CN117447149A - A kind of high crack resistance and radiation resistance large volume concrete and its preparation method - Google Patents

Abstract

The invention discloses high-crack-resistance radiation-resistance large-volume concrete, which comprises the following components in parts by weight: 250-300 parts of cement, 10-30 parts of modified boron-containing mine tailings, 60-90 parts of grade II fly ash, 600-900 parts of common sand, 250-1250 parts of cooling aggregate, 250-1250 parts of normal-temperature aggregate and 165 parts of water; the modified boron-containing mine tailings are obtained by grinding industrial waste residues discharged after borax is produced by using boron magnesium ores through high-temperature calcination modification; the loss on ignition is 20% -30%; the content of MgO in the chemical composition is 40-50wt%, B ₂ O ₃ The content is 25-40 wt%; the average particle diameter is 20-50 μm; the invention carries out treatment modification on the boron-containing mine tailings, increases the utilization efficiency of the boron-containing mine tailings in the anti-radiation concrete, and particularly improves the shrinkage cracking resistance of the boron-containing mine tailings in the concrete; through the ice coating and cooling measures of the coarse aggregate, the outlet and pouring temperature of the concrete can be effectively ensured; simultaneously combines the modified boron-containing mine tailings, the ice-coating cooling of aggregate and the physicochemical properties of modified clay to effectively improve the radiation resistance and cracking resistance of mass concrete。

Description

A kind of high crack resistance and radiation resistance large volume concrete and its preparation method

Technical field

The invention belongs to the technical field of concrete materials, and specifically relates to a high-crack-resistant and radiation-resistant large-volume concrete and a preparation method thereof.

Background technique

Due to traditional historical reasons and resource limitations, a large part of my country's electricity comes from coal-fired and other fossil energy power generation. However, coal-fired power generation has low utilization rate, causes serious air pollution, and is the main emission source of greenhouse gases. As an efficient and clean new energy source, nuclear power has unique advantages and is an inevitable choice for optimizing the energy use structure. It is necessary to correctly deal with the problems caused by nuclear energy. A large number of rays produced by the nuclear reaction of nuclear energy, such as α, β, γ, X-rays and neutron rays, can induce a variety of diseases and genetic mutations, posing a great threat to the environment and human health. In order to prevent radiation from harming the human body and the environment, protective bodies must be installed when building buildings with radiation sources. Cement concrete is currently the most widely used radiation protection material, such as the inner and outer shells of nuclear reactors and the solidification of nuclear waste. Currently, the protective materials used for radiation protection mainly include steel plates, lead plates, water, concrete, etc. After comprehensive consideration of the sources, costs, and implementation difficulties of these materials, among these radiation protection materials, the comprehensive technical and economic effect of concrete is undoubtedly the optimal.

On the other hand, the current methods for enhancing the radiation protection capability of concrete mainly include: 1. Increasing the content of heavy metals in single concrete; 2. Increasing the content of light elements in solutions in concrete, etc. With the development of nuclear energy, there are more and higher requirements for nuclear power concrete, such as larger volume, high crack resistance and constant temperature. Therefore, by preparing a low-temperature and high-crack-resistant large-volume nuclear power concrete, it will be of great significance to improve the diversity and adaptability of nuclear power concrete.

Boron-containing mine tailings are industrial waste residues discharged after producing borax from boron-magnesium (iron) ores. More than one million tons of boron-containing mine tailings are produced nationwide every year, and the pollution is serious. Therefore, it is very necessary and urgent to recycle boron-containing mine tailings on a large scale and in new forms to fundamentally solve the pollution problem of boron-containing mine tailings. Chinese invention patent CN 104817304 discloses a method for preparing radiation-resistant concrete from boron-containing mine tailings. The radiation-resistant performance of the concrete is improved by directly adding boron-containing mine tailings to the concrete. However, this invention does not affect the radiation resistance of boron-containing mine tailings. All chemicals are not fully and efficiently utilized.

Contents of the invention

The purpose of the present invention is to provide a high-crack-resistant and radiation-resistant large-volume concrete and a preparation method thereof, by processing and modifying boron-containing mine tailings to increase its utilization efficiency in radiation-resistant concrete, and in particular to improve its resistance in concrete. Shrinkage and cracking performance; through ice-coating and cooling measures for coarse aggregates, the machine-out and pouring temperatures of concrete can be effectively guaranteed; at the same time, combined with the physical and chemical properties of modified boron-containing mine tailings, ice-coating cooling of aggregates, and modified clay, Effectively improve the radiation resistance and cracking resistance of large-volume concrete.

In order to achieve the above purpose, the following technical solutions are adopted:

A high-crack-resistant and radiation-resistant large-volume concrete whose composition is as follows in parts by weight:

250-300 parts of cement, 10-30 parts of modified boron-containing mine tailings, 60-90 parts of grade II fly ash, 600-900 parts of ordinary sand, 250-1250 parts of cooling aggregate, 250-1250 parts of normal temperature aggregate , 165 parts of water.

According to the above plan, the cement uses P·O 42.5 cement, 300m ² /kg ≤ specific surface area ≤ 370m ² /kg.

According to the above plan, the modified boron-containing mine tailings are obtained by grinding the industrial waste residue discharged from the production of borax from boron magnesium ore through high-temperature calcination and modification; the loss on ignition is 20%-30%; the MgO content in the chemical composition is 40 -50wt%, B ₂ O ₃ content is 25~40wt%; the average particle diameter is 20-50μm.

According to the above plan, the high-temperature calcination temperature of the modified boron-containing mine tailings is 600-1100°C and the calcination time is 30min-60min. At the same time, the specific content is determined by the content of internal magnesium oxide, light burnt magnesium and the activity of the boron-containing tailings. Calcining temperature and time.

According to the above plan, the cooling aggregate is obtained by covering the accumulated normal temperature aggregate with ice and cooling; the accumulation thickness of the aggregate is 2-2.5m, the ice coating thickness range of the aggregate is 0.1m-0.3m, and the ice coating duration is 2d. -4d, the aggregate temperature range after ice coating is 18-22℃.

According to the above solution, the ordinary sand is medium-coarse sand, and its fineness modulus is between 2.3-3.0.

According to the above plan, the fineness range of the Grade II fly ash is 30-40%, the loss on ignition range is 3%-8%, the CaO content in the chemical composition is 4-10%, and the K ₂ O content is 1-4 %, _SiO2 content is 45-55%, _{Fe2O3 content} is 3%-8%, _{Al2O3 content} is 25%-35%.

The preparation method of the above-mentioned highly crack-resistant and radiation-resistant large-volume concrete includes the following steps:

Pour the cooling aggregate, normal temperature aggregate, cement, Grade II fly ash, modified boron-containing mine tailings and ordinary sand into the mixer and mix evenly. Add water and mix evenly to obtain high-crack-resistant and radiation-resistant large-volume concrete.

According to the characteristics of relevant elements in boron-containing mine tailings, the present invention modifies boron-containing mine tailings and further uses them in the preparation of large-volume nuclear power concrete to effectively improve the crack resistance and radiation resistance of concrete. Specifically: 1. When the boron-containing mine tailings are heated at high temperatures, the magnesite contained inside will decompose to obtain magnesium oxide or light burnt magnesium (that is, MgCO ₃ =MgO + CO _2. Magnesite is heated to 640°C After the above reaction, it begins to decompose into magnesium oxide and carbon dioxide. After heating to 750-1000°C, all the carbon dioxide does not escape. The product is a powdery substance (light burnt magnesium), which can effectively improve the crack resistance of concrete; 2. Boron-containing mine tailings contain a high content of boron-containing compounds (B ₂ O ₃ ), and adding them to concrete will effectively improve the radiation resistance of concrete.

By processing and modifying boron-containing mine tailings, the present invention increases its utilization efficiency in radiation-resistant concrete, and particularly improves its anti-shrinkage and cracking performance in concrete.

The invention adopts ice-coating cooling measures for coarse aggregate, which can effectively ensure the temperature of concrete coming out of the machine and pouring. In addition, through theoretical calculation, the temperature of the coarse aggregate used in concrete is controlled by means of ice coating time and quantity adjustment, so that the cooling aggregate can maintain a lower temperature during the hydration reaction of concrete (15-30h), thereby completing the physical Thermal process reduces the heat of hydration of large-volume concrete and further reduces the possibility of concrete cracking.

The invention organically combines the physical and chemical properties of modified boron-containing mine tailings, aggregate ice cooling and modified clay. It not only effectively improves the radiation resistance and cracking resistance of large-volume concrete, but also provides a Highly crack-resistant and radiation-resistant large-volume concrete with cement, boron-containing mine tailings and modified clay as the main components and its preparation method make resource utilization of boron-containing mine tailings and clay, and are highly consistent with the requirements of national environmental protection policies. And the application prospects are huge.

During the long-term work of nuclear power projects, the inventor found that when pouring important concrete parts, the performance and temperature of the concrete are required to be higher. For example, in terms of concrete temperature, the pouring temperature needs to be kept at normal temperature all year round, which is not suitable for concrete production and construction in summer. produce greater difficulties and impacts. The invention makes full use of the characteristics that the amount of coarse aggregate (stone) in the single concrete is much larger than the amount of water, and the specific heat capacity is larger than other materials except water and the heat conduction rate is relatively low. The coarse aggregate is pre-cooled to keep the temperature rise rate of the concrete at a low level after mixing and leaving the machine, thereby ensuring that the concrete pouring temperature is qualified (one degree of temperature rise of one concrete aggregate is equivalent to a 3°C rise in water temperature) (calculation The total heat absorbed by the stones in a square of concrete is greater than the amount of heat absorbed by water).

Compared with the prior art, the beneficial effects of the present invention are as follows:

In terms of radiation resistance, the present invention uses modified boron-containing mine tailings, which are obtained by grinding the industrial waste residue discharged from the production of borax from boron magnesium ore after high-temperature calcination. It contains a large amount of boron-containing compounds (B ₂ O ₃ ). Adding it to concrete can improve the ability to absorb nuclear radiation and effectively improve the radiation resistance; in addition, after direct roasting, the boronite in the boron-containing mine tailings that is not easily alkali decomposed is decomposed into suian that is easy to alkali decompose after roasting and dehydration. Stone, boron (B ₂ O ₃ ) activity is further improved, thereby greatly improving the radiation resistance of the prepared concrete.

In terms of crack resistance, the modified boron-containing mine tailings used in the present invention contain relatively high contents of magnesium oxide and light burnt magnesium (magnesite begins to decompose into magnesium oxide and carbon dioxide when heated to above 640°C, and when heated to After 750-1100℃, all the carbon dioxide does not escape, and the product is a powdery substance (light burned magnesium). Magnesium oxide and light burned magnesium are important components of the expansion agent and play a role in inhibiting cracks in the development of concrete. ; In addition, due to the high internal hydration heat release of large-volume concrete, the possibility of cracks in the concrete is greatly increased, and the highest hydration heat release time is between 20-30 hours after pouring and molding. At the same time, in the summer ambient temperature, it takes about 40 hours for the cooling aggregate to rise from 20°C to 30°C. Therefore, the cooling aggregate used in the present invention has the function of absorbing heat during the hydration and exothermic process of concrete, which can reduce The heat of hydration inside the concrete reduces the possibility of temperature cracks.

In terms of high temperature resistance, the forsterite component contained in the ground modified boron-containing mine tailings used in the present invention can effectively improve the high temperature resistance of concrete. When used in nuclear power concrete, it can play a better protective role. , improve the safety performance of nuclear power projects.

Detailed ways

The following examples further illustrate the technical solutions of the present invention, but are not intended to limit the scope of the present invention.

Specific embodiments provide a high-crack-resistant and radiation-resistant large-volume concrete, the composition of which is as follows in parts by weight:

250-300 parts of cement, 10-30 parts of modified boron-containing mine tailings, 60-90 parts of grade II fly ash, 600-900 parts of ordinary sand, 250-1250 parts of cooling aggregate, 250-1250 parts of normal temperature aggregate , 165 parts of water.

Specifically, the cement uses P·O 42.5 cement, 300m ² /kg ≤ specific surface area ≤ 370m ² /kg.

Specifically, the modified boron-containing mine tailings are industrial waste residues discharged from boron magnesia ores after producing borax, which are modified by high-temperature calcination and then grinded; the loss on ignition is 20%-30%; the MgO content in the chemical composition is 40-50wt% , B ₂ O ₃ content is 25-40wt%; the average particle diameter is 20-50μm.

Specifically, the high-temperature calcination temperature of modified boron-containing mine tailings is 600-1000°C and the calcination time is 30min-120min. At the same time, the specific calcination temperature and time are determined by the content of internal magnesium oxide and light burned magnesium.

The high-temperature calcination time of boron-containing mine tailings used in this example is 90 minutes.

Specifically, the cooling aggregate is obtained by covering the accumulated normal temperature aggregate with ice and cooling; the aggregate accumulation thickness is 2-2.5m, the aggregate ice coating thickness range is 0.1m-0.3m, and the ice coating duration is 2d-4d. The temperature range of the aggregate after ice coating is 18-22℃.

Specifically, ordinary sand is medium-coarse sand, and its fineness modulus is between 2.3-3.0.

Specifically, the fineness range of Grade II fly ash is 30-40%, the loss on ignition range is 3%-8%, the CaO content in the chemical composition is 4-10%, the K ₂ O content is 1-4%, and SiO ₂ content is 45-55%, Fe ₂ O ₃ content is 3% - 8%, and Al ₂ O ₃ content is 25% - 35%.

The mix ratio of high-crack-resistant and radiation-resistant large-volume concrete in the specific embodiment is shown in Table 1. The water-cement ratio is fixed at 0.46, which is similar to the water-cement ratio of C30 large-volume concrete mix in actual nuclear power projects.

Table 1

The performance characterization of the concrete obtained in each specific example is shown in Table 2. The adiabatic temperature rise of concrete was tested in accordance with the provisions of GB/T 50080-2016 "Standard for Test Methods for Performance of Ordinary Concrete Mixtures". To analyze the gamma ray shielding performance of concrete, the front of the concrete slab is 40cm away from the radioactive source and the back is 5cm away from the detector. The absorbed dose rate of the concrete slab is measured, and then the linear absorption is calculated theoretically.

Table 2

It can be seen from the test data that the concrete specimens of the embodiments of the present invention exhibit good resistance to cracking, reduce hydration heat and radiation resistance, and maintain good working performance and mechanical properties. Among them, observing the comparative examples and Examples 2-5, it can be seen that adding modified boron-containing waste powder can effectively improve the resistance to gamma rays and neutron rays of concrete. As the amount of modified boron-containing waste powder gradually increases, The linear attenuation coefficient of concrete continues to decrease. This is because as the dosage gradually increases, the B ₂ O ₃ content in the concrete also gradually increases, which effectively enhances the radiation resistance performance of concrete. Observing Examples 4 and 7-11, it can be seen that as the dosage increases, the As the calcination temperature of boron-containing tailings increases, the radiation resistance of concrete first increases and then weakens. When the temperature is about 700°C, its radiation resistance is the best; in addition, the change pattern of concrete's anti-cracking performance is further analyzed. It can be seen that as the amount of modified boron-containing waste powder gradually increases, the cracking resistance of concrete is significantly improved. This is due to the increasing MgO content inside the concrete. The delayed expansion of MgO hydration effectively improves the strength of the concrete. anti-cracking properties.

In addition, further observation of Comparative Example 1 and Examples 12-16 shows that as the cooling aggregate content continues to increase, the adiabatic temperature rise temperature value of concrete continues to decrease. The reason is that after the aggregate is ice-coated and cooled, it will be able to cool down during the cement hydration period. Absorb the heat released, thereby reducing the heat of hydration inside the concrete, thereby reducing the possibility of temperature cracks in the concrete.

It should be noted that the above-mentioned embodiments are only some embodiments of preferred ways to implement the present invention, rather than all embodiments. Obviously, based on the above-mentioned embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts should fall within the scope of protection of the present invention.

Claims (8)

1. The high-crack-resistance radiation-resistance large-volume concrete is characterized by comprising the following components in parts by weight:

250-300 parts of cement, 10-30 parts of modified boron-containing mine tailings, 60-90 parts of grade II fly ash, 600-900 parts of common sand, 250-1250 parts of cooling aggregate, 250-1250 parts of normal-temperature aggregate and 165 parts of water.

2. The high crack resistance and radiation resistance large volume concrete according to claim 1, wherein said cement is P.O42.5 cement, 300m ² The specific surface area of the catalyst is not more than/kg and not more than 370m ² /kg。

3. The high-crack-resistance radiation-resistance mass concrete of claim 1, wherein the modified boron-containing mine tailings are obtained by grinding industrial waste residues discharged after borax is produced by boron magnesium ore through high-temperature calcination modification; the loss on ignition is 20% -30%; the content of MgO in the chemical composition is 40-50wt%, B ₂ O ₃ The content is 25-40 wt%; the average particle diameter is 20-50 μm.

4. The high-crack-resistant radiation-resistant mass concrete according to claim 3, wherein the high-temperature calcination temperature of the modified boron-containing mine tailings is 600-1100 ℃ and the calcination time is 30-120 min, and the specific calcination temperature and time are determined by the content of internal magnesium oxide and light-burned magnesium and the activity of the boron-containing mine tailings.

5. The high anti-cracking radiation-resistant mass concrete of claim 1, wherein said cooling aggregate is obtained by ice-coating and cooling stacked normal temperature aggregates; the stacking thickness of the aggregate is 2-2.5m, the icing thickness range of the aggregate is 0.1-0.3 m, the icing duration time is 2d-4d, and the temperature range of the aggregate after icing is 18-22 ℃.

6. The high crack resistance radiation resistant bulk concrete of claim 1 wherein said normal sand is medium coarse sand having a fineness modulus of between 2.3 and 3.0.

7. The high crack resistance and radiation resistance mass concrete as recited in claim 1, wherein said class II fly ash has fineness of 30-40%, loss on ignition of 3% -8%, caO content of 4-10% and K in chemical composition ₂ O content is 1-4%, siO ₂ The content is 45-55%, fe ₂ O ₃ 3-8% of Al ₂ O ₃ The content is 25% -35%.

8. The method for preparing the high-crack-resistance radiation-resistance large-volume concrete of any one of claims 1 to 7, which is characterized by comprising the following steps:

pouring the cooling aggregate, the normal temperature aggregate, the cement, the class II fly ash, the modified boron-containing mine tailings and the common sand into a stirrer, uniformly mixing, and then adding water and uniformly stirring to obtain the high-crack-resistance radiation-resistance mass concrete.