Method for preparing concrete admixture from waste incineration bottom slag

Abstract

The invention discloses a method for preparing a concrete admixture by using waste incineration bottom slag, which comprises the following steps: (1) crushing: crushing and screening the waste incineration bottom slag; (2) aging: standing the crushed waste incineration bottom slag for 4-6 weeks for aging pretreatment, and keeping the surface of a waste incineration bottom slag pile body wet in the aging process; (3) drying: drying the aged waste incineration bottom slag, and controlling the water content to be less than or equal to 1%; and (4) grinding: grinding the dried waste incineration bottom slag, controlling the specific surface area of the waste incineration bottom slag to be 400-600m / kg, and controlling the screen residue of a 45-micron screen to be less than 15%, thereby obtaining the concrete admixture. According to the method for preparing the concrete admixture from the waste incineration bottom slag, the waste bottom slag is successfully converted into the concrete admixture with the high additional value, the preparation method is simple, the leaching toxicity of chloride ions and heavy metal is detected to be qualified, and the concrete admixture can replace cement to be used for preparing concrete according to the mass proportion of 10-20%.

Description

Technical Field

[0002] This invention relates to the field of waste incineration bottom ash recycling technology, and in particular to a method for preparing concrete admixtures using waste incineration bottom ash. Background Technology

[0003] With the acceleration of urbanization and the improvement of living standards in my country, the amount of municipal solid waste generated is increasing year by year. Incineration has become the mainstream treatment method due to its advantages of volume reduction, harmlessness, and high resource recovery. The main byproducts of waste incineration are bottom ash and fly ash. The incineration process produces a large amount of byproduct—bottom ash (BA), which accounts for approximately 20% to 30% of the total weight of incinerated waste. The disposal of this massive amount of bottom ash has become a serious challenge hindering sustainable urban development. Currently, the main method of disposal is landfill, but this not only occupies valuable land resources and poses an environmental risk of heavy metal leaching and contamination of soil and groundwater, but also represents a huge waste of the resources contained within, which is inconsistent with the development concepts of "zero-waste cities" and a circular economy.

[0004] The main chemical components of the waste incineration bottom ash produced after waste incineration are oxides of silicon, calcium, and aluminum, which are somewhat similar to natural mineral admixtures such as fly ash and slag powder. Theoretically, it has the potential to be used as a building material, especially as a mineral admixture for concrete. Based on the current utilization status of various countries around the world, its main resource utilization methods are: (1) as a substitute aggregate for petroleum asphalt pavement; (2) as a substitute aggregate for cement or concrete; (3) as landfill covering material; (4) as filling material for embankments, roadbeds, etc. At present, waste bottom ash is mainly used as roadbed filling material and as a substitute for sand and gravel aggregates, neglecting the higher utilization value of waste incineration bottom ash. For example, waste incineration bottom ash has a certain pozzolanic activity and can be used as an auxiliary cementitious material in cement concrete. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing concrete admixtures using waste incineration bottom ash, which can realize the transformation of waste into treasure, with low cost, simple process, environmental friendliness, and industrialization, and provides a new type of auxiliary cementitious material for the development of green concrete technology.

[0006] The technical solution adopted by this invention to solve its technical problem is: a method for preparing concrete admixtures using waste incineration bottom ash, comprising the following steps: (1) Crushing: Crushing and screening the bottom ash from waste incineration: (2) Aging: The crushed waste incineration bottom ash is left to stand for 4 to 6 weeks for aging pretreatment. During the aging process, the surface of the waste incineration bottom ash pile is kept moist. (3) Drying: Dry the aged waste incineration bottom ash to control the moisture content to ≤1%; (4) Grinding: Grind the dried waste incineration bottom ash to control its specific surface area to be 400-600 m² / kg and the residue on a 45 μm sieve to be less than 15%, thus obtaining concrete admixture.

[0007] Furthermore, in step (4), 0.01% to 0.05% of the bottom ash from waste incineration is added as a grinding aid during the grinding process.

[0008] Furthermore, the grinding aid is selected from ethanolamine.

[0009] Furthermore, during the aging process in step (2), the bottom ash from the waste incineration is piled into long strips, and the pile is sprayed with water every 3 to 4 days.

[0010] Furthermore, step (3) involves drying in a dryer with hot air at 100°C.

[0011] A method for using concrete admixtures prepared from waste incineration bottom ash, wherein 10-20% of the cement content is replaced with any of the concrete admixtures prepared above during concrete mix design.

[0012] Furthermore, the amount of water-reducing agent in the concrete mix design is increased by 5-10%.

[0013] The beneficial effects of this invention are: This invention provides a method for preparing concrete admixtures using waste incineration bottom ash, which successfully transforms waste bottom ash into high-value-added concrete admixtures. The preparation method is simple, and the chloride ion and heavy metal leaching toxicity tests are qualified. It can replace cement in concrete preparation at a mass ratio of 10-20%. Detailed Implementation

[0014] The present invention will be further described below with reference to embodiments.

[0015] Example 1: (1) Raw material preparation: Take 10 tons of fresh waste incineration bottom ash (BA) after sorting and crushing from the municipal solid waste incineration power plant. Its initial moisture content is about 15%, and it contains a small amount of unreacted aluminum flakes and non-ferrous metals. (2) Aging and stabilization treatment: The above-mentioned fresh waste incineration bottom ash was transported to the seepage-proof storage site and piled into a long strip with a height of 1.5 meters. Water was sprayed every 3 days by a water truck to keep the surface of the pile moist for 6 weeks of aging treatment. After the aging was completed, samples were taken and tested to confirm that there was no bubbling phenomenon, indicating that the volume stability was good. (3) Drying and grinding: Drying: The aged bottom residue particles are placed in a dryer and dried with hot air at 100°C until the moisture content is reduced to 0.8%; Grinding: The dried bottom slag particles were placed in a ball mill for the experiment, and 0.03% of the bottom slag mass of triethanolamine was added as a grinding aid. A closed-loop circulation system was used for grinding, and the fineness of the product was controlled by adjusting the speed of the classifier. Finally, about 7.2 tons of concrete admixture (MBAP) with a specific surface area of ​​525 m² / kg and a sieve residue of 12% on a 45 μm sieve was obtained.

[0016] Samples were taken and sent for testing. The key indicators for testing are as follows: Chemical composition: Total content of SiO2+Al2O3+Fe2O3 >70%; Chloride ion (Cl⁻) content: 0.045% (meets the requirements for admixtures in the "General Silicate Cement" standard); Heavy metal leaching toxicity: Tested according to the "Solid Waste Leaching Toxicity Leaching Method Sulfuric Acid-Nitric Acid Method" (HJ / T299), the leaching concentrations of lead (Pb), cadmium (Cd), chromium (Cr), copper (Cu), etc. are far below the standard limits, classifying it as an environmentally safe product; Activity index: Measured according to the "Fly Ash Used in Cement and Concrete" (GB / T1596), its 7-day activity index is 68%, and its 28-day activity index is 78%.

[0017] (4) Concrete application test Mix design: C30 strength grade concrete was prepared. The cement dosage of the baseline group was 300 kg / m³. The experimental group adopted a 15% equivalent mass substitution rate, that is, 45 kg of concrete admixture MBAP was used to replace 45 kg of cement, and the cement dosage was adjusted to 255 kg / m³. In order to maintain the same slump (180±20 mm), the dosage of high-efficiency polycarboxylate superplasticizer in the experimental group was slightly increased from 4.0 kg / m³ in the baseline group to 4.3 kg / m³.

[0018] The workability of the prepared C30 concrete was tested, and the results are as follows: Workability: Freshly mixed concrete has good workability and exhibits no bleeding or segregation. Compressive strength: The compressive strength of the experimental group reached 95% of that of the baseline group after 28 days and 102% of that of the baseline group after 56 days, showing good late-stage strength growth characteristics; Durability: Through the chloride ion penetration resistance (electric flux method) level test, the chloride ion penetration resistance of the experimental group concrete is at the same level QⅣ as the benchmark group.

Claims

1. A method for preparing concrete admixtures using waste incineration bottom ash, characterized in that, Includes the following steps: (1) Crushing: Crushing and screening the bottom ash from waste incineration: (2) Aging: The crushed waste incineration bottom ash is left to stand for 4 to 6 weeks for aging pretreatment. During the aging process, the surface of the waste incineration bottom ash pile is kept moist. (3) Drying: Dry the aged waste incineration bottom ash to control the moisture content to ≤1%; (4) Grinding: Grind the dried waste incineration bottom ash to control its specific surface area to be 400-600 m² / kg and the residue on a 45 μm sieve to be less than 15%, thus obtaining concrete admixture.

2. The method for preparing concrete admixtures using waste incineration bottom ash according to claim 1, characterized in that: In step (4), 0.01% to 0.05% of the bottom ash from waste incineration is added as a grinding aid during the grinding process.

3. The method for preparing concrete admixtures using waste incineration bottom ash according to claim 2, characterized in that: The grinding aid is ethanolamine.

4. The method for preparing concrete admixtures using waste incineration bottom ash according to claim 1, characterized in that: In step (2), the bottom ash from the waste incineration is piled into long strips, and water is sprayed onto the pile every 3 to 4 days.

5. The method for preparing concrete admixtures using waste incineration bottom ash according to claim 1, characterized in that: The step (3) involves drying in a dryer with hot air at 100°C.

6. A method for using concrete admixture prepared from waste incineration bottom ash, characterized in that: In concrete mix design, 10-20% of the cement content is replaced with concrete admixtures prepared according to any one of claims 1-5.

7. A method for using a concrete admixture prepared from waste incineration ash according to claim 6, characterized in that: The amount of water-reducing agent in the concrete mix design should be increased by 5-10%.