A concrete with steel fiber added

Abstract

The invention relates to a concrete mixed with steel fiber, and belongs to the technical field of concrete. In the invention, the presence of maleic anhydride grafted polymer builds a "bridge" between steel fiber and concrete raw materials, significantly improving the bonding force between steel fiber and matrix, thereby improving the tensile strength and flexural strength of concrete; in the preparation of maleic anhydride grafted polymer, polyacrylate with fluorine structure reacts with ammonia water to generate amide groups, and hydrogen bonding can be formed between the amide groups of each molecule, which significantly improves the tensile strength and flexural strength of concrete; the anhydride group reacts with the carboxyl group in the carboxyl styrene butadiene latex emulsion, and the introduction of maleic anhydride can form a cross-linked structure between molecules, thereby improving the tensile strength and flexural strength of concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete, and in particular relates to concrete mixed with steel fibers. Background Art

[0002] In order to improve the actual utilization value of concrete, researchers have added different types of fibers into concrete. The reinforcement and crack-resistance of fibers can improve the bonding performance between cement and aggregate, reduce cracks caused by shrinkage in concrete, and improve the overall performance of concrete. However, through experimental research on concrete mixed with steel fibers, it was found that in concrete that was damaged by pulling, the steel fibers were pulled out of the fracture surface instead of being pulled apart, indicating that the bonding strength between the steel fibers and the matrix was insufficient. Summary of the invention

[0003] The object of the present invention is to provide concrete mixed with steel fibers, further improving the bonding force between the steel fibers and a matrix, thereby improving the flexural strength thereof.

[0004] The purpose of the present invention can be achieved through the following technical solutions:

[0005] A concrete mixed with steel fiber, comprising the following raw materials in parts by weight:

[0006]

[0007] The concrete is mixed with steel fibers and modified polymers, wherein the steel fibers account for 0.8-1.4wt% of the concrete raw materials after being mixed, and the modified polymer accounts for 8-14wt% of the concrete raw materials after being mixed. The modified polymer is made of maleic anhydride grafted polymer, and the maleic anhydride grafted polymer is made of maleic anhydride and polyacrylate.

[0008] As a preferred embodiment of the present invention, the maleic anhydride grafted polymer is prepared by the following operation: maleic anhydride, tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate and glycidyl methacrylate are mixed, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate are added, nitrogen is introduced, heated to 80-85° C., reacted for 2-2.5 hours, then heated to 90-95° C., and then an initiator is added dropwise, and reacted for 1-1.5 hours to obtain the maleic anhydride grafted polymer;

[0009] The modified polymer is specifically prepared by the following operation: adding 5 wt% ammonia water to the maleic anhydride grafted polymer, stirring for 1 to 1.2 hours, then adding a binder and a promoter, stirring for 1 to 2 hours, to prepare the modified polymer.

[0010] As a preferred embodiment of the present invention, the volume ratio of the ammonia water to the maleic anhydride grafted polymer is 1.8-2.2:1.

[0011] As a preferred solution of the present invention, the adhesive is a carboxyl styrene butadiene latex emulsion with a solid content of 50 to 52%, and the added amount thereof is 30 to 50 wt % of the total system after addition.

[0012] As a preferred embodiment of the present invention, the accelerator is one of 2-thiolmethylimidazoline, 2-methylimidazoline or 2-propylimidazoline.

[0013] As a preferred embodiment of the present invention, the mass ratio of tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate is 4.8-5.2:4-4.5:8-8.3:2.8-3.2:1:0.1-0.12:25-30.

[0014] As a preferred embodiment of the present invention, the maleic anhydride accounts for 25-30wt% of the total raw material system after addition, and the total raw material system is maleic anhydride, tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate.

[0015] As a preferred embodiment of the present invention, the initiator is ammonium persulfate, and the added amount thereof is 0.1 to 0.5 wt % of the total system after addition.

[0016] Beneficial effects of the present invention:

[0017] Concrete is mixed with a modified polymer, which is prepared by modifying a maleic anhydride grafted polymer, which is prepared by maleic anhydride and polyacrylate, and has the characteristics of both maleic anhydride and polyacrylate. The carboxylic acid group in the polyacrylate can form a coordination bond with the iron ions in the steel fiber, thereby improving the adhesion between the polyacrylate and the surface of the steel fiber, enhancing the bonding strength between the two, and improving the bonding between the steel fiber and the matrix. At the same time, there are a large number of hydroxyl groups in cement in the concrete raw material, and the use of maleic anhydride introduces a large number of anhydride groups. These anhydride groups will combine with the hydroxyl groups to form a hydrogen bond, which plays an interface strengthening function, that is, the presence of the maleic anhydride grafted polymer builds a "bridge" between the steel fiber and the concrete raw material, significantly improving the bonding between the steel fiber and the matrix, thereby improving the tensile strength and flexural strength of the concrete.

[0018] Furthermore, the modified polymer is specifically prepared by modifying a maleic anhydride grafted polymer with ammonia water. In the preparation of the maleic anhydride grafted polymer, methacrylate tridecafluorooctyl introduces fluorine into the polyacrylate structure. The polyacrylate with a fluorine structure reacts with ammonia water to generate an amide group, and hydrogen bonds are formed between the amide groups of each molecule, so that the tensile strength and flexural strength of the concrete are significantly improved; the anhydride group in the polyacrylate in the modified polymer reacts with the carboxyl group in the carboxyl styrene butadiene latex emulsion, and the introduction of maleic anhydride can form a cross-linked structure between molecules, which promotes the cross-linking and curing of the latex, and further enhances the adhesion between the steel fiber and the matrix, thereby improving the tensile strength and flexural strength of the concrete. DETAILED DESCRIPTION

[0019] The present invention is further described in detail below in conjunction with specific implementation methods.

[0020] The steel fiber described in the present invention is purchased from Wuhan Xintu Engineering New Material Technology Co., Ltd., has a tensile strength greater than 980 MPa, a length of 30 mm and a diameter of 0.51 mm.

[0021] Examples 1 to 3 respectively prepare maleic anhydride grafted polymers, Examples 4 to 6 respectively use the maleic anhydride grafted polymers prepared in Examples 1 to 3 to prepare modified polymers, and Examples 7 to 9 respectively use the modified polymers prepared in Examples 4 to 6 as raw materials to provide concrete mixed with steel fibers.

[0022] Example 1

[0023] A maleic anhydride grafted polymer was prepared by:

[0024] 5 kg of maleic anhydride is mixed with 13 fluorooctyl methacrylate, methyl methacrylate, butyl acrylate and glycidyl methacrylate, then hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate are added, nitrogen is introduced, heated to 80°C, reacted for 2 hours, then heated to 90°C, and then initiator ammonium persulfate is dripped in an amount of 0.1 wt% of the total system after addition, and after reacting for 1 hour, a maleic anhydride grafted polymer is obtained. Among them, maleic anhydride accounts for 25 wt% of the total raw material system after addition (i.e. maleic anhydride, 13 fluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate); the mass ratio of 13 fluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate is 4.8:4:8:2.8:1:0.1:25.

[0025] Example 2

[0026] A maleic anhydride grafted polymer was prepared by:

[0027] Mix 5 kg of maleic anhydride with tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate and glycidyl methacrylate, then add hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate, introduce nitrogen, heat to 83°C, react for 2.2 hours, then heat to 93°C, and then drop in initiator ammonium persulfate in an amount of 0.3 wt% of the total system after addition. After reacting for 1.3 hours, a maleic anhydride grafted polymer is obtained. Among them, maleic anhydride accounts for 25-30wt% of the total raw material system after addition (i.e., maleic anhydride, tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate); the mass ratio of tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate is 5:4.2 8.2:3:1:0.11:28.

[0028] Example 3

[0029] A maleic anhydride grafted polymer was prepared by:

[0030] Mix 5 kg of maleic anhydride with tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate and glycidyl methacrylate, then add hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate, introduce nitrogen, heat to 85°C, react for 2.5 hours, then heat to 95°C, and then drop in initiator ammonium persulfate in an amount of 0.5 wt% of the total system after addition. After reacting for 1.5 hours, a maleic anhydride grafted polymer is obtained. Among them, maleic anhydride accounts for 30wt% of the total raw material system after addition (i.e., maleic anhydride, tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate); the mass ratio of tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate is 5.2:4.5:8.3:3.2:1:0.12:30.

[0031] Example 4

[0032] A modified polymer was prepared by:

[0033] 5 wt % of ammonia water was added to 5 kg of the maleic anhydride grafted polymer obtained in Example 1, the volume ratio of ammonia water to maleic anhydride grafted polymer was 1.8:1, and stirred for 1 hour. Then, the adhesive carboxyl styrene butadiene latex emulsion and the accelerator 2-thiolmethylimidazoline were added, the solid content of the adhesive was 50%, and the addition amount was 30 wt % of the total system after addition. After stirring for 1 hour, a modified polymer was obtained.

[0034] Example 5

[0035] A modified polymer was prepared by:

[0036] 5 wt % of ammonia water was added to 5 kg of the maleic anhydride grafted polymer obtained in Example 2, the volume ratio of ammonia water to maleic anhydride grafted polymer being 2:1, and the mixture was stirred for 1.1 h. Then, the adhesive carboxyl styrene butadiene latex emulsion and the accelerator 2-methylimidazoline were added, the solid content of the adhesive being 51%, and the addition amount being 40 wt % of the total system after addition. The mixture was stirred for 1.5 h to obtain a modified polymer.

[0037] Example 6

[0038] A modified polymer was prepared by:

[0039] 5 wt % of aqueous ammonia was added to 5 kg of the maleic anhydride grafted polymer obtained in Example 3, the volume ratio of aqueous ammonia to maleic anhydride grafted polymer being 2.2:1, and the mixture was stirred for 1.2 h. Then, an adhesive carboxyl styrene butadiene latex emulsion and an accelerator 2-propyl imidazoline were added, the solid content of the adhesive being 52%, and the amount added being 50 wt % of the total system after addition. The mixture was stirred for 2 h to obtain a modified polymer.

[0040] Example 7

[0041] 4 kg of cement, 6.5 kg of river sand, 9 kg of crushed stone and 1.5 kg of water were used as raw materials, and 0.8 wt % of steel fiber and 8 wt % of the modified polymer prepared in Example 4 were added as concrete raw materials.

[0042] Example 8

[0043] 4.5 kg of cement, 7.8 kg of river sand, 10.5 kg of crushed stone and 2 kg of water were used as raw materials, and 1.1 wt % of steel fiber and 11 wt % of the modified polymer prepared in Example 5 were added as concrete raw materials.

[0044] Example 9

[0045] 5kg of cement, 9kg of river sand, 12kg of crushed stone and 2.5kg of water were used as raw materials, and 1.4wt% of steel fiber and 14wt% of the modified polymer prepared in Example 6 were added as concrete raw materials.

[0046] Example 10

[0047] A concrete raw material, which is different from Example 8 only in that the maleic anhydride grafted polymer prepared in Example 2 is used instead of the modified polymer prepared in Example 5, and the rest is the same as Example 8.

[0048] Comparative Example 1

[0049] A concrete raw material, which is different from Example 8 only in that maleic anhydride is not added when preparing the maleic anhydride grafted polymer in Example 2, and the rest is the same as Example 8.

[0050] Comparative Example 2

[0051] A concrete raw material, which is different from Example 8 only in that tridecafluorooctyl methacrylate is not added when preparing the maleic anhydride grafted polymer in Example 2, and the rest is the same as Example 8.

[0052] Comparative Example 3

[0053] A concrete raw material, which is different from Example 8 only in that, when preparing the modified polymer in Example 5, the adhesive carboxyl styrene butadiene latex emulsion is not added, and an equal mass of maleic anhydride grafted polymer is used instead, and the rest is the same as Example 8.

[0054] Comparative Example 4

[0055] A concrete raw material, which is different from Example 8 only in that a carboxylated styrene butadiene latex emulsion with a solid content of 51% is used to replace the modified polymer obtained in Example 5, and the rest is the same as Example 8.

[0056] Comparative Example 5

[0057] A concrete raw material, which is different from Example 8 only in that the modified polymer prepared in Example 5 is not added, and the rest is the same as Example 8.

[0058] The concrete of Examples 7 to 10 and Comparative Examples 1 to 5 were tested as follows:

[0059] Test Example 1

[0060] Referring to JTG 3420-2020 "Testing Procedures for Cement and Cement Concrete for Highway Engineering", the slump and water retention of concrete are tested. The water retention is divided into three levels: "high", "low" and "none":

[0061] "Large amount": means that after the slump cone is lifted, more water is precipitated from the bottom;

[0062] "A small amount": means that after the slump cone is lifted, a small amount of water precipitates from the bottom;

[0063] “None”: It means that after lifting the slump cylinder, no water precipitates from the bottom;

[0064] The results are shown in Table 1.

[0065] Table 1

[0066]

[0067]

[0068] As can be seen from Table 1, the concrete raw materials provided by the present invention have good slump and water retention. The slumps of Examples 7 to 10 are all less than 40 mm; and the water retention performance is good. After the slump tube is lifted, no water is precipitated from the bottom. In Example 2 of Comparative Example 1, maleic anhydride grafted polymer was prepared without adding maleic anhydride, and the slump of the obtained concrete was 62 mm. A small amount of water was precipitated from the bottom in the water retention test, which was significantly lower than that of Example 8; in Example 2 of Comparative Example 2, tridecafluorooctyl methacrylate was not added when preparing maleic anhydride grafted polymer, and the slump of the obtained concrete was 44 mm. No water was precipitated from the bottom in the water retention test, and the slump was slightly lower than that of Example 8, and the water retention did not change significantly; in Example 5 of Comparative Example 3, the adhesive carboxyl styrene butadiene latex emulsion was not added when preparing the modified polymer, and an equal mass of maleic anhydride grafted polymer was used. In Comparative Example 4, the modified polymer prepared in Example 5 was replaced by a carboxylated styrene butadiene latex emulsion with a solid content of 51%, and the slump of the obtained concrete was 32 mm. In the water retention test, a small amount of water was precipitated from the bottom, which was slightly lower than that of Example 8, and the water retention was not significantly changed; in Comparative Example 4, the modified polymer prepared in Example 5 was replaced by a carboxylated styrene butadiene latex emulsion with a solid content of 51%, and the slump of the obtained concrete was 50 mm. In the water retention test, a small amount of water was precipitated from the bottom, which was significantly lower than that of Example 8; in Comparative Example 5, the modified polymer prepared in Example 5 was not added, and the slump of the obtained concrete was 68 mm. In the water retention test, a small amount of water was precipitated from the bottom, which was significantly lower than that of Example 8. It can be seen that the content of maleic anhydride grafted polymer has a significant effect on the slump and water retention of concrete.

[0069] Test Example 2 Mechanical Properties

[0070] The compressive strength, flexural strength and compression-flexure ratio of concrete were tested with reference to GB / T50081-2019 “Standard for Test Methods for Mechanical Properties of Ordinary Concrete”, and the results are shown in Table 2.

[0071] Table 2

[0072]

[0073]

[0074] It can be seen from Table 2 that the compressive strength of the concrete raw material embodiments 7 to 9 provided by the present invention is greater than 56 MPa, the flexural strength is greater than 8.2 MPa, and the compression-flexure ratio is greater than 6.8; the compressive strength of embodiment 10 is 50 MPa, the flexural strength is 7.69 MPa, and the compression-flexure ratio is 5.55, which is slightly lower than that of embodiments 7 to 9; and the concrete raw materials obtained in comparative examples 1 to 5 are less than 45 in compressive strength, less than 7 in flexural strength, and less than 5.3 in compression-flexure ratio compared with embodiment 8, which is significantly lower. It can be seen that the presence of the modified polymer in the present invention significantly improves the mechanical properties of concrete.

[0075] Test Example 3 Fracture Performance Test

[0076] The size of the point bending fracture test specimen is 100mm×100mm×400mm. Three specimens are prepared for each test group, and the age is 72d. The specimen cutout is 2mm wide and 25mm high. The loading equipment is a CSS-44020 electronic universal testing machine, with a loading rate of 0.002mm / s, a data acquisition frequency of 2 times / s, and a support distance of 300mm. The load and mid-span deformation are measured by load sensors and displacement meters, respectively, and the critical load and the crack mouth opening width corresponding to the critical load are recorded. The results are shown in Table 3.

[0077] Table 3

[0078]

[0079]

[0080] As shown in Table 3, the concrete provided by the present invention has good critical load and critical load corresponding crack mouth opening width. The critical loads of Examples 7 to 9 are all greater than 1, and the critical load corresponding crack mouth opening width is greater than 0.38 mm. Even under large deformation, it still has a high bearing capacity. In Comparative Examples 1 to 5, the critical load and critical load corresponding crack mouth opening width of the concrete show different degrees of decline.

[0081] The above is only an implementation method of the invention, and does not limit the scope of patent protection. Those skilled in the art can make non-substantial changes or substitutions based on the invention, which still fall within the scope of patent protection.

Claims

1. A concrete mixed with steel fiber, comprising the following raw materials in parts by weight: It is characterized in that The concrete is mixed with steel fibers and modified polymers, wherein the steel fibers account for 0.8-1.4wt% of the concrete raw materials after mixing, and the modified polymer accounts for 8-14wt% of the concrete raw materials after mixing, and the modified polymer is made of maleic anhydride grafted polymer, and the maleic anhydride grafted polymer is made of maleic anhydride and polyacrylate; The maleic anhydride grafted polymer is prepared by the following operation: maleic anhydride, tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate and glycidyl methacrylate are mixed, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate are added, nitrogen is introduced, heated to 80-85°C, reacted for 2-2.5 hours, then heated to 90-95°C, initiator is added dropwise, reacted for 1-1.5 hours, and the maleic anhydride grafted polymer is obtained; The modified polymer is specifically prepared by the following operation: adding 5 wt% ammonia water to the maleic anhydride grafted polymer, stirring for 1 to 1.2 hours, then adding a binder and a promoter, stirring for 1 to 2 hours, to prepare the modified polymer; The adhesive is a carboxylated styrene-butadiene latex emulsion with a solid content of 50-52%, and the amount of the adhesive added is 30-50wt% of the total system after addition; The accelerator is one of 2-thiolmethylimidazoline, 2-methylimidazoline or 2-propylimidazoline.

2. A steel fiber-incorporated concrete according to claim 1, It is characterized in that The volume ratio of the ammonia water to the maleic anhydride grafted polymer is 1.8-2.2:

1.

3. The concrete incorporating steel fibers according to claim 1, It is characterized in that The mass ratio of tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate is 4.8-5.2:4-4.5:8-8.3:2.8-3.2:1:0.1-0.12:25-30.

4. The concrete incorporating steel fibers according to claim 1, It is characterized in that The maleic anhydride accounts for 25-30wt% of the total raw material system after addition, and the total raw material system is maleic anhydride, tridecafluorooctyl methacrylate, methyl methacrylate, butyl acrylate, glycidyl methacrylate, hydroxyethyl methacrylate, benzoyl peroxide and butyl acetate.

5. The concrete incorporating steel fibers according to claim 1, It is characterized in that The initiator is ammonium persulfate, and its addition amount is 0.1-0.5wt% of the total system after addition.

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