A kind of building concrete based on silicate cement and its manufacturing process

Abstract

The invention relates to the technical field of building materials and discloses a Portland cement-based building concrete and a manufacturing process thereof. The building concrete comprises the following raw materials: sand, crushed stone, fly ash, ordinary Portland cement, functionalized fibers, a composite additive, and water. The functionalized fibers are prepared by introducing sulfonic acid groups and amide groups into sepiolite fibers. The composite additive is an additive prepared by sequentially reacting polymalic acid with epoxy soybean oil and 2,3-epoxypropyltrimethylammonium chloride. The present invention utilizes the advantages of the functionalized fibers and the composite additive to ensure that the prepared building concrete has good anti-cracking performance, compressive strength, water retention performance, and mud resistance, thereby improving the stability and durability of the building concrete and having wide engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a building concrete based on Portland cement and a manufacturing process thereof. Background Art

[0002] Concrete refers to a building material made by mixing cement as a binder with water, sand, gravel, and, when necessary, chemical admixtures and mineral admixtures in appropriate proportions, and then evenly stirring, compacting, forming, and curing to harden it. It is one of the most important building materials in contemporary times and has a wide range of uses. It can be used to build houses, roads, bridges and other building structures. Among them, Portland cement is one of the most widely used binders in concrete and has good mechanical properties and durability.

[0003] With the acceleration of urbanization and the continuous development of infrastructure construction, the demand for concrete has gradually increased. However, due to the diversity of building types and the complexity of construction conditions, the functional requirements for concrete are also getting higher and higher. In a large number of existing cement concrete engineering structures, concrete cracking is very common, and cracks are channels for moisture, chemicals, etc. to enter the interior of the concrete. Once cracks are formed, these substances will accelerate the corrosion and deterioration of the concrete, thereby reducing the durability of the structure. Secondly, as the main material in building structures, concrete needs to withstand various external loads, such as gravity loads, wind loads, seismic loads, etc., and compressive strength is an important indicator to measure the ability of concrete to resist these loads. In addition, the rapid loss of water on the surface of concrete in the early plastic stage will lead to the generation of plastic cracks. Therefore, construction concrete needs to have good crack resistance, compressive strength and water retention properties to ensure that the performance can be maintained stable during long-term use and avoid deformation, cracking and other problems.

[0004] In the prior art, a common method for improving the functionality of concrete is to impart a variety of special properties to the concrete by incorporating various functional fillers and additives. For example, the invention patent with publication number CN113105193B discloses an anti-cracking concrete and its production process. This invention adds cellulose ether, calcium chloride, calcium acetate, and barium zirconate to the concrete formula and heat-treats the concrete to strengthen the bonding between the cement colloid and the aggregate, making it less likely to separate from the aggregate, thereby giving the prepared concrete good anti-cracking properties. Summary of the Invention

[0005] The object of the present invention is to provide a building concrete based on Portland cement and a manufacturing process thereof, which solves the following technical problems:

[0006] (1) Solved the problem of poor crack resistance of conventional concrete;

[0007] (2) Solved the problem of poor compressive strength of conventional concrete;

[0008] (3) Solved the problem of rapid surface water loss of conventional concrete in the early plastic stage.

[0009] The purpose of the present invention can be achieved through the following technical solutions:

[0010] A Portland cement-based building concrete comprises the following raw materials in parts by weight: 80-120 parts of sand, 200-260 parts of crushed stone, 20-40 parts of fly ash, 100-140 parts of ordinary Portland cement, 8-12 parts of functionalized fiber, 6-8 parts of composite additives, and 100-120 parts of water.

[0011] Through the above technical solution, sand is used as fine aggregate, which is mixed with the slurry and then filled into the gaps between the coarse aggregates, which helps to improve the overall density and strength of the concrete; the addition of crushed stone can improve the compressive strength and tensile strength of the concrete, ensuring the durability and stability of the concrete structure; the addition of fly ash can effectively improve the workability of the concrete, and its small particle size can fill the gaps between the cement particles and improve the density of the concrete; the addition of ordinary Portland cement can improve the mechanical properties and durability of the concrete.

[0012] Furthermore, the method for preparing the functionalized fiber comprises the following steps:

[0013] S1: adding sepiolite fibers to a hydrochloric acid solution, treating at 75-85° C. for 10-15 hours, filtering, washing, and drying to obtain pretreated sepiolite fibers;

[0014] S2: adding the pretreated sepiolite fiber and N,N-dimethylformamide to a nitrogen-protected reactor, ultrasonically dispersing for 20 to 40 minutes, and then adding maleic anhydride and p-toluenesulfonic acid to the reactor. After the addition is complete, the temperature is raised to 60 to 80°C, and the mixture is stirred for 2 to 4 hours. Then, the heating is stopped and the nitrogen is removed. The material is allowed to cool naturally, filtered, washed, and vacuum-dried to obtain the modified sepiolite fiber.

[0015] S3: Add modified sepiolite fiber and 2-aminoethanesulfonic acid to the dimethyl sulfoxide solution, and sonicate to form a uniform dispersion. Under nitrogen protection, add the accelerator and dehydrating agent to the dispersion. After addition, stir at room temperature for 4 to 8 hours, filter and separate the solid material, and wash and dry it to obtain the functionalized fiber.

[0016] Furthermore, in step S1, the average diameter of the sepiolite fibers is 2 μm, and the average length is 4 mm.

[0017] Furthermore, in step S1, the mass fraction of the hydrochloric acid solution is 2% to 4%.

[0018] Furthermore, in step S3, the accelerator is any one of 4-dimethylaminopyridine, 1-hydroxybenzotriazole or N-hydroxysuccinimide; the dehydrating agent is any one of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N,N'-diisopropylcarbodiimide or dicyclohexylcarbodiimide.

[0019] Furthermore, the preparation method of the composite additive comprises the following steps:

[0020] SS1: Mix polymalic acid and N-methylpyrrolidone, stir evenly, then add epoxidized soybean oil and catalyst. After the addition is complete, turn on the heat. After the system temperature reaches 60-80°C, stir at a constant temperature for 4-6 hours, cool and discharge to obtain the intermediate material.

[0021] SS2: Add the intermediate material and dimethyl sulfoxide into the reactor, stir mechanically to uniformity, add 2,3-epoxypropyltrimethylammonium chloride and boron trifluoride etherate, raise the temperature to 75-85°C, keep stirring at this temperature for 4-8 hours, and remove the solvent by reduced pressure distillation to obtain a composite additive.

[0022] Furthermore, in step SS1, the number average molecular weight of the polymalic acid is 1000 to 2000.

[0023] Furthermore, in step SS1, the catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate or tetramethylammonium bromide.

[0024] Furthermore, in step SS2, the mass ratio of the intermediate material to 2,3-epoxypropyltrimethylammonium chloride is 1:0.1 to 0.4.

[0025] A process for producing building concrete based on Portland cement comprises the following steps:

[0026] (1) Add sand, gravel, fly ash, ordinary Portland cement and functionalized fiber into a mixer, set the mixer speed to 500-700 r / min, and stir for 20-40 minutes to obtain a blend;

[0027] (2) adding the composite additive and water to the blend prepared in step (1), and continuing stirring for 10 to 30 minutes to obtain a concrete slurry;

[0028] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain construction concrete.

[0029] Beneficial effects of the present invention:

[0030] (1) The present invention utilizes a chemical grafting method to introduce sulfonic acid groups and amide groups into sepiolite fibers to prepare functionalized fibers, wherein the sulfonic acid groups and amide groups can react with calcium hydroxide in the slurry to promote the hydration of tricalcium aluminate, a mineral component in the slurry, so that calcium aluminate is generated faster, thereby improving the early strength of the concrete. At the same time, cement particles can be loaded on the surface of the sepiolite fibers, promoting the uniform distribution of the sepiolite fibers in the slurry. By utilizing the excellent properties of the sepiolite fibers, the microstructure of the concrete can be improved and the compressive strength of the concrete can be increased. When tiny cracks appear inside the concrete, the sepiolite fibers can play a "bridging role" in the concrete, filling the cracks and forming bridges, which can effectively prevent the generation and development of cracks, thereby improving the crack resistance of the concrete. In addition, the hydrophilic sulfonic acid groups can absorb a large amount of water, thereby enhancing the water retention of the concrete and avoiding the problem of too fast hydration rate of the slurry causing cracks in the concrete.

[0031] (2) The present invention prepares a composite additive as a filling modifier for concrete. Since the composite additive has a hyperbranched structure, it can extend into the gaps in cement, providing more contact points for the attachment of cement particles and is less likely to shrink, which helps to evenly distribute cement particles in the solution and balance internal stress, thereby enhancing the anti-cracking performance of concrete. The polymalic acid in the composite additive can improve the water retention performance of concrete. During the mortar hydration stage, polymalic acid can absorb and store a large amount of water. During the mortar hardening stage, the water absorbed by polymalic acid is gradually released and produces a continuous hydration effect, reducing the volume shrinkage caused by cement hardening and preventing cracks and deformation caused by shrinkage. At the same time, the epoxy soybean oil in the composite additive has good fluidity, can better fill gaps, and reduce the formation of voids and defects. In addition, the quaternary ammonium salt cations in the composite additive can react with components such as silicate in concrete, thereby improving the thixotropy of concrete, further increasing fluidity, and enhancing the anti-mud performance of concrete.

[0032] Of course, any product implementing the present invention does not necessarily need to achieve all of the advantages described above at the same time. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0034] Figure 1 This is an infrared spectrum test chart of the functionalized fiber prepared in Example 1 of the present invention.

[0035] Figure 2 This is the infrared spectrum test chart of the intermediate material and composite additive prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0036] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0037] Example 1

[0038] 1. Preparation of functionalized fibers

[0039] S1: 10 g of sepiolite fibers with an average diameter of 2 μm and an average length of 4 mm were added to a 3% hydrochloric acid solution, treated at 80°C for 12 h, filtered, washed, and dried to obtain pretreated sepiolite fibers;

[0040] S2: 5 g of pretreated sepiolite fiber and N,N-dimethylformamide were added to a nitrogen-protected reactor and ultrasonically dispersed for 30 min. 1.2 g of maleic anhydride and 0.05 g of p-toluenesulfonic acid were then added to the reactor. After the addition was complete, the temperature was raised to 70°C and stirred for 3 h. The heating was stopped and the nitrogen was removed. The material was allowed to cool naturally, filtered, washed, and vacuum-dried to obtain modified sepiolite fiber.

[0041] S3: Add 5 g of modified sepiolite fiber and 1.5 g of 2-aminoethanesulfonic acid to the dimethyl sulfoxide solution, and sonicate until a uniform dispersion is formed. Under nitrogen protection, add 0.08 g of 4-dimethylaminopyridine and 0.1 g of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide to the dispersion. After the addition, stir at room temperature for 6 hours, filter and separate the solid material, and wash and dry it to obtain functionalized fiber.

[0042] Through the above technical solution, the anhydride groups in the maleic anhydride structure are highly active. Under the action of p-toluenesulfonic acid, they can undergo a ring-opening esterification reaction with the hydroxyl groups on the surface of the sepiolite fiber, thereby introducing carboxyl groups on the surface of the sepiolite fiber to obtain modified sepiolite fibers. The carboxyl groups on its surface serve as active sites. Under the action of a dehydrating agent, 2-aminoethanesulfonic acid is introduced onto the surface of the sepiolite fiber by utilizing the mechanism that the carboxyl groups can react with the amino groups in the 2-aminoethanesulfonic acid structure, thereby obtaining functionalized fibers.

[0043] The functionalized fibers were analyzed by infrared spectroscopy using a Nicolet 380 FT-IR Fourier transform infrared spectrometer. Figure 1 As shown by Figure 1 It can be seen that in the infrared spectrum of the functionalized fiber, 1731 cm -1 The absorption peak of the ester group C=O appears at 3440 cm -1 The absorption peak of NH in amide appears at 1665 cm -1 The absorption peak of C=O in amide appears at 1238cm -1 and 1092cm -1 The absorption peak of sulfonic acid group appears at

[0044] 2. Preparation of composite additives

[0045] SS1: Mix 6 g of polymalic acid with a number average molecular weight of 2000 with N-methylpyrrolidone, stir evenly, then add 2.6 g of epoxidized soybean oil and 0.1 g of tetrabutylammonium bromide. After the addition is complete, turn on the heat. After the system temperature reaches 70°C, stir at a constant temperature for 5 hours, cool and discharge to obtain the intermediate material.

[0046] SS2: Add 6 g of the intermediate material and dimethyl sulfoxide into the reactor, stir mechanically to obtain a uniform mixture, add 1.8 g of 2,3-epoxypropyltrimethylammonium chloride and 0.08 g of boron trifluoride etherate, raise the temperature to 80°C, keep stirring at this temperature for 6 hours, and then remove the solvent by distillation under reduced pressure to obtain a composite additive.

[0047] Through the above technical solution, the carboxyl groups in the polymalic acid structure can undergo a ring-opening reaction with the epoxy groups in the epoxidized soybean oil structure under the action of a catalyst to produce an intermediate material. At the same time, the hydroxyl groups in its structure produced by the ring-opening reaction can react with the epoxy groups in the 2,3-epoxypropyltrimethylammonium chloride structure under the action of tetrabutylammonium bromide to obtain a composite additive.

[0048] The intermediate material and compound additives were analyzed by infrared spectroscopy using Nicolet 380FT-IR Fourier transform infrared spectrometer. Figure 2 As shown by Figure 2 It can be seen that in the infrared spectrum of the intermediate material, 1759cm -1 The absorption peak of the ester group C=O appears at 3270 cm -1 The absorption peak of hydroxyl group OH appears at 3279cm -1 The absorption peak of hydroxyl group OH appears at 1020 cm -1 The absorption peak of ether bond COC appears at 1410 cm -1 The absorption peak of CN in quaternary ammonium salt appears at

[0049] 3. Preparation of building concrete

[0050] (1) 80 g of sand, 200 g of crushed stone, 20 g of fly ash, 100 g of ordinary Portland cement, and 8 g of functionalized fiber were added to a mixer, the mixer speed was set to 500 r / min, and stirred for 20 min to obtain a blend;

[0051] (2) adding 6 g of the composite additive and 100 g of water to the blend prepared in step (1) and continuing stirring for 10 min to obtain a concrete slurry;

[0052] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain building concrete.

[0053] Example 2

[0054] Preparation of building concrete

[0055] (1) Add 100 g of sand, 230 g of crushed stone, 30 g of fly ash, 120 g of ordinary Portland cement, and 10 g of functionalized fiber into a mixer, set the mixer speed to 600 r / min, and stir for 30 min to obtain a blend;

[0056] (2) adding 7 g of the composite additive and 110 g of water to the blend prepared in step (1) and continuing stirring for 20 min to obtain a concrete slurry;

[0057] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain construction concrete.

[0058] The preparation method of the functionalized fiber and the composite additive is the same as that in Example 1.

[0059] Example 3

[0060] Preparation of building concrete

[0061] (1) Add 120 g of sand, 260 g of crushed stone, 40 g of fly ash, 140 g of ordinary Portland cement, and 12 g of functionalized fiber into a mixer, set the mixer speed to 700 r / min, and stir for 40 min to obtain a blend;

[0062] (2) adding 8 g of the composite additive and 120 g of water to the blend prepared in step (1) and continuing stirring for 30 min to obtain a concrete slurry;

[0063] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain building concrete.

[0064] The preparation method of the functionalized fiber and the composite additive is the same as that in Example 1.

[0065] Comparative Example 1

[0066] Preparation of building concrete

[0067] (1) Add 100 g of sand, 230 g of crushed stone, 30 g of fly ash, 120 g of ordinary Portland cement, and 10 g of functionalized fiber into a mixer, set the mixer speed to 600 r / min, and stir for 30 min to obtain a blend;

[0068] (2) adding 110 g of water to the blend prepared in step (1) and continuing stirring for 20 min to obtain a concrete slurry;

[0069] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain building concrete.

[0070] The preparation method of the functionalized fiber is the same as that in Example 1.

[0071] Comparative Example 2

[0072] Preparation of building concrete

[0073] (1) Add 100 g of sand, 230 g of crushed stone, 30 g of fly ash, and 120 g of ordinary Portland cement into a mixer, set the mixer speed to 600 r / min, and stir for 30 min to obtain a blend;

[0074] (2) adding 7 g of the composite additive and 110 g of water to the blend prepared in step (1) and continuing stirring for 20 min to obtain a concrete slurry;

[0075] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain building concrete.

[0076] The preparation method of the composite additive is the same as that in Example 1.

[0077] Comparative Example 3

[0078] Preparation of building concrete

[0079] (1) Add 100 g of sand, 230 g of crushed stone, 30 g of fly ash, and 120 g of ordinary Portland cement into a mixer, set the mixer speed to 600 r / min, and stir for 30 min to obtain a blend;

[0080] (2) adding 110 g of water to the blend prepared in step (1) and continuing stirring for 20 min to obtain a concrete slurry;

[0081] (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain building concrete.

[0082] Performance testing

[0083] ① According to GB / T 50081-2019 "Standard for Test Methods for Physical and Mechanical Properties of Concrete", the compressive strength of the architectural concrete prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 was tested after curing for 7 days, 28 days, and 56 days. The specific test results are shown in the following table:

[0084]

[0085] From the test results in the above table, it can be seen that the construction concrete prepared in Examples 1 to 3 all have good early strength properties and later compressive strength; the construction concrete prepared in Comparative Example 1 added functionalized fibers, and the compressive strength of the concrete reached 13.7 MPa on the first day, and the compressive strength of the concrete reached 76.6 MPa on the 28th day. The prepared construction concrete has good early strength properties and later compressive strength; the construction concrete prepared in Comparative Example 2 added composite additives but no functionalized fibers. Compared with the examples, the early strength properties and later compressive strength of the concrete were poor; in the construction concrete prepared in Comparative Example 3, neither functionalized fibers nor composite additives were added, so the early strength properties and later compressive strength of the concrete were the worst.

[0086] ② According to JGJ / T 70-2009 "Standard for Test Methods for Basic Properties of Building Mortar", the water retention rate of the building concrete prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 was tested; according to JC / T 951-2005 "Test Method for Crack Resistance of Cement Mortar", the cracking index of the building concrete prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 was tested; according to GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures", the fluidity of the building concrete prepared in Examples 1 to 3 of the present invention and Comparative Examples 1 to 3 was tested, using a cement-clay slurry system with a mass ratio of 1:1, and the initial fluidity and fluidity after 1 hour of the slurry were tested. The specific test results are shown in the following table:

[0087]

[0088] From the test results in the above table, it can be seen that the construction concrete prepared in Examples 1 to 3 all have excellent anti-cracking performance, water retention performance, fluidity and mud resistance; the construction concrete prepared in Comparative Example 1 only added functionalized fibers. Compared with the examples, the cracking index of the concrete is smaller, the water retention rate decreases more, the initial fluidity and the fluidity after 1 hour change greatly, the anti-cracking performance of the concrete is good, the water retention performance is average, and the fluidity and mud resistance performance are poor; the construction concrete prepared in Comparative Example 2 did not add functionalized fibers, but only used composite additives for filling and modification. The initial fluidity and fluidity after 1 hour of the concrete changed little, therefore, the fluidity and mud resistance performance were good, but the water retention and anti-cracking performance were average; the construction concrete prepared in Comparative Example 3 was not modified with a modifier, so the performance of various indicators was extremely poor.

[0089] The above content is merely an example and explanation of the concept of the present invention. Those skilled in the art may make various modifications or additions to the described specific embodiments or replace them in a similar manner. As long as they do not deviate from the concept of the invention or exceed the scope defined by the claims, they should all fall within the scope of protection of the present invention.

Claims

1. A building concrete based on Portland cement, characterized in that The method comprises the following raw materials in parts by weight: 80 to 120 parts of sand, 200 to 260 parts of crushed stone, 20 to 40 parts of fly ash, 100 to 140 parts of ordinary Portland cement, 8 to 12 parts of functionalized fiber, 6 to 8 parts of composite additives, and 100 to 120 parts of water; The preparation method of the composite additive comprises the following steps: SS1: Mix polymalic acid and N-methylpyrrolidone, stir evenly, then add epoxidized soybean oil and catalyst. After the addition is complete, turn on the heat. After the system temperature reaches 60-80°C, stir at a constant temperature for 4-6 hours, cool and discharge to obtain the intermediate material. SS2: Add the intermediate material and dimethyl sulfoxide into the reactor, stir mechanically to uniformity, add 2,3-epoxypropyltrimethylammonium chloride and boron trifluoride etherate, raise the temperature to 75-85°C, keep stirring at this temperature for 4-8 hours, and remove the solvent by reduced pressure distillation to obtain a composite additive.

2. A Portland cement-based building concrete according to claim 1, characterized in that: The preparation method of the functionalized fiber comprises the following steps: S1: adding sepiolite fibers to a hydrochloric acid solution, treating at 75-85° C. for 10-15 hours, filtering, washing, and drying to obtain pretreated sepiolite fibers; S2: adding the pretreated sepiolite fiber and N,N-dimethylformamide to a nitrogen-protected reactor, ultrasonically dispersing for 20 to 40 minutes, and then adding maleic anhydride and p-toluenesulfonic acid to the reactor. After the addition is complete, the temperature is raised to 60 to 80°C, and the mixture is stirred for 2 to 4 hours. Then, the heating is stopped and the nitrogen is removed. The material is allowed to cool naturally, filtered, washed, and vacuum-dried to obtain the modified sepiolite fiber. S3: Add modified sepiolite fiber and 2-aminoethanesulfonic acid to the dimethyl sulfoxide solution, and sonicate to form a uniform dispersion. Under nitrogen protection, add the accelerator and dehydrating agent to the dispersion. After addition, stir at room temperature for 4 to 8 hours, filter and separate the solid material, and wash and dry it to obtain the functionalized fiber.

3. A Portland cement-based building concrete according to claim 2, characterized in that: In step S1, the average diameter of the sepiolite fibers is 2 μm, and the average length is 4 mm.

4. The Portland cement-based building concrete according to claim 2, characterized in that: In step S1, the mass fraction of the hydrochloric acid solution is 2% to 4%.

5. The Portland cement-based building concrete according to claim 2, characterized in that: In step S3, the accelerator is any one of 4-dimethylaminopyridine, 1-hydroxybenzotriazole or N-hydroxysuccinimide; the dehydrating agent is any one of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide, N,N'-diisopropylcarbodiimide or dicyclohexylcarbodiimide.

6. The Portland cement-based building concrete according to claim 1, characterized in that: In step SS1, the number average molecular weight of the polymalic acid is 1000-2000.

7. The Portland cement-based building concrete according to claim 1, characterized in that: In step SS1, the catalyst is any one of tetrabutylammonium bromide, tetrabutylammonium hydrogen sulfate or tetramethylammonium bromide.

8. The Portland cement-based building concrete according to claim 1, characterized in that: In step SS2, the mass ratio of the intermediate material to 2,3-epoxypropyltrimethylammonium chloride is 1:0.1-0.

4.

9. A process for producing building concrete based on Portland cement as claimed in claim 1, characterized in that: The following steps are involved: (1) Add sand, gravel, fly ash, ordinary Portland cement and functionalized fiber into a mixer, set the mixer speed to 500-700 r / min, and stir for 20-40 min to obtain a blend; (2) adding the composite additive and water to the blend prepared in step (1), and continuing stirring for 10 to 30 minutes to obtain a concrete slurry; (3) The concrete slurry prepared in step (2) is sequentially subjected to pouring treatment, vibrating treatment, leveling treatment and curing treatment to obtain construction concrete.

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