Phosphogypsum-phosphorus slag-based environment-friendly mortar and preparation method thereof

Abstract

The application discloses a kind of phosphogypsum-phosphor slag-based environmental protection mortar and preparation method thereof, mortar weight fraction components: phosphogypsum 25-40 parts, phosphor slag 25-40 parts, micron grade silico-alumina powder 10-20 parts, cement 10-20 parts, water 40-60 parts, aggregate 150-450 parts, starch ether 0.01-0.05 parts, bacteriostatic agent 0.01-0.05 parts, alkali activator 0.05-0.1, viscosity regulator 0.2-1 part, effect one is to utilize abundant and cheap phosphogypsum phosphor slag and other solid waste resources.Two is to use cycle heat baking technology to carry out low-cost simple processing to raw phosphogypsum, and obtain gypsum product with certain cementing property.Three is that alkali activation technology and sulfate activation technology synergistically react to achieve better use effect, and no retarder is needed.Four is to solve the problem of mortar mildewing caused by organic impurities in phosphogypsum product by incorporating viscosity regulator and bacteriostatic agent.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of building materials, and particularly relates to a phosphogypsum-phosphorus slag-based environment-friendly mortar and a preparation method thereof. BACKGROUND

[0002] China's phosphorus chemical industry is rich, and its products such as phosphoric acid and P2O5 can be used in many fields such as chemical fertilizers, new energy, chemical industry, food and the like. A large amount of industrial by-products such as phosphogypsum and phosphorus slag are produced. Data shows that 4.5-5.5 tons of phosphogypsum are produced for every ton of phosphoric acid, and 8-10 tons of waste slag are discharged for every ton of yellow phosphorus. A series of problems such as land occupation, resource waste and environmental pollution are caused by the large amount of solid waste discharge but cannot be effectively disposed of on a large scale. Therefore, it is of great significance to improve the utilization rate of phosphogypsum and phosphorus slag and develop phosphorus slag products that meet the actual production needs.

[0003] At present, the phosphogypsum mortar product has low strength and poor water resistance, and the raw phosphogypsum mainly contains dihydrate gypsum which has no cementitious properties and needs to be treated by a series of processes such as high-temperature calcination and alkali neutralization, which greatly limits its popularization and application. In the application of building materials, the high content of soluble phosphorus pentoxide in the phosphorus slag causes significant retarding effect on cement hydration, so the content of the phosphorus slag as a mineral admixture is also at a low level. SUMMARY

[0004] The application provides a phosphogypsum-phosphorus slag-based environment-friendly mortar and a preparation method thereof, so as to solve the problems of low use amount and low product quality of the two phosphorus chemical by-products of phosphogypsum and phosphorus slag under the current technical conditions, and make them be used for preparing various mortar products such as building, decoration and thermal insulation.

[0005] The technical scheme of the application is as follows: a phosphogypsum-phosphorus slag-based environment-friendly mortar comprises the following components in parts by weight: 25-40 parts of phosphogypsum, 25-40 parts of phosphorus slag, 10-20 parts of micron-sized silicon-aluminum powder, 10-20 parts of cement, 40-60 parts of water, 150-450 parts of aggregate, 0.01-0.05 parts of starch ether, 0.01-0.05 parts of bacteriostatic agent, 0.05-0.1 parts of alkali activator and 0.2-1 parts of viscosity regulator.

[0006] Further, the phosphogypsum is prepared by baking for 2 h at 80℃ in a circulating heat baking system, and has a specific surface area of 250-400 cm 2 / kg,

[0007] Further, the phosphogypsum comprises beta hemihydrate gypsum and dihydrate gypsum, and the mass ratio of the beta hemihydrate gypsum is 30%-70%.

[0008] Further, the micrometer-sized silico-alumina powder is one of ground powder of slag with basicity <1, coal gangue, fly ash or other natural silico-aluminate minerals, and the specific surface area is 350-450 cm 2 / kg.

[0009] Further, the aggregate is machine-made sand, and the fineness modulus is 2.6-3.3, and the MB value is ≤1.4.

[0010] Further, the bacteriostatic agent is nanometer-sized zinc oxide, and the ZnO2 content is 97%, and the particle size is about 50 nm.

[0011] Further, the alkali activator is one of NaOH and KOH.

[0012] Further, the viscosity regulator is sodium-based bentonite, and the average particle size is 20 μm, and the apparent density is 2400-2500 kg / m 3 , and the water absorption expansion rate is 30-40 ml / 2g.

[0013] The preparation method of the environment-friendly mortar comprises the following steps: weighing phosphogypsum, phosphorus slag, micrometer-sized silico-alumina powder, cement, aggregate, water, starch ether, a bacteriostatic agent, an alkali activator and a viscosity regulator according to the mass ratio; mixing the phosphogypsum, the phosphorus slag, fly ash, the cement and the viscosity regulator to obtain mixed powder; stirring the starch ether, the alkali activator and water to obtain a mixed solution; adding the mixed solution into a stirring pot; adding the mixed powder into the stirring pot, adding the aggregate after stirring for 1 min, and stirring for 3-4 min to obtain the phosphogypsum-phosphorus slag-based environment-friendly mortar.

[0014] The main mechanism of the present application is as follows: 1. The original phosphogypsum is treated by a 80℃ circulating drying process to form a state of coexistence of dihydrate gypsum and hemihydrate gypsum, and the content of β-type hemihydrate gypsum is controlled at about 50%. The β-type hemihydrate gypsum reacts quickly with water to generate dihydrate gypsum to provide early strength of the mortar, but on the one hand, the content of hemihydrate gypsum in the gypsum is reduced, and on the other hand, the free phosphate ions in the phosphogypsum and the phosphorus slag combine with Ca 2+ in the system to generate calcium phosphate attached to the surface of the gypsum particles to delay the hydration process, prolong the conversion of β-type hemihydrate gypsum to dihydrate gypsum, and prolong the overall setting time to play the role of a retarder. The phosphorus slag can better play its pozzolanic activity in an alkali environment to generate C-S-H gel and C-A-S-H gel, but the reaction needs OH — slowly dissociates Ca 2+ , Si 4+, In the early hydration stage, it mainly plays the role of inert filler, and delays the overall hydration reaction process. The micron-sized silico-alumina powder and phosphorus slag have similar effects in the early stage of the cementitious system, but the higher content of silico-aluminate minerals can also react with OH — and excess SO4 2— to generate tri-sulfur type hydrated calcium sulphoaluminate (AFt), which also consumes part of the easily soluble gypsum in the mortar, improves the strength and water resistance of the mortar.

[0015] 2. By adding an alkali activator to the mortar, more OH - can be provided to convert the acidic system of the phosphogypsum-phosphorus slag system into an alkaline environment, providing a suitable hydration environment for the silico-alumina powder and phosphorus slag. Generally, the silico-alumina powder is rich in silico-alumina, which accelerates the hydration of C-S-H gel and C-A-S-H gel under the action of the activator, but in an alkaline environment, a large amount of SO4 2- and AFm in the mortar produces a sulfate activation effect to generate a large amount of tri-sulfur type hydrated calcium sulphoaluminate (Aft). A large amount of needle-like Aft interlocks with the previously generated dihydrate gypsum, C-S-H gel, and C-A-S-H gel to fill the voids and improve the overall performance of the mortar.

[0016] The beneficial effects of the present application are: 1. In Guizhou region, the abundant and inexpensive phosphogypsum, phosphorus slag and other solid waste resources can be used for the production of building materials, reducing the production cost of the mortar and improving the product benefit. 2. The original phosphogypsum is treated at low cost by using the circulating heat baking technology to obtain a gypsum product with certain cementitious properties. 3. The reaction mode of the alkali activation technology and the sulfate activation technology is reasonably utilized, and the originally low-activity waste slag is promoted by the mutual promotion of the reaction mode, and the whole process does not need a retarder. 4. The technical problem of mold caused by organic impurities in the phosphogypsum product is solved by adding a viscosity regulator and a bacteriostatic agent, which makes a technical innovation for further popularization of the application of the phosphogypsum product. DETAILED DESCRIPTION

[0017] The technical solutions of the present application will be further described in detail below, which are an explanation of the present application rather than a limitation.

[0018] A preparation method of a phosphogypsum-phosphorus slag-based environmentally friendly mortar comprises the following steps:

[0019] Step 1: weigh the phosphogypsum, phosphorus slag, micron-sized silico-alumina powder, cement, aggregate, water, starch ether, alkali activator, and viscosity regulator according to the mass ratio of each component;

[0020] Step two: the phosphogypsum, phosphorus slag, fly ash, cement, viscosity modifier are mixed in advance to obtain a mixed powder; the weighed starch ether and alkali activator are added into water and stirred to obtain a mixed solution.

[0021] Step three: the mixed solution is added into a stirring pot; the mixed powder is added into the stirring pot, and after stirring for 1 min, the weighed aggregate is added, and then stirred for 3-4 min to obtain the phosphogypsum-phosphorus slag-based environment-friendly mortar.

[0022] The phosphogypsum-phosphorus slag-based environment-friendly mortar refers to a mortar product meeting the performance requirements of wet-mixed or dry-mixed plastering mortar and masonry mortar in the standard GB / T 25181-2019 "Pre-mixed mortar", which can be used for building wall plastering, mortar insulation layer, wall masonry, etc.

[0023] The mass ratio of the specific comparative example 1-2 and the example 1-5 is as follows:

[0024] Table 1 mass ratio of example 1-5 and comparative example 1-2

[0025]

[0026] The performance of the comparative example and the example is tested, and the results are as follows:

[0027] Table 2 performance index of freshly mixed mortar of comparative example 1-2 and example 1-5

[0028] Comparative Example 1 Comparative Example 2 Example 1 Example 2 Example 3 Example 4 Example 5 Water retention / % 80 85 93 97 95 95 96 Plastic consistency time / h 4.5 6.5 4 3.7 4.2 6.3 3.1 Consistency / mm 120 118 107 79 85 78 87 Initial setting time / min 300 420 290 300 325 400 320 Final setting time / min 730 460 450 430 435 465 395

[0029] Table 2 performance index of hardened mortar of comparative example 1-2 and example 1-5

[0030]

[0031] The above table data shows that by comparing comparative example 1 with example 1, it can be concluded that when no alkali activator is added, the compressive strength, bonding strength and water resistance of the mortar at each age are poor. In comparative example 2, no micron-sized silicon-aluminum powder (this part of the silicon-aluminum powder is replaced by phosphogypsum and phosphorus slag at a mass ratio of 0.35:0.45) is added, and under the same amount of alkali activator as in example 1, the mechanical properties and water resistance of the mortar are significantly lower than those of the mortar in example 1 which contains a certain proportion of micron-sized silicon-aluminum powder. After the introduction of the silicon-aluminum powder, the aluminate minerals in it can further produce a sulfate activation effect under the joint action of the sulfate environment and the alkali environment, generating a large amount of Aft crystals, thereby improving the compressive strength, bonding properties and water resistance of the mortar.

[0032] In example 1-3, by adjusting the relative ratio of phosphogypsum and phosphorus slag, it can be concluded that the ratio of the two has a certain influence on the performance of the mortar. The amount of phosphogypsum will affect the SO4 2—The content of phosphogypsum, the relative proportion of phosphogypsum in example 1 is lower (the mass ratio of phosphogypsum to phosphorus slag is 0.35:0.45), the 1d, 3d and 28d compressive strength is reduced by 10.5% and 8.0% and 6.4% respectively compared with example 3, the softening coefficient is reduced by 0.3, and the bonding strength is reduced by 14.3%. In example 2, the relative proportion of phosphogypsum is higher (the mass ratio of phosphogypsum to phosphorus slag is 0.45:0.35), the 1d, 3d and 28d compressive strength of the mortar is reduced by 12.6%, 16.7%, 20.7% respectively compared with example 3, the bonding strength is reduced by 14.3%, and the softening coefficient is reduced by 0.4. In summary, based on example 3, in the case of reducing the relative proportion of phosphogypsum, the early performance of the mortar will decrease to a large extent, and the 28d bonding strength decreases by 14.3%; in the case of reducing the relative proportion of phosphorus slag, the 28d compressive strength of the mortar decreases significantly, and the 28d bonding strength also decreases by 14.3%.

[0033] By comparing the experimental results of example 3, example 4 and example 5, it can be concluded that under different alkali activator dosages, the effect of alkali-sulfate synergistic effect is also different. In the case of lower alkali activator dosage (example 4), the compressive strength of the mortar at each age and the 28d bonding strength are all less than those of example 3 and example 5, but the plastic retention time and setting time are longer than those of example 3 and example 5. With the increase of alkali activator dosage, the initial setting time and final setting time of the mortar gradually shorten, and the 28d compressive strength and bonding strength gradually increase.

[0034] The above data show that the performance of the mortar in the patent is guaranteed at the same time, which needs the aluminate component provided by the micron-sized silicon-aluminum powder, the large amount of sulfate ions in phosphogypsum, the high pozzolanic activity substance in phosphorus slag and the strong alkaline environment. The alkali activation effect and the sulfate activation effect complement each other and jointly promote the improvement of the performance of the mortar.

[0035] Through experiments, it can be found that the technical scheme of the present application can obtain phosphogypsum-phosphorus slag-based mortar products that meet market demand. The use value of phosphogypsum and phosphorus slag can be effectively improved, the production cost of traditional cement-based mortar can be reduced, and at the same time, environment-friendly mortar with excellent quality and high water resistance can be obtained, which meets the demand of various mortar products such as masonry, decoration and thermal insulation, and has obvious performance advantages when compared with similar products, and has strong market competitiveness.

Claims

1. An environmentally friendly phosphogypsum-phosphorus slag-based mortar, characterized in that, The composition comprises the following components by weight: 25-40 parts of phosphogypsum, 25-40 parts of phosphorus slag, 10-20 parts of micron-sized silico-alumina powder, 10-20 parts of cement, 40-60 parts of water, 150-450 parts of aggregate, 0.01-0.05 parts of starch ether, 0.01-0.05 parts of bacteriostatic agent, 0.05-0.1 parts of alkali activator, and 0.2-1 parts of viscosity regulator, wherein the phosphogypsum comprises beta-type hemihydrate gypsum and dihydrate gypsum, the mass ratio of beta-type hemihydrate gypsum is 30%-70%, the alkali activator is one of NaOH and KOH, and the viscosity regulator is sodium-based bentonite with an average particle size of 20 μm, an apparent density of 2400-2500 kg / m 3 , and a water absorption expansion rate of 30-40 ml / 2g.

2. The environmentally friendly mortar according to claim 1, wherein The phosphogypsum is prepared by a circulating heat baking system at 80°C for 2h, and has a specific surface area of 250-400cm 2 / g.

3. The environmentally friendly mortar according to claim 1, wherein The micrometer-sized silico-alumina powder is a ground powder of one of the following: a slag having a basicity < 1, a coal gangue, a fly ash or another natural silico-aluminate mineral, having a specific surface area of 350-450 cm 2 / kg.

4. The environmentally friendly mortar according to claim 1, wherein The aggregate is machine-made sand, fineness modulus is 2.6-3.3, and MB value is less than or equal to 1.

4.

5. The environmentally friendly mortar as set forth in claim 1, wherein The bacteriostatic agent is nano-sized zinc oxide, ZnO content is 97%, and particle size is 50nm.

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