CN117902874A

CN117902874A - Quick-hardening high-strength steel fiber reinforced concrete and preparation method thereof

Info

Publication number: CN117902874A
Application number: CN202410080655.8A
Authority: CN
Inventors: 沈汝堉; 伍开盛; 方舒; 姜海波
Original assignee: Guangdong University of Technology
Current assignee: Guangdong University of Technology
Priority date: 2024-01-19
Filing date: 2024-01-19
Publication date: 2024-04-19
Anticipated expiration: 2044-01-19
Also published as: CN117902874B

Abstract

The invention relates to the technical field of concrete, in particular to quick-hardening high-strength steel fiber reinforced concrete and a preparation method thereof. The quick-hardening high-strength steel fiber reinforced concrete comprises the following preparation raw materials in parts by weight: 450-530 parts of sulphoaluminate cement, 150-180 parts of silicate cement, 134-198 parts of gypsum, 400-1025 parts of quartz sand, 200-650 parts of bauxite, 187-240 parts of silica fume, 20-67 parts of heavy calcium powder, 134-217 parts of steel fiber, 23-67 parts of water reducer and 204-331 parts of water; according to the scheme, under the mutual synergistic effect of the sulphoaluminate cement, the silicate cement, the gypsum, the quartz sand, the bauxite, the silica fume, the heavy calcium powder, the steel fiber, the water reducing agent and the water, the cracking risk of the concrete is reduced, the strength of the concrete is improved, the cement consumption is reduced, and the manufacturing cost of the concrete is reduced.

Description

Quick-hardening high-strength steel fiber reinforced concrete and preparation method thereof

Technical Field

The invention relates to the technical field of concrete, in particular to quick-hardening high-strength steel fiber reinforced concrete and a preparation method thereof.

Background

The fast hardening concrete has extremely high setting speed, high early strength, good freezing resistance and excellent cohesiveness, and is widely applied to the construction process of emergency rescue or crack repair. Early strength agents are often added to promote cement hydration when preparing fast hardening concrete, thereby achieving the aim of accelerating early strength development of the concrete. However, after the early strength agent is used, the internal structure of the concrete is uneven and not compact, a certain amount of expansion can be generated, and honeycomb pitting surface is easy to appear on the surface of the concrete, so that the concrete is easy to crack and deform in the later period. Meanwhile, the non-uniformity of the internal structure also reduces the long-term strength of the concrete.

In summary, in the process of preparing fast hardening concrete, the problems of reducing the risk of cracking concrete, improving the strength of concrete, reducing the consumption of cement and saving the cost are needed to be solved.

Disclosure of Invention

In view of the above, the invention provides a rapid hardening high-strength steel fiber reinforced concrete and a preparation method thereof, which are used for solving the technical problems of high risk of cracking, low strength and high cost of the existing rapid hardening concrete.

The invention provides a rapid hardening high-strength steel fiber reinforced concrete, which comprises the following preparation raw materials in parts by weight:

450-530 parts of sulphoaluminate cement, 150-180 parts of silicate cement, 134-198 parts of gypsum, 400-1025 parts of quartz sand, 200-650 parts of bauxite, 187-240 parts of silica fume, 20-67 parts of heavy calcium powder, 134-217 parts of steel fiber, 23-67 parts of water reducer and 204-331 parts of water.

Specifically, sulfoaluminate cement, silicate cement, gypsum, silica fume and heavy calcium powder in the concrete can react with water to form needle-shaped crystals such as ettringite and branch-tendril-shaped fiber crystals, gaps in the concrete can be filled by adding quartz sand and bauxite, the compactness of a concrete interface is further improved, the shrinkage rate and the expansion rate of the concrete are reduced, meanwhile, the bauxite is used as an internal curing agent, and the loose porous structure can release water in the concrete to promote the unhydrated cement matrix to be continuously hydrated, so that the occurrence of delay ettringite is reduced, and the cracking of the concrete is reduced; the compressive strength of the steel fibers uniformly distributed in the concrete is further improved, and the problems of poor concrete fluidity and lower workability caused by adding the steel fibers are solved under the action of the silica fume, the heavy calcium powder and the water reducing agent, so that the practicability of the concrete is improved.

Preferably, the preparation raw materials comprise the following components in parts by weight:

480-500 parts of sulphoaluminate cement, 160-170 parts of silicate cement, 145-165 parts of gypsum, 400-1025 parts of quartz sand, 200-650 parts of bauxite, 187-240 parts of silica fume, 30-50 parts of heavy calcium powder, 150-190 parts of steel fiber, 30-55 parts of water reducer and 220-300 parts of water.

It can be understood that the invention optimizes the raw material proportion of the concrete, can further improve the compressive strength and the workability of the concrete, and has the effect of quick hardening and retarding.

Preferably, the strength of the sulphoaluminate cement is greater than or equal to 42.5MPa.

More preferably, the sulphoaluminate cement is gray low-alkalinity quick hardening sulphoaluminate cement.

Specifically, the gray low-alkalinity quick-hardening sulphoaluminate cement has the advantages of quick hardening, high strength, low alkalinity and low expansion, and the gray low-alkalinity quick-hardening sulphoaluminate cement also has the characteristic of low production energy consumption, realizes quick hardening of concrete, reduces the energy consumption of concrete production while achieving high strength, and saves energy and reduces emission.

Preferably, the strength of the Portland cement is greater than or equal to 52.5MPa.

Preferably, the water-powder ratio of the gypsum is 22-26% when the gypsum is mixed, and the compressive strength of the gypsum after the gypsum is mixed with water is 98MPa is yellow high-strength gypsum.

Specifically, the yellow high-strength gypsum is a novel building material, and the yellow high-strength gypsum is selected to promote hydration reaction of cement, increase the generation of cement gel, and enable the internal structure of concrete to be more compact, thereby enhancing the strength of the concrete and improving the crack resistance of the concrete.

Preferably, the quartz sand is medium sand with the grain diameter of 0.35-0.50 mm and the fineness modulus of 2.5-3.0.

Preferably, the bauxite has a particle size of 1-3mm and a fineness modulus of 2.5-3.0.

More preferably, the bauxite is calcined bauxite.

Specifically, the calcined bauxite has more pores, can retain moisture, can keep the interior of the concrete moist in the concrete, and can prevent the concrete from being dried prematurely, thereby reducing the cracking probability of the concrete and enhancing the strength of the concrete.

Preferably, the silica fume contains more than 85% of silica by mass of silica fume;

The specific gravity of heavy calcium in the heavy calcium powder is greater than or equal to 2.711.

Preferably, the length of the steel fiber is 10-15 mm, and the diameter is 0.2-0.5 mm.

More preferably, the length of the steel fiber is 13mm, the diameter is 0.2mm, and the tensile strength is 2850MPa.

Preferably, the water reducer is a polycarboxylic acid high-performance water reducer.

More preferably, the water reducing agent has a water reducing effect of 40% and the weight percentage of the effective solid components is 20%.

The invention provides a preparation method of quick-hardening high-strength steel fiber reinforced concrete, which comprises the following steps:

step 1: mixing sulphoaluminate cement, portland cement, gypsum, quartz sand, bauxite, silica fume and heavy calcium powder, and fully and uniformly stirring to obtain a mixture 1;

Step 2: fully mixing water and a water reducing agent, adding the mixture of water and the water reducing agent into the mixture 1, and fully stirring to obtain a mixture 2;

Step 3: and (3) uniformly adding the steel fibers into the mixture 2 through a screen, and fully stirring to obtain the rapid hardening high-strength steel fiber reinforced concrete.

From the above technical scheme, the invention has the following advantages:

The invention provides a rapid hardening high-strength steel fiber reinforced concrete, which comprises the following preparation raw materials in parts by weight: 450-530 parts of sulphoaluminate cement, 150-180 parts of silicate cement, 134-198 parts of gypsum, 400-1025 parts of quartz sand, 200-650 parts of bauxite, 187-240 parts of silica fume, 20-67 parts of heavy calcium powder, 134-217 parts of steel fiber, 23-67 parts of water reducer and 204-331 parts of water. According to the scheme, under the mutual synergistic effect of the sulphoaluminate cement, the silicate cement, the gypsum, the quartz sand, the bauxite, the silica fume, the heavy calcium powder, the steel fiber, the water reducing agent and the water, the cracking risk of the concrete is reduced, the strength of the concrete is improved, the cement consumption is reduced, and the manufacturing cost of the concrete is reduced.

Drawings

In order to more clearly illustrate the embodiments of the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only some embodiments of the invention, and that other drawings can be obtained from these drawings without inventive faculty for a person skilled in the art.

Fig. 1 is a flowchart of a preparation of a rapid hardening high strength steel fiber reinforced concrete according to an embodiment of the present invention.

Detailed Description

The following description of the technical solutions in the embodiments of the present invention will be clear and complete, and it is obvious that the described embodiments are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.

The invention provides a quick-hardening high-strength steel fiber reinforced concrete and a preparation method thereof, which are used for improving the strength of the concrete and reducing the cracking risk and the manufacturing cost of the concrete.

Wherein, the raw materials or reagents used in the following examples are all commercially available or self-made.

Example 1

The present embodiment provides a first rapid hardening high strength steel fiber reinforced concrete, the preparation process of which is shown in fig. 1, and the specific preparation steps are as follows:

Step 1: adding sulphoaluminate cement, portland cement, gypsum, quartz sand, bauxite, silica fume and heavy calcium powder into a stirrer according to the mass parts of each component in the example 1 in the following table 1, and stirring for 120 seconds to obtain a mixture 1;

Step 2: adding water and a water reducing agent into the mixture 1 in the step 1, and continuously stirring for 60 seconds to obtain a mixture 2;

step 3: and (3) uniformly adding the steel fibers into the mixture 2 in the step (2) through a screen, and continuously stirring for 60 seconds to obtain the rapid hardening high-strength steel fiber reinforced concrete.

In this embodiment, all the raw materials are required to be stirred uniformly, the particle sizes of the quartz sand and the bauxite are required to be controlled to be 1-3 mm, and when the steel fibers are added, the steel fibers are required to be added into the mixture uniformly by using a screen mesh, so that the concrete fluidity and the like are prevented from being influenced by agglomeration. The strength of the sulphoaluminate cement is 42.5MPa or more, the strength of the silicate cement is 52.5MPa, the water-powder ratio of gypsum is 24%, the fineness modulus of quartz sand is 2.5-3.0, the fineness modulus of bauxite is 2.5-3.0, steel fibers are copper-plated straight steel fibers with the length of 13mm and the tensile strength of 2850MPa with the diameter of 0.2mm, and the water reducer is a polycarboxylic acid high-performance water reducer.

The concrete of the embodiment is naturally cured for 7 days, the concrete needs to be subjected to watering curing during the natural curing period, the surface of a concrete test piece needs to be completely wetted, and the concrete test piece is subjected to conventional curing for 21 days after the natural curing is completed three times a day, and the concrete curing is performed for 28 days in total. The concrete of this example was tested for 4h compressive strength, 7d compressive strength, 28 day compressive strength, slump, initial setting time and final setting time during this period, respectively, for 6 data, and the test results are shown in table 2.

After 28 days of concrete curing is completed, a temperature cycle experiment is carried out on a concrete test piece, the condition of the concrete under sunlight temperature cycle is simulated through uninterrupted 4h heating and 3h cooling, the experiment cycle times are 100 times, the target temperature of each heating is 75 ℃, the target temperature of cooling is 25 ℃, the compressive strength experiment is carried out on the concrete after the temperature cycle experiment is completed, and the detection result is shown in table 2.

Compared with the rapid hardening concrete prepared by using an early strength agent, the rapid hardening high-strength steel fiber reinforced concrete prepared by the embodiment has the advantages that on one hand, the water-cement ratio is reduced by using the water reducer, so that the service life of the prepared concrete is longer, the cracking possibility of the concrete is smaller, honeycomb pitting surfaces are less likely to occur, and under the condition that the proportion of various raw materials and the strength of the concrete are not changed, the water reducer of the concrete with the mass of about 0.5 percent of the mixed cement is adopted, the cement amount is saved by more than 15-30 percent, and the manufacturing cost of the rapid hardening concrete is greatly reduced; on the other hand, the concrete internal curing technology of the implementation is to mix the dispersed pre-water absorbing material into the concrete, and the water absorbing material releases water within a period of time after the concrete is coagulated and hardened, so that the hardened concrete is cured, thereby reducing the cracking risk caused by the self shrinkage of the concrete, and in the preparation of the concrete, the high-strength aggregate with a porous structure, namely the calcined bauxite fine aggregate, is added to replace the fine aggregate, thereby effectively reducing the cracking risk and improving the mechanical property of the concrete.

Example 2

This example provides a second type of rapid hardening high strength steel fiber reinforced concrete, prepared in the same manner as in example 1, with the proportions of the components as described in example 2 of table 1.

In the embodiment, all the raw materials are required to be uniformly stirred, the particle sizes of quartz sand and bauxite are required to be controlled to be 1-3 mm, and when steel fibers are added, a screen is required to be used for uniformly adding the steel fibers into the mixture, so that the concrete fluidity and the like are prevented from being influenced by agglomeration; the strength of the sulphoaluminate cement is 42.5MPa or more, the strength of the silicate cement is 52.5MPa, the water-powder ratio of gypsum is 24%, the fineness modulus of quartz sand is 2.5-3.0, the fineness modulus of bauxite is 2.5-3.0, steel fibers are copper-plated straight steel fibers with the length of 13mm and the tensile strength of 2850MPa with the diameter of 0.2mm, and the water reducer is a polycarboxylic acid high-performance water reducer.

Example 3

This example provides a third fast hardening high strength steel fiber reinforced concrete, prepared in the same manner as in example 1, with the proportions of the components as described in example 3 of table 1.

Example 4

This example provides a fourth fast hardening high strength steel fiber reinforced concrete prepared in the same manner as in example 1, with the proportions of the components as described in example 4 of table 1.

In the embodiment, all the raw materials are required to be uniformly stirred, the particle sizes of quartz sand and bauxite are required to be controlled to be 1-3 mm, and when steel fibers are added, a screen is required to be used for uniformly adding the steel fibers into the mixture, so that the concrete fluidity and the like are prevented from being influenced by agglomeration; the strength of the sulphoaluminate cement is 42.5MPa or more, the strength of the silicate cement is 52.5MPa, the water-powder ratio of gypsum is 24%, the fineness modulus of quartz sand is 2.5-3.0, the steel fiber is copper-plated straight steel fiber with the length of 13mm and the diameter of 0.2mm and the tensile strength of 2850MPa, and the water reducing agent is a polycarboxylic acid high-performance water reducing agent.

Example 5

This example provides a fifth rapid hardening high strength steel fiber reinforced concrete, prepared in the same manner as in example 1, with the proportions of the components described with reference to example 5 in table 1.

Example 6

This example provides a sixth fast hardening high strength steel fiber reinforced concrete prepared in the same manner as in example 1, with the proportions of the components as described in example 5 of table 1.

In this embodiment, all the raw materials are required to be stirred uniformly, the particle sizes of the quartz sand and the bauxite are required to be controlled to be 1-3 mm, and when the steel fibers are added, the steel fibers are required to be added into the mixture uniformly by using a screen mesh, so that the concrete fluidity and the like are prevented from being influenced by agglomeration.

Wherein the strength of the sulphoaluminate cement is 42.5MPa or more, the strength of the silicate cement is 52.5MPa, the water-powder ratio of gypsum is 24%, the fineness modulus of quartz sand is 2.5-3.0, the steel fiber is copper-plated straight steel fiber with the length of 13mm and the diameter of 0.2mm and the tensile strength of 2850MPa, and the water reducing agent is a polycarboxylic acid high-performance water reducing agent.

Comparative example 1

The comparative example provides a concrete, which is prepared as follows:

Step 1: according to the mass parts of each component of comparative example 1 in Table 1, sulphoaluminate cement, portland cement, gypsum, quartz sand, silica fume and heavy calcium powder are added into a stirrer, and stirred for 120 seconds to obtain a mixture 1;

step 3: and (3) uniformly adding the steel fibers into the mixture 2 in the step (2) through a screen, and continuously stirring for 60 seconds to obtain the concrete. In this embodiment, all the raw materials are required to be stirred uniformly, the particle sizes of the quartz sand and the bauxite are required to be controlled to be 1-3 mm, and when the steel fibers are added, the steel fibers are required to be added into the mixture uniformly by using a screen mesh, so that the concrete fluidity and the like are prevented from being influenced by agglomeration.

TABLE 1 preparation raw material ratios of examples 1 to 6 and comparative example 1

Remarks: the data of each component in Table 1 represents the parts by mass of each component.

TABLE 2 detection results for examples 1-6 and comparative example 1

Remarks: the original height of the concrete test pieces prepared in examples 1 to 6 and comparative example 1 was 30.2cm.

As can be seen from the detection results in the present invention,

In examples 1-3, the proportion of quartz sand to bauxite is adjusted, and the bauxite can reach better compressive strength in the amount of 200-650 parts, wherein the best effect of example 2. The invention reduces the use amount of quartz sand and the use amount of cement to reduce the cost by adding a large amount of bauxite materials on the premise of not reducing the strength of concrete as much as possible, and the bauxite is about 2.5 yuan per kilogram and the bauxite is about 1.2 yuan per kilogram.

Examples 4 to 6 were adjusted in terms of the amount of the water reducing agent used in examples 1 to 3, and the amount of the water reducing agent used in examples 4 to 5 was smaller than that used in examples 1 to 2, because the use of the water reducing agent can increase fluidity of concrete but impair the strength of such concrete, and therefore the concrete in examples 4 to 5 was stronger, but too small an amount of the water reducing agent was added, resulting in deterioration of fluidity, which was unfavorable for actual construction conditions of engineering. In example 6, too much water reducing agent was added to lower the strength of concrete. The components of examples 1 to 3, namely, the amount of the water reducer of 55 parts, are selected to satisfy both the strength and fluidity requirements.

In comparative example 1, bauxite was not added, and the strength of the prepared concrete was significantly lower than that of example.

From experimental data, each performance of the embodiment of the invention is superior to that of the comparative example, the highest compressive strength of the embodiment reaches 83.6MPa, and the slump is 251mm at the maximum. By utilizing the steel fiber bridging effect, the high-temperature resistant property and internal curing technology of gypsum retarder and bauxite and combining a composite cementing material system of sulfate cement, silicate cement, quartz sand, silica fume and heavy calcium powder, the invention develops the high-strength quick-hardening steel fiber reinforced concrete, and solves the problems of low long-term strength, low durability and easy cracking of the traditional quick-hardening concrete. The high-strength rapid hardening steel fiber reinforced concrete prepared by the technical method has strong processability, larger slump, extremely high early strength and higher long-term strength, the compressive strength of the concrete can reach more than 30MPa after 4 hours, the compressive strength of 7d reaches more than 54.2MPa, and the compressive strength of 28d reaches more than 72.5 MPa; the concrete has the characteristic of temperature change resistance, can still keep higher strength under the condition of multiple day and night temperature difference changes, reduces the use of quartz sand by using bauxite, and reduces the preparation cost of the concrete by using less than 710kg/m ³ of cement.

The concrete slump is larger, so that the concrete slump is better in fluidity and strong in easiness, meets the requirements of construction sites, and can be used for casting construction more conveniently.

In summary, the scheme of the invention has the following beneficial effects:

the cement mortar adopts the optimized cementing material and the proportion thereof, utilizes the hydration reaction of gypsum and sulphoaluminate cement to achieve the effect of rapid hardening and retarding, avoids cracking of concrete caused by severe hydration reaction and meets the actual time requirement of emergency repair engineering.

The invention utilizes the internal curing mechanism of bauxite to reduce the cracking probability of concrete, and meanwhile, the average elastic modulus of the bauxite is 207GPa, so that the bauxite has higher compressive strength, and the compressive strength of the concrete can be improved by about 20 percent by adding the bauxite.

And thirdly, the invention reduces the use amount of quartz sand and the use amount of cement by adding materials such as silica fume, bauxite and the like on the premise of not reducing the strength of concrete as much as possible, thereby reducing the cost and reducing the manufacturing cost.

The invention utilizes the bridging effect and high tensile property of copper-plated straight steel fibers with the tensile strength of 2850MPa, and the steel fibers are uniformly distributed in the concrete through the screen mesh, so that the compressive strength of the concrete is further improved.

The polycarboxylic acid water reducer can generate a layer of water film on the surfaces of cement and aggregate to reduce the sliding resistance among particles, so that the interior of the concrete is uniform and compact, and the problem of nonuniform and non-compact internal structure of the concrete after the early strength agent is used is avoided.

The rapid hardening steel fiber reinforced concrete can be used in a plurality of fields such as bridge expansion joints, bridge deck pavement, rescue repair engineering and the like, and has the characteristics of wide application range and easiness in construction.

The foregoing is merely a preferred embodiment of the present invention and it should be noted that modifications and adaptations to those skilled in the art may be made without departing from the principles of the present invention, which are intended to be comprehended within the scope of the present invention.

Claims

1. The quick-hardening high-strength steel fiber reinforced concrete is characterized by comprising the following preparation raw materials in parts by weight:

2. The rapid hardening high strength steel fiber reinforced concrete according to claim 1, wherein the preparation raw materials comprise, in parts by mass:

3. The rapid hardening high strength steel fiber reinforced concrete of claim 1, wherein the strength of the sulfoaluminate cement is greater than or equal to 42.5MPa.

4. The rapid hardening high strength steel fiber reinforced concrete of claim 1, wherein the portland cement has a strength of 52.5MPa or greater.

5. The rapid hardening high strength steel fiber reinforced concrete according to claim 1, wherein the quartz sand has a particle size of 0.35-0.50 mm and a fineness modulus of 2.5-3.0.

6. The rapid hardening high strength steel fiber reinforced concrete according to claim 1, wherein the bauxite has a particle size of 1 to 3mm and a fineness modulus of 2.5 to 3.0.

7. The rapid hardening high strength steel fiber reinforced concrete according to claim 1, wherein the mass content of silica in the silica fume is 85% or more;

8. The rapid hardening high strength steel fiber reinforced concrete according to claim 1, wherein the length of the steel fiber is 10 to 15mm and the diameter is 0.2 to 0.5mm.

9. The rapid hardening high strength steel fiber reinforced concrete of claim 1, wherein the water reducing agent is a polycarboxylic acid high performance water reducing agent.

10. A method of preparing a rapid hardening high strength steel fiber reinforced concrete according to any one of claims 1 to 9, comprising the steps of: