CN115368091B - Early-strength ultrahigh-performance cement-based material for rapid reinforcement of flexural member and preparation method thereof - Google Patents

Abstract

The invention relates to an early strength ultra-high performance cement-based material for rapid reinforcement of a flexural member and a preparation method thereof, wherein the cement-based material comprises the following raw material components in parts by weight: 500-1000 parts of cementing material, 1000-2000 parts of aggregate, 10-60 parts of reinforcing fiber, 10-35 parts of latex powder, 1-3 parts of cellulose ether, 2-5 parts of water reducer and 150-300 parts of water. Compared with the prior art, the sulphoaluminate cement used by the invention has the excellent characteristics of quick hardening, early strength, good freezing resistance, corrosion resistance, good impermeability and controllable shrinkage compensation, solves the problems of insufficient early strength, poor toughness, easiness in cracking and peeling again and the like of common repairing and reinforcing cement-based materials, and has obvious popularization significance and application prospect for the maintenance of the existing flexural members.

Description

Early-strength ultra-high performance cement-based material for rapid strengthening of flexural members and its preparation method

technical field

The invention relates to the technical field of building materials, in particular to an early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members and a preparation method thereof.

Background technique

Flexural members are the most widely used members in reinforced concrete structures, and a typical example is bridge structures in the field of transportation. At present, the number of bridges in China is close to one million, and the number is still increasing every year, and the number of dangerous bridges is also showing explosive growth. It is foreseeable that as the corresponding traffic load continues to increase and natural disasters continue to increase, there will be a large number of flexural components such as bridges that will need to be repaired and strengthened after 20 or 30 years.

At this stage, the main repair and reinforcement technologies for damaged and flexural components in service include: (1) external carbon fiber cloth or external steel reinforcement method, but it affects the appearance and is not easy to redecorate. (2) The internal reinforcement method can greatly improve the toughness (making the ultimate strain of concrete reach about 7%), but the cost is relatively high, and the operation process also requires a lot of space. Therefore, in order to effectively prolong the service life of service-damaged and flexural members, the most convenient and effective method is to repair and strengthen them in situ. Cement-based materials are often used as repair materials due to their low cost and good compatibility with old substrates. But in essence, cement-based materials are brittle materials, and their tensile strength is only about 1/10 of the compressive strength. With the increase of service life, concrete structures are prone to serious problems such as cracking, leakage and steel corrosion under the coupling effects of various vehicle loads and erosive environments, which bring huge losses to the national economy. A cement-based material with early strength and high performance.

Contents of the invention

The object of the present invention is to provide an early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members and a preparation method thereof in order to overcome the above-mentioned defects in the prior art.

Sulphoaluminate cement, as a kind of rapid-hardening and early-strength cement, has a lower calcining temperature than ordinary Portland cement and has good environmental benefits. And its strength mostly comes from the symbiotic interlaced network of acicular ettringite crystals. The mechanical interlocking effect of the network can better dissipate energy under the action of external force, showing better toughness. In addition, sulfoaluminate cement can produce stronger bonding strength and greater resistance to peeling shear stress with fibers, and is more suitable for repairing and strengthening damaged and flexural members in service.

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

One of the technical solutions of the present invention: provide an early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members, which is composed of the following raw material components in parts by weight:

Further, the cementitious material is selected from any one of sulphoaluminate cement, Portland cement or mineral powder or a combination thereof.

It is further preferred that the cementitious material is a combination of sulphoaluminate cement, Portland cement and mineral powder.

Further, the aggregate is selected from any one or combination of quartz sand, machine-made sand or iron tailings sand.

Further, the aggregates have a particle size of 0.125mm-0.212mm (including 0.125mm and 0.212mm), 0.212mm-0.425mm (including 0.425mm, but excluding 0.212mm), 0.425mm-0.85mm (including 0.85mm, but not including 0.425mm) and 0.85mm ~ 2mm (including 2mm, but not including 0.85mm) range of particle mixture composition, the particle size is 0.125mm ~ 0.212mm, 0.212mm ~ 0.425mm, 0.425mm ~ 0.85mm The mass ratio of aggregate particles in the range of mm to 0.85mm to 2mm is 1:2:3:4. The gradation curve of the aggregate is zone 2.

Further, the reinforcing fibers are selected from PVA fibers or basalt fibers or a combination of PVA fibers and basalt fibers;

When the reinforcing fibers are selected from PVA fibers, the amount of PVA fibers is 10-20 parts;

When the reinforcing fibers are selected from basalt fibers, the amount of basalt fibers is 20 to 40 parts;

When the reinforcing fiber is selected from the combination of PVA fiber and basalt fiber, the amount of PVA fiber is 10-20 parts, and the amount of basalt fiber is 20-40 parts;

Further, the PVA fiber is a PVA fiber whose surface is coated with an oil agent, and the oil agent accounts for 12% of the mass of the PVA fiber.

It is further preferred that the oil agent is oxidized polyethylene.

Further, the latex powder is an acetic acid-vinyl acetate copolymer with a bulk density of 550 g/L and a pH of 8.

Further, the viscosity of the cellulose ether is 400 Pa.s, and the residual moisture is less than 1%.

Further, the water reducer is a polycarboxylate water reducer, and the water reducing rate is greater than 35%.

The second technical solution of the present invention is to provide a method for preparing an early-strength ultra-high-performance cement-based material for rapid reinforcement of flexural members, comprising the following steps:

(1) prepare each raw material;

(2) Add the water reducing agent into the water in advance and mix well to prepare the water reducing agent solution;

(3) After mixing the remaining raw materials except the reinforcing fibers, add them to the water reducer solution in step (2), and stir to obtain a mixed solution;

(4) Slowly add the reinforcing fiber to the mixed solution in the step (3), and stir to prepare the mortar;

(5) After pouring the mortar in step (4) into the mold, vibrate to obtain the target product.

Further, the stirring condition in step (3) is stirring at 40±5 rpm for 2 minutes, and the stirring condition in step (4) is stirring at 285±10 rpm for 2 minutes.

It is further preferred that the mold in step (4) is a steel mold.

The third technical solution of the present invention is to provide an application of an early-strength ultra-high-performance cement-based material for rapid reinforcement of flexural members, and the early-strength ultra-high-performance cement-based material for rapid reinforcement of flexural members is used as a damaged flexural member repair reinforcement materials.

Compared with the prior art, the present invention has the following beneficial effects:

(1) The sulphoaluminate cement used in the present invention has the excellent characteristics of fast hardening, early strength and high strength, good frost resistance, good corrosion resistance and impermeability, and controllable shrinkage compensation, which can well meet the bending requirements of bridges and the like. The construction requirements for component repair and reinforcement, and the same cement-based material as the old flexural components, have better volume compatibility and chemical compatibility. It solves the problems of insufficient early strength, poor toughness, and easy cracking and peeling of common repair and reinforcement cement-based materials, and has significant promotion significance and application prospects for the repair and reinforcement of existing bending components.

(2) Compared with the traditional Portland cement, the sulfoaluminate cement used in the present invention has a denser microstructure after hydration, which is conducive to the bridging effect of the fibers, and the composite material has better toughness. In addition, the calcination temperature of sulphoaluminate cement is about 1250°C, which is 150-200°C lower than Portland cement clinker, and has the advantages of low calcination temperature, easy grinding, and low carbon emissions.

(3) The particle size distribution of the aggregate sand used in the present invention conforms to the second zone gradation, which can effectively improve the workability and mechanical properties of the mortar (or concrete).

(4) The PVA fiber and basalt fiber in the present invention can greatly improve the strength and toughness of the cement-based material, especially after the two fibers are mixed, the synergistic effect between the fibers can be brought into play. In addition, considering that bridges and other bending components are mostly water structures, PVA fibers and basalt fibers are not easily corroded by harmful ions, can maintain their performance for a long time, and have lower costs.

(5) The present invention uses solid waste material iron tailings sand as an admixture to effectively realize green energy saving and efficient recycling of resources.

Description of drawings

Fig. 1 is the specific operation flowchart of the present invention.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments.

In each of the following examples and comparative examples, if there is no special stated raw material or processing technology, then it shows that it is a conventional commercially available raw material product or conventional processing technology in the art.

The following examples and comparative examples are prepared according to the preparation method as shown in Figure 1 to prepare the target product. Include the following steps:

(1) prepare each raw material;

(2) Add the water reducing agent into the water in advance and mix well to prepare the water reducing agent solution;

(3) After mixing the rest of the raw materials except for the reinforcing fibers, add them to the water reducer solution in step (2), stir at a low speed of 40±5rpm for 2min, and obtain a mixed solution;

(4) Slowly add the reinforcing fiber to the mixed solution in step (3), and stir at 285±10rpm for 2min at a high speed to prepare the mortar;

(5) After pouring the mortar in step (4) into the mold, vibrate to obtain the target product.

Finally, the performance test of the target product is carried out.

The above implementation manners will be described in more detail below in conjunction with specific examples.

Example 1:

This embodiment provides a kind of early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members, including the following raw material components in parts by weight: 350 parts of sulphoaluminate cement, 100 parts of Portland cement, and 50 parts of mineral powder 1000 parts of quartz sand, 20 parts of PVA fiber, 10 parts of latex powder, 1 part of cellulose ether, 4 parts of water reducing agent, and 150 parts of water.

Example 2:

This embodiment provides a kind of early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members, including the following raw material components in parts by weight: 350 parts of sulphoaluminate cement, 50 parts of Portland cement, and 100 parts of mineral powder 500 parts of quartz sand, 500 parts of machine-made sand, 20 parts of PVA fiber, 20 parts of latex powder, 1 part of cellulose ether, 4 parts of water reducing agent, and 150 parts of water.

Example 3:

This embodiment provides a kind of early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members, including the following raw material components in parts by weight: 350 parts of sulphoaluminate cement, 100 parts of Portland cement, and 50 parts of mineral powder 500 parts of quartz sand, 300 parts of machine-made sand, 200 parts of iron tailings sand, 40 parts of basalt fiber, 10 parts of latex powder, 1 part of cellulose ether, 2 parts of water reducing agent, and 150 parts of water.

Example 4:

This embodiment provides a kind of early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members, including the following raw material components in parts by weight: 350 parts of sulphoaluminate cement, 100 parts of Portland cement, and 50 parts of mineral powder 500 parts of quartz sand, 300 parts of machine-made sand, 200 parts of iron tailings sand, 10 parts of PVA fiber, 20 parts of basalt fiber, 20 parts of latex powder, 1 part of cellulose ether, 3 parts of water reducing agent, and 150 parts of water.

Example 5:

This embodiment provides an early-strength ultra-high-performance cement-based material for rapid reinforcement of bending members, including the following raw material components in parts by weight: 1000 parts of cementitious material, 2000 parts of aggregate, 10 parts of PVA fiber, and basalt fiber 20 parts, latex powder 35 parts, cellulose ether 3 parts, water reducer 5 parts, water 300 parts.

Comparative example 1:

The difference from Example 1 is that no sulphoaluminate cement is added.

Comparative example 2:

The difference from Example 4 is that no PVA fiber is mixed.

Comparative example 3:

The difference from Example 4 is that no basalt fiber is mixed.

The main performance index of above each embodiment and comparative example is as shown in table 1:

Table 1 Main properties of cement-based materials

It can be seen from Table 1 that the setting time of the embodiment of the present invention is between 26 and 35 minutes, which meets the demand for rapid repair; the 4h flexural strength is between 5.6MPa and 6.1MPa; the 3d flexural strength is between 8.0MPa and 8.6MPa, which has Early strength, high strength performance; 28d drying shrinkage is between 0.05% and 0.09%, with good volume stability; 3d tensile strain is between 3.5% and 5.1%, with good toughness; low chloride ion diffusion resistance , with good durability. And compared with the single-factor change control example, the performance indicators of the embodiment are better, reflecting the importance of the blending of sulfoaluminate cement and fiber to the present invention.

The above descriptions of the embodiments are for those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments, and apply the general principles described here to other embodiments without creative effort. Therefore, the present invention is not limited to the above-mentioned embodiments. Improvements and modifications made by those skilled in the art according to the disclosure of the present invention without departing from the scope of the present invention should fall within the protection scope of the present invention.

Claims (8)

1. An early-strength ultra-high-performance cement-based material for rapid reinforcement of flexural members, characterized in that it is composed of the following raw material components in parts by weight: The cementitious material is a combination of sulphoaluminate cement, Portland cement and mineral powder, and the ratio of the sulphoaluminate cement, Portland cement and mineral powder is 7:1:2～7:2: 1; The reinforcing fiber is a combination of PVA fiber and basalt fiber, the amount of PVA fiber is 10-20 parts, and the amount of basalt fiber is 20-40 parts; The PVA fiber is a PVA fiber whose surface is coated with an oil agent, and the oil agent accounts for 12% of the mass of the PVA fiber. 2. The early-strength ultra-high-performance cement-based material for rapid reinforcement of a bending member according to claim 1, wherein the aggregate is selected from any one of quartz sand, machine-made sand or iron tailings sand or a combination thereof; The aggregate is composed of particles with particle sizes ranging from 0.125mm to 0.212mm, 0.212mm to 0.425mm, 0.425mm to 0.85mm and 0.85mm to 2mm, and the particle sizes are 0.125mm to 0.212mm, 0.212mm to The mass ratio of aggregate particles in the range of 0.425mm, 0.425mm-0.85mm and 0.85mm-2mm is 1:2:3:4. 3. The early-strength ultra-high-performance cement-based material for rapid reinforcement of a flexural member according to claim 1, wherein the latex powder is acetic acid-vinyl acetate copolymer. 4. The early-strength ultra-high-performance cement-based material for rapid reinforcement of flexural members according to claim 1, wherein the viscosity of the cellulose ether is 400 Pa.s, and the residual moisture is less than 1%. 5. The early-strength ultra-high-performance cement-based material for rapid reinforcement of flexural members according to claim 1, wherein the water-reducing agent is a polycarboxylate water-reducing agent, and the water-reducing rate is greater than 35%. 6. A preparation method for the rapid reinforcement of flexural members as claimed in any one of claims 1-5, characterized in that it comprises the following steps: (1) prepare each raw material; (2) Add the water reducer to the water in advance, mix well, and prepare the water reducer solution; (3) After mixing the remaining raw materials except the reinforcing fibers, add them to the water reducer solution in step (2), and stir to obtain a mixed solution; (4) Twisting the reinforcing fibers, slowly adding the mixed solution in step (3), stirring to prepare mortar; (5) Pour the mortar in step (4) into the mold and vibrate to obtain the early-strength ultra-high performance cement-based material. 7. the preparation method of a kind of fast reinforcement of bending member according to claim 6 is characterized in that, the condition of stirring in the step (3) is: stirring 2min under 40 ± 5rpm rotating speed , the stirring condition in step (4) is stirring at 285±10rpm for 2min. 8. An application of the early-strength ultra-high performance cement-based material for rapid reinforcement of flexural members as claimed in any one of claims 1-5, characterized in that, the early-strength ultra-high performance cement for rapid reinforcement of said flexural members The base material is used as a repair and reinforcement material for damaged and flexural members.