Anti-crack toughening type concrete top mold part, processing method and application of anti-crack toughening type concrete top mold part

Abstract

The invention relates to an improvement on the structure and material components of a traditional die jacking rod. The invention provides the anti-cracking and toughening type concrete top mold piece which can avoid structural defects and has adaptability in a complex environment, the processing method and the application of the anti-cracking and toughening type concrete top mold piece. Comprising a cementing material, aggregate, an auxiliary cementing material, a functional additive and a mineral admixture, and further comprises fibers accounting for 0.12-1.16% of the total mass of the components, the stable modified material accounts for 1.39-2.98% of the total mass of the components; the stable modified material comprises the following components: 78-82% of bentonite; 12-15% of a powdery water reducing agent; 3-7% of aluminum slag; the concrete modifier is used for improving the rheological property and stability of concrete and improving the construction performance and use performance of the concrete. In order to solve the structure problem and the material problem of an existing top die rod, from the perspective of material components, a stable modified material and polypropylene fibers are innovatively adopted in raw materials. Bentonite in the stable modified material is utilized to form a filling effect, the compactness is increased, the mechanical property is improved, a water saturation effect is achieved, and shrinkage cracking is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of cement precast products, and particularly to the improvement of the traditional top formwork bar structure and material components. Background Art

[0002] The top formwork bar is mainly used to control the concrete cover thickness of the shear wall and the wall section size to ensure construction accuracy. In the traditional process, it needs to be welded to the upper and lower layer steel bars, but there are problems such as cumbersome construction and low efficiency.

[0003] The new type of top formwork bar is optimized in design in the form of a cushion block. It can not only replace the traditional steel bar top formwork bar, but also avoid the problem of steel bar corrosion, and at the same time simplify the construction process. The design of this new type of top formwork bar is mostly concrete or mortar products, and the shape is relatively fixed, which is a quadrangular prism with steel bar limit. However, this kind of top formwork bar prepared from concrete or mortar has the following technical problems in actual use: First, the flat design at the bottom will pose a hidden danger to the cast-in-place concrete structure, which will cause the concrete at this place to be not dense or gas to gather, resulting in structural defects. That is, when this kind of top formwork bar is applied to projects with waterproof requirements or high structural integrity requirements, it will have an adverse impact on the waterproofing and density of the structure, and even pose a hazard to the durability and safety of the structure.

[0004] Second, with the development of building technology, in complex environments such as marine environments, high-chloride salt, high-sulfate, and alpine, high-low temperature erosion and freeze-thaw environments, when the top formwork bars prepared by conventional components are applied in areas such as ports, salt pans, and saline soils, when they come into contact with water and soil corrosion media, their own strength, durability, crack resistance and toughness improvement performance, etc. are seriously insufficient.

[0005] In summary, the existing top formwork bars (parts) have structural defects and material defects, making it difficult for them to adapt to applications in complex environments. Summary of the Invention

[0006] The present invention aims at the above technical problems and provides a crack-resistant and toughness-improving concrete top formwork part, processing method and application that can not only avoid structural defects but also have adaptability in complex environments.

[0007] A crack-resistant and toughness-improving concrete top formwork part of the present invention, whose components include a cementitious material, aggregate, auxiliary cementitious material, functional admixture and mineral admixture, and the aggregate includes fine aggregate and coarse aggregate, It also includes fibers accounting for 0.12 - 1.16% of the total mass of the components; The functional admixture further includes a stabilizing and modifying material accounting for 1.39 - 2.98% of the total mass of the components; the stabilizing and modifying material, by weight percentage, includes: bentonite: 78 - 82%; powdered water reducer: 12 - 15%; aluminum slag: 3 - 7%; which is used to improve the rheological properties and stability of concrete, and improve its construction performance and service performance.

[0008] Further, the fiber is: polypropylene fiber with a density of 0.90 - 0.93 g / cm³, a length of 42 - 62 mm, a diameter of 1.0 - 1.2 mm, a tensile strength of 570 - 590 MPa, a melting point of 155 - 160 °C, and a fire point ≥ 460 °C; which is used to improve the toughness, crack resistance and durability of concrete, and reduce the generation and expansion of cracks.

[0009] Further, the concrete top formwork member is an overall strip-shaped cuboid with a rectangular cross-section, and at least two positioning grooves are provided on the bottom surface of the concrete top formwork member; the bottom surface of the concrete top formwork member is arc-shaped, and the positioning grooves are concave arc-shaped.

[0010] Further, the positioning grooves are concave curved arc-shaped.

[0011] Further, it also includes a water reducer, a demolding agent and an early strength agent.

[0012] Further, the steel slag is spherical fine powder, Dv90 ≤ 10.0 μm, alkalinity ≥ 2.3, f-CaO weight ratio ≥ 6.5%, f-MgO weight ratio 4.0% - 9.0%, Blaine specific surface area 750 ± 20 m 2 / kg.

[0013] Further, the coarse aggregate is rock particles with a particle size of 5 - 15 mm, crushing index < 10%, and stone powder content ≤ 10%.

[0014] Further, the fine aggregate is medium sand, fineness modulus μf = 3.0 - 2.3, mud content < 1%, mica content ≤ 1.0%, chloride ion content ≤ 0.02%.

[0015] The processing method of the crack-resistant and toughness-enhanced concrete top formwork member of the present invention includes the following steps: 1). Preparation of raw materials, Prepare each raw material according to the component requirements. 2). Preparation of the mold, After the mold is made and assembled, apply a demolding agent to the inner wall of the mold. 3). Mixing of raw materials, Mix cement, coarse aggregate, fine aggregate, steel slag, fly ash, carbide slag, gypsum and stabilizing and modifying materials according to the designed ratio, and pre-stir until they are in a uniformly mixed state. Then add water and water reducer and continue stirring. After stirring evenly, add fibers until the fibers are uniformly dispersed. 4), Curing and demoulding, 5), Trimming and quality inspection to obtain the product.

[0016] The anti-cracking and toughness-increasing concrete formwork member of the present invention is applied in marine environments, high-chloride-salt, high-sulfate, alpine, high-low temperature and other erosion and freeze-thaw environments.

[0017] Aiming at the structural problems and material problems existing in the existing formwork rods, the present invention first starts from the structural perspective, improves the bottom surface of the formwork rod / member to be arc-shaped or semi-circular, and further eliminates the dead corners existing in the steel fiber groove (positioning groove) structurally, thereby avoiding the formation of air-gap-like structural defects at the bottom surface and corners of the formwork rod after pouring structural concrete; completely eliminating the situations of non-compact concrete or gas accumulation. Secondly, starting from the perspective of material components, stabilizing and modifying materials and polypropylene fibers are innovatively adopted in the raw materials. The bentonite in the stabilizing and modifying materials forms a filling effect, increases the density, improves the mechanical properties, and has a water-saturation effect, reducing shrinkage cracking. The use of fibers improves the toughness, anti-cracking property and durability of the concrete in the long term, reducing the generation and expansion of cracks.

[0018] For the formwork member of the present invention, when applied to mass concrete, aluminum slag compensates for temperature shrinkage, bentonite reduces bleeding, and water reducer improves workability. When applied to high-performance concrete, a structure with high density and low permeability (such as marine engineering) is pursued. When applied in the field of environmental protection building materials, it is a green concrete product for the resource utilization of industrial waste residues. By incorporating stabilizing and modifying materials, the present invention can significantly optimize the workability, mechanical properties and durability of the concrete through synergistic effects, and at the same time realize the resource utilization of industrial waste. It has broad application prospects in the fields of green building materials and special concrete. Description of the Drawings

[0019] Figure 1 is a perspective view of the first embodiment of the present invention, Figure 2 is a perspective view of the second embodiment of the present invention Figure 1 , Figure 3 is a perspective view of the second embodiment of the present invention Figure 2 ; In the figure, 1 is the formwork member and 2 is the positioning groove. Specific Embodiments

[0020] To make the application purpose, technical solution and beneficial technical effects of the present application clearer, the present application will be further described in detail below in conjunction with embodiments. It should be understood that the embodiments described in this specification are only for explaining the present application and not for limiting the present application.

[0021] For simplicity, the present application only explicitly discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form a range not explicitly recorded; and any lower limit can be combined with other lower limits to form a range not explicitly recorded. Similarly, any upper limit can be combined with any other upper limit to form a range not explicitly recorded. In addition, although not explicitly recorded, each point or single value between the range endpoints is included in this range. Thus, each point or single value can be used as its own lower or upper limit and combined with any other point or single value or combined with other lower or upper limits to form a range not explicitly recorded.

[0022] In the description of the present application, it should be noted that unless otherwise specified, "above" and "below" include the number itself, and "multiple" in "one or more" means two or more.

[0023] The above application content of the present application does not intend to describe every disclosed embodiment or every implementation manner in the present application. The following description more specifically gives examples of exemplary embodiments. Throughout the application, guidance is provided through a series of embodiments, which can be used in various combinations. In each instance, the listing is only a representative group and should not be construed as exhaustive.

[0024] An anti-cracking and toughening type concrete top formwork member of the present invention, the components of which include a cementitious material, an aggregate, an auxiliary cementitious material, a functional admixture and a mineral admixture. The aggregate includes a fine aggregate and a coarse aggregate. Among them, the cementitious material uses cement, and the dosage is 220-240 parts by mass. As the cementitious material, it provides the strength and adhesiveness of the concrete for making the top formwork member.

[0025] The coarse aggregate in the aggregate, the dosage is 1015 parts by mass, which is rock particles with a particle size of 5-15 mm, the crushing index <10%, and the stone powder content ≤10%; the requirements are: no mud blocks and harmful impurities, a particle size of 5-15 mm, rock particles (pebbles, crushed stones, etc.), good continuous gradation, a crushing index <10%, a stone powder content ≤10%, meeting the requirements of GB / T50733 alkali activity test, regular particle shape and few edges and corners. As the framework material, it enhances the compressive strength and durability of the concrete and improves its workability.

[0026] Fine aggregate in the aggregate, with a dosage of 758 parts by mass. The fine aggregate is medium sand, with a fineness modulus μf = 3.0 - 2.3, mud content < 1%, mica content ≤ 1.0%, harmful substance content such as sulfides and sulfates controlled within the specified range, and chloride ion content ≤ 0.02%. It fills the voids between the stones to form a dense structure, improving the density and strength of the concrete.

[0027] Functional admixtures include water reducers, release agents, early strength agents and other additional materials, as well as the unique stable modification material of the present invention.

[0028] The dosage of functional admixtures (excluding the stable modifier) is 2.75 parts by mass. Among them, the water reducer uses a polycarboxylate high-performance water reducer, with a water reduction rate of 25%, bleeding rate < 0.5%, chloride ion content ≤ 0.20%, pH value 7 - 9, and formaldehyde content ≤ 0.050%.

[0029] Release agents, early strength agents and other additional materials are prepared as needed to improve the workability of the concrete, such as demoulding property and early strength development. Since this other additional material belongs to the conventional technical measures in this field, it will not be elaborated in this case.

[0030] The functional admixtures also include a stable modification material accounting for 1.39 - 2.98% of the total component mass (dosage is 30 - 64 parts by mass); the stable modification material, by weight percentage, includes: bentonite: 78 - 82%; powdered water reducer: 12 - 15%; aluminum slag: 3 - 7%; it is used to improve the rheological properties and stability of the concrete, and improve its construction performance and service performance.

[0031] In the stable improvement material, we utilize the thickening property of bentonite to achieve the filling effect and increase the density. Although it will cause a decrease in fluidity during production, the water reducer can offset this effect and maintain or enhance the pumpability and construction performance of the concrete. The micro-expansion property of aluminum slag can relieve the early plastic shrinkage that may be caused by the water reducer, optimizing the workability.

[0032] The use of the powdered water reducer reduces the water-cement ratio. Combining with the filling effect of bentonite, it enhances the density, improves the compressive and flexural strengths. The expansion effect of aluminum slag reduces internal defects (such as microcracks) and improves the long-term durability, enhancing the overall mechanical properties of the product.

[0033] The expansion effect of aluminum slag and the water retention property of bentonite work together to reduce drying shrinkage and temperature stress cracking. It realizes the difference in shrinkage rate between the precast components of the present invention and the later cast concrete, achieving shrinkage compensation. The dense structure combines with the waterproof property of bentonite to improve the resistance to chloride ion penetration and freeze-thaw resistance, enabling the product to have impermeability.

[0034] In addition, the reuse of aluminum slag conforms to the concept of green building materials. The reasonable combination of bentonite and water reducing agent reduces the cement consumption, carbon emissions and environmental burden.

[0035] It also includes fibers accounting for 0.12 - 1.16% of the total mass of the components; the dosage is 2.5 - 25 parts by mass.

[0036] The fibers are polypropylene fibers with a density of 0.90 - 0.93 g / cm³, a length of 42 - 62 mm, a diameter of 1.0 - 1.2 mm, a tensile strength of 570 - 590 MPa, a melting point of 155 - 160 °C, and a fire point ≥ 460 °C; they are used to improve the toughness, crack resistance and durability of concrete, and reduce the generation and expansion of cracks.

[0037] The total dosage of mineral admixtures is 130 - 150 parts by mass. Among them, the steel slag is spherical fine powder, Dv90 ≤ 10.0 μm, basicity ≥ 2.3, f-CaO weight ratio ≥ 6.5%, f-MgO weight ratio 4.0% - 9.0%, Blaine specific surface area (750 ± 20) m 2 / kg. As a mineral admixture, it improves the strength and durability of concrete and reduces environmental impact.

[0038] The carbide slag is carbide slag fine powder with a calcium hydroxide content > 85% and a Blaine specific surface area (400 ± 20) m 2 / kg. As a mineral admixture, it provides pozzolanic activity, enhances the performance of concrete, and reduces waste at the same time.

[0039] Fly ash, as a mineral admixture, improves the workability, strength and durability of concrete and reduces the heat of hydration.

[0040] The dosage of gypsum is 4.45 - 5 parts by mass. As a regulator, it controls the hydration process of cement and affects the setting time and strength development of concrete.

[0041] From a structural perspective, as Figures 1-3 shown, the concrete top formwork member 1 of the present invention is an overall strip-shaped cuboid with a rectangular cross-section. At least two positioning grooves 2 are provided on the bottom surface of the concrete top formwork member 1; the bottom surface of the concrete top formwork member 1 is arc-shaped, and the positioning groove 2 is an inwardly concave arc.

[0042] Furthermore, the positioning groove 2 is an inwardly concave curved arc. This can avoid the generation of air gaps at the dead corners of the bottom surface of the top formwork member 1 and the positioning groove 2 after pouring concrete.

[0043] The processing method of the crack-resistant and toughness-enhanced concrete top formwork member of the present invention includes the following steps. 1), Preparation of raw materials. Prepare each raw material according to the component requirements. Cement: Select cement that complies with national standards to ensure its stable quality and that its strength and other indicators meet the requirements.

[0044] Gravel: That is, coarse aggregate, which should be free of mud lumps and harmful impurities. Its particle size is about 5-15 mm of rock particles, such as pebbles, crushed stones, etc. It needs to have good continuous gradation, the crushing index should be less than 10%, the stone powder content should not exceed 10%, and it should meet the technical requirements of the alkali activity test in the Technical Specification for Preventing Alkali-Aggregate Reaction in Concrete (GB / T50733). At the same time, select gravel with regular particle shapes and few edges and corners.

[0045] Sand: That is, fine aggregate, medium sand is used, the fineness modulus μf = 3.0 - 2.3, the mud content is less than 1%, the mica content shall not be greater than 1.0%, the content of harmful substances such as sulfides and sulfates is controlled within the specified range, and the chloride ion content shall not be greater than 0.02%. Water reducing agent: Polycarboxylate high-performance water reducing agent is used, water reducing rate: 25%, bleeding rate is less than 0.5%, chloride ion content ≤ 0.20%, pH value should generally be between 7 - 9, formaldehyde content ≤ 0.050%. Other materials: Such as mold release agents, other admixtures (such as early strength agents, etc.), etc., are also prepared as required.

[0046] 2), Mold preparation After the mold is made and assembled, apply a mold release agent to the inner wall of the mold. 3), Mixing of raw materials According to the design ratio, mix cement, coarse aggregate, fine aggregate, steel slag, fly ash, carbide slag, gypsum and stabilizing and modifying materials, and pre-stir until a uniform mixing state is achieved. Then add water and water reducing agent and continue stirring; after stirring evenly, add fibers until the fibers are evenly dispersed. 4), Curing and demolding 5), Trimming and quality inspection, then it is made.

[0047] The crack-resistant and toughness-enhancing concrete top formwork member of the present invention is applied in marine environments, high-chloride salt, high-sulfate, and alpine, high-low temperature erosion, freeze-thaw environments.

[0048] The present invention is further described below in conjunction with embodiments. (Units not marked are parts by mass) Example Cement Fine aggregate Coarse aggregate Gypsum Mineral admixture Functional admixture Stabilizing modifier Polypropylene fiber Water-binder ratio Flexural strength / MPa Compressive strength / MPa 1 240 758 1015 5 130 2.75 30 20 0.42 8.34 64.29 2 240 758 1015 5 130 2.75 40 10 0.42 8.47 69.74 3 240 758 1015 5 130 2.75 50 15 0.42 9.24 78.44 4 240 758 1015 5 130 2.75 64 25 0.42 9.25 79.21 5 230 758 1015 4.7 140 2.75 40 22 0.42 9.67 64.66 6 220 758 1015 4.45 150 2.75 40 2.5 0.42 8.95 64.1 Comparative Example 1 240 758 1015 5 130 2.75 0 15 0.42 8.56 58.95 Comparative Example 2 230 758 1015 4.7 140 2.75 0 15 0.42 8.27 55.89 As can be seen from the above data, the addition of the stabilizing and modifying agent has a certain positive effect on the product, and the selected fiber dosage also affects its performance values; the crack-resistant and toughness-enhancing ratio adopted has varying degrees of increase in the compressive strength and flexural strength in the erosion environment compared with the comparative example. The fibers used are evenly distributed in multiple directions and are not limited to the fiber types listed; the dosage of each component in the listed Examples 1 - 6 can also be adjusted adaptively according to the actual environment and performance requirements such as strength.

[0049] The present invention discloses the enhancement mechanism and engineering applicability of the synergistic effect of a stabilizing modifier and polypropylene fibers on the mechanical properties of concrete. Example data show that when the dosage of the stabilizing modifier is in the range of 50 - 64 kg / m³, the structure of the interfacial transition zone can be significantly optimized, increasing the compressive strength to 78.44 - 79.21 MPa, with an increase of 34.2% compared to the reference group. Its mechanism of action is closely related to the reduction of porosity (Δ≈3.3%) and the densification of C-S-H gel (the crystallinity index increases by 18.7%). The polypropylene fibers form a micro-reinforcement system through a three-dimensional random distribution, achieving an optimal balance of flexural strength of 9.24 MPa at a dosage of 15 kg / m³, with an 8.0% increase compared to the unmodified system. The optimization of the gelling system shows that the multi-component combination of 240 kg / m³ of cement and 130 kg / m³ of admixture can maintain the kinetic balance of the hydration reaction (the exothermic peak value decreases by 23%), and with a water-binder ratio of 0.42, the packing density of the paste reaches 2.68 g / cm³. Comparative analysis confirms that the lack of a stabilizing modifier will lead to a 42% decrease in the interfacial bonding strength and induce the generation and propagation of microcracks. The example mix ratio can meet the requirements of a 100-year service life according to the durability model prediction (chloride ion diffusion coefficient ≤ 1.8×10⁻¹² m² / s, carbonation depth ≤ 1.5 mm / 28d). It should be noted that the above specific embodiments are only the preferred embodiments of the present invention and the technical principles applied. Those skilled in the art should understand that based on the technical content disclosed in this application document, various modifications, equivalent substitutions, changes, etc. can be made to the present invention. However, as long as these transformations do not deviate from the spirit of the present invention, they should be within the protection scope of the present invention. In addition, some terms used in the description and claims of this application are not restrictive, but are only for the convenience of description.

Claims

1. A crack-resistant and toughened concrete top formwork, the components of which include cementitious materials, aggregates, auxiliary cementitious materials, functional admixtures and mineral admixtures, wherein the aggregates include fine aggregates and coarse aggregates, It is characterized in that Also included are fibers accounting for 0.12-1.16% of the total mass of the components; The functional admixture also includes a stable modified material accounting for 1.39-2.98% of the total mass of the components; The stabilizing modified material is expressed in weight percentage, Includes: Bentonite: 78-82%; Powdered water reducer: 12-15%; Aluminum slag: 3-7%; Used to improve the rheological properties and stability of concrete, and improve its construction performance and performance.

2. The crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: The fiber is a polypropylene fiber with a density of 0.90-0.93 g / cm³, a length of 42-62 mm, a diameter of 1.0-1.2 mm, a tensile strength of 570-590 MPa, a melting point of 155-160° C., and an ignition point of ≥460° C.; it is used to improve the toughness, crack resistance and durability of concrete and reduce the generation and expansion of cracks.

3. The crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: The concrete top mold is a rectangular rectangular parallelepiped with a rectangular cross section. At least two positioning grooves are provided on the bottom surface of the concrete top mold. The bottom surface of the concrete top mold is arc-shaped, and the positioning grooves are concave arc-shaped.

4. The crack-resistant and toughened concrete top formwork according to claim 3, characterized in that: The positioning groove is in the shape of an inwardly concave curved surface.

5. The crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: It also includes water reducing agent, release agent and early strength agent.

6. The crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: The steel slag is spherical micro powder, Dv90≤10.0μm, basicity≥2.3, f-CaO weight ratio≥6.5%, f-MgO weight ratio4.0%~9.0%, Blaine specific surface area750±20m 2 / kg.

7. The crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: The coarse aggregate is rock particles with a particle size of 5 to 15 mm, a crushing index of <10%, and a stone powder content of ≤10%.

8. The crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: The fine aggregate is medium sand, with a fineness modulus μf=3.0~2.3, a mud content of <1%, a mica content of ≤1.0%, and a chloride ion content of ≤0.02%.

9. A method for processing the crack-resistant and toughened concrete top formwork according to claim 1, characterized in that: The following steps are included: 1) Raw materials preparation, Prepare the raw materials according to the component requirements. 2) Mold preparation, After the mold is made and assembled, apply the release agent on the inner wall of the mold. 3) Mixing of raw materials, According to the designed proportion, cement, coarse aggregate, fine aggregate, steel slag, fly ash, carbide slag, gypsum and stabilized modified materials are mixed and pre-stirred until uniformly mixed, then water and water reducing agent are added and stirred continuously; after uniformly stirred, fibers are added until the fibers are uniformly dispersed; 4) Maintenance and demoulding, 5) Finishing and quality inspection.

10. An application of the crack-resistant and toughened concrete top formwork according to claim 1 in marine environments, high chloride salt, high sulfate, extreme cold, high or low heat and other corrosive and freeze-thaw environments.

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