking agent for concrete in high-wind and dry areas.

[0052] Example 6:

[0053] An anti-cracking agent for concrete in a high-wind and dry area, comprising the following components in parts by weight: 52 parts of chopped basalt fiber, 38 parts of vitrified microspheres, 5 parts of superfine water-absorbing resin, and 8 parts of polyvinyl alcohol. Among them, the chopped basalt fiber has a length of 6 mm and a diameter of 14 μm; the true density of the vitrified microspheres is 0.6 g / cm 3 , with a diameter of 250 μm; the water absorption rate of the superfine water-absorbing resin is 220, and the particle size is 400 mesh; the molecular weight of the polyvinyl alcohol is 220,000, and the alcoholysis degree is 89%.

[0054] A preparation method of an anti-cracking agent for concrete in a high-wind and dry area successively comprises the following steps:

[0055] (1) Dissolve the superfine water-absorbing resin and polyvinyl alcohol in water, add the vitrified microspheres, and stir evenly; among them, the weight ratio of the superfine water-absorbing resin to water is 1:450;

[0056] (2) After dissolving and dispersing evenly, pour it into an autoclave, pressurize to 12 MPa, and keep the pressure for 3 min, relieve the pressure and filter to obtain the post-fracture vitrified microspheres, dry them at 70 °C for 20 min, add the chopped basalt fiber, and mix evenly to obtain the anti-cracking agent for concrete in a high-wind and dry area.

[0057] Test Example

[0058] I. Microscopic Morphology Detection

[0059] Perform SEM detection on the post-fracture vitrified microspheres of Example 1, and the results are shown in Figure 1 .

[0060] It can be seen from Figure 1 that most of the shell layers of the vitrified microspheres are broken, but it is not a pulverizing damage, and the internal cavity structure is intact, indicating that the solution can effectively remain in the cavities of the post-fracture vitrified microspheres. When the moisture in the concrete is lost too quickly, it can release moisture outward from the break.

[0061] II. Performance Detection

[0062] Use the anti-cracking agents for concrete in a high-wind and dry area prepared in Examples 1-4 to prepare C40 concrete according to the mix ratios in Table 1 respectively, and conduct compressive strength, splitting tensile strength, and flat plate cracking tests.

[0063] The specific detection methods are as follows: The compressive strength and splitting tensile strength are tested according to GB / T 50081—2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" for the 100 mm×100 mm×100 mm cube compressive strength and the 150 mm×150 mm×150 mm splitting tensile strength test;

[0064] For the flat slab cracking test, plane thin plate specimens with dimensions of 800mm×600mm×100mm were used to conduct early cracking test research. There were two specimens in each group. The mold included 7 crack inductors. After the concrete was formed, the following curing method was adopted: Immediately turn on the fan after forming, so that the wind speed at 100mm directly above the center of the concrete surface was 5m / s. At the same time, turn on a 1000w iodine-tungsten lamp, and the lamp was 1.2m away from the concrete surface. After the test, according to the crack data recorded 24 hours after the concrete was poured, calculate the average cracking area of each specimen, the number of cracks per unit area, and the total cracking area per unit area.

[0065] Table 1 Concrete Mix Ratio

[0066]

[0067] The results are shown in Table 2-3.

[0068] Table 2 Concrete Compressive Strength, Splitting Tensile Strength

[0069]

[0070] Table 3 Concrete Cracking Test Results

[0071]

[0072] As can be seen from Table 2, after adding the crack inhibitor, the compressive strength of the concrete decreased slightly, but the decrease amplitude was very small. Since the crack inhibitor contains chopped basalt fibers, it is beneficial to improve the splitting tensile strength of the concrete. The splitting tensile strength of Test Examples 1-4 at 3d and 28d was significantly higher than that of the control examples, which is beneficial to improving the crack resistance of the concrete.

[0073] As can be seen from Table 3, after adding the crack inhibitor, the crack resistance of the concrete was significantly improved, the number of cracks in the concrete decreased significantly, and the cracking problem under the conditions of strong wind and dry environment could be effectively reduced.

[0074] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. An anti-cracking agent for concrete in windy and dry areas, characterized in that: The invention is composed of the following components in parts by weight: 40-65 parts of chopped basalt fibers, 24-38 parts of glass microspheres, 2-5 parts of superfine water-absorbing resin and 4-8 parts of polyvinyl alcohol; The length of the chopped basalt fibers is 3-6 mm and the diameter is 8-14 μm; The true density of the vitrified microspheres is 0.4-0.6 g / cm 3 , diameter 50-250μm; The water absorption rate of the superfine water-absorbent resin is greater than 200, and the particle size is 200-400 mesh; The molecular weight of the polyvinyl alcohol is 170,000-220,000, and the alcoholysis degree is 85-89%; The method for preparing the anti-cracking agent for concrete in windy and dry areas comprises the following steps in sequence: (1) Dissolve the superfine water-absorbent resin and polyvinyl alcohol in water, add vitrified microbeads, and stir evenly; (2) Pressurize to 8-12 MPa and maintain the pressure for 3-6 minutes, release the pressure and filter to obtain the vitrified microbeads after fracturing, dry them, add chopped basalt fibers, mix them evenly, and obtain the anti-cracking agent for concrete in windy and dry areas.

2. The anti-cracking agent for concrete in windy and dry areas according to claim 1, characterized in that: The invention comprises the following components in parts by weight: 65 parts of chopped basalt fibers, 29 parts of glass microspheres, 2 parts of superfine water-absorbent resin and 4 parts of polyvinyl alcohol.

3. The anti-cracking agent for concrete in windy and dry areas according to claim 1, characterized in that: In step (1), the weight ratio of the superfine water-absorbent resin to water is 1:350-450.

4. The anti-cracking agent for concrete in windy and dry areas according to claim 1, characterized in that: In step (2), drying is performed at 60-80°C for 10-30 minutes.

5. Use of the anti-cracking agent for concrete in windy and dry areas according to claim 1 or 2 in the preparation of concrete.

Images