Rubber concrete and method for improving shear resistance of new and old concrete interface

Abstract

The invention discloses rubber concrete and a method for improving shear resistance of a new and old concrete interface. The rubber concrete is prepared from the following components in parts by weight: 350 to 450 parts of cement, 30 to 180 parts of rubber particles, 500 to 700 parts of sand, 1000 to 1200 parts of gravel, 20 to 30 parts of carboxymethyl cellulose sodium and 160 to 180 parts of water. According to the invention, the rubber particles are added into the new concrete, so that gaps generated due to non-uniform distribution of aggregates can be effectively filled, and the raw materials are supplemented and reasonably proportioned, so that the bonding degree between the new concrete and the old concrete is improved, and the shear resistance of a joint surface is enhanced.

Description

Technical Field

[0001] The invention relates to the technical field of building materials, and in particular to a rubber concrete and a method for improving the shear resistance of the interface between new and old concrete. Background Art

[0002] In the face of natural disasters such as floods, the safety protection of buildings across rivers is particularly critical. The damage caused by floods to such buildings is usually direct and irreversible, so impact-resistant materials can be used as covering layers to resist the impact of floods on buildings. However, when the impact-resistant covering layer material impacts the old concrete structure inside, in addition to resisting its impact damage, the shear stress on the bonding surface between the external new concrete and the internal old concrete generated during the impact damage to the concrete structure must also be considered. This shear stress will significantly affect the performance of the bonding surface, and thus affect the stability and service life of the structure during continuous impact.

[0003] As we all know, the interface between new and old concrete is a mechanical weakness, and the strength of the interface is often lower than that of integrally cast concrete. In addition, due to the porosity of concrete, the density of concrete with different proportions after hardening varies greatly, resulting in weaker adaptability and bearing capacity on the interface.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The purpose of the present invention is to provide a rubber concrete and method for improving the shear resistance of the interface between new and old concrete. The rubber concrete of the present invention can improve the bonding degree between new and old concrete and enhance the shear resistance of the bonding surface by limiting the raw materials and the dosage.

[0006] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0007] The first aspect of the present invention provides a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete comprises the following components in parts by weight:

[0008] 350-450 parts of cement, 30-180 parts of rubber particles, 500-700 parts of sand, 1000-1200 parts of crushed stone, 20-30 parts of sodium hydroxymethyl cellulose and 160-180 parts of water.

[0009] Preferably, the rubber concrete comprises the following components in parts by weight:

[0010] 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone, 25 parts of sodium hydroxymethyl cellulose and 170 parts of water.

[0011] Preferably, the rubber particles are waste tire rubber particles.

[0012] Preferably, the rubber particles have a particle size of 1 to 3 mm.

[0013] Preferably, the sand is natural medium sand.

[0014] Preferably, the cement is Portland cement.

[0015] Preferably, among the gravel, gravel with a size of 20 to 30 mm accounts for 20% to 25%, gravel with a size of 10 to 20 mm accounts for 40% to 50%, and the remainder is gravel with a size of 5 to 10 mm.

[0016] 20~30mm means greater than 20mm and less than or equal to 30mm; 10~20mm means greater than 10mm and less than or equal to 20mm; 5~10mm means greater than 5mm and less than or equal to 10mm.

[0017] A second aspect of the present invention provides a method for improving the shear resistance of the interface between new and old concrete, the method comprising the following steps:

[0018] (a) Roughening the old concrete surface;

[0019] (b) pouring and molding the rubber concrete on the surface of old concrete.

[0020] Preferably, the roughness is processed to a roughness not less than 1.8 mm.

[0021] Preferably, the step (a) further comprises implanting reinforcement on the surface of the old concrete, and the implantation rate of the reinforcement is not less than 0.9%.

[0022] Compared with the prior art, the beneficial effects of the present invention include at least:

[0023] The present invention adds rubber particles to new concrete, which can effectively fill the gaps caused by uneven distribution of aggregates while exerting an impact resistance effect, and then with the assistance of various raw materials, after reasonable proportioning, the bonding degree between new and old concrete is improved, and the shear resistance of the bonding surface is enhanced. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following is a brief introduction to the drawings required for the specific embodiments or the description of the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts are not necessarily drawn according to the actual scale.

[0025] Figure 1 Schematic diagram of the groove structure in the roughness treatment of the old concrete surface in the experimental example of the present invention;

[0026] Figure 2 This is a test diagram of a Z-type specimen prepared in an experimental example of the present invention. DETAILED DESCRIPTION

[0027] The following embodiments of the technical solution of the present invention are described in detail in conjunction with the embodiments. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and are therefore only used as examples, and cannot be used to limit the protection scope of the present invention.

[0028] It should be noted that, unless otherwise specified, the technical terms or scientific terms used in this application should have the common meanings understood by those skilled in the art to which the present invention belongs.

[0029] The following raw materials are used:

[0030] The sand is natural medium sand with a fineness modulus of 2.8 and an apparent density of 2610 kg / m 3 .

[0031] Portland cement: P.O42.5 Portland cement;

[0032] The rubber particles are produced by Jiangxi Wanzai Rubber, with a particle size of 60 mesh, 1-3mm, 3-6mm, and apparent density of 1100kg / m 3 、960kg / m 3 , 930kg / m 3 .

[0033] Example 1

[0034] This embodiment is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete includes the following components in parts by weight:

[0035] 350 parts of cement, 30 parts of rubber particles, 500 parts of sand, 1200 parts of crushed stone, 30 parts of sodium hydroxymethyl cellulose and 160 parts of water;

[0036] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is 1 to 3 mm;

[0037] Portland cement

[0038] Among the gravel, 20-30 mm gravel accounts for 25%, 10-20 mm gravel accounts for 40%, and the remainder is 5-10 mm gravel.

[0039] Example 2

[0040] This embodiment is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete includes the following components in parts by weight:

[0041] 450 parts of cement, 180 parts of rubber particles, 700 parts of sand, 1000 parts of crushed stone, 20 parts of sodium hydroxymethyl cellulose and 180 parts of water;

[0042] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is 1 to 3 mm;

[0043] Portland cement

[0044] Among the gravel, 20-30 mm gravel accounts for 20%, 10-20 mm gravel accounts for 50%, and the remainder is 5-10 mm gravel.

[0045] Example 3

[0046] This embodiment is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete includes the following components in parts by weight:

[0047] 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone, 25 parts of sodium hydroxymethyl cellulose and 170 parts of water;

[0048] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is 1 to 3 mm;

[0049] Portland cement

[0050] Among the gravel, 20-30 mm gravel accounts for 22%, 10-20 mm gravel accounts for 45%, and the rest is 5-10 mm gravel.

[0051] Example 4

[0052] This embodiment is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0053] (a) roughening the surface of the old concrete to a roughness of 1.8 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0054] (b) After mixing the components in the rubber concrete of Example 3, pouring and molding are performed on the surface of old concrete.

[0055] Example 5

[0056] This embodiment is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0057] (a) roughening the surface of the old concrete to a roughness of 2.2 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0058] (b) After mixing the components in the rubber concrete of Example 2, pouring and molding are performed on the surface of old concrete.

[0059] Example 6

[0060] This embodiment is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0061] (a) The surface of the old concrete is roughened to a roughness of 1.8 mm, and a reinforcement is planted on the surface of the old concrete. The reinforcement rate is 0.9%, and the diameter of the steel bar is 10 mm. The roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete. The depth of the grooves is 5 mm and the width is 3 mm.

[0062] (b) After mixing the components in the rubber concrete of Example 1, pouring and molding are performed on the surface of old concrete.

[0063] Comparative Example 1

[0064] This comparative example is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete comprises the following components in parts by weight:

[0065] 400 parts of cement, 690 parts of sand, 1100 parts of crushed stone, 25 parts of sodium hydroxymethyl cellulose and 170 parts of water;

[0066] Portland cement

[0067] Among the gravel, 20-30 mm gravel accounts for 22%, 10-20 mm gravel accounts for 45%, and the rest is 5-10 mm gravel.

[0068] Comparative Example 2

[0069] This comparative example is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete comprises the following components in parts by weight:

[0070] 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone, 25 parts of sodium hydroxymethyl cellulose and 170 parts of water;

[0071] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is 1 to 3 mm;

[0072] Portland cement

[0073] Among the gravel, 20-30 mm gravel accounts for 30%, 10-20 mm gravel accounts for 55%, and the remainder is 5-10 mm gravel.

[0074] Comparative Example 3

[0075] This comparative example is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete comprises the following components in parts by weight:

[0076] 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone and 170 parts of water;

[0077] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is 1 to 3 mm;

[0078] Portland cement

[0079] Among the gravel, 20-30 mm gravel accounts for 22%, 10-20 mm gravel accounts for 45%, and the rest is 5-10 mm gravel.

[0080] Comparative Example 4

[0081] This comparative example is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete comprises the following components in parts by weight:

[0082] 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone and 170 parts of water;

[0083] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is 3 to 6 mm;

[0084] Portland cement

[0085] Among the gravel, 20-30 mm gravel accounts for 22%, 10-20 mm gravel accounts for 45%, and the rest is 5-10 mm gravel.

[0086] Comparative Example 5

[0087] This comparative example is a rubber concrete for improving the shear resistance of the interface between new and old concrete. The rubber concrete comprises the following components in parts by weight:

[0088] 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone and 170 parts of water;

[0089] The rubber particles are waste tire rubber particles, and the particle size of the rubber particles is not less than 60 mesh;

[0090] Portland cement

[0091] Among the gravel, 20-30 mm gravel accounts for 22%, 10-20 mm gravel accounts for 45%, and the rest is 5-10 mm gravel.

[0092] Comparative Example 6

[0093] This comparative example is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0094] (a) roughening the surface of the old concrete to a roughness of 1.8 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0095] (b) After mixing the components in the rubber concrete of Comparative Example 1, pouring and molding are performed on the surface of old concrete.

[0096] Comparative Example 7

[0097] This comparative example is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0098] (a) roughening the surface of the old concrete to a roughness of 1.8 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0099] (b) After mixing the components of the rubber concrete of Comparative Example 2, pouring and molding are performed on the surface of old concrete.

[0100] Comparative Example 8

[0101] This comparative example is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0102] (a) roughening the surface of the old concrete to a roughness of 1.8 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0103] (b) After mixing the components of the rubber concrete of Comparative Example 3, pouring and molding are performed on the surface of old concrete.

[0104] Comparative Example 9

[0105] This comparative example is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0106] (a) roughening the surface of the old concrete to a roughness of 1.8 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0107] (b) After mixing the components in the rubber concrete of Comparative Example 4, pouring and molding are performed on the surface of old concrete.

[0108] Comparative Example 10

[0109] This comparative example is a method for improving the shear resistance of the interface between new and old concrete, and the method comprises the following steps:

[0110] (a) roughening the surface of the old concrete to a roughness of 1.8 mm, wherein the roughening treatment is to carve transverse and longitudinal grooves on the surface of the old concrete, with a groove depth of 5 mm and a width of 3 mm;

[0111] (b) After mixing the components in the rubber concrete of Comparative Example 5, pouring and molding are performed on the surface of old concrete.

[0112] Experimental example

[0113] This experimental example is an experiment on the shear force at the interface between new and old concrete:

[0114] Weigh each raw material according to the ratio of each raw material in the rubber concrete;

[0115] Put rubber particles, cement, sand and water into a mixer and stir them thoroughly, then add crushed stone as needed to obtain cement slurries of rubber concrete of Example 3 and Comparative Examples 1 to 5 respectively;

[0116] The old concrete was C30 concrete;

[0117] The shear test adopts the Z-shaped improved shear test method composed of new and old L-shaped concrete. The overall size of the Z-shaped specimen used in the experiment is 500mm×300mm×150mm. The specimens are made according to the methods of Example 4 and Comparative Examples 6 to 10 respectively; each is repeated 3 specimens.

[0118] When making the specimen, the surface of the L-shaped C30 reinforced concrete specimen that has been cured is roughened. The roughness treatment is to carve horizontal and vertical grooves on the surface of the old concrete (the schematic diagram of the groove structure is shown in Figure 1 Then, put the L-shaped C30 reinforced concrete specimen into a pre-processed 500mm×300mm×150mm wooden rectangular mold; first add rubber particles, cement, sand and appropriate amount of water into the mixer and mix them thoroughly, then add crushed stone and the remaining water. After sufficient mixing, measure the slump. After the slump meets the standard, pour concrete into the test mold, vibrate it thoroughly with a vibrator, smooth it after no bubbles are generated, apply plastic wrap, let it stand in the laboratory for 24 hours, then remove the mold and cure it for 28 days; after the curing is completed, take out the specimen for shear test (the specimen shear test is as shown in Figure 2 shown).

[0119] In the experiment, a microcomputer servo universal testing machine was used to carry out shear tests on the interface between new rubber concrete and old concrete. In order to observe the damage of the interface during the shear test loading process, strain gauges were pasted on the side of the interface, and the dynamic signal test and analysis system was used to collect the shear slip phenomenon of the interface of the Z-type shear specimen.

[0120] Specifically, the formed shear specimen is taken out of the curing room and placed in a dry environment at room temperature for 24 hours. After the surface of the specimen is fully dried, one side of the surface near the joint of the bonding surface is polished with sandpaper. After polishing, in order to observe the displacement changes before and after the joint of the bonding surface, an electrical strain gauge is pasted on the surface. Due to the high sensitivity of the strain gauge, in order to prevent the strain gauge vibration and residual strain caused by improper pasting, the pasted strain gauge should be left to stand until the glue is fully dried.

[0121] After completing the preparation work, debug the dynamic signal test and analysis system. Connect the strain gauge and the analysis system wire, open the dynamic signal test software in the system, and observe whether the detected fluctuations are orderly and within the fluctuation range of ±1mm before the test begins. If the range requirements are met, start the universal testing machine to load the specimen.

[0122] In order to reduce measurement errors and ensure that all test devices can work normally, pre-loading is performed before formal loading. After pre-loading 10kN, it is slowly unloaded to 0kN, and then graded loading is performed. The loading rate of the universal testing machine is controlled at 0.1kN / s. When the load reaches the ultimate shear force that the bonding surface can withstand, a "crackling" fracture sound will be emitted at the joint of the bonding surface of the specimen, and the specimens on both sides of the joint of the bonding surface will have relative displacement. Then the loading is stopped immediately, and the camera and strain acquisition instrument are stopped. The damage load is recorded, and the crack trend and specific location at the shear damage surface are observed and described, and the test is over.

[0123] Experimental Results

[0124] This test sequentially carried out shear tests on 6 groups of 18 specimens. In order to improve the accuracy of the test, the data of the maximum failure load of the joint surface of the three specimens in each group were processed. The processing process compared the measured results of the three specimens in each group and calculated the average value, and then the maximum average failure load of the specimen under each working condition was obtained. The shear stress of the joint surface was calculated as follows:

[0125] τ=Pm / A; where: Pm is the failure load of the interface between rubber concrete and old concrete (kN); A is the area of ​​the interface between rubber concrete and old concrete (mm 2 ), the bonding surface area used in the test is 150mm*150mm=22500mm 2 。

[0126] The calculation results are shown in Table 1;

[0127] Table 1

[0128]

[0129] From Table 1, we can see that:

[0130] The technical solution of the present application, through the selection of various raw materials, ensures that the interface between the prepared rubber concrete and the old concrete has better shear resistance while maintaining impact resistance.

[0131] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

Claims

1. A rubber concrete for improving the shear resistance of the interface between new and old concrete, characterized in that: The rubber concrete comprises the following components in parts by weight: 350-450 parts of cement, 30-180 parts of rubber particles, 500-700 parts of sand, 1000-1200 parts of crushed stone, 20-30 parts of sodium hydroxymethyl cellulose and 160-180 parts of water.

2. The rubber concrete according to claim 1, characterized in that: The rubber concrete comprises the following components in parts by weight: 400 parts of cement, 90 parts of rubber particles, 600 parts of sand, 1100 parts of crushed stone, 25 parts of sodium hydroxymethyl cellulose and 170 parts of water.

3. The rubber concrete according to claim 1 or 2, characterized in that: The rubber particles are waste tire rubber particles.

4. The rubber concrete according to claim 1 or 2, characterized in that: The rubber particles have a particle size of 1 to 3 mm.

5. The rubber concrete according to claim 1 or 2, characterized in that: The sand is natural medium sand.

6. The rubber concrete according to claim 1 or 2, characterized in that: The cement is silicate cement.

7. The rubber concrete according to claim 1 or 2, characterized in that: Among the crushed stones, 20-30 mm crushed stones account for 20%-25%, 10-20 mm crushed stones account for 40%-50%, and the remainder is 5-10 mm crushed stones.

8. A method for improving the shear resistance of the interface between new and old concrete, characterized in that: The steps include: (a) Roughening the old concrete surface; (b) pouring and molding the rubber concrete according to any one of claims 1 to 7 on the surface of old concrete.

9. The method according to claim 8, characterized in that The roughness is processed to a roughness of not less than 1.8 mm.

10. The method according to claim 8, characterized in that The step (a) further comprises implanting reinforcement on the surface of the old concrete, wherein the implantation rate of the reinforcement is not less than 0.9%.

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