Method for physical-chemical synergistic activation to improve cementitious activity of waste glass powder

Abstract

The application discloses a method for improving cementitious activity of waste glass powder by physical and chemical synergistic activation, and belongs to the field of building materials. The method aims to solve the problems of insufficient cementitious activity, low activation efficiency and unstable activation effect of waste glass powder. The method adopts a segmented feeding strategy to put waste glass and a chemical activator (any one of silica fume, nano-silicon dioxide, nano-titanium dioxide, calcite and alum) into a ball mill, adopts a four-stage matching grinding ball and a variable-speed intermittent process of "high-speed ball milling-stopping-moderate-speed ball milling", and significantly improves the cementitious activity of the waste glass powder through physical and chemical synergistic activation. The method has the characteristics of high activation efficiency, significant activity improvement and controllable process, and can be widely applied to resource utilization of waste glass powder.

Description

Technical Field

[0001] This invention belongs to the field of building cementitious material preparation technology, specifically relating to a physicochemical synergistic activation method for improving the cementitious activity of waste glass powder. Background Technology

[0002] With the acceleration of urbanization, the amount of waste glass generated is increasing year by year. The treatment and resource utilization of waste glass has become an environmental problem that urgently needs to be solved. Since waste glass is mainly composed of silicon dioxide, calcium oxide and other components, its chemical composition is similar to that of auxiliary cementing materials such as fly ash. Therefore, using waste glass powder as an auxiliary cementing material in building materials has important application value.

[0003] However, the application of waste glass powder in building materials still faces the following technical challenges: (1) Insufficient gelling activity of waste glass powder. Waste glass powder obtained by conventional mechanical grinding has low activity, which is difficult to meet the needs of actual engineering applications and limits its application ratio in building materials (Zhao Haidong et al., 2018); (2) Low efficiency of existing activation methods. Traditional physical activation methods are energy-intensive and inefficient, while single chemical activation methods are unstable and costly (Ke Guojun et al., 2015); (3) Poor controllability of the activation process. Existing activation process parameters are not optimized enough, making it difficult to achieve controllable improvement of the activity of waste glass powder, resulting in large fluctuations in product quality (Mejdi et al., 2019).

[0004] Therefore, there is an urgent need to develop an efficient, stable, and controllable activation method for waste glass powder to enhance its gelling activity, promote the resource utilization of waste glass, and achieve a balance between environmental and economic benefits. Summary of the Invention

[0005] The purpose of this invention is to provide a method for enhancing the gelling activity of waste glass powder through synergistic physicochemical activation, aiming to solve the technical problems of insufficient gelling activity of waste glass powder, as well as the low activation efficiency and unstable activation effect of traditional activation technologies.

[0006] To achieve the above objectives, the present invention adopts the following technical solution.

[0007] This invention provides a method for enhancing the gelling activity of waste glass powder through physicochemical synergistic activation. The method employs a segmented feeding strategy to feed waste glass and chemical activators into a ball mill, and performs synergistic activation treatment through optimized ball milling process parameters.

[0008] Further optimized requirements for waste glass raw materials:

[0009] 1) Raw material type: Sodium-calcium waste glass, including architectural glass, beverage bottle glass, or daily-use glass products.

[0010] 2) Chemical composition requirements: SiO2 content ≥ 65%, CaO content 15-25%, Na2O content 10-15%.

[0011] 3) Particle size requirement before activation: D90≤80μm

[0012] 4) Specific surface area before activation: 350-400 m² 2 / kg

[0013] 5) Moisture content: ≤1%.

[0014] In a further optimized manner, the chemical activator is selected from any one of silica fume, nano silica, nano titanium dioxide, calcite, and alum, and the activity of waste glass powder is enhanced through the synergistic effect of the chemical activation of the activator and the physical activation of mechanical ball milling.

[0015] Further optimization is required for the performance of the chemical activator:

[0016] 1) Silica fume: specific surface area ≥15000m² 2 / kg, SiO2 content ≥90%

[0017] 2) Nano-silica: Specific surface area ≥180,000 m² 2 / kg, purity ≥99%

[0018] 3) Nano-titanium dioxide: specific surface area ≥150,000 m² 2 / kg, purity ≥98%

[0019] 4) Calcite: Specific surface area ≥ 800 m² 2 / kg, CaCO3 content ≥95%

[0020] 5) Alum: KAl(SO4)2, analytical grade.

[0021] Furthermore, the segmented feeding strategy includes two stages:

[0022] 1) First stage: 70% waste glass and 80% activator are added;

[0023] 2) Second stage: Add 30% waste glass and 20% activator. Segmented feeding can effectively avoid material agglomeration and improve ball mill efficiency.

[0024] Furthermore, the ball milling process is further optimized by employing a variable-speed intermittent process of "high-speed ball milling → residence → medium-speed ball milling":

[0025] 1) High-speed section: The ball mill speed is 55-60 r / min (80-85% of the critical speed) for 20 minutes;

[0026] 2) Duration of stay: 5 minutes;

[0027] 3) Medium speed range: Run at 55-65% of the critical speed for 15 minutes;

[0028] 4) Repeat the cycle 3 times after each feeding.

[0029] Furthermore, the milling media uses four-grade milling balls:

[0030] 1) 20%

[0031] 2) 30%

[0032] 3) 30%

[0033] 4) 20%.

[0034] Further optimized performance requirements for the activated product:

[0035] 1) Physical properties:

[0036] Specific surface area: 500~600m² 2 / kg; Particle size distribution: D90≤45μm, D50≤15μm

[0037] 2) Activity indicators: 7-day activity index ≥ 75%; 28-day activity index ≥ 90%

[0038] 3) Performance: Initial setting time: ≥45min; Final setting time: ≤600min.

[0039] Further optimizations are required for the activation process control:

[0040] 1) Ball mill feed-to-ball ratio: 4:1 to 5:1

[0041] 2) Ball milling temperature: ≤60℃

[0042] 3) Equipment speed fluctuation: ±2 r / min

[0043] 4) Time interval for segmented feeding: 10-15 minutes.

[0044] Compared with the prior art, the present invention has the following advantages and technical effects:

[0045] This invention solves the problems of insufficient gelling activity, low activation efficiency, and unstable activation effect of waste glass powder. The method employs a segmented feeding strategy, adding waste glass and a chemical activator (any one of silica fume, nano-silica, nano-titanium dioxide, calcite, or alum) into a ball mill. It utilizes a four-stage grinding ball distribution and a variable-speed intermittent process of "high-speed ball milling – residence – medium-speed ball milling," significantly improving the gelling activity of waste glass powder through synergistic physicochemical activation. This method features high activation efficiency, significant activity enhancement, and controllable process, and can be widely applied to the resource utilization of waste glass powder. Detailed Implementation

[0046] The implementation of the present invention will be further described below with reference to specific embodiments, but the implementation and protection of the present invention are not limited thereto.

[0047] Example 1

[0048] 1. Raw material preparation:

[0049] 1) Waste Glass: Construction waste glass is used, with main chemical components of 68.5% SiO2, 18.2% CaO, and 12.3% Na2O. The specific surface area before activation is 372 m². 2 / kg, D 90 It has a diameter of 75 μm and a moisture content of 0.8%.

[0050] 2) Activator: Silica fume with a specific surface area of ​​16500 m² is selected. 2 / kg, SiO2 content 87.3%.

[0051] 2. Activation process:

[0052] 1) Segmented feeding: The first stage involves feeding 70% waste glass (3.5 kg) and 80% silica fume (0.04 kg); the second stage involves feeding 30% waste glass (1.5 kg) and 20% silica fume (0.01 kg).

[0053] 2) Ball mill parameters: High speed section: 58 r / min, continuous for 20 minutes, residence period: 5 minutes; Medium speed section: 42 r / min, continuous for 15 minutes, with 3 cycles after each feeding.

[0054] 3. Milling media: Four-grade milling balls are used ( 20% 30% 30% 20%), material-to-ball ratio: 4.5:1.

[0055] Example 2

[0056] 1. Raw material preparation:

[0057] 1) Waste glass: Utilizing waste glass from beverage bottles, the main chemical components are SiO2 71.2%, CaO 16.8%, and Na2O 11.5%, with a specific surface area of ​​385 m² before activation. 2 / kg, D90 is 72μm, moisture content is 0.6%.

[0058] 2) Activator: Nano-silica with a specific surface area of ​​185,000 m² is selected. 2 / kg, purity 99.2%.

[0059] 2. Activation process:

[0060] 1) Segmented feeding: The first stage involves feeding 70% waste glass (3.5 kg) and 80% nano-silica (0.04 kg); the second stage involves feeding 30% waste glass (1.5 kg) and 20% nano-silica (0.01 kg).

[0061] 2) Ball mill parameters: High speed section: 57 r / min, continuous for 20 minutes, residence period: 5 minutes; Medium speed section: 40 r / min, continuous for 15 minutes, with 3 cycles after each feeding.

[0062] 3. Milling media: Four-grade milling balls are used ( 20% 30% 30% 20%); Particle size ratio: 4.8:1.

[0063] Example 3

[0064] 1. Raw material preparation:

[0065] 1) Waste glass: Made from everyday glass products, with main chemical components of 69.8% SiO2, 17.5% CaO, and 11.8% Na2O, and a specific surface area of ​​368 m² before activation. 2 / kg, D90 is 78μm, moisture content is 0.9%.

[0066] 2) Activator: Alum, analytical grade.

[0067] 2. Activation process:

[0068] 1) Segmented feeding: The first stage involves feeding 70% waste glass (3.5 kg) and 80% alum (0.04 kg); the second stage involves feeding 30% waste glass (1.5 kg) and 20% alum (0.01 kg).

[0069] 2) Ball mill parameters: High speed section: 56 r / min, continuous for 20 minutes, residence period: 5 minutes; Medium speed section: 39 r / min, continuous for 15 minutes, with 3 cycles after each feeding.

[0070] 3) Milling media: Four-grade milling balls are used ( 20% 30% 30% 20%), material-to-ball ratio: 4.2:1.

[0071] Comparative Example 1 (Single Physical Activation):

[0072] Using the same waste glass raw material as in Example 1, without adding chemical activators, only ball milling was performed;

[0073] Comparative Example 2 (Single Chemical Activation):

[0074] Using the same waste glass raw materials and silica fume as in Example 1, only simple mixing was performed;

[0075] Comparative Example 3 (High-ball material ratio):

[0076] The ball-to-material ratio was increased to 6:1 (exceeding the 4:1 to 5:1 of the claims), with other conditions remaining the same, and silica fume was used as the activator.

[0077] Comparative Example 4 (Inappropriate segmented feeding ratio):

[0078] 1) First stage: Add 55% waste glass and 90% activator;

[0079] 2) Second stage: Add 45% waste glass and 10% activator, with other conditions remaining the same, and use silica fume as the activator.

[0080] Comparative Example 5 (Inappropriate activator):

[0081] 1) The activator used is ordinary silicon powder (specific surface area 8000 m²). 2 / kg, below the requirement ≥15000m 2 / kg; SiO2 content 85%, lower than the required ≥90%), other conditions are the same.

[0082] Comparative Example 6 (insufficient number of iterations):

[0083] 1) Each feeding stage is circulated only once (lower than the required 2-4 times), with other conditions remaining the same, and silica fume is used as the activator.

[0084] Performance test results:

[0085] Table 1 Particle characteristics

[0086]

[0087] Table 2 Basic Performance

[0088]

[0089] Table 3 Activity Index

[0090]

[0091] Test method description:

[0092] Activity index: Determined according to "GB / T 18736-2017 Mineral admixtures for high-strength and high-performance concrete", activity index = (compressive strength of admixture group / compressive strength of reference group) × 100%;

[0093] Standard consistency water requirement, setting time, and final setting time: determined in accordance with "GB / T 1346-2011 Standard consistency water requirement, setting time, and soundness test method for cement".

[0094] As can be seen from Tables 1-3:

[0095] 1. The synergistic activation of physicochemicals has a significant but minimal impact on the fineness of waste glass powder.

[0096] 2. The standard consistency water consumption of the physicochemically activated waste glass powder was 28.5%–29.2%, slightly higher than the control group, but the change was small, indicating that the activation process had little impact on water consumption. The setting time was moderate, with initial setting time between 180–195 min and final setting time between 478–495 min, meeting the requirements for engineering applications.

[0097] 3. All three activators significantly improved the activity of waste glass powder, with an activity index of 77.5–81.2% at 7 days and 91.8–94.5% at 28 days. The order of activity index improvement was: nano-silica > alum > silica fume. Compared with single physical activation (7 days: 65.3%, 28 days: 82.1%) and single chemical activation (7 days: 58.5%, 28 days: 75.6%), the synergistic activation effect was significantly improved.

[0098] 4. Although some comparative examples adopted the approach of synergistic physicochemical activation, the activation effects were not as good as those of the examples because the key process parameters exceeded the limits of this invention. In particular, Comparative Example 3 had an excessively high ball-to-material ratio (6:1), exceeding the optimal range of 4:1 to 5:1 of this invention, resulting in reduced ball milling efficiency and limited activity improvement. Although its activity index was better than that of single physical and chemical activation, its 28-day activity index was only 85.6%, far lower than the 92.3% in Example 1.

[0099] 5. Comparative Example 4 used an unreasonable staged feeding ratio. The excessively high proportion of activator in the first stage (90%) easily caused agglomeration, while the excessively high proportion of waste glass in the second stage (45%) was not conducive to uniform activation. This deviation in the feeding ratio affected the dispersibility and activation uniformity of the material. Its 28-day activity index was 84.8%, indicating that a reasonable staged feeding ratio plays an important role in improving the activation effect.

[0100] 6. Comparative Example 5 uses ordinary silicon powder as an activator, and its specific surface area (8000 m²) is... 2 The specific surface area ( / kg) and purity (85%) did not meet the requirements of this invention. The lower specific surface area resulted in a reduced contact area with waste glass, while the lower purity affected the reactivity of the activator, ultimately resulting in an activity index of only 83.2% after 28 days. This indicates that the performance indicators of the activator have a significant impact on the synergistic activation effect.

[0101] 7. In Comparative Example 6, the number of cycles was insufficient (only 1 cycle), falling short of the 2-4 cycles required by this invention. This resulted in insufficient physical activation of the waste glass powder, inadequate contact time between the activator and the waste glass, and limited chemical activation effect. Its 28-day activity index was 83.8%, clearly demonstrating the importance of sufficient cycles for ensuring activation effectiveness.

[0102] In summary, physical activation enhances specific surface area and surface activity through mechanical force, while chemical activators react with the glass surface during ball milling to form new active products. These two activation methods mutually promote each other, producing a synergistic effect. Furthermore, considering both activation effectiveness and economic efficiency, it is recommended to use nano-silica as the activator, employing a segmented feeding and variable-speed intermittent ball milling process, and strictly controlling process parameters to ensure stable product quality.

[0103] The physicochemical synergistic activation method proposed in this invention significantly improves the gelling activity of waste glass powder through optimized process parameters and appropriate activator selection, providing a feasible technical solution for the resource utilization of waste glass.

Claims

1. A method for physical-chemical synergistic activation to enhance cementitious activity of waste glass powder, characterized in that, The method comprises the following steps: The waste glass and chemical activators are put into a ball mill by a segmented feeding strategy, and the waste glass powder cementitious activity is improved by controlling the ball milling process parameters for synergistic activation treatment; the chemical activators are selected from one or more of silica fume, nano-silicon dioxide, nano-titanium dioxide, calcite, and alum; The ball milling process comprises: 1) high-speed section: 80-85% of the critical speed, lasting for 15-25 minutes; 2) residence period: 3-7 minutes; 3) medium-speed section: 55-65% of the critical speed, lasting for 10-20 minutes; 4) 2-4 cycles after each feeding section; The ball milling process parameters comprise: 1) ball mill ball-to-material ratio: 4:1-5:1; 2) ball milling temperature: ≤60°C; 3) equipment speed fluctuation control: ±2 r / min; 4) time interval for segmented feeding: 10-15 minutes; The segmented feeding strategy comprises: 1) first stage: feeding 65-75% of the waste glass and 75-85% of the chemical activators; 2) second stage: feeding 25-35% of the waste glass and 15-25% of the chemical activators; The ball milling medium adopts four-stage grinding balls: 1) diameter φ50 mm: 18-22%; 2) diameter φ25 mm: 28-32%; 3) diameter φ20 mm: 28-32%; 4) diameter φ5 mm: 18-22%.

2. The method of physical-chemical synergistic activation to enhance cementitious activity of waste glass powder according to claim 1, characterized in that, The waste glass is sodium-calcium waste glass, which comprises one or more of architectural glass, beverage bottle glass, or daily-use glass products.

3. The method of claim 2, wherein the physical-chemical synergistic activation of the waste glass powder to enhance the cementitious activity is characterized by, The waste glass raw material meets the following requirements: 1) main chemical component requirement: SiO2 content: ≥65%, CaO content: 15-25%, Na2O content: 10-15%; 2) Particle size D before activation 90 ≤ 80 μm; 3) specific surface area before activation: 350-400 m² / kg; 4) water content: ≤1%.

4. The method of synergistically activating the cementitious activity of waste glass powder by physical and chemical activation according to claim 1, characterized in that, The specific surface area of the waste glass before activation is 350-400 m² / kg, and the specific surface area after activation is 500-600 m² / kg.

5. The method of synergistically activating the cementitious activity of waste glass powder by physical and chemical activation according to claim 1, characterized in that, The performance requirements of the chemical activators are as follows: 1) silica fume: specific surface area: ≥15000 m² / kg, SiO2 content: ≥90%; 2) nano-silicon dioxide: specific surface area: ≥180000 m² / kg, purity: ≥99%; 3) nano-titanium dioxide: specific surface area: ≥150000 m² / kg, purity: ≥98%; 4) calcite: specific surface area: ≥800 m² / kg, CaCO3 content: ≥95%; 5) alum: analytical pure, KAl(SO4)2 content: ≥98%.

6. The waste glass powder according to claim 1, which is prepared by the method according to any one of claims 1-5.

7. The waste glass powder according to claim 6, characterized in that, The waste glass powder has the following characteristics: 1) the particle size distribution satisfies: D 90 ≤ 55 μm, D 50 ≤ 15 μm; 2) specific surface area: 500-600 m² / kg; 3) initial setting time: ≥45 minutes, final setting time: ≤600 minutes; 4) 7d activity index: ≥75%, 28d activity index: ≥90%.

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