A low-grade mixed sand concrete, test block forming device and strength detection method

Abstract

The present invention discloses a low-grade mixed sand concrete, which is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, crushed stone, water, sand and stone regulator and workability admixture. The components are as follows by mass: 300-400 parts of cement, 30-60 parts of mineral powder, 30-60 parts of fly ash, 0-30 parts of silica fume, 800-900 parts of low-grade mixed sand, 900-1000 parts of coarse aggregate, 140-160 parts of water, 5-10 parts of sand and stone regulator, and 5-15 parts of workability admixture. The present invention also discloses a concrete compressive strength test block forming device and a strength detection method. The beneficial effects of the present invention are as follows: the present invention conducts concrete strength test by simulating the actual pouring process, ensuring the authenticity of the strength and guaranteeing to reach its design strength, and ensuring the quality of concrete projects.

Description

Technical Field

[0001] The present invention belongs to the technical field of building materials, and particularly relates to a low-grade mixed sand concrete, a test block forming device and a strength detection method. Background Art

[0002] Sand is one of the necessary components of concrete, and the quality of sand plays a decisive role in the performance of concrete. Sand and gravel resources are non-renewable resources.

[0003] During the production process of concrete, mainly poor-quality coarse manufactured sand and stone powder are mixed and used. Using low-quality manufactured sand is likely to result in low-quality concrete with poor workability, and there may also be cases where the strength is unqualified during underwater pouring. In addition, there is currently a lack of an effective strength detection method for underwater-poured concrete, and it is impossible to accurately judge its true strength during production. Therefore, how to produce concrete that can be underwater-poured using low-grade sand, and how to detect the strength of low-grade mixed sand concrete that can be underwater-poured, are urgent problems to be solved at present. Summary of the Invention

[0004] The purpose of the present invention is to provide a low-grade mixed sand concrete, a test block forming device and a strength detection method in view of the deficiencies of the prior art, aiming to detect the strength of low-grade mixed sand concrete that can be underwater-poured.

[0005] The technical solution adopted by the present invention is as follows: A low-grade mixed sand concrete is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, crushed stone, water, a sand and stone regulator and a workability admixture, and the components are as follows by mass:

[0006] 300 - 400 parts of cement, 30 - 60 parts of mineral powder, 30 - 60 parts of fly ash, 0 - 30 parts of silica fume, 800 - 900 parts of low-grade mixed sand, 900 - 1000 parts of coarse aggregate, 140 - 160 parts of water, 5 - 10 parts of sand and stone regulator, and 5 - 15 parts of workability admixture.

[0007] According to the above scheme, the sand and stone regulator is obtained by uniformly mixing a modified alkanolamine compound, a carboxylic acid ester compound, hydroxypropyl methyl cellulose and water.

[0008] According to the above scheme, the workability admixture is a polycarboxylate water reducer with a water reduction rate of more than 20%.

[0009] According to the above scheme, the specific surface area of the silica fume ≥ 15 m 2 / g, and the water demand ratio ≤ 125%.

[0010] According to the above scheme, the low-grade mixed sand is composed of fine stone powder sand and coarse manufactured sand, and the ratio of fine stone powder sand to coarse manufactured sand is 1:(2 - 3).

[0011] According to the above scheme, the fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine-made sand is 3.1 - 3.4.

[0012] The present invention also provides a device for forming concrete compressive strength test blocks, which includes a test bench, a test block mold, a retaining wall, and an underwater pouring funnel;

[0013] The test bench is placed horizontally; the test block mold has a hollow internal structure and is fixed on the test bench;

[0014] The retaining wall is in a cylindrical structure, and the lower end of the retaining wall is installed in the annular slot of the test block mold, and the retaining wall is coaxially arranged with the test block mold;

[0015] The underwater pouring funnel is arranged above the retaining wall, and the discharge pipe of the underwater pouring funnel extends into the retaining wall;

[0016] The underwater pouring funnel is connected to a support device, and the underwater pouring funnel can move vertically.

[0017] According to the above scheme, the device for forming concrete compressive strength test blocks is also provided with a funnel baffle; a notch penetrating left and right is opened in the upper part of the discharge pipe of the underwater pouring funnel, and the funnel baffle is horizontally inserted into the notch.

[0018] According to the above scheme, the device for forming concrete compressive strength test blocks is also provided with a partition net, and the partition net is horizontally installed in the middle of the discharge pipe of the pouring funnel to simulate the resistance of the concrete during long-distance pouring in the discharge pipe during the actual pouring process.

[0019] The present invention also provides a method for detecting concrete strength, and the method is as follows:

[0020] 1) Preparation before the test, provide the device for forming concrete compressive strength test blocks as described above and install it;

[0021] 2), Select a pouring funnel with an appropriate length according to the underwater pile depth of the concrete mixture during construction;

[0022] 3), Take a sample of the concrete mixture and fill the pouring funnel with the concrete mixture;

[0023] 4), According to the water level during actual construction, pour water into the retaining wall in proportion;

[0024] 5), Open the baffle, and make the concrete mixture pour along the inner wall of the discharge pipe of the pouring funnel and through the partition net into the test block mold;

[0025] 6), Slowly lift the pouring funnel upward and take out the retaining wall upward;

[0026] 7), Take out the test block mold, place it in the standard curing room for curing. After curing, conduct a compressive strength test to obtain the strength of the test block at 28 days.

[0027] The beneficial effects of the present invention are as follows:

[0028] 1. The present invention simultaneously proposes a forming device and a detection method for the compressive strength test block of low-grade mixed sand concrete for underwater pouring. By simulating the actual pouring process to conduct the concrete strength test, it ensures the authenticity of the strength and guarantees to reach its designed strength, thus ensuring the quality of the concrete project.

[0029] 2. The low-grade mixed sand concrete provided by the present invention is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, gravel, water, sand and stone regulator, and workability admixture. The sand and stone regulator and the workability regulating admixture are used in combination. The sand and stone regulator has the characteristic of preferentially adsorbing clay, soil or other porous non-active materials in the low-quality manufactured sand over the polycarboxylate superplasticizer molecules, thereby reducing the adsorption of polycarboxylate molecules and enabling the dispersion and slump retention components of polycarboxylate to function normally. At the same time, the sand and stone regulator has a super dispersing property, which can effectively reduce the surface tension in the liquid phase system of the concrete, promote the rapid spreading of the admixture on the surface of the powder particles, and improve the powder dispersibility. The workability regulating admixture adjusts the hydrophilic properties of the coarse and fine aggregates of the concrete through hydrophobic association, forms a permeable and dispersed stone powder slurry and cement slurry from the fine particles and colloidal particles in the manufactured sand, and flows into the voids left by the coarse sand of the manufactured sand during stirring, thereby playing a role in filling, lubricating and wrapping, increasing the wrapping property of the paste on the sand and stone aggregates, and enhancing the yield stress and stability of the paste, greatly improving the workability and cohesion of the manufactured sand concrete, and meeting the requirements of good fluidity, anti-dispersion and low bleeding of the concrete during underwater pouring. The obtained concrete has excellent workability and stable underwater pouring strength, solving the technical problems such as easy bleeding and segregation and too fast slump loss of low-grade mixed sand concrete under the requirements of underwater pouring construction. Description of the Drawings

[0030] Figure 1 It is a schematic diagram of the overall structure of the strength detection device in the present invention.

[0031] Figure 2 It is a sectional view of the strength detection device in the present invention.

[0032] Figure 3 It is an exploded view of the strength detection device in the present invention.

[0033] Among them: 1. Test bench; 2. Test block mold; 3. Retaining wall; 4. Underwater pouring funnel; 4.1. Discharge pipe; 5. Funnel baffle; 6. Support rod; 7. Mounting rack; 8. Partition net; 9. Test block. Detailed Embodiments

[0034] To better understand the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0035] A low-grade mixed sand concrete, specifically a low-grade mixed sand concrete capable of underwater casting, is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, crushed stone, water, sand and stone regulator and workability admixture. The components are as follows by mass:

[0036] 300 - 400 parts of cement, 30 - 60 parts of mineral powder, 30 - 60 parts of fly ash, 0 - 30 parts of silica fume, 800 - 900 parts of low-grade mixed sand, 900 - 1000 parts of coarse aggregate, 140 - 160 parts of water, 5 - 10 parts of sand and stone regulator, 5 - 15 parts of workability admixture.

[0037] In the above solution, the cement is P·O 42.5 cement, the mineral powder is S95 mineral powder, the fly ash is class F grade I fly ash, and the specific surface area of the silica fume ≥ 15m 2 / g, and the water demand ratio ≤ 125%.

[0038] Preferably, the low-grade mixed sand is composed of fine stone powder sand and coarse machine-made sand, and the ratio of fine stone powder sand to coarse machine-made sand is 1:(2 - 3). The fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine-made sand is 3.1 - 3.4.

[0039] Preferably, the crushed stone is 5 - 31.5mm continuously graded crushed stone.

[0040] Preferably, the sand and stone regulator is a light yellow liquid, and is obtained by mixing 10 - 15 parts of modified alkanolamine compounds, 5 - 10 parts of carboxylic acid ester compounds, 1 - 5 parts of hydroxypropyl methyl cellulose and 70 - 80 parts of water by mass. The carboxylic acid ester compound is one of ethyl acrylate, n-propyl acrylate, lauryl acrylate and isopropyl acrylate; the modified alkanolamine compound is obtained by reacting alkanolamine with allyl polyoxyethylene ether, acrylic acid and mercaptoacetic acid; the alkanolamine is one of diethanolamine, dipropanolamine and triethanolamine; the molecular weight of the allyl polyoxyethylene ether is 1000 - 3300.

[0041] The sand and stone regulator has the characteristic of preferentially adsorbing clay, soil or other porous non-active materials in low-quality machine-made sand over polycarboxylate superplasticizer molecules, thereby reducing the adsorption of polycarboxylic acid molecules and enabling the polycarboxylic acid dispersion and slump retention components to function normally; at the same time, the sand and stone regulator has super dispersing performance, can effectively reduce the surface tension in the concrete liquid phase system, promote the rapid spreading of the admixture on the surface of the powder particles, and improve the powder dispersibility.

[0042] In the above solution, the workability admixture is a polycarboxylate water reducer with a water reduction rate of more than 20%.

[0043] In the above solution, the water is tap water.

[0044] As Figures 1 - 3 shown, a device for forming a compression strength test block of underwater cast concrete includes a test bench 1, a test block mold 2, a retaining wall 3, and an underwater casting funnel 4;

[0045] The test bench 1 is placed horizontally; the test block mold 2 has a hollow internal structure, and the test block mold 2 is fixed on the test bench 1;

[0046] The retaining wall 3 is a cylindrical structure, the lower end of the retaining wall 3 is installed in the annular slot of the test block mold 2, and the retaining wall 3 is coaxially arranged with the test block mold 2;

[0047] The underwater casting funnel 4 is arranged above the retaining wall 3, and the discharge pipe 4.1 of the underwater casting funnel 4 extends into the retaining wall 3;

[0048] The underwater casting funnel 4 is connected to a support device, and the underwater casting funnel 4 can move vertically.

[0049] In the present invention, the bottom of the test block mold 2 is sealed.

[0050] Preferably, the test block 9 forming device further includes a funnel baffle 5; a through slot is provided in the upper part of the discharge pipe 4.1 of the underwater casting funnel 4, and the funnel baffle 5 is horizontally inserted into the slot.

[0051] In the present invention, the funnel baffle 5 is installed in the slot in the upper part of the discharge pipe 4.1, and plays a role in closing the large end of the funnel and continuously adding concrete during pouring.

[0052] Preferably, the support device includes a support rod 6 and a mounting bracket 7; the lower end of the support rod 6 is fixed on the test bench 1; one end of the mounting bracket 7 is connected to the upper part of the support rod 6, and a clamping ring adapted to the discharge pipe 4.1 is provided at the other end of the mounting bracket 7, and the discharge port of the underwater casting funnel 4 is installed on the clamping ring.

[0053] In the present invention, by adjusting the relative position of the clamping ring and the discharge port of the underwater casting funnel 4, the underwater casting funnel 4 can be moved up and down vertically, so as to adjust the position of the discharge pipe 4.1 of the underwater casting funnel 4 in the retaining wall 3 during pouring.

[0054] Preferably, the device for forming a compression strength test block of concrete further includes a partition net 8, and the partition net 8 is horizontally installed in the middle of the discharge pipe 4.1 of the underwater casting funnel 4, and is used to simulate the resistance of concrete during long-distance pouring in the discharge pipe 4.1 during the actual pouring process.

[0055] In the present invention, the retaining wall 3 has a cylindrical structure with openings at both the top and the bottom.

[0056] In the present invention, a fixing groove adapted to the test block mold 2 is provided on the test bench 1, and the test block mold 2 is installed in the fixing groove.

[0057] In the present invention, the center lines of the underwater pouring funnel 4, the funnel baffle 5, the partition net 8, the retaining wall 3, the test block mold 2 and the test bench 1 are all located on the same vertical line.

[0058] A method for detecting the strength of concrete, which is as follows:

[0059] 1) Preparation before the test, providing the underwater pouring concrete compressive strength test block forming device as described above and installing it. Specifically as follows:

[0060] A. Place the test bench 1 on a flat surface in the laboratory, and install the support rod 6 on one side of the test bench 1;

[0061] B. Place the test block mold 2 in the test groove in the middle of the test bench 1, and install the retaining wall 3 in the test block mold 2;

[0062] C. Install the partition board and the partition net 8 at the corresponding positions of the discharge pipe 4.1 of the underwater pouring funnel 4 respectively;

[0063] D. Install the discharge pipe 4.1 of the underwater pouring funnel 4 at the snap ring of the support rod 6, and ensure that there is a gap between the lower end of the discharge pipe 4.1 of the underwater pouring funnel 4 and the surface of the test bench 1;

[0064] E. Pour an appropriate amount of water along the inner wall of the retaining wall 3 into the retaining wall 3 to complete the preparation before the test.

[0065] 2). Select an underwater pouring funnel 4 with an appropriate length according to the depth of the underwater pile poured with the concrete mixture during construction.

[0066] In this embodiment, when the pouring depth of the concrete during construction is respectively below 3m, 3 - 5m, 5 - 10m, and above 10m, it is set that the total length of the underwater pouring funnel 4 (including the length of the discharge pipe 4.1) is 0.5m, 0.8m, 1.2m, and 1.5m respectively.

[0067] 3). Take a sample of the concrete mixture and fill the underwater pouring funnel 4 with the concrete mixture;

[0068] 4). According to the actual water level during construction, pour water into the retaining wall 3 in proportion;

[0069] 5). Open the funnel baffle 5, and make the concrete mixture flow along the inner wall of the discharge pipe 4.1 of the underwater pouring funnel 4 and be poured into the test block mold 2 through the partition net 8.

[0070] 6), Slowly lift the underwater pouring funnel 4 upwards and remove the retaining wall 3 upwards;

[0071] 7), Remove the test block mold 2, place it in the standard curing room for curing, and after curing is completed, conduct compressive strength testing according to GB / T50081 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete" to obtain the strength of the test block at 928d, and this strength is closer to the strength of the actual concrete pouring component.

[0072] Example 1

[0073] A low-grade mixed sand concrete capable of underwater pouring is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, crushed stone, water, sand and stone regulator and workability admixture. The mass of each component is as follows:

[0074] 300 parts of cement, 30 parts of mineral powder, 30 parts of fly ash, 0 parts of silica fume, 880 parts of low-grade mixed sand, 980 parts of coarse aggregate, 160 parts of water, 5 parts of sand and stone regulator, and 5 parts of workability admixture;

[0075] Among them, the cement used is P·O 42.5 cement, the mineral powder is S95 mineral powder, the fly ash is Class F Grade I fly ash, and the specific surface area of the silica fume is 16m 2 / g, and the water demand ratio is 123%; the low-grade mixed sand is composed of fine stone powder sand and coarse machine-made sand, and the ratio of fine stone powder sand to coarse machine-made sand is 1:2.5. The fineness modulus of the fine stone powder sand is 2.0, and the fineness modulus of the coarse machine-made sand is 3.2; the crushed stone is 5~31.5mm continuously graded crushed stone; the components and their mass fractions in the sand and stone regulator are 10 parts of modified alkanolamine compounds, 5 parts of carboxylic acid ester compounds, 5 parts of hydroxypropyl methyl cellulose and 80 parts of water; the workability admixture is a polycarboxylate water reducer with a water reduction rate of 20%~30%; tap water is used.

[0076] The device for forming the compressive strength test block of the low-grade mixed sand concrete for underwater pouring in this example is as Figure 1 shown, the connection relationship and functions of each component are as described above, and the steps for detecting the strength of the low-grade mixed sand concrete for underwater pouring using this device are as described above.

[0077] Example 2:

[0078] A low-grade mixed sand concrete capable of underwater pouring is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, crushed stone, water, sand and stone regulator and workability admixture. The mass of each component is as follows:

[0079] 300 parts of cement, 40 parts of mineral powder, 40 parts of fly ash, 10 parts of silica fume, 880 parts of low-grade mixed sand, 980 parts of coarse aggregate, 155 parts of water, 5 parts of sand and gravel regulator, and 7 parts of workability admixture;

[0080] Among them, the cement is P·O 42.5 cement, the mineral powder is S95 mineral powder, the fly ash is Class F Grade I fly ash, and the specific surface area of the silica fume is ≥15 m 2 / g, and the water demand ratio is ≤125%; the low-grade mixed sand is composed of fine stone powder sand and coarse machine-made sand, and the ratio of fine stone powder sand to coarse machine-made sand is 1:(2 - 3), the fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine-made sand is 3.1 - 3.4; the crushed stone is 5 - 31.5 mm continuously graded crushed stone; the components and their mass fractions in the sand and gravel regulator are 15 parts of modified alkanolamine compounds, 10 parts of carboxylic acid ester compounds, 5 hydroxypropyl methyl cellulose and 70 parts of water; the workability admixture is a polycarboxylate water reducer with a water reduction rate of more than 20%; the water is tap water.

[0081] The device for forming the compressive strength test block of the low-grade mixed sand concrete for underwater pouring in this embodiment is as Figure 1 shown, the connection relationship and functions of each component are as described above, and the steps for detecting the strength of the low-grade mixed sand concrete for underwater pouring using this device are as described above.

[0082] Example 3:

[0083] A low-grade mixed sand concrete capable of underwater pouring is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, crushed stone, water, sand and gravel regulator and workability admixture. The mass of each component is as follows:

[0084] 340 parts of cement, 40 parts of mineral powder, 40 parts of fly ash, 20 parts of silica fume, 850 parts of low-grade mixed sand, 960 parts of coarse aggregate, 150 parts of water, 8 parts of sand and gravel regulator, and 8 parts of workability admixture;

[0085] Among them, the cement is P·O 42.5 cement, the mineral powder is S95 mineral powder, the fly ash is Class F Grade I fly ash, and the specific surface area of the silica fume is ≥15 m 2 / g, and the water demand ratio is ≤125%; the low-grade mixed sand is composed of fine stone powder sand and coarse machine-made sand, and the ratio of fine stone powder sand to coarse machine-made sand is 1:(2 - 3), the fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine-made sand is 3.1 - 3.4; the crushed stone is 5 - 31.5 mm continuously graded crushed stone; the components and their mass fractions in the sand and gravel regulator are 10 parts of modified alkanolamine compounds, 10 parts of carboxylic acid ester compounds, 5 hydroxypropyl methyl cellulose and 75 parts of water; the workability admixture is a polycarboxylate water reducer with a water reduction rate of more than 20%; the water is tap water.

[0086] The device for forming the compression strength test blocks of low - grade mixed - sand concrete for underwater pouring in this embodiment is as Figure 1 shown. The connection relationships and functions of each component are as described above. The steps for testing the strength of low - grade mixed - sand concrete for underwater pouring using this device are as described above.

[0087] Example 4:

[0088] A kind of low - grade mixed - sand concrete that can be poured underwater is prepared by mixing cement, mineral powder, fly ash, silica fume, low - grade mixed sand, crushed stone, water, sand and stone regulator and workability admixture. The mass of each component is as follows:

[0089] 380 parts of cement, 50 parts of mineral powder, 50 parts of fly ash, 30 parts of silica fume, 850 parts of low - grade mixed sand, 950 parts of coarse aggregate, 145 parts of water, 10 parts of sand and stone regulator, and 10 parts of workability admixture;

[0090] Among them, the cement is P·O 42.5 cement, the mineral powder is S95 mineral powder, the fly ash is class F grade I fly ash, and the specific surface area of the silica fume is ≥15m 2 / g, and the water demand ratio is ≤125%; the low - grade mixed sand is composed of fine stone powder sand and coarse machine - made sand, and the ratio of fine stone powder sand to coarse machine - made sand is 1:(2 - 3), the fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine - made sand is 3.1 - 3.4; the crushed stone is 5 - 31.5mm continuously graded crushed stone; the components and their mass fractions in the sand and stone regulator are 12 parts of modified alkanolamine compounds, 10 parts of carboxylic acid ester compounds, 3 parts of hydroxypropyl methyl cellulose and 75 parts of water; the workability admixture is a polycarboxylate water - reducing agent with a water - reducing rate of more than 20%; the water is tap water.

[0091] The device for forming the compression strength test blocks of low - grade mixed - sand concrete for underwater pouring in this embodiment is as Figure 1 shown. The connection relationships and functions of each component are as described above. The steps for testing the strength of low - grade mixed - sand concrete for underwater pouring using this device are as described above.

[0092] Example 5

[0093] A kind of low - grade mixed - sand concrete that can be poured underwater is prepared by mixing cement, mineral powder, fly ash, silica fume, low - grade mixed sand, crushed stone, water, sand and stone regulator and workability admixture. The mass of each component is as follows:

[0094] 300 - 400 parts of cement, 30 - 60 parts of mineral powder, 30 - 60 parts of fly ash, 0 - 30 parts of silica fume, 800 - 900 parts of low - grade mixed sand, 900 - 1000 parts of coarse aggregate, 140 - 160 parts of water, 5 - 10 parts of sand and gravel regulator, 5 - 15 parts of workability admixture.

[0095] Among them, the cement is P·O 42.5 cement, the mineral powder is S95 mineral powder, the fly ash is F - class grade - I fly ash, and the specific surface area of the silica fume ≥ 15 m 2 / g, and the water demand ratio ≤ 125%; the low - grade mixed sand is composed of fine stone powder sand and coarse machine - made sand, and the ratio of fine stone powder sand to coarse machine - made sand is 1:(2 - 3), the fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine - made sand is 3.1 - 3.4; the crushed stone is 5 - 31.5 mm continuously graded crushed stone; the components and their mass fractions in the sand and gravel regulator are 12 parts of modified alkanolamine compounds, 7 parts of carboxylic acid ester compounds, 1 part of hydroxypropyl methylcellulose and 80 parts of water; the workability admixture is a polycarboxylate water - reducing agent with a water - reducing rate of more than 20%; the water is tap water.

[0096] The device for forming the compression strength test blocks of the low - grade mixed sand concrete for underwater pouring in this embodiment is as Figure 1 shown, and the connection relationship and functions of each component are as described above. The steps for testing the strength of the low - grade mixed sand concrete for underwater pouring using this device are as described above.

[0097] Comparative Example 1:

[0098] Repeat Example 1, and adjust the components of the low - grade mixed sand concrete for underwater pouring: 300 parts of cement, 30 parts of mineral powder, 30 parts of fly ash, 0 parts of silica fume, 900 parts of low - grade mixed sand, 980 parts of coarse aggregate, 160 parts of water, 2 parts of sand and gravel regulator, 5 parts of workability admixture.

[0099] Comparative Example 2:

[0100] Repeat Example 1, and adjust the components of the low - grade mixed sand concrete for underwater pouring: 300 parts of cement, 30 parts of mineral powder, 30 parts of fly ash, 0 parts of silica fume, 900 parts of low - grade mixed sand, 980 parts of coarse aggregate, 160 parts of water, 5 parts of sand and gravel regulator, 3 parts of workability admixture.

[0101] Comparative Example 3:

[0102] Repeat Example 1, and adjust the components of the low - grade mixed sand concrete for underwater pouring: 300 parts of cement, 30 parts of mineral powder, 30 parts of fly ash, 0 parts of silica fume, 900 parts of low - grade mixed sand, 980 parts of coarse aggregate, 160 parts of water, 0 parts of sand and gravel regulator, 5 parts of workability admixture.

[0103] Comparison of Test Results

[0104] The following table shows the compressive strength, cement loss rate, pH value, slump / expansion data of low-grade mixed sand concrete that can be cast underwater measured in Examples 1-5 and Comparative Examples 1-3.

[0105]

[0106] The test results show that:

[0107] For the compressive strength, when casting an 8m underwater pile, the low-grade mixed sand concrete that can be cast underwater in the present invention has good workability and no unqualified strength occurs. However, for the ordinary concrete using low-grade sand in the comparative examples, serious low strength appears, which does not meet the strength standard of underwater cast concrete.

[0108] For the anti-dispersion property, the cement loss and pH of each group of fresh non-dispersible concrete in Examples 1 to 5 meet the requirements in Specification DL / T 5117-2000 that the cement loss is less than 1.5% and the pH value is less than 12. The underwater non-dispersible concrete in the present invention has good anti-dispersion property. In Comparative Examples 1-3, the cement loss is close to the 1.5% limit of the standard requirement, the pH value rises above 11.8, and the anti-dispersion performance is poor. Moreover, the cement loss of Comparative Example 3 is greater than 1.5%.

[0109] For the fluidity, at 0h, the slump of each group of underwater non-dispersible concrete can be greater than 230mm, and the slump expansion of each group can be greater than 600mm, which can meet the self-leveling and self-compacting effects. During the time period from 0h to 2h, the slump and slump expansion of each group of underwater non-dispersible concrete do not decrease significantly, the time-dependent loss is controllable, and it has good fluidity, which can meet the requirements of fluidity. The slump and expansion of Comparative Examples 1-3 are significantly lower than those of Examples 1-5, and the time-dependent loss changes greatly.

[0110] The above embodiments are only for clearly illustrating the examples made, rather than limiting the implementation modes. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation modes here. Therefore, the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A device for forming test blocks of concrete compressive strength, characterized in that It includes a test bench, a test block mold, a retaining wall, and an underwater pouring funnel; The test bench is placed horizontally; the test block mold has a hollow internal structure and is fixed on the test bench; The retaining wall is a cylindrical structure, and the lower end of the retaining wall is installed in the annular slot of the test block mold, and the retaining wall is coaxially arranged with the test block mold; The underwater pouring funnel is arranged above the retaining wall, and the discharge pipe of the underwater pouring funnel extends into the retaining wall; The underwater pouring funnel is connected to a support device and moves vertically; The concrete compressive strength test block forming device is also provided with a funnel baffle; a horizontally penetrating notch is opened in the upper part of the discharge pipe of the underwater pouring funnel, and the funnel baffle is horizontally inserted into the notch; The concrete compressive strength test block forming device is also provided with a partition net, which is horizontally installed in the middle of the discharge pipe of the underwater pouring funnel to simulate the resistance of concrete during long-distance pouring in the discharge pipe during the actual pouring process.

2. A method for detecting the strength of concrete, characterized in that, The method is as follows: 1) Preparation before the test, provide and install the concrete compressive strength test block forming device described in claim 1; 2) Select an underwater pouring funnel with an appropriate length according to the depth of the underwater pile poured with the concrete mixture during construction; 3) Take a sample of the concrete mixture and fill the underwater pouring funnel with the concrete mixture; 4) According to the water level during actual construction, pour water into the retaining wall in proportion; 5) Open the funnel baffle to make the concrete mixture flow along the inner wall of the discharge pipe of the underwater pouring funnel, and pour it into the test block mold through the partition net; 6) Slowly lift the underwater pouring funnel upward and take out the retaining wall upward; 7) Detect the strength of the low-grade mixed sand concrete poured underwater by using the concrete compressive strength test block forming device: Take out the test block mold, place it in a standard curing room for curing, and conduct a compressive strength test after curing to obtain the strength of the test block at 28 days.

3. The concrete strength detection method according to claim 2, characterized in that, The low-grade mixed sand concrete is prepared by mixing cement, mineral powder, fly ash, silica fume, low-grade mixed sand, gravel, water, sand and stone regulator, and workability admixture. The mass of each component is as follows: 300 - 400 parts of cement, 30 - 60 parts of mineral powder, 30 - 60 parts of fly ash, 0 - 30 parts of silica fume, 800 - 900 parts of low-grade mixed sand, 900 - 1000 parts of coarse aggregate, 140 - 160 parts of water, 5 - 10 parts of sand and stone regulator, 5 - 15 parts of workability admixture.

4. The concrete strength detection method according to claim 3, wherein, The sand and stone regulator is obtained by uniformly mixing a modified alkanolamine compound, a carboxylic acid ester compound, hydroxypropyl methyl cellulose, and water.

5. The concrete strength detection method according to claim 3, characterized in that, The workability admixture is a polycarboxylate water reducer with a water reduction rate of more than 20%.

6. The concrete strength detection method according to claim 3, characterized in that, The specific surface area of the silica fume ≥ 15 m 2 / g, and the water demand ratio ≤ 125%.

7. The concrete strength detection method according to claim 3, characterized in that, The low-grade mixed sand is composed of fine stone powder sand and coarse machine-made sand, and the ratio of fine stone powder sand to coarse machine-made sand is 1:(2 - 3).

8. The concrete strength detection method according to claim 7, characterized in that, The fineness modulus of the fine stone powder sand is 1.9 - 2.1, and the fineness modulus of the coarse machine-made sand is 3.1 - 3.4.

Images