Modification method for improving cracking resistance and durability of iron tailing dry-mixed mortar and application

Abstract

The invention discloses a modification method for improving cracking resistance and durability of iron tailing dry-mixed mortar in the technical field of iron tailing resource utilization, the modification method is used for modifying an iron tailing raw material for preparing the iron tailing dry-mixed mortar, and the specific process is as follows: firstly, coarsely grinding the iron tailing raw material, adding an activating agent, and finely grinding to obtain iron tailing fine powder; the obtained iron tailing fine powder is subjected to surface modification through N-phenylacrylamide and then is subjected to gelatinization modification through crosslinking, the iron tailing powder composite material is obtained, the water absorption performance of the modified iron tailing powder composite material is improved, the iron tailing powder composite material is mixed with cement, fly ash, machine-made sand and an auxiliary agent, and iron tailing dry powder is obtained; the iron powder ore dry-mixed mortar obtained by adding water and mixing has better mechanical properties, the durability of the dry-mixed mortar is promoted to be effectively improved, and the method also has positive significance in promoting resource utilization of the iron tailings.

Description

Technical Field

[0001] The present invention relates to the technical field of iron tailings resource utilization, and in particular to a modification method for iron tailings dry powder mortar for preventing cracking and improving durability. Background Art

[0002] Iron tailings are solid waste discharged after iron ore is refined into iron concentrate. The discharge of large amounts of iron tailings not only encroaches on arable land, pollutes the environment, and threatens human safety, but also seriously restricts the sustainable development of the local economy. Currently, the resource utilization methods for iron tailings include: iron tailings re-selection, production of building materials, recycling of silicon to prepare silicon products, etc., and the comprehensive utilization rate is low. Therefore, it is of great significance to study the comprehensive utilization technology of iron tailings.

[0003] The activation and modification of iron tailings is a key technology to improve its application value in building materials and other fields. Common activation and modification methods include mechanical activation, chemical activation, thermal activation, etc. Among them, mechanical activation is to grind the iron tailings through equipment such as ball mills to reduce the particle size and increase the specific surface area, thereby increasing its surface free energy and reaction activity. Chemical activation is to add inorganic or organic chemical activators, such as sodium hydroxide, sodium sulfate, etc., to the iron tailings to stimulate the potential activity of the iron tailings through chemical reactions. Thermal activation is to react with clay components such as chlorite and illite in the iron tailings through high-temperature calcination, decomposing them into active silica and alumina to improve activation, but it requires a lot of energy consumption.

[0004] With the vigorous development of the construction industry, the demand for mortar is increasing. Among them, dry-mixed mortar, also known as dry powder or dry-mixed mortar, is a mixture of cement, dry aggregate or powder, additives and other components determined according to performance in a certain proportion. Sand has a huge impact on the preparation and performance of dry-mixed mortar. In recent years, machine-made sand has developed rapidly and has become the main source of construction sand. The physical properties of iron tailings powder are similar to those of natural sand. It can replace part of machine-made sand in dry-mixed mortar, which promotes the improvement of mortar workability and mechanical properties, further improves the crack resistance and durability of iron tailings dry-mixed mortar, and promotes the application of iron tailings in building materials and other fields. Summary of the Invention

[0005] The purpose of the present invention is to solve the technical problems mentioned in the background technology and provide a modification method for iron tailings dry powder mortar to prevent cracking and improve durability.

[0006] The present invention achieves the above-mentioned purpose through the following technical solutions: The first aspect of the present invention provides a modification method for preventing cracking and improving durability of iron tailings dry powder mortar, specifically the modification of iron tailings raw materials for preparing iron tailings dry powder mortar. The specific process is: first, the iron tailings raw materials are coarsely ground, and then an activator is added to finely grind to obtain iron tailings fine powder, and then the obtained iron tailings are finely divided and surface modified with N-phenylacrylamide, and then cross-linked to achieve gelation modification to obtain an iron tailings powder composite material.

[0007] As a further optimization solution of the present invention, the amount of the activator is 0.2%-0.8% of the mass of the coarse iron tailings powder.

[0008] As a further optimization solution of the present invention, the activator is at least one of desulfurization gypsum, water glass, and steel slag powder.

[0009] As a further optimized solution of the present invention, the particle size of the iron tailings fine powder is 100-200 μm.

[0010] As a further optimization solution of the present invention, the gelling modification includes the following steps: (1) Add the iron tailings fine powder into the N-phenylacrylamide solution and stir mechanically for standby use; (2) Sodium alginate is added to the above solution system and stirred evenly, and then a mixed solution of calcium chloride and propylene glycol is poured into the solution system. The solution system is treated at 40-50°C for 20-30 minutes. After the treatment is completed, the obtained product is dried at a constant temperature and finely ground into powder to obtain an iron tailings powder composite material.

[0011] As a further optimized solution of the present invention, the mass concentration of the N-phenylacrylamide solution is 0.2%-0.5%.

[0012] As a further optimized solution of the present invention, the particle size of the iron tailings powder composite material is 0.1-0.5 mm.

[0013] The second aspect of the present invention also provides an application of any of the modification methods described above in the preparation of iron tailings dry powder mortar, wherein the iron tailings dry powder mortar is obtained by mixing the iron tailings powder composite material with cement, fly ash, machine-made sand and processing aids to obtain iron tailings dry powder, and then adding water to mix.

[0014] As a further optimization solution of the present invention, the replacement rate of the iron tailings powder composite material for machine-made sand is 15%-30%.

[0015] As a further optimized solution of the present invention, the processing aid includes a water reducer and sodium gluconate.

[0016] The beneficial effects of the present invention are: (1) The present invention obtains iron tailings fine powder by coarse grinding of iron tailings raw materials and fine grinding with the addition of an activator, and then subdivides the obtained iron tailings into fine powder, performs surface modification with N-phenylacrylamide, and then performs gelation modification by cross-linking to obtain an iron tailings powder composite material, thereby improving the water absorption performance of the iron tailings powder.

[0017] (2) The improvement of the water absorption performance of iron tailings powder can improve the workability of dry-mix mortar and enhance the water retention of dry-mix mortar, which makes it less likely for the mortar to dry out and crack during the construction process and maintains good working performance. After the water absorption performance of iron tailings powder is improved, it can better fill the pores inside the mortar, make the mortar structure more compact, and improve the mechanical properties of the mortar. After the water absorption performance of iron tailings powder is improved, it can reduce the evaporation rate of water in the mortar during the drying process, thereby reducing the drying shrinkage rate of the mortar, helping to improve the durability of the mortar and reduce cracking caused by shrinkage.

[0018] (3) The present invention mixes the iron tailings powder composite material with cement, fly ash, machine-made sand and additives to obtain iron tailings dry powder, and then adds water to mix to obtain iron tailings dry powder mortar. The iron tailings powder composite material replaces the machine-made sand, and the replacement rate is 15%-30%. It can adjust the consistency of the dry powder mortar. Compared with the dry powder mortar without replacing the machine-made sand, it has better mechanical properties, promotes the effective improvement of the durability of the dry powder mortar, and also has positive significance for promoting the resource utilization of iron tailings. DETAILED DESCRIPTION

[0019] The present application is described in further detail below. It is necessary to point out that the following specific implementation methods are only used to further illustrate the present application and cannot be understood as limiting the scope of protection of the present application. Technicians in this field can make some non-essential improvements and adjustments to the present application based on the above application content.

[0020] The iron tailings raw material selected in this embodiment is commercially available iron tailings slag, and its chemical composition is shown in Table 1.

[0021] Table 1 Chemical composition of iron ore tailings This example uses N-phenylacrylamide, CAS number 2210-24-4, molecular weight 147.17; This embodiment uses PO42.5 ordinary Portland cement, Class I fly ash, and machine-made sand with a fineness modulus of 2.70. Polycarboxylate water reducer, sodium gluconate, and cellulose ether are used as processing aids, and tap water is used as mixing water.

[0022] The reagents and materials used in the following examples, unless otherwise specified, are commercially available products.

[0023] Example 1: Modification of iron ore tailings 1. Preparation of iron tailings fine powder After the iron tailings slag is deironed and crushed to a particle size of less than 5 mm, a coarse iron tailings powder is obtained. The coarse iron tailings powder is finely ground together with an activator to obtain a fine iron tailings powder with a particle size of 100-200 μm. The activator is selected from at least one of desulfurization gypsum, water glass, and steel slag powder (desulfurization gypsum is selected in this embodiment), and the amount used is 0.2%-0.8% of the coarse iron tailings powder (0.5% is selected in this embodiment).

[0024] 2. Gelatinization modification of iron tailings fine powder 100 g of iron tailings fine powder was added to 50 ml of N-phenylacrylamide solution with a mass concentration of 0.2% (the solvent was ethanol), and mechanically stirred at 150 r / min for 6 h, and then set aside. 50 g of sodium alginate with a concentration of 3% was added to the above solution system and stirred evenly. Then 20 ml of calcium chloride with a concentration of 5% and 20 ml of propylene glycol with a concentration of 2% were poured into the mixture and mixed. The solution system was treated at 40-50° C. for 20-30 min (in this embodiment, 50° C. was selected for treatment for 20 min). After the treatment, the obtained product was dried at a constant temperature and finely ground into powder to complete the gelation modification of the iron tailings fine powder, thereby obtaining an iron tailings powder composite material. The particle size of the iron tailings powder composite material was 0.1-0.5 mm. The obtained iron tailings composite material was recorded as sample A-1.

[0025] Improving the water absorption of iron tailings powder helps improve the durability of mortar and reduce cracking caused by shrinkage. Therefore, based on the above method, this example explores the effect of iron tailings slag modification on its water absorption performance, and sets the following treatment groups: Treatment group A: no activator was added during fine grinding; Treatment group B: no gelling modification; Treatment group C: no activator was added during fine grinding, and no gelling modification was performed; Treatment group D: During gelation modification, a 0.5% mass concentration of N-phenylacrylamide solution was used; Treatment group E: During gelation modification, acrylamide solution with a mass concentration of 0.2% was used; The iron tailings composite materials obtained from treatment groups AE were recorded as samples A-2 to A-6.

[0026] The water absorption performance of samples A-1 to A-6 was tested as follows: (1) Immerse the sample in a beaker filled with tap water. After fully absorbing water, let it stand for a while, filter out the water on the surface of the sample, and then weigh it. Calculate the water absorption rate (%) of the sample based on the weight difference before and after water absorption.

[0027] (2) Immerse the prepared sample in a beaker filled with 5% NaCl solution and allow it to absorb water until saturated. After standing for a while, filter out the salt water on the surface of the sample and weigh it. Calculate the water absorption rate (%) of the sample based on the weight difference before and after water absorption.

[0028] The results are shown in Table 2.

[0029] Table 2 Performance test results of different iron tailings powder composite materials As can be seen from Table 2, the water absorption rate of the iron tailings powder composite material obtained after the activator composite gel modification treatment for tap water reached 78.4%, and the water absorption rate for 5% NaCl solution reached 70.8%, which was significantly better than other groups. The coarse iron tailings powder was finely ground together with the activator, which changed the surface properties of the iron tailings particles, reduced the agglomeration between the particles, and improved the activity. Subsequently, it was treated with N-phenylacrylamide solution. N-phenylacrylamide has extremely strong reactivity due to its own acrylamide group. It cross-linked with the monomer in the solution polymerization reaction to form a three-dimensional network water-locking structure, which improved the water absorption performance of the iron tailings powder composite material.

[0030] In addition, by comparing sample A-1 and sample A-5, it can be seen that the mass concentration of N-phenylacrylamide solution between 0.2% and 0.5% can exert a good modification effect.

[0031] Example 2: Preparation of dry iron ore mortar Iron tailings powder composite material sample A-5 was mixed with cement, fly ash, machine-made sand and additives to obtain iron tailings dry powder, which was then mixed with water to obtain iron tailings dry powder mortar. The mix ratio of each component of the mortar was designed as follows: cement 208kg / m 3 , fly ash is 48kg / m 3 , machine-made sand is 1700kg / m 3 , water reducing agent is 1.5kg / m 3 , sodium gluconate is 0.06kg / m 3 , based on the ratio of the weight of mixing water to the total weight of cementitious materials being 0.5, the amount of mixing water was determined, and the following treatment groups were set up: Treatment group B-1: Iron tailings powder composite material sample A-5 was used to replace machine-made sand at a replacement rate of 15%; Treatment group B-2: Iron tailings powder composite material sample A-5 was used to replace machine-made sand at a replacement rate of 20%; Treatment group B-3: Iron tailings powder composite material sample A-5 was used to replace machine-made sand at a replacement rate of 25%; Treatment group B-4: Iron tailings powder composite material sample A-5 was used to replace machine-made sand at a replacement rate of 30%; Control group 1: Iron tailings powder composite material sample A-5 was not used to replace machine-made sand.

[0032] Control group 2: Iron tailings fine powder with a particle size range of 0.1-0.5 mm was used to replace the manufactured sand at a replacement rate of 20%.

[0033] According to treatment groups B-1 to B-4, after the mortar samples were stirred, test slurry was obtained. At the same time, a portion of the test slurry was placed in a mold with a size of 50mm×50mm×50mm. After removing the mold, mortar specimens were obtained. They were cured under standard conditions (20±2℃, humidity above 90%) to the corresponding age. Five parallel samples were made for each treatment group, and the results were averaged.

[0034] The specimens were prepared and cured in accordance with the Standard for Test Methods for Basic Properties of Building Mortar (JGJ / T 70-2009), and the consistency and consistency loss rate of the mortar, the tensile bond strength of the mortar, and the cubic compressive strength of the specimens were measured.

[0035] The results of the consistency and consistency loss rate of the mortar are shown in Table 4.

[0036] Table 4 Results of consistency and consistency loss rate As can be seen from Table 4, compared with the control group 1 in which the iron tailings powder composite material was not used to replace the machine-made sand, the consistency of the treatment groups B-1 to B-4 increased, and the corresponding consistency loss rate also increased. At the same replacement rate, the use of iron tailings fine powder has a comparable consistency increase effect compared to the iron tailings powder composite material, but its consistency loss rate is higher than that of the present invention.

[0037] It can be seen from treatment groups B-1 to B-4 that with the increase of the replacement rate of iron tailings powder composite materials for machine-made sand, the consistency of the mortar sample is improved, and the consistency loss rate of the mortar sample also increases at the same time, but all reach the standard requirement of less than 30%.

[0038] The 14d tensile bond strength of the mortar and the cubic compressive strength of the mortar specimens are shown in Table 5.

[0039] Table 5 Tensile bond strength and cubic compressive strength results ; It can be seen from Table 5 that with the increase of the replacement rate of iron tailings powder composite material for machine-made sand, the 14-d tensile bond strength of the mortar increases. The reason is that the iron tailings powder composite material can fill the pores in the mortar and further improve the density of the mortar. When the content of iron tailings powder composite material continues to increase, the 14-d tensile bond strength of the mortar will be affected by the structural defects produced by the cement and iron tailings powder composite material.

[0040] When the iron tailings powder composite material replaced manufactured sand at a rate of 15-20%, it effectively improved the cubic compressive strength of the mortar specimens. The iron tailings powder composite material has a small particle size and a significant filling effect, filling the mortar pores and compacting the internal structure. It also accelerated the degree of cement hydration. The increase in cement hydration products promoted the early compressive strength of the dry-mix mortar. However, when the replacement rate increased to 25% and above, there was no significant effect on the compressive strength of the mortar specimens, and the effect was comparable to that of the control group 1.

[0041] The above-described embodiments merely illustrate several implementations of the present invention. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that a person skilled in the art would be able to make numerous variations and improvements without departing from the spirit of the present invention, and all such variations and improvements fall within the scope of protection of the present invention.

Claims

1. A modification method for preventing cracking and improving durability of iron tailings dry powder mortar, characterized in that: The modification method is for modifying iron tailings raw materials for preparing iron tailings dry powder mortar. The specific process is: first, the iron tailings raw materials are coarsely ground, and then an activator is added to finely grind to obtain iron tailings fine powder; then the obtained iron tailings fine powder is surface-modified with N-phenylacrylamide and then cross-linked to achieve gelation modification, thereby obtaining an iron tailings powder composite material.

2. The method for modifying iron tailings dry powder mortar to prevent cracking and improve durability according to claim 1, characterized in that: The amount of the activator used is 0.2%-0.8% of the mass of the coarse iron tailings powder.

3. The method for modifying iron tailings dry powder mortar to prevent cracking and improve durability according to claim 1, characterized in that: The activator is at least one of desulfurized gypsum, water glass and steel slag powder.

4. The modification method for simulating cracking and improving durability of iron tailings dry powder mortar according to claim 1, characterized in that: The particle size of the iron tailings fine powder is 100-200 μm.

5. The method for modifying iron tailings dry powder mortar to prevent cracking and improve durability according to claim 1, characterized in that: The gelling modification comprises the following steps: (1) Add the iron tailings fine powder into the N-phenylacrylamide solution and stir mechanically for standby use; (2) Sodium alginate is added to the above solution system and stirred evenly, and then a mixed solution of calcium chloride and propylene glycol is poured into the solution system. The solution system is treated at 40-50°C for 20-30 minutes. After the treatment is completed, the obtained product is dried at a constant temperature and finely ground into powder to obtain an iron tailings powder composite material.

6. The method for modifying iron tailings dry powder mortar to prevent cracking and improve durability according to claim 5, characterized in that: The mass concentration of the mixed solution of N-phenylacrylamide is 0.2%-0.5%.

7. The method for modifying iron tailings dry powder mortar to prevent cracking and improve durability according to claim 5, characterized in that: The particle size of the iron tailings powder composite material is 0.1-0.5 mm.

8. An application of the modification method according to any one of claims 1 to 7 in preparing iron tailings dry powder mortar, characterized in that: The iron tailings dry powder mortar is obtained by mixing the iron tailings powder composite material with cement, fly ash, machine-made sand and processing aids to obtain iron tailings dry powder, and then adding water to mix.

9. The iron tailings dry powder mortar according to claim 8, characterized in that: The iron tailings powder composite material has a replacement rate of 15%-30% for machine-made sand.

10. The use according to claim 8, characterized in that The processing aids include water reducer and sodium gluconate.

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