Strontium ferrite-based sacrificial mortar and its preparation method

Abstract

The invention discloses a strontium ferrite-based sacrificial mortar and its preparation method, the strontium ferrite-based sacrificial mortar mainly comprises 720-1000 parts of sulphoaluminate cement, 100-300 parts of strontium ferrite, 600-650 parts of quartz sand, 400-450 parts of water and 0.01-35 parts of superplasticizer. The preparation process is simple, and the strontium ferrite-based sacrificial mortar can be prepared by using a conventional forced single horizontal shaft concrete mixer. The obtained mortar has excellent working performance, compressive strength and corrosion resistance. It can be used in the current third and future fourth generation nuclear power plant core catchers, and has obvious engineering application value.

Claims

1. A strontium ferrite-based sacrificial mortar, comprising the following raw materials in parts by weight: 720-1000 parts of sulphoaluminate cement, 100-300 parts of strontium ferrite, 600-650 parts of quartz sand, 400-450 parts of water and 0.01-35 parts of superplasticizer; wherein the cement is sulphoaluminate cement of grade 42.5, with CaO in a mass content of larger than 40%, and Al.sub.2O.sub.3 in a mass content of greater than 20%; the quartz sand is a high-quality quartz powder, with SiO.sub.2 mass content greater than or equal to 99%, and a particle size distribution of 0.075 mm-4.75 mm; the superplasticizer is polycarboxylic acid superplasticizer, with a colorless to light yellow appearance, a density of 1.05-1.15 g/mL, a solid content greater than or equal to 40% (mass content), a gas content of 6%-8% (volume content), a pH of 6-8, and a water reducing rate greater than or equal to 33%; a preparation method comprising the steps as follows: (1) mixing sulphoaluminate cement of 42.5 grade, strontium ferrite powder and quartz sand to obtain a mixed material M1 after uniformly dry mixing; and (2) adding a mixed solution of water and superplasticizer into the uniformly mixed material M1, and stirring to obtain a uniformly mixed material M2, then obtaining the strontium ferrite-based sacrificial mortar; in step (1), the raw materials for mixing are added into a single-shaft horizontal forced concrete mixer, with a mixing speed of 40-50 revolutions/min, a mixing duration of 200-240 seconds; and in step (2), ½ of the water is firstly mixed with all the superplasticizer to develop a uniformly mixed solution by uniformly mixing, and adding the uniformly mixed solution into the mixed material M1, then a remaining water is used to wash a container holding the superplasticizer, and the remaining water used for washing is added into the mixed material M1, followed by mixing for a duration of 200-240 seconds.

2. The strontium ferrite-based sacrificial mortar as claimed in claim 1, wherein the strontium ferrite is in a form of powder with SrFe.sub.12O.sub.19 in a mass content of greater or equal to 95%.

3. The strontium ferrite-based sacrificial mortar as claimed in claim 1, wherein the water is tap water or drinking water, in line with requirements of Standard of Water for Concrete (JGJ 63-2006).

Description

DESCRIPTION OF THE INVENTION

(1) The present invention will be further illustrated with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and not to limit the scope of the present invention. After reading the present invention, various modifications of equivalent forms made by those technicians in the technical field should be under the protection scope defined by the appended claims of this application. In addition, the advantages of the present invention are emphasized by comparing the experimental results of the embodiments.

(2) The raw materials used in the following embodiments meet the following requirements:

(3) The 42.5 grade sulphoaluminate cement is used, in which CaO content is 42.6% and Al.sub.2O.sub.3 content is 22.5%.

(4) The content of SrFei.sub.12O.sub.19 in the strontium ferrite powder is 96.3%.

(5) The quartz sand is high quality quartz powder, its SiO.sub.2 content is 99.3%, and its particle size distribution is 0.075-4.75 mm.

(6) The water is tap water.

(7) The polycarboxylate superplasticizer is used, which with colorless to light yellow appearance, density of 1.10 g/ml. Specifically, solid content is 41.2% (by mass percentage), gas content is 7% (by volume), pH value is 7.2, and water reducing rate is 33.5%.

Embodiment 1

(8) A strontium ferrite-based sacrificial mortar comprises the following components in parts by weight:

(9) 900 parts of sulphoaluminate cement, 100 parts of strontium ferrite, 600 parts of quartz sand, 400 parts of water and 0.30 parts of superplasticizer.

(10) Preparation Method:

(11) (1) Weighing required materials, including sulphoaluminate cement, strontium ferrite powder, quartz sand, tap water and superplasticizer.

(12) (2) Wetting mixer and all necessary tools and moulds with water.

(13) (3) The weighed sulphoaluminate cement, strontium ferrite powder and quartz sand are added to the forced single horizontal shaft concrete mixer in turn. The mixing speed is 45 revolutions per minute and the mixing time is 200 seconds. The mixed material M1 is obtained by mixing evenly.

(14) (4) First, ½ of water is mixed with all the superplasticizer, and then the mixed solution is added into the mixture M1. Then the remaining water is used to clean the container containing the superplasticizer. After cleaning, the remaining water is added to the mixture M1. After 200 seconds of mixing, the mixture M2 is obtained, and then the molding and curing are carried out according to Chinese national standards.

Embodiment 2

(15) A strontium ferrite-based sacrificial mortar comprises the following components in parts by weight:

(16) 800 parts of sulphoaluminate cement, 200 parts of strontium ferrite, 600 parts of quartz sand, 400 parts of water and 1.0 parts of superplasticizer.

(17) Preparation Method:

(18) (1) Weighing required materials, including sulphoaluminate cement, strontium ferrite powder, quartz sand, tap water and superplasticizer.

(19) (2) Wetting mixer and all necessary tools and moulds with water.

(20) (3) The weighed sulphoaluminate cement, strontium ferrite powder and quartz sand are added to the forced single horizontal shaft concrete mixer in turn. The mixing speed is 45 revolutions per minute and the mixing time is 200 seconds. The mixed material M1 is obtained by mixing evenly.

(21) (4) First, ½ of water is mixed with all the superplasticizer, and then the mixed solution is added into the mixture M1. Then the remaining water is used to clean the container containing the superplasticizer. After cleaning, the remaining water is added to the mixture M1. After 200 seconds of mixing, the mixture M2 is obtained, and then the molding and curing are carried out according to Chinese national standards.

Embodiment 3

(22) A strontium ferrite-based sacrificial mortar comprises the following components in parts by weight:

(23) 700 parts of sulphoaluminate cement, 300 parts of strontium ferrite, 600 parts of quartz sand, 400 parts of water and 35.0 parts of superplasticizer.

(24) Preparation Method:

(25) (1) Weighing required materials, including sulphoaluminate cement, strontium ferrite powder, quartz sand, tap water and superplasticizer.

(26) (2) Wetting mixer and all necessary tools and moulds with water.

(27) (3) The weighed sulphoaluminate cement, strontium ferrite powder and quartz sand are added to the forced single horizontal shaft concrete mixer in turn. The mixing speed is 45 revolutions per minute and the mixing time is 200 seconds. The mixed material M1 is obtained by mixing evenly.

(28) (4) First, ½ of water is mixed with all the superplasticizer, and then the mixed solution is added into the mixture M1. Then the remaining water is used to clean the container containing the superplasticizer. After cleaning, the remaining water is added to the mixture M1. After 200 seconds of mixing, the mixture M2 is obtained, and then the molding and curing are carried out according to Chinese national standards.

(29) The above three embodiments have the same preparation process. The differences are as follows: 900 parts of sulphoaluminate cement and 100 parts of strontium ferrite in Embodiment 1. 800 parts of sulphoaluminate cement and 200 parts of strontium ferrite in Embodiment 2. 700 parts of sulphoaluminate cement and 300 parts of strontium ferrite in Embodiment 3. The sum of the mass of sulphoaluminate cement and strontium ferrite in the three embodiments is 1000 parts, while the mass of strontium ferrite in the three embodiments increases in turn. The quartz sand in all three embodiments was 600 parts and the water in all three embodiments was 400 parts, which remained unchanged. In order to make the prepared strontium ferrite-based sacrificial mortar achieve the required working performance, the dosage of superplasticizer in the three embodiments is very different.

(30) Performance Testing

(31) According to Chinese national standard GB/T 14902-2012, the working performance of the strontium ferrite-based sacrificial mortar in the above embodiments was tested, and the measurement index was slump flow. According to Chinese national standard GB/T 50107-2010, the 28-day compressive strength of strontium ferrite-based sacrificial mortar was tested. The enthalpy of strontium ferrite-based sacrificial mortar was tested by thermogravimetric analysis, and the decomposition temperature was tested by high temperature experiment. The decomposition enthalpy of strontium ferrite-based sacrificial mortar was obtained by combining the two experiments. The experimental results of the three embodiments are shown in Table 1.

(32) TABLE-US-00001 TABLE 1 Experimental results Slump 28-day compressive Decomposition Embodiments flow (mm) strength (MPa) enthalpy (J/kg) Embodiment 1 253 45.3 509.9 Embodiment 2 249 40.4 572.9 Embodiment 3 252 37.1 627.7

(33) It can be seen from Table 1 that the slump flow of the three embodiments is greater than 245 mm, which meets the requirements of self-compacting performance. With the increase of strontium ferrite content, the 28-day compressive strength of strontium ferrite-based sacrificial mortar gradually decreases, but the minimum strength is 37.1 MPa, which is still 23.67% higher than the technical requirement of 30 MPa. With the increase of strontium ferrite content, the decomposition enthalpy of strontium ferrite-based sacrificial mortar gradually increases, which indicates that the corrosion rate gradually decreases, thus improving the safety of nuclear power plants.

(34) In addition, it should be noted that the above embodiments are only used to illustrate the technical scheme of the present invention. If the technical embodiment of the present invention is modified or replaced by an ordinary technician in the technical field without departing from the purpose of the present invention, it shall be covered in the protection scope of the claims of the present invention.

(35) The following explains why the decomposition enthalpy of strontium ferrite-based sacrificial mortar increases, which leads to the decrease of its corrosion rate:

(36) According to the heat conduction theory, the relationship between the erosion rate of strontium ferrite-based sacrificial mortar and the heat flux transferred to its interior is shown in the following formula:
V=Q/(ρ×A×ΔH)  (1)

(37) In the above formula, V is the erosion rate of strontium ferrite-based sacrificial mortar, Q is the heat flux transferred to the interior of strontium ferrite-based sacrificial mortar, A is the erosion area of strontium ferrite-based sacrificial mortar, and ΔH is the decomposition enthalpy of strontium ferrite-based sacrificial mortar.

(38) It can be seen from the above formula (1) that the erosion rate of strontium ferrite-based sacrificial mortar is inversely proportional to its decomposition enthalpy. This indicates that when the decomposition enthalpy of strontium ferrite-based sacrificial mortar increases, the corrosion rate decreases.