A concrete aggregate based on desert sand and recycled materials and its preparation method

Abstract

This invention discloses a concrete aggregate based on desert sand and recycled materials, which is composed of the following components by mass percentage: 40.0% to 48.0% desert sand powder, 35.0% to 45.0% manufactured sand and slag powder, 5.0% to 15.0% copper slag powder, 2.0% to 4.0% mineralizer, and 2.0% water. This invention also discloses a method for preparing the above-mentioned concrete aggregate, specifically: manufactured sand and desert sand are placed in a high-temperature furnace and calcined at 800°C, then naturally cooled to room temperature; the calcined desert sand, manufactured sand, and copper slag particles are ground into 200-mesh powders to obtain desert sand powder, manufactured sand powder, and copper slag powder, respectively; the desert sand powder, manufactured sand powder, copper slag powder, and mineralizer are mixed in a ball mill to obtain a mixed powder; the mixed powder is mixed with the prescribed amount of water to obtain a moist powder, which is then pressed into dense blocks and placed in a vacuum drying oven for vacuuming; the blocks are placed in a high-temperature furnace and calcined at 1100°C, then naturally cooled to room temperature to obtain the aggregate.

Description

Technical Field

[0001] This invention relates to a concrete aggregate based on desert sand and recycled materials, and also to a method for preparing the aforementioned concrete aggregate. Background Technology

[0002] Industrial production generates a large amount of solid waste annually, such as copper slag and manufactured sand. Copper slag powder has low hydration activity, making it difficult to use in large quantities as an auxiliary cementitious material in concrete production. Manufactured sand, lacking hydration activity, cannot be used directly as an auxiliary cementitious material, and simple stockpiling and landfilling would place a heavy burden on the environment. Furthermore, desert sand regions contain large amounts of desert sand, but due to its poor mechanical properties, high impurity content, excessively fine particle size, and smooth surface, it cannot be used as fine aggregate in concrete. Summary of the Invention

[0003] Objectives of the invention: One objective of the invention is to provide a concrete aggregate based on desert sand and recycled materials; another objective of the invention is to provide a method for preparing the above-mentioned concrete aggregate.

[0004] Technical solution: The concrete aggregate based on desert sand and recycled materials described in this invention is composed of the following components by mass percentage: 40.0% to 48.0% desert sand powder, 35.0% to 45.0% manufactured sand and slag powder, 5.0% to 15.0% copper slag powder, 2.0% to 4.0% mineralizer, and 2.0% water.

[0005] The desert sand powder is desert sand that has been calcined at 800-850℃ and then ground to a powder of 200 mesh. Desert sand contains small amounts of calcium carbonate, kaolinite, and organic matter. If it is not calcined beforehand to decompose and volatilize, the gas produced during the calcination of aggregates will generate bubbles inside the aggregates. Calcination can decompose the calcium carbonate, kaolinite, and organic impurities it contains into gases and volatilize them.

[0006] The desert sand mentioned is Tengger Desert sand with a particle size of 60-120 mesh.

[0007] The manufactured sand and slag powder is produced by calcining manufactured sand and slag at 800-850℃ and then grinding it to a powder of 200 mesh. The manufactured sand and slag powder is composed of soil and limestone (calcium carbonate) powder. The soil contains a small amount of kaolinite and organic impurities. Pre-calcination decomposes the kaolinite, organic matter, and limestone, preventing the formation of air bubbles within the aggregate during calcination. Calcination also decomposes the kaolinite, organic matter, and limestone into gases that then volatilize.

[0008] The manufactured sand slag used in this invention is a mixture of clay and stone powder produced during the manufactured sand production process. The manufactured sand slag is a solid waste obtained by crushing natural gravel into manufactured sand, washing the manufactured sand with water, and settling the sand washing wastewater.

[0009] The copper slag powder is copper slag particles ground to 200 mesh.

[0010] The copper slag particles are slag produced during the copper smelting process, with a particle size of 1-3 mm; they are taken from Feiyue Stone Processing Plant in Hongqiao District, Tianjin.

[0011] The mineralizing agent is sodium fluorosilicate.

[0012] The above-mentioned method for preparing aggregates for concrete includes the following steps:

[0013] (1) Place the manufactured sand and desert sand in a high-temperature furnace and calcine them at 800-850°C, then let them cool naturally to room temperature;

[0014] (2) The calcined desert sand, machine-made sand slag and copper slag particles were ground into 200 mesh powder respectively to obtain desert sand powder, machine-made sand slag powder and copper slag powder respectively.

[0015] (3) Mix the desert sand powder, machine-made sand slag powder, copper slag powder and mineralizer in a ball mill to obtain a mixed powder;

[0016] (4) Mix the mixed powder with the amount of water in the formula to obtain a moist powder, press it into a dense block, and place it in a vacuum drying oven to vacuum. By vacuuming, the residual gas and some moisture in the block are evaporated, reducing the proportion of pores left in the aggregate after calcination, thereby making the aggregate denser and improving the mechanical properties of the aggregate.

[0017] (5) Place the block in a high-temperature furnace and calcine it at 1100-1150℃, then let it cool naturally to room temperature to obtain aggregate.

[0018] In step (1), the calcination time is not less than 30 minutes.

[0019] In step (4), the vacuuming time is no more than 3 minutes.

[0020] In step (5), the calcination time is not less than 1 hour.

[0021] Beneficial effects: Compared with the prior art, the present invention has the following significant advantages: The method of the present invention utilizes industrial solid waste to prepare high-strength concrete aggregate, which significantly reduces the environmental impact of waste while effectively reducing the consumption of natural resources; the present invention produces hard, high-strength aggregate (containing diopside and forsterite) from the materials mentioned above (as referred to in the background art) that are unsuitable for producing concrete aggregate, and its mechanical properties (characterized by crushing index) meet the national standard requirements and can be used to produce concrete; since diopside and forsterite do not have the possibility of reacting with cement, the aggregate obtained by the present invention is ensured to exist stably in concrete. Attached Figure Description

[0022] Figure 1 The XRD pattern of the desert sand used in this invention;

[0023] Figure 2 The XRD pattern of the manufactured sand and slag soil used in this invention;

[0024] Figure 3 The XRD pattern of the copper slag used in this invention;

[0025] Figure 4 The image shows the XRD pattern of the aggregate prepared in Example 1. Detailed Implementation

[0026] The raw materials used in the concrete aggregate of this invention are: desert sand from the Tengger Desert with a particle size of 60-120 mesh; copper slag particles provided by Feiyue Stone Processing Plant in Hongqiao District, Tianjin, with a particle size of 1-3 mm; copper slag powder obtained by grinding copper slag particles; and manufactured sand and slag soil, which is the solid waste obtained by crushing natural gravel into manufactured sand, washing the manufactured sand with water, and settling the sand washing wastewater. The specific compositional analysis of the manufactured sand and slag soil is detailed below. Figure 2 Sodium fluorosilicate, analytical grade, produced by Tianjin Kemei Chemical Reagent Co., Ltd.

[0027] Example 1

[0028] The present invention provides a method for preparing aggregates for concrete, comprising the following steps:

[0029] (1) Place the manufactured sand and desert sand in a high-temperature furnace and calcine them at 800℃ for 30 minutes. Let them cool naturally to room temperature. Weigh out 1224.5g of the calcined manufactured sand and 1224.5g of the desert sand for later use.

[0030] (2) 1224.5g of desert sand, 1224.5g of machine-made sand and slag and 459.2g of copper slag particles after calcination were ground into 200-mesh powder respectively to obtain desert sand powder, machine-made sand and slag powder and copper slag powder respectively.

[0031] (3) Desert sand powder, manufactured sand slag powder, copper slag powder and 91.8g of mineralizer are put into a ball mill and mixed to obtain a mixed powder; the mineralizer is sodium fluorosilicate;

[0032] (4) Mix the mixed powder with 61.2g of water to obtain a moist powder, press it into a dense block, and place it in a vacuum drying oven for 3 minutes;

[0033] (5) The block is placed in a high-temperature furnace and calcined at 1100℃ for 1 hour, then naturally cooled to room temperature to obtain aggregate; after calcination, aggregate containing diopside and forsterite is generated, which is the hard aggregate of this invention, such as Figure 4 The XRD pattern is shown below.

[0034] The formulations of the aggregates in Examples 2 to 7 are shown in Table 1. Examples 2 to 7 were prepared using the same process as in Example 1.

[0035] Table 1

[0036]

[0037] Crushing index tests were conducted on the aggregates of Examples 1 to 7, and the results are shown in Table 2.

[0038] Table 2

[0039]

[0040] GB / T 14685-2022, "Construction Gravel and Crushed Stone," specifies that mechanical properties are characterized by the crushing index. Approximately 3000g of aggregate is taken each time, and the crushing index for grade I, II, and III crushed stone is ≤10%, 20%, and 30%, respectively. Due to the irregular shape of the crushed stone, the crushing index is used to characterize its mechanical properties. Table 2 shows that Example 4 exhibits the best mechanical properties, while Example 7 shows the worst. The excessive mineralizer in Example 7 negatively impacts its mechanical properties.

[0041] Comparative Example 8

[0042] The formula is exactly the same as that of Example 1. The only difference is that the manufactured sand and desert sand in step (1) are not calcined and are directly ground into 200-mesh powder. As a result, Comparative Example 8 cannot form the hard aggregate containing diopside and forsterite of the present invention because the lack of calcination in the early stage will generate a large number of bubbles during the calcination process in step (5), making it difficult to form the hard aggregate of the present invention.

Claims

1. A concrete aggregate based on desert sand and recycled materials, characterized in that, It is composed of the following components by mass percentage: desert sand powder 40.0%~48.0%, manufactured sand and slag powder 35.0%~45.0%, copper slag powder 5.0%~15.0%, mineralizer 2.0%~4.0%, and water 2.0%; the desert sand powder is natural desert sand calcined at 800~850℃ and then ground to 200 mesh powder; the manufactured sand and slag powder is manufactured sand and slag calcined at 800~850℃ and then ground to 200 mesh powder; The above-mentioned method for preparing concrete aggregates based on desert sand and recycled materials includes the following steps: (1) Place the manufactured sand and desert sand in a high-temperature furnace and calcine them at 800~850℃, then let them cool naturally to room temperature; (2) The calcined desert sand, machine-made sand slag and copper slag particles are ground into 200 mesh powder respectively to obtain desert sand powder, machine-made sand slag powder and copper slag powder respectively; (3) Mix the desert sand powder, machine-made sand slag powder, copper slag powder and mineralizer in a ball mill to obtain a mixed powder; (4) Mix the mixed powder with the amount of water specified in the formula to obtain a moist powder, press it into a dense block, and place it in a vacuum drying oven to evacuate the vacuum. (5) Place the block in a high-temperature furnace and calcine it at 1100~1150℃, then let it cool naturally to room temperature to obtain aggregate.

2. The concrete aggregate based on desert sand and recycled materials according to claim 1, characterized in that: The mineralizing agent is sodium fluorosilicate.

3. The concrete aggregate based on desert sand and recycled materials according to claim 1, characterized in that: In step (1), the calcination time is not less than 30 minutes.

4. The concrete aggregate based on desert sand and recycled materials according to claim 1, characterized in that: In step (4), the vacuuming time shall not exceed 3 minutes.

5. The concrete aggregate based on desert sand and recycled materials according to claim 1, characterized in that: In step (5), the calcination time is not less than 1 hour.

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