Concrete admixture based on washed sand sludge and preparation method thereof

Abstract

The invention discloses a concrete admixture based on washed sand sludge and a preparation method thereof, comprising the following steps: 1) drying and crushing the sludge to obtain sludge powder; 2) drying and grinding coal gangue, and then feeding it into a decomposition furnace as fuel; 3) feeding the sludge powder obtained in step 1) into a preheater for preheating, and then feeding it into a decomposition furnace after preheating; 4) feeding the material decomposed in the decomposition furnace into a rotary kiln for calcining into clinker, and cooling it in a grate cooler to obtain clinker; 5) roller pressing and ball milling the clinker to obtain a finished product. The admixture prepared by using washed sand sludge as raw material has good performance, a fluidity ratio of 105%, a water content of 0.34%, a loss on ignition of 1.34%, and a 28d activity index of 88%.

Description

Technical Field

[0001] The invention relates to the technical field of concrete admixtures, in particular to a method for preparing concrete admixtures based on water-washed sand sludge. Background Art

[0002] Concrete admixtures are natural or artificial powdered minerals added to concrete during mixing to improve concrete properties, conserve water, and adjust concrete strength. Admixtures can be divided into active and inactive admixtures. Active mineral admixtures do not harden on their own or harden very slowly. However, when mixed with calcium-rich materials such as lime and slaked lime and water, they can solidify and harden, thereby developing strength. Alternatively, they can react with calcium hydroxide produced by cement hydration to form hydration products with gelling properties, such as fly ash, granulated blast furnace slag powder, zeolite powder, and silica fume. In engineering practice, a "double admixture" technique is often used: adding a water reducer simultaneously with fly ash. Conventional, high-strength, and high-performance concrete formulated in this way can conserve cement, improve concrete workability, strength, and durability, and significantly reduce the heat of hydration of large-volume concrete, meeting the construction requirements of various projects.

[0003] The sand washing process generates muddy wastewater. The greater the sand washing volume, the greater the amount of mud and wastewater produced. Direct discharge without treatment not only pollutes the environment but can also cause river blockages. Sand washing plants typically have large sedimentation tanks to allow the mud to settle naturally. The clear water is then drained from the tanks, and the settled sludge at the bottom is excavated. The resulting washed sand sludge is typically landfilled or piled directly, making it difficult to dispose of. However, the main components of the sludge include SiO2, CaMg(CO3)2, CaCO3, Al2SiO5, Al2O3, and CaO. SiO2 and Al2O3 react with cement to produce Ca(OH)2, forming CSH and CAH, which hydrate calcium sulfoaluminate. This improves both the early and late strength of concrete, while reducing cement usage. Therefore, using washed sand sludge as a raw material to prepare concrete admixtures could be considered, enabling the recycling of waste sludge, saving costs, and addressing the treatment issues of washed sand sludge.

[0004] Gangue is an industrial solid waste emitted during coal mining. Over the years, it has accumulated in mountains in coal mines and their surrounding areas, and discharge continues year by year, occupying land and polluting the environment. The comprehensive utilization of gangue has long been a key research and development topic in the coal and building materials industries. Currently, some gangue, which contains a certain calorific value, is used in brick making and power generation. Natural gangue's main components include Al2O3 and SiO2, along with varying amounts of Fe2O3, CaO, MgO, Na2O, K2O, P2O5, SO3, and trace elements. Therefore, it is also used as a cement admixture. However, due to its calorific value, direct use of gangue as an admixture raw material can easily lead to low-temperature, oxygen-deficient combustion during calcination and preheating, potentially causing clogging of the cyclone. Because the composition of gangue varies significantly depending on its origin, insufficient theoretical research on gangue has significantly constrained its application and development. Summary of the Invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing concrete admixture based on water-washed sand sludge.

[0006] The purpose of the present invention is achieved through the following technical solution: A method for preparing concrete admixture based on washed sand sludge, comprising the following steps:

[0007] 1) Drying and crushing the sludge to obtain sludge powder;

[0008] 2) The gangue is dried, ground and then fed into the decomposition furnace as fuel;

[0009] 3) The sludge powder from step 1) is fed into a preheater for preheating, and then fed into a decomposition furnace;

[0010] 4) The material decomposed in the calciner is sent to the rotary kiln for calcination into clinker, and then cooled in the grate cooler to obtain clinker;

[0011] 5) The clinker is rolled and ball milled to obtain the finished product;

[0012] Furthermore, the tail gas from the preheater in step 3) is fed into step 1) to supplement the heat source for drying and crushing the sludge;

[0013] Furthermore, the waste heat exhaust gas from the grate cooler in step 4) is fed into step 2) to provide a drying heat source for the gangue grinding; a portion of the high-temperature exhaust gas at the front end of the grate cooler is used as secondary air for the kiln; a portion is fed to the decomposition furnace via the tertiary air duct as combustion air; and another portion is fed to step 2) via the waste heat air duct to provide a drying heat source for the gangue grinding; the remaining exhaust gas is cooled, then passed through a dust collector to collect dust, and then discharged into the atmosphere;

[0014] Furthermore, in step 3), auxiliary materials are added to the sludge powder when entering the preheater; the auxiliary materials are black soil powder or green shale powder;

[0015] Furthermore, in step 3), dust removal ash is added to the sludge powder when entering the preheater; the dust removal ash comes from the tail gas dust removal system of the sludge drying and crushing in step 1) and the tail gas dust removal system of the coal gangue drying and grinding in step 2);

[0016] Furthermore, the tail gas from the sludge drying and crushing in step 1) is separated and dusted by a collector, and then enters a heat exchanger under the action of a high-temperature fan. After heat exchange and cooling, it enters a bag dust removal system, and the dust separated and collected by the bag dust removal system is used as dust removal ash;

[0017] Furthermore, the gangue and exhaust gas after drying and grinding in step 2) enter the bag dust removal system, the separated gangue is sent to the decomposition furnace as fuel, and the separated dust is used as dust removal ash;

[0018] Furthermore, in step 3), the preheater is preheated to 200°C to 400°C and then fed into the decomposition furnace, the decomposition temperature in the decomposition furnace is 500°C to 800°C, and the decomposition time is 2h to 24h;

[0019] Furthermore, in step 4), the calcination temperature in the rotary kiln is 1100° C. to 1150° C., and the calcination time is 5 h to 48 h.

[0020] The present invention also provides a concrete admixture based on water-washed sand sludge, which is prepared by using the above-mentioned method for preparing the concrete admixture based on water-washed sand sludge.

[0021] The present invention has the following advantages:

[0022] 1. The admixture prepared by using water-washed sand sludge as raw material in the present invention has good performance, with a fluidity ratio of 105%, a water content of 0.34%, a loss on ignition of 1.34%, and a 28d activity index of 88%. Since the sludge in the admixture raw material contains active SiO2 and Al2O3, which react with the components in cement to produce Ca(OH)2 to generate CSH and CAH, and hydrate calcium sulfoaluminate, it can improve the early strength of concrete, while improving the later strength of concrete and reducing the amount of cement. The coal gangue in the admixture raw material is dried and ground and used as fuel in the decomposition furnace to avoid clogging of the cyclone during the preheating process. At the same time, after being burned in the decomposition furnace, it is sent to the rotary kiln and calcined together with the sludge to form a concrete composite admixture, which can fully utilize the coal gangue and help solve the problem of limited application of coal gangue in concrete admixtures. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 It is a process flow chart of the present invention.

[0024] Figure 2 This is the XRD pattern of sludge raw clinker. DETAILED DESCRIPTION

[0025] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0026] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort are also within the scope of protection of the present invention.

[0027] It should be noted that, in the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other.

[0028] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0029] In the description of the present invention, it should be noted that the terms "center," "upper," "lower," "left," "right," "vertical," "horizontal," "inner," "outer," etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is typically placed when in use, or are the orientations or positional relationships commonly understood by those skilled in the art. These terms are intended only to facilitate the description of the present invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, be constructed, or operate in a specific orientation. Therefore, they should not be construed as limiting the present invention. Furthermore, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0030] In the description of the present invention, it should also be noted that, unless otherwise expressly specified or limited, the terms "disposed," "installed," "connected," and "connected" should be understood in a broad sense. For example, they may refer to fixed connections, detachable connections, or integral connections; they may refer to mechanical connections or electrical connections; they may refer to direct connections or indirect connections through an intermediate medium; and they may refer to internal communication between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0031] Example 1: Figure 1 As shown, a method for preparing concrete admixture based on washed sand sludge comprises the following steps:

[0032] 1) Drying and crushing the sludge to obtain sludge powder;

[0033] 2) The gangue is dried, ground and then fed into the decomposition furnace as fuel;

[0034] 3) The sludge powder from step 1) is fed into a preheater for preheating, and then fed into a decomposition furnace;

[0035] 4) The material decomposed in the calciner is sent to the rotary kiln for calcination into clinker, and then cooled in the grate cooler to obtain clinker;

[0036] 5) The clinker is rolled and ball milled to obtain the finished product;

[0037] Furthermore, the tail gas from the preheater in step 3) is fed into step 1) to supplement the heat source for drying and crushing the sludge;

[0038] Furthermore, the waste heat exhaust gas from the grate cooler in step 4) is fed into step 2) to provide a drying heat source for the gangue grinding;

[0039] Furthermore, in step 3), auxiliary materials are added to the sludge powder when entering the preheater; the auxiliary materials are black soil powder or green shale powder;

[0040] Furthermore, in step 3), dust removal ash is added to the sludge powder when entering the preheater; the dust removal ash comes from the tail gas dust removal system of the sludge drying and crushing in step 1) and the tail gas dust removal system of the coal gangue drying and grinding in step 2);

[0041] Furthermore, the tail gas from the sludge drying and crushing in step 1) is separated and dusted by a collector, and then enters a heat exchanger under the action of a high-temperature fan. After heat exchange and cooling, it enters a bag dust removal system, and the dust separated and collected by the bag dust removal system is used as dust removal ash;

[0042] Furthermore, the gangue and exhaust gas after drying and grinding in step 2) enter the bag dust removal system, the separated gangue is sent to the decomposition furnace as fuel, and the separated dust is used as dust removal ash;

[0043] Furthermore, in step 3), the preheater is preheated to 200°C to 400°C and then fed into the decomposition furnace, the decomposition temperature in the decomposition furnace is 500°C to 800°C, and the decomposition time is 2h to 24h;

[0044] Furthermore, in step 4), the calcination temperature in the rotary kiln is 1100° C. to 1150° C., and the calcination time is 5 h to 48 h.

[0045] Example 2: A method for preparing a concrete admixture based on washed sand sludge, comprising the following steps:

[0046] 1) Drying and crushing the sludge to obtain sludge powder;

[0047] 2) The gangue is dried, ground and then fed into the decomposition furnace as fuel;

[0048] 3) The sludge powder from step 1) is fed into a preheater for preheating, and then fed into a decomposition furnace;

[0049] 4) The material decomposed in the calciner is sent to the rotary kiln for calcination into clinker, and then cooled in the grate cooler to obtain clinker;

[0050] 5) The clinker is rolled and ball milled to obtain the finished product;

[0051] Furthermore, the tail gas from the preheater in step 3) is fed into step 1) to supplement the heat source for drying and crushing the sludge;

[0052] Furthermore, the waste heat exhaust gas from the grate cooler in step 4) is fed into step 2) to provide a drying heat source for the gangue grinding;

[0053] Furthermore, in step 3), dust removal ash is added to the sludge powder when entering the preheater; the dust removal ash comes from the tail gas dust removal system of the sludge drying and crushing in step 1) and the tail gas dust removal system of the coal gangue drying and grinding in step 2);

[0054] Furthermore, the tail gas from the sludge drying and crushing in step 1) is separated and dusted by a collector, and then enters a heat exchanger under the action of a high-temperature fan. After heat exchange and cooling, it enters a bag dust removal system, and the dust separated and collected by the bag dust removal system is used as dust removal ash;

[0055] Furthermore, the gangue and exhaust gas after drying and grinding in step 2) enter the bag dust removal system, the separated gangue is sent to the decomposition furnace as fuel, and the separated dust is used as dust removal ash;

[0056] Furthermore, in step 3), the preheater is preheated to 200°C to 400°C and then fed into the decomposition furnace, the decomposition temperature in the decomposition furnace is 500°C to 800°C, and the decomposition time is 2h to 24h;

[0057] Furthermore, in step 4), the calcination temperature in the rotary kiln is 1100° C. to 1150° C., and the calcination time is 5 h to 48 h.

[0058] Example 3: A method for preparing a concrete admixture based on washed sand sludge, comprising the following steps:

[0059] 1) Drying and crushing the sludge to obtain sludge powder;

[0060] 2) The gangue is dried, ground and then fed into the decomposition furnace as fuel;

[0061] 3) The sludge powder from step 1) is fed into a preheater for preheating, and then fed into a decomposition furnace;

[0062] 4) The material decomposed in the calciner is sent to the rotary kiln for calcination into clinker, and then cooled in the grate cooler to obtain clinker;

[0063] 5) The clinker is rolled and ball milled to obtain the finished product;

[0064] Furthermore, the tail gas from the preheater in step 3) is fed into step 1) to supplement the heat source for drying and crushing the sludge;

[0065] Furthermore, the waste heat exhaust gas from the grate cooler in step 4) is fed into step 2) to provide a drying heat source for the gangue grinding;

[0066] Furthermore, in step 3), when the sludge powder enters the preheater, an auxiliary material is added to the sludge powder; the auxiliary material is black soil powder;

[0067] Furthermore, in step 3), dust removal ash is added to the sludge powder when entering the preheater; the dust removal ash comes from the tail gas dust removal system of the sludge drying and crushing in step 1) and the tail gas dust removal system of the coal gangue drying and grinding in step 2);

[0068] Furthermore, the tail gas from the sludge drying and crushing in step 1) is separated and dusted by a collector, and then enters a heat exchanger under the action of a high-temperature fan. After heat exchange and cooling, it enters a bag dust removal system, and the dust separated and collected by the bag dust removal system is used as dust removal ash;

[0069] Furthermore, the gangue and exhaust gas after drying and grinding in step 2) enter the bag dust removal system, the separated gangue is sent to the decomposition furnace as fuel, and the separated dust is used as dust removal ash;

[0070] Furthermore, in step 3), the preheater is preheated to 200°C to 400°C and then fed into the decomposition furnace, the decomposition temperature in the decomposition furnace is 500°C to 800°C, and the decomposition time is 2h to 24h;

[0071] Furthermore, in step 4), the calcination temperature in the rotary kiln is 1100° C. to 1150° C., and the calcination time is 5 h to 48 h.

[0072] Example 4: A method for preparing a concrete admixture based on washed sand sludge, comprising the following steps:

[0073] 1) Drying and crushing the sludge to obtain sludge powder;

[0074] 2) The gangue is dried, ground and then fed into the decomposition furnace as fuel;

[0075] 3) The sludge powder from step 1) is fed into a preheater for preheating, and then fed into a decomposition furnace;

[0076] 4) The material decomposed in the calciner is sent to the rotary kiln for calcination into clinker, and then cooled in the grate cooler to obtain clinker;

[0077] 5) The clinker is rolled and ball milled to obtain the finished product;

[0078] Furthermore, the tail gas from the preheater in step 3) is fed into step 1) to supplement the heat source for drying and crushing the sludge;

[0079] Furthermore, the waste heat exhaust gas from the grate cooler in step 4) is fed into step 2) to provide a drying heat source for the gangue grinding;

[0080] Furthermore, in step 3), auxiliary materials are added to the sludge powder when entering the preheater; the auxiliary materials are green shale powder;

[0081] Furthermore, in step 3), dust removal ash is added to the sludge powder when entering the preheater; the dust removal ash comes from the tail gas dust removal system of the sludge drying and crushing in step 1) and the tail gas dust removal system of the coal gangue drying and grinding in step 2);

[0082] Furthermore, the tail gas from the sludge drying and crushing in step 1) is separated and dusted by a collector, and then enters a heat exchanger under the action of a high-temperature fan. After heat exchange and cooling, it enters a bag dust removal system, and the dust separated and collected by the bag dust removal system is used as dust removal ash;

[0083] Furthermore, the gangue and exhaust gas after drying and grinding in step 2) enter the bag dust removal system, the separated gangue is sent to the decomposition furnace as fuel, and the separated dust is used as dust removal ash;

[0084] Furthermore, in step 3), the preheater is preheated to 200°C to 400°C and then fed into the decomposition furnace, the decomposition temperature in the decomposition furnace is 500°C to 800°C, and the decomposition time is 2h to 24h;

[0085] Furthermore, in step 4), the calcination temperature in the rotary kiln is 1100° C. to 1150° C., and the calcination time is 5 h to 48 h.

[0086] Example 5: The technical indexes of the concrete admixtures prepared by the concrete admixture preparation method based on washed sand sludge in Examples 2-4 were tested, and the results are shown in Table 1 below.

[0087] Table 1 Test results of technical indicators of concrete admixtures based on washed sand sludge

[0088]

[0089] The test results in Table 1 show that the LOI of the sewage sludge + black soil mixture exceeded the standard by more than 5.0 due to the free calcium oxide content of 7.49% in the black soil. Therefore, the LOI of 9.68% is considered unacceptable under this standard, but it complies with the Grade III standard for fly ash in GB1596-91. The active SiO2 and Al2O3 in the sewage sludge admixture react with cement components to produce Ca(OH)2, forming CSH and CAH, which hydrate calcium sulfoaluminate. This improves both the early and late strengths of concrete, reducing cement usage. The results in Table 1 demonstrate that washed sand sludge, whether combined with other minerals and then physically or chemically activated, is a promising concrete admixture, effectively reducing concrete costs.

[0090] Example 6: The physical phase and composition of the sludge raw material and clinker were tested, and the results were as follows: Figure 2 and as shown in Table 2 below.

[0091] Table 2 Comparison of sludge raw and clinker components

[0092]

[0093] Combined with the results in Table 2 Figure 2 It can be seen that the main components of sludge raw materials and clinker are SiO2, CaMg(CO3)2, CaCO3, Al2SiO5, Al2O3 and CaO. The content of CaMg(CO3)2 is significantly reduced after calcination, while the content of SiO2 is increased after calcination.

[0094] Although the present invention has been described in detail with reference to the aforementioned embodiments, it is still possible for those skilled in the art to modify the technical solutions described in the aforementioned embodiments, or to make equivalent substitutions for some of the technical features therein. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for preparing concrete admixture based on washed sand sludge, characterized by: The steps include: 1) Drying and crushing the sludge to obtain sludge powder; 2) The gangue is dried, ground and then fed into the decomposition furnace as fuel; 3) The sludge powder from step 1) is fed into a preheater for preheating, and then fed into a decomposition furnace. When the preheater is preheated to 200°C to 400°C, the sludge powder is fed into the decomposition furnace. The decomposition temperature in the decomposition furnace is 500°C to 800°C, and the decomposition time is 2h to 24h. 4) The material decomposed in the calciner is sent to the rotary kiln for calcination into clinker, which is then cooled by the grate cooler to obtain clinker. The calcination temperature in the rotary kiln is 1100℃~1150℃, and the calcination time is 5h~48h; 5) The clinker is rolled and ball milled to obtain the finished product.

2. The method for preparing concrete admixture based on washed sand sludge according to claim 1, characterized in that: The tail gas from the preheater in step 3) is fed into step 1) to supplement the heat source for drying and crushing the sludge.

3. The method for preparing concrete admixture based on washed sand sludge according to claim 1, characterized in that: The waste heat exhaust gas from the grate cooler in step 4) is fed into step 2) to provide a drying heat source for the gangue grinding.

4. The method for preparing concrete admixture based on washed sand sludge according to claim 1, characterized in that: In step 3), auxiliary materials are added to the sludge powder when entering the preheater; the auxiliary materials are black soil powder or green shale powder.

5. The method for preparing concrete admixture based on washed sand sludge according to claim 1, characterized in that: In step 3), dust removal ash is added to the sludge powder when entering the preheater; the dust removal ash comes from the tail gas dust removal system of the sludge drying and crushing in step 1) and the tail gas dust removal system of the coal gangue drying and grinding in step 2).

6. The method for preparing concrete admixture based on washed sand sludge according to claim 5, characterized in that: In step 1), the tail gas from the sludge drying and crushing is separated and dusted by the collector, and then enters the heat exchanger under the action of the high-temperature fan. After heat exchange and cooling, it enters the bag dust removal system. The dust separated and collected by the bag dust removal system is used as dust removal ash.

7. The method for preparing concrete admixture based on washed sand sludge according to claim 5, characterized in that: In step 2), the dried and ground gangue and exhaust gas enter the bag dust removal system, the separated gangue is sent to the decomposition furnace as fuel, and the separated dust is used as dust removal ash.

8. A concrete admixture based on washed sand sludge, characterized by: The concrete admixture is prepared by the method for preparing concrete admixture based on washed sand sludge according to any one of claims 1 to 7.

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