CN113773025B

CN113773025B - Radiation-proof ultra-high performance concrete and preparation method thereof

Info

Publication number: CN113773025B
Application number: CN202111170471.3A
Authority: CN
Inventors: 吕亚军; 管俊峰; 白卫峰; 陈记豪; 秦一鸣; 樊付军; 徐军翔
Original assignee: North China University of Water Resources and Electric Power
Current assignee: North China University of Water Resources and Electric Power
Priority date: 2021-10-08
Filing date: 2021-10-08
Publication date: 2022-12-27
Anticipated expiration: 2041-10-08
Also published as: CN113773025A

Abstract

The invention discloses novel radiation-proof ultrahigh-performance concrete and a preparation method thereof, and belongs to the technical field of radiation-proof concrete. The novel radiation-proof ultrahigh-performance concrete is prepared by replacing fine aggregates in the ultrahigh-performance concrete with partial or all magnetite powder in equal volume; the raw materials of the ultra-high performance concrete comprise: cementing material, fine aggregate, high efficiency water reducing agent, water and high tensile strength fiber. The MUHPC prepared by replacing fine aggregates in the ultra-high performance concrete with partial or total equivalent volume of magnetite powder has the advantages of high density, excellent radiation resistance, good working performance, satisfactory static and dynamic compressive strength and good high temperature resistance.

Description

Radiation-proof ultrahigh-performance concrete and preparation method thereof

Technical Field

The invention relates to the technical field of radiation-proof concrete, in particular to novel radiation-proof ultrahigh-performance concrete and a preparation method thereof.

Background

Currently, different radiation sources and instruments are widely used in various medical and research centers, petrochemical and oil refining industries, nuclear power plants, agriculture and other fields. Meanwhile, nuclear shielding technology is also receiving high attention from the public. Generally, gamma rays and neutron rays are the most damaging types of radiation released by nuclear explosions or radioactive wastes. The risk of these radiations comes mainly from their high osmotic and ionizing energies, which can destroy normal human cells and cause genetic mutations. Effective radiation shielding of nuclear facilities is important because of the problems of reduced immunity, cancer, and even immediate death associated with long-term exposure to nuclear radiation.

The existing results show that the high atomic number element and the high-density material have good radiation attenuation effect. Common gamma ray shielding materials include iron, tungsten, lead, concrete, metal alloys and heavy aggregates, with lead being the most widely used element since the discovery of gamma rays. Lead has a high atomic number and density and has a good probability of photoelectric effect. Currently, most hospitals and laboratories use lead plates as the primary radiation barrier. However, certain characteristics of lead, such as toxicity, low mechanical properties and poor stability, are undesirable. Concrete has become the most widely used radiation shielding material due to the characteristics of abundant raw materials, low cost, good durability, simple production and the like. However, the radiation-proof concrete prepared at present generally has the problems of good radiation-proof performance and low strength. With the development of nuclear power technology, the power of a nuclear reactor is higher and higher, and the design service life is longer and longer. Therefore, the development of the radiation-proof concrete with high strength and high durability has important practical significance.

Disclosure of Invention

The invention aims to provide novel radiation-proof ultrahigh-performance concrete (MUHPC) and a preparation method thereof.

In order to achieve the purpose, the invention provides the following technical scheme:

one of the technical schemes of the invention is as follows: the novel radiation-proof ultrahigh-performance concrete is prepared by replacing fine aggregates in the ultrahigh-performance concrete with part or all of magnetite powder in equal volume.

The ultra-high performance concrete (UHPC) is a novel cement-based composite material, has ultra-high strength, good toughness and durability, and has very wide application prospect. The superior performance of UHPC benefits from its compact design. The good grading makes it compact and the low porosity makes it effective against the attack of harmful media. The low water-gel ratio causes a large amount of unhydrated cement particles in the interior, so that the cement particles have certain self-repairing capability and can meet the high-performance requirements of engineering structures in various severe environments. The magnetite powder is partially or completely substituted for fine aggregate in the ultrahigh-performance concrete in equal volume, so that the novel radiation-proof ultrahigh-performance concrete with the radiation-proof function is prepared.

Preferably, the ultra-high performance concrete comprises the following raw materials in parts by mass: 850-1100 parts of cementing material, 900-1100 parts of fine aggregate, 25-50 parts of high-efficiency water reducing agent, 180-210 parts of water and 78-156 parts of high tensile strength fiber.

Preferably, the cementing material comprises cement, fly ash and silica fume, wherein the mass ratio of the cement to the fly ash to the silica fume is 8 (1.8-2.0) to (0.9-1).

Preferably, the fine aggregate is river sand.

Preferably, the water reducing rate of the high-efficiency water reducing agent is 25-35%.

Preferably, the high tensile strength fibers are steel fibers.

Preferably, the steel fibers have a length of 6 to 18mm and a diameter of 0.12 to 0.30mm.

Preferably, the grain diameters of the magnetite powder and the fine aggregate are both less than or equal to 1.18mm.

The second technical scheme of the invention is as follows: the preparation method of the novel radiation-proof ultrahigh-performance concrete comprises the following steps: and (3) uniformly mixing the cementing material and the fine aggregate, continuously adding water and a water reducing agent, uniformly stirring, finally adding the high-tensile-strength fiber, and uniformly stirring to prepare the novel radiation-proof ultrahigh-performance concrete.

The invention has the following beneficial technical effects:

the MUHPC prepared by replacing fine aggregates in the ultra-high performance concrete with partial or total equivalent volume of magnetite powder has the advantages of high density, excellent radiation resistance, good working performance, satisfactory static and dynamic compressive strength and good high temperature resistance.

The addition of the magnetite powder can effectively improve the radiation shielding performance of UHPC, and the higher the substitution rate of the magnetite powder is, the higher the radiation resistance performance of the magnetite powder is. Compared with UHPC, the radiation resistance of MUHPC is respectively improved by 8.4%, 10.1%, 23.0%, 24.6% and 31.3% under the condition that the replacement rate of magnetite powder in MUHPC is 20%, 40%, 60%, 80% and 100%.

Magnetite powder, as an inert fine aggregate, does not change the type of cement hydration products, but improves the microporous structure of MUHPC by irregular shape and packing effect, making it more dense, thus contributing to its mechanical and radiation shielding properties.

Drawings

FIG. 1 is a macroscopic view of magnetite powder and natural river sand used in the present invention, wherein (a) is magnetite powder and (b) is natural river sand.

FIG. 2 is a scanning electron micrograph of magnetite powder used in the present invention.

FIG. 3 shows the results of fluidity measurements of UHPC and MUHPC in example 1.

FIG. 4 is the static compressive strength measurements of UHPC and MUHPC in example 1.

FIG. 5 shows the results of measurement of dynamic compressive strength of UHPC in R0 group in example 1.

FIG. 6 shows the results of the dynamic compressive strength measurements of the R100 group MUHPC of example 1.

FIG. 7 shows the results of the measurement of the shielding properties at room temperature of R0 group UHPC and R100 group MUHPC in example 1.

FIG. 8 is a graph of the compressive strength measurements of UHPC and MUHPC of example 1 after various high temperature exposures.

FIG. 9 is a macroscopic view of the R100 group of MUHPCs of example 1 after different high temperature exposures, where (a) is at 200 deg.C, (b) is at 400 deg.C, and (c) is at 600 deg.C.

Figure 10 is an XRD pattern of UHPC and MUHPC in example 1.

Fig. 11 is an SEM image of a sample of R100 group MUHPC particles of example 1, wherein (a) is an SEM image at 200 x magnification and (b) is an SEM image at 500 x magnification.

FIG. 12 is a histogram of the pore size distribution of UHPC and MUHPC in example 1.

FIG. 13 is a graph of pore structure of the R100 group MUHPC in example 1 for different temperature vs. pore size distributions, where (a) is cumulative pore volume and (b) is pore size distribution.

Detailed Description

Reference will now be made in detail to various exemplary embodiments of the invention, the detailed description should not be construed as limiting the invention but as a more detailed description of certain aspects, features and embodiments of the invention. It is to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

In addition, for numerical ranges in the present disclosure, it is understood that each intervening value, to the upper and lower limit of that range, is also specifically disclosed. Every smaller range between any stated value or intervening value in a stated range and any other stated or intervening value in a stated range is encompassed within the invention. The upper and lower limits of these smaller ranges may independently be included or excluded in the range.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention.

As used herein, the terms "comprising," "including," "having," "containing," and the like are open-ended terms that mean including but not limited to.

The cement used in the invention is P.II 52.5 Portland cement produced by Henan Yongan cement Co.Ltd; the used fly ash is first-grade fly ash provided by Rongchang environmental protection material factories; the used silica fume is produced by Luoyang Yumin micro silicon powder limited company; the chemical composition of each raw material is shown in table 1.

The density of the magnetite powder used in the invention produced by a factory for strengthening Jiashu water purification material is 5100 kg/m ³ The chemical components of the magnetite powder with the grain diameter less than or equal to 1.18mm are shown in a table 2.

The fine aggregate used in the invention has a density of 2650kg/m ³ Natural river sand with grain size less than or equal to 1.18mm.

The high-efficiency water reducing agent used by the invention is a polycarboxylic acid high-efficiency water reducing agent produced by Jiangsu Subert company, and has the water reducing rate of 30 percent and the solid content of 30 percent.

The high tensile strength fiber used in the invention is a copper-plated steel fiber with the length of 13mm and the diameter of 0.22mm produced by Iphiger company.

TABLE 1 chemical composition of cement, silica fume and fly ash used in the present invention (%)

	Na ₂ O	MgO	Al ₂ O ₃	SiO ₂	P ₂ O ₅	SO ₃	K ₂ O	CaO	Fe ₂ O ₃	LOI
											Cement	0.07	1.73	4.24	18.25	0.08	3.25	0.87	65.03	3.38	3.10
Silica fume	0.25	0.37	0.22	94.85	0.13	0.79	0.64	0.32	0.18	2.25
											Fly ash	0.28	0.36	38.85	46.82	0.07	0.62	0.84	7.8	2.85	1.51

TABLE 2 chemical composition of magnetite used according to the invention

	MgO	Al ₂ O ₃	SiO ₂	CaO	Fe ₂ O ₃	TiO ₂	LOI
								Content (%)	1.99	5.52	13.8	4.15	49.31	24	1.23

Example 1

Respectively replacing 20%, 40%, 60%, 80% and 100% of fine aggregates in UHPC with magnetite powder in the same volume to prepare MUHPC, which is respectively marked as R20, R40, R60, R80 and R100; UHPC without magnetite powder is R0.

When magnetite powder is made of fine aggregate with the same volume, an improved Andreasen and Andersen (A & A) model is adopted, see formula (1), a compact particle stacking framework is designed, and MATLAB software is used for adjusting the proportion of each material, so that the best fit between a synthetic mixture and a target curve is achieved. On the basis of constant volume replacement, magnetite powder with different replacement levels of 20%, 40%, 60%, 80% and 100% is used to replace the fine aggregate to obtain the mixing ratio of MUHPC.

In the formula (1), D represents a particle size (mm), P (D) represents a solid portion smaller than the size D, and D _max Denotes the maximum dimension (mm), D, of the particles used _min Represents the minimum size (mm) of the particles used, q represents the distribution modulus, and the q value of river sand and magnetite powder is fixed to 0.23 in this example.

The raw material mixing ratio of each set of experiments is shown in table 3.

TABLE 3 mixing ratio (kg/m) of UHPC and MUHPC ³ )

The preparation steps are as follows:

putting the silica fume, the cement, the fly ash and the fine aggregate into a mortar stirrer, and stirring for 2 minutes at a low speed (140 +/-5 r/min); adding water and a polycarboxylic acid high-efficiency water reducing agent, and continuing stirring at a low speed for 3 minutes; finally, copper-plated steel fibers were slowly added and mixing was continued at high speed (285. + -.5 r/min) for 2 minutes to produce UHPC and MUHPC.

And (3) performance measurement:

(1) Flowability of UHPC and MUHPC prepared in example 1

The flowability of freshly stirred UHPC and MUHPC was tested according to BS EN1015-3 using a truncated cone with a top diameter of 70mm, a bottom diameter of 100mm and a height of 60 mm. First, freshly mixed UHPC or MUHPC is placed in two layers into a mold. Then, the jump stand is started after the mold is vertically lifted. After 25 jumps, the two diameters of the mortar perpendicular to each other were measured, and the average of the measurements for each group was the fluidity of fresh UHPC and MUHPC, and the measurements are shown in FIG. 3.

As can be seen from fig. 3, the fluidity of MUHPC decreases significantly with increasing magnetite content, and the relationship between the two is approximately linear. The flow of MUHPC decreased to 233mm corresponding to 100% displacement, which was about 16% lower than UHPC. This is probably due to the fact that river sand particles are generally round and smooth, while magnetite is irregular and rough-surfaced. Therefore, substitution of magnetite powder will increase the friction between the particles in the MUHPC mixture and result in a reduction of its flowability. However, it is important to note that the fluidity of MUHPC mixture is only slightly reduced, and even MUHPC with a substitution rate of 100% can maintain a high fluidity, and thus it is not important to affect its application in engineering construction.

(2) Determination of static compressive Strength of UHPC and MUHPC prepared in example 1

The prepared UHPC and MUHPC were cast to 40X 160mm ³ In the mold of (1), the sample is demolded 24 hours after casting, and then put into a standard curing room (temperature =20 ± 2 ℃, relative humidity is more than or equal to 95%) for curing for 28 days. Measurement static compressive strengths of UHPC and MUHPC were determined according to BS EN-196-1 using an electrohydraulic servo tester with a load rate of 2.4kN/s, and the results are shown in FIG. 4.

As can be seen from fig. 4, the compressive strength of the UHPC and MUHPC samples varied similarly with the age of maintenance, i.e. the longer the age of maintenance, the higher the compressive strength. Meanwhile, after the magnetite powder is used for replacing natural river sand, the compressive strength of MUHPC is slightly reduced. Compared with UHPC, the 28-day compressive strength of MUHPC samples with 20%, 40%, 60%, 80%, and 100% magnetite replacement was reduced by 2.56%, 4.49%, 3.2%, and 4.49%, respectively. The average reduction rate was 3.6%, indicating that the addition of magnetite did not have a significant negative impact on the compressive strength of MUHPC.

(3) Determination of the dynamic compressive Strength of the R0 group UHPC and R100 group MUHPC in example 1

Test blocks of R0 group UHPC and R100 group MUHPC after being cured for 28 days according to standard curing procedures are cut into the size of 12mm multiplied by 45mm, the UHPC and MUHPC test blocks are subjected to dynamic compressive strength test by adopting an electro-hydraulic servo high-speed test system, the sampling frequency of a data acquisition system is 65kHz, the impact speed is respectively set to be 0.5m/s, 1m/s, 3m/s and 5m/s, the measurement result of the R0 group UHPC is shown in figure 5, and the measurement result of the R100 group MUHPC is shown in figure 6.

As can be seen in fig. 5 and 6, the stress development at different impact loading rates for R0 and R100 are very similar, with high impact rates generally corresponding to high dynamic compressive strength. For example, the dynamic strength of R100 is 149MPa, 160MPa, 206MPa and 218MPa corresponding to impact velocities of 0.5m/s, 1m/s, 3m/s and 5m/s, respectively, and the dynamic strength is improved by 0-46.3% compared to the static compressive strength of R100. The dynamic compressive strength of R100 is slightly lower than R0 at the same impact load, probably due to the lower Mohs hardness of magnetite. It is noted, however, that the dynamic compressive strength of R100 is still close to or in excess of 150MPa, indicating that MUHPC can provide high impact resistance.

(4) Determination of the Shielding Performance at Room temperature of UHPC and MUHPC in example 1

The shielding performance of the 28-day-old blocks of 150X 150mm cross-sectional size and 1, 2, 3, 4 and 5cm thickness was tested by gamma-ray spectroscopy (Cs-137 as radiation source, 662keV energy) and evaluated by the linear attenuation coefficient of μ, the calculation results are given in Table 4. Mu represents the probability of gamma ray being absorbed through the material per unit distance, and is defined as formula (2), wherein the higher mu, the stronger the shielding performance of the material, and the linear attenuation coefficients of R0 group UHPC and R100 group MUHPC are shown in FIG. 7.

In formula (2), I0 is the initial radiation intensity (keV), I is the intensity after transmission of the radiation (keV), and x is the thickness of the test material (cm).

TABLE 4 Density and Linear attenuation coefficient of each set of samples

As can be seen from table 4, the linear damping coefficient increases as the content of magnetite powder increases, and specifically, the linear damping coefficients of R20, R40, R60, R80 and R100 are 8.4%, 10.1%, 23.0%, 24.6% and 31.3% higher than that of R0. Therefore, it can be concluded that the radiation shielding performance of MUHPC is significantly improved as the magnetite powder content increases.

The strong radiation shielding performance of MUHPC can be attributed to two aspects. On the one hand, as can be seen from table 4, the density of MUHPC increases significantly with magnetite replacement. Compared with R0, the density of R100 is improved by 40.0%; on the other hand, magnetite powder contains high contents of iron, titanium and other elements having high atomic numbers (table 2). When gamma rays enter concrete, photons of the gamma rays collide with extra-nuclear electrons of the elements, so that the transmission force of the gamma rays is weakened, and the radiation shielding performance of the MUHPC is improved.

(5) The high temperature resistance of UHPC and MUHPC in example 1 was determined

The 28-day-old UHPC and MUHPC samples were prepared for high temperature treatment and were dried in an oven at 105 ℃ for 24 hours in advance to avoid high temperature decrepitation. According to the RILEM standard, a UHPC or MUHPC sample is heated in a muffle furnace at a rate of 3 ℃/min to a target temperature and held constant for 1 hour, after which the sample is cooled to room temperature at a rate of 3 ℃/min. The target temperatures were set to 200, 400 and 600 ℃. After high temperature exposure, the samples were tested for compressive strength and gamma ray shielding performance.

The results of the measurements of the compressive strength of the samples after various high temperature exposures are shown in FIG. 8. It can be seen from FIG. 8 that the compressive strength of all the samples shows a similar trend with the change of the exposure temperature, i.e., the compressive strength increases and then decreases with the increase of the temperature. Specifically, the compressive strength of the sample reached a maximum at 200 ℃ and then gradually decreased. For example, after 200 ℃ exposure, the compressive strength of the R0, R20, R40, R60, R80, and R100 samples increased by 1.28%, 4.6%, 6.71%, 11.26%, 13.25%, and 6%, respectively, over room temperature. This may be attributed to the activation of the unhydrated and insufficiently hydrated cement material by high temperatures, thereby increasing the compressive strength of the test specimen through rehydration reactions. As the temperature increased to 400 ℃ and 600 ℃, the compressive strength of the test specimens began to gradually decrease. For example, after 600 ℃ exposure, the compressive strength of the R0, R20, R40, R60, R80, and R100 samples decreased by 33.3%, 18.4%, 14.1%, 16.6%, and 18.8%, respectively. After adding magnetite powder, the compressive strength of MUHPC was higher than that of UHPC regardless of the exposure temperature of 200 ℃, 400 ℃ or 600 ℃. For example, the compressive strength of MUHPC with 20%, 40%, 60%, 80% and 100% magnetite replacement was increased by 19.2%, 23.1%, 21.1% and 16.3%, respectively, compared to UHPC. After the magnetite powder is added, the compressive strength is averagely improved by 20.2 percent, which shows that the MUHPC has good high-temperature performance.

Fig. 9 shows the macroscopic change of the R100 specimens after different high temperature exposures, from fig. 9 it can be observed that there is little change in the appearance of the specimens after 200 c or 400 c exposure, while the specimens after 600 c exposure show significant microcracking. The cleavage of MUHPC can be by Ca (OH) ₂ The conversion to CaO in the range of 400-600 c explains that the hardened cement slurry expands and then contracts, the calcium hydroxide is converted to lime and water vapor during heating, and the expansion of lime during cooling causes severe damage, which may be the main cause of the decrease in concrete strength.

The radiation shielding performance of the MUHPC specimens of the R100 group was measured at high temperatures according to the method for measuring shielding performance of item (4), taking into account the presence of significant microcracks when the MUHPC specimens of the R100 group were exposed to 600 ℃ (fig. 9), only exposure temperatures of 200 ℃ and 400 ℃ were used. The corresponding linear attenuation coefficients of R100 after the temperature exposure are respectively 0.1738cm ^-1 And 0.1908cm ^-1 Respectively 13.18% and 5.5% lower than the room temperature. Clearly, the radiation shielding performance of MUHPC is reduced after high temperature exposure. The reason for the reduced radiation protection performance may be that the MUHPC pore structure is damaged by high temperatures, resulting in increased porosity. However, it can be noted that the linear decay coefficient of R100 is still 13.0% and 24.1% higher than UHPC after 200 ℃ and 400 ℃ exposure. This means that MUHPC has good radiation shielding properties even after high temperature exposure (below 400 ℃).

(6) The hydration products, microscopic morphology and pore structure of UHPC and MUHPC in example 1 were determined

XRD measurement of powder samples extracted from 28-day-old UHPC and MUHPC samples was performed using an X-ray diffractometer (Bruker D8), and the measurement results are shown in FIG. 10, wherein each result in FIG. 10 is R0, R20, R40, R60, R80, R100 in the order from bottom to top, and A in FIG. 10 represents albite; CH represents Boragite; c ₂ S represents dicalcium silicate; c ₃ S represents tricalcium silicate; e represents ettringite; p represents potassium feldspar; q represents quartz.

As can be seen from FIG. 10, the hydration products remained unchanged in the samples with and without magnetite powder, and only ettringite and Portland stone, C, were detected in the hydration products of all samples ₃ S and C ₂ The peak intensity of S is evident in all mixtures, especially in the magnetite-containing samples, while Ca (OH) ₂ The peak intensity of (2) decreased with the increase in magnetite powder, which means that Ca (OH) was generated in MUHPC ₂ And less. This phenomenon may be due to inhibition of the hydration process due to dilution effects. At the same time, it also reduces Ca (OH) ₂ Damage caused when heated at high temperatures explains the excellent thermal performance of MUHPC.

The microstructure of the UHPC and MUHPC particle samples was observed using a hitachi S4800 field emission scanning electron microscope and the samples were soaked in ethanol for 24 hours and then dried in a vacuum oven to stop hydration in advance, and the pore structure of the UHPC and MUHPC particle samples was analyzed using a mercury intrusion tester (maximum mercury pressure 413MPa, contact angle 140 °) from AutoPore IV 9510 (U.S. Micro metrology Instrument Corporation).

The SEM image of the samples of MUHPC particles of group R100 is shown in fig. 11, and it can be seen from fig. 11 that the microstructure of MUHPC containing magnetite powder appears very dense, and no significant cracks are found in the interface transition zone between magnetite powder and cement slurry, which may be the reason why MUHPC containing magnetite powder still has good mechanical properties, indicating that the addition of magnetite powder has no adverse effect.

The microporous structure information for the UHPC and MUHPC samples is shown in table 5.

TABLE 5 MIP results for UHPC and MUHPC samples

As can be seen from table 5, the total porosity of MUHPC decreases with the addition of magnetite powder. For example, as the magnetite content in MUHPC increases from 0% to 20%, 40%, 60%, 80%, and 100%, the total porosity decreases from 9.41% to 6.7%, 7.84%, 8.5%, 8.03%, and 6.15%.

The pore diameters measured for the UHPC and MUHPC samples were classified into harmless pores (< 20 nm), mesopores (20-50 nm), intermediate capillaries (50-200 nm) and macroscopic capillaries (> 200 nm), and the distribution histograms of pore diameters are shown in fig. 12 (the histogram in fig. 12 is from bottom to top, harmless pores, mesopores, intermediate capillaries and macroscopic capillaries), as can be seen from fig. 12, the proportion of harmless pores in the R0 group is 45%, with the addition of magnetite, the proportion of harmless pores in the R20, R40, R60, R80 and R100 samples is increased to 79%, 57%, 63%, 59% and 70%, respectively, compared to the R0 group, the proportion of harmless pores is significantly increased, while the proportion of large capillaries mainly affecting MUHPC performance is decreased by 55%, 2.5%, 10%, 12.5% and 32.5%, respectively. Porosity is one of the factors affecting the compressive strength of the concrete, and overall, the porosity of each MUHPC sample is low, which is one of the important reasons why MUHPC maintains high strength.

The effect of different temperatures on the pore structure of the R100 group MUHPC is shown in fig. 13, and it can be seen from fig. 13 that the total pore volume increases significantly after heating at 200 ℃ and 400 ℃ compared to the cumulative pore volume of R100 at room temperature. Meanwhile, the number of pores in the 10nm range is significantly increased after heating at 200 ℃, and the pores in the 10nm range are called harmless pores, which may be the reason why the strength of MUHPC is increased after heating at 200 ℃. With increasing temperature, when heating at 400 ℃, MUHPC has significantly deteriorated pore size, larger pore size distribution, and significantly increased harmful porosity, which is also a major cause of the decrease in MUHPC strength.

According to the measurement results, the compression strength of the MUHPC prepared by the invention is in the range of 149-156 MPa, which is much higher than that of most radiation-proof concrete (the compression strength is in the range of 25-58 MPa)Inner). In terms of radiation protection performance, the linear attenuation coefficient of MUHPC is 0.1538-0.2019 cm ^-1 And the radiation protection performance is excellent. Overall, the MUHPC prepared by the present invention has an excellent overall performance.

The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims

1. The radiation-proof ultrahigh-performance concrete is characterized by comprising the following raw materials in parts by mass: 850-1100 parts of cementing material, 900-1100 parts of fine aggregate, 25-50 parts of high-efficiency water reducing agent, 180-210 parts of water and 78-156 parts of high tensile strength fiber;

the cementing material comprises cement, fly ash and silica fume, wherein the mass ratio of the cement to the fly ash to the silica fume is 8 (1.8-2.0) to 0.9-1;

the high tensile strength fiber is steel fiber;

the fine aggregate is magnetite powder with the particle size of less than or equal to 1.18mm;

the water reducing rate of the high-efficiency water reducing agent is 25-35%;

the length of the steel fiber is 6-18 mm, and the diameter of the steel fiber is 0.12-0.30 mm.

2. The preparation method of the radiation-proof ultra-high performance concrete as claimed in claim 1, characterized by comprising the following steps: and (3) uniformly mixing the cementing material and the fine aggregate, continuously adding water and a water reducing agent, uniformly stirring, finally adding the high-tensile-strength fiber, and uniformly stirring to obtain the radiation-proof ultrahigh-performance concrete.