Method for rapidly evaluating gelling activity of waste glass powder based on hydration heat

Abstract

The invention provides a hydration heat-based waste glass powder gelatinization activity rapid evaluation method. According to the method, a corresponding relation between hydration heat and 28-day activity indexes is established by measuring hydration heat curve characteristics of the waste glass powder blended cement paste, so that rapid evaluation of the activity of the waste glass powder is realized. The method comprises three steps of sample preparation, hydration heat test and activity evaluation. The research finds that the 72-hour accumulated hydration heat and the activity index have good linear correlation. The waste glass powder activity evaluation system based on hydration heat characteristics is established, and the goal of predicting the 28-day activity index from 3-day hydration heat is achieved. The method has the characteristics of short test period, simplicity in operation, no need of preparation of complex reagents and the like, is suitable for waste glass powder with different sources and different activation treatments, and has important engineering application value.

Description

Technical Field

[0001] The present invention relates to the technical field of building material testing, and particularly relates to a rapid evaluation method for the pozzolanic activity of waste glass powder based on hydration heat characteristic parameters. Background Art

[0002] As a new type of supplementary cementitious material, the evaluation of the pozzolanic activity of waste glass powder is of great significance for engineering applications. With the continuous advancement of the resource utilization of construction waste, waste glass powder is increasingly widely used as a cementitious material admixture. Due to the large amount of amorphous silica it contains, waste glass powder can undergo a pozzolanic reaction with calcium hydroxide in the alkaline environment generated during cement hydration to form calcium silicate hydrate gel (C-S-H), thus exhibiting good supplementary cementitious properties.

[0003] Currently, the evaluation methods for the pozzolanic activity of waste glass powder at home and abroad mainly include various types such as strength method, chemical method, physical method, and microstructure method. Among them:

[0004] (1) The strength method is the most commonly used evaluation method, mainly using the 28-day compressive strength ratio to evaluate the pozzolanic activity of waste glass powder. Although this method has high reliability, its test period is long, and it is difficult to meet the requirements of rapid evaluation in engineering practice.

[0005] (2) The chemical method includes selective dissolution method and calcium hydroxide consumption method. Although the test period of this type of method is relatively short, the operation is complex, requiring professional experimental equipment and personnel, and the reproducibility of the test results is poor.

[0006] (3) The physical method mainly indirectly evaluates the pozzolanic activity of waste glass powder by measuring its physical properties, including methods such as specific surface area measurement and particle size analysis. This type of method is simple and fast to operate, but it is difficult to accurately reflect the supplementary cementitious performance of the material in actual applications.

[0007] (4) The microstructure method mainly includes methods such as scanning electron microscopy observation and X-ray diffraction analysis. This type of method can deeply understand the pozzolanic reaction mechanism of the material, but the equipment is expensive, the test cost is high, and it is difficult to achieve quantitative evaluation.

[0008] In recent years, the R 3 (Rapid, relevant, reliable) test method developed internationally is considered to have great potential. This method is based on a simulated formula, using chemical reagents such as Ca(OH)2, CaSO4·2H2O, K2SO4, KOH, CaCO3, etc. to undergo pozzolanic reactions or hydraulic reactions with supplementary cementitious materials, and measuring the heat release amount during the reaction at 40°C for 7 days. Although this method has been improved compared with the traditional 28-day strength method, it still requires a 7-day test period, and the reagent components are numerous, and the operation is relatively complex.

[0009] Therefore, it is of great theoretical significance and practical value to develop a rapid, accurate and reliable evaluation method for the cementitious activity of waste glass powder. Summary of the Invention

[0010] The object of the present invention is to provide a rapid determination method for the cementitious activity of waste glass powder based on the comprehensive evaluation of multiple parameters of heat of hydration. By analyzing multiple characteristic parameters of the heat of hydration curve, a scoring system is established to achieve rapid and accurate evaluation of the activity of waste glass powder. (1) Shorten the evaluation period from the traditional 28 days or 7 days to 3 days. (2) Improve the accuracy and reliability of the evaluation. (3) Simplify the test operation and reduce the evaluation cost.

[0011] The specific technical solution of the present invention is as follows:

[0012] 1. Specimen Preparation

[0013] 1.1 Requirements for Raw Materials

[0014] (1) Cement: 42.5 ordinary Portland cement meeting the requirements of GB175

[0015] (2) Waste glass powder: Specific surface area not less than 300 m 2 / kg, moisture content not more than 1%

[0016] (3) Mixing water: Laboratory water meeting the requirements of JGJ63

[0017] 1.2 Mix Proportion

[0018] (1) Mass ratio of waste glass powder to cement is 30:70

[0019] (2) Water-binder ratio is fixed at 0.5

[0020] 1.3 Mixing and Preparation

[0021] (1) Ambient temperature: 20 ± 2 °C

[0022] (2) Relative humidity: 60 ± 5%

[0023] (3) Mixing time: Low-speed mixing for 1 min, high-speed mixing for 2 min

[0024] 2. Heat of Hydration Test

[0025] 2.1 Instrument and Equipment

[0026] (1) Isothermal calorimeter

[0027] (2) Precision: ±0.1 °C

[0028] (3) Number of test channels: ≥4

[0029] 2.2 Test Conditions

[0030] (1) Test temperature: 25 ± 0.1 °C

[0031] (2) Test time: 72 hours

[0032] (3) Data acquisition interval: ≤ 10 min

[0033] 3. Activity evaluation model

[0034] 3.1 Cumulative heat index

[0035] (1) Cumulative heat release Q72 (J / g) in 72 hours

[0036] (2) Activity index AI28 (%) at 28 days

[0037] 3.2 Correlation

[0038] AI28 = a × Q72 + b

[0039] Where: AI28 is the activity index at 28 days (%); Q72 is the cumulative heat release in 72 hours (J / g), and a and b are fitting coefficients.

[0040] 4. Quality control

[0041] 4.1 Test condition control

[0042] (1) Ambient temperature: 25 ± 0.1 °C

[0043] (2) Relative humidity: 60 ± 5%

[0044] 4.2 Data quality control

[0045] (1) Test error of parallel samples ≤ 5%.

[0046] A rapid evaluation method for the gelling activity of waste glass powder based on hydration heat in the present invention includes the following steps:

[0047] (1) Specimen preparation:

[0048] a) Select 42.5 ordinary Portland cement, waste glass powder with a specific surface area of not less than 300 m 2 / kg and a moisture content of not more than 1%, and laboratory water meeting the requirements of JGJ63;

[0049] b) Prepare according to the mass ratio of waste glass powder to cement of 30:70 and the water-binder ratio of 0.5;

[0050] c) Stir at a low speed for 1 min and then at a high speed for 2 min under the conditions of a temperature of 20 ± 2 °C and a relative humidity of 60 ± 5%;

[0051] (2) Hydration heat test:

[0052] a) Use an isothermal calorimeter with an accuracy of ±0.1 °C;

[0053] b) Conduct continuous testing for 72 hours under the condition of 25 ± 0.1 °C;

[0054] c) The data acquisition interval is not more than 10 min;

[0055] (3) Activity evaluation:

[0056] a) Record the cumulative heat release Q72 (J / g) in 72 hours;

[0057] b) Calculate the 28-day activity index through the relational expression AI28 = a × Q72 + b, where a and b are fitting coefficients.

[0058] Further, the number of test channels of the isothermal calorimeter is not less than 4.

[0059] Further, the test error of parallel samples is not more than 5%.

[0060] Further, the waste glass powder is a product obtained by ball milling any one of float glass, bottle glass or flat glass.

[0061] Further, the waste glass powder is a product obtained by activation treatment such as high-energy ball milling, co-milling with silica fume or co-milling with nano-silica.

[0062] Further, the correlation coefficient R2 of the relational expression is not less than 0.96.

[0063] Compared with the prior art, the advantages of the present invention are as follows:

[0064] This method significantly shortens the evaluation period, from the traditional 28-day strength method to 3 days, greatly improving the evaluation efficiency. In terms of operation, this method does not require the preparation of complex chemical reagents and only needs to use conventional cement paste preparation equipment to complete the entire test process, greatly simplifying the operation process. At the same time, this method has wide applicability, not only applicable to waste glass powders from different sources (such as float, bottle, flat, etc.), but also applicable to waste glass powders treated by different methods (such as ball milling, high-energy ball milling, surfactant modification, etc.), fully meeting the diverse needs in engineering practice. In terms of the reliability of the evaluation results, the correlation coefficient R of this method with the 28-day activity index 2 is as high as 0.965, and the prediction error does not exceed 1.5%, ensuring the accuracy of the evaluation results. Compared with the R widely used internationally at present 3Compared with the [method], this method does not require the use of expensive chemical reagents, significantly reducing the testing cost. In addition, under strictly controlled testing conditions, the parallel sample error of this method does not exceed 5%, with good repeatability, providing reliable technical support for engineering practice. Detailed implementation manners Description of the drawings

[0065] Figure 1 It is the relationship between the heat of hydration (Q72) in 3 days and the activity index (AI28) in 28 days.

[0066] Example 1: Establishing the relationship between the heat of hydration and the activity index

[0067] 1. Preparation of raw materials

[0068] (1) Select 42.5 ordinary Portland cement that complies with the GB175 standard, with a specific surface area of 360 m 2 / kg and a density of 3.15 g / cm 3 .

[0069] (2) Collect waste glass from three different sources (float glass, bottle glass, and flat glass). After cleaning and drying, conduct ball milling: a) Use a ball mill with a ball-to-material ratio of 4:1; b) Maintain the rotation speed at 68 r / min; c) The ball milling time is 30 min.

[0070] (3) Prepare the activated samples:

[0071] a) High-energy ball milling: Use a QM-3SP04 planetary ball mill with a rotation speed of 300 r / min and a ball-to-material ratio of 6:1; b) Co-milling with silica fume: Add 5% silica fume and co-mill for 30 min using a standard ball mill; c) Co-milling with nano-silica: Add 3% nano-SiO2 and co-mill for 30 min using a standard ball mill.

[0072] 2. Physical property testing

[0073] Specific surface area testing: Use the Blaine method to measure the specific surface area. Each sample is tested 3 times, and the average value is taken. Control the room temperature at 23 ± 2 °C and the relative humidity at 50 ± 5%.

[0074] 3. Process of heat of hydration testing

[0075] (1) Sample preparation: Accurately weigh the cement and waste glass powder (with an accuracy of 0.1 g), mix them evenly according to a mass ratio of 30:70, add mixing water at a temperature of 20 ± 1 °C, and strictly control the stirring time and speed;

[0076] (2) Calorimeter test: Preheat the equipment for 2 hours to ensure temperature stability. The sample loading is uniformly controlled at 100 ± 0.1 g. Set 3 parallel samples for each group, and monitor the temperature fluctuation throughout the process to ensure it is controlled within the range of ±0.1 °C.

[0077] 4. Activity index test

[0078] (1) Specimen preparation: Prepare specimens with dimensions of 40 × 40 × 160 mm according to the standard of GB / T 17671-1999. Immediately cover with plastic wrap after molding, remove the mold after 24 hours, and place in the standard curing room.

[0079] (2) Compressive strength test: Strictly execute the standard loading rate of 50 ± 10 N / s, record the fracture load of each specimen, and calculate the 28-day activity index.

[0080] Select waste glass from different sources and different treatment methods, test their 3-day heat of hydration and 28-day activity index, and establish a correlation.

[0081] Table 1 Test results of waste glass powder

[0082]

[0083] By analyzing the above 7 groups of data, establish a relationship between the 3-day heat of hydration (Q 72 ) and the 28-day activity index (AI 28 ) (as shown in Figure 1 ).

[0084] From the analysis of the data in Table 1, it can be seen that after ball milling for 30 minutes under the same conditions, the activity indices of waste glass from different sources are different. The highest activity index of float glass reaches 84.2%, and the lowest of flat glass is only 79.1%. This is mainly due to the differences in chemical composition and physical structure of waste glass from different sources. To improve the activity, flat glass with the lowest activity is selected for activation treatment. The results show that through high-energy ball milling for 30 minutes, its activity index can be increased to 104.8%; by co-milling with silica fume and nano-silica, the activity indices can reach 94.8% and 96.5% respectively. This shows that the activation treatment can significantly improve the activity of waste glass powder.

[0085] Example 2: Verify the accuracy of the correlation

[0086] 1. Verification sample preparation

[0087] (1) Raw material selection: Use the same batch of cement as in Example 1, and select new waste glass samples for treatment.

[0088] (2) Treatment process: Strictly follow the process parameters of Example 1, and record the parameters of each treatment step in detail.

[0089] 2. Test process

[0090] (1) Hydration heat test: Monitor the environmental parameters during the sample preparation process, record the temperature changes during the stirring process, collect data continuously for 72 hours at intervals of 5 minutes.

[0091] (2) Activity index test: Prepare 6 standard specimens of the same batch, use the three-point loading method to test the compressive strength, and take the average value after excluding abnormal data.

[0092] 3. Data analysis

[0093] (1) Error calculation: Use the relative error to evaluate the prediction accuracy, and analyze the error sources and influencing factors.

[0094] (2) Correlation analysis: Establish a scatter plot of hydration heat and activity index, calculate the correlation coefficient, and evaluate the reliability of the prediction model.

[0095] To verify the accuracy of the established relationship, 4 new groups of samples are selected for verification tests:

[0096] Table 2 Relationship verification results

[0097]

[0098]

[0099] It can be seen from the verification results that the error between the activity index predicted by this method and the measured value does not exceed 1.5%, indicating that the established relationship has good prediction accuracy. This method is not only applicable to the reference samples ball-milled for 30 minutes, but also has good prediction effects on the samples modified by high-energy ball milling and activators.

[0100] Example 3: R 3 Method verification

[0101] Use the internationally common R 3 test method to further verify the above verification samples:

[0102] 1. Reagent preparation

[0103] (1) Preparation of standard reagents: Ca(OH)2: analytically pure, purity ≥ 95%, K2SO4: analytically pure, purity ≥ 99%, CaSO4·2H2O: analytically pure, purity ≥ 99%, KOH: analytically pure, purity ≥ 85%;

[0104] (2) Preparation process: Use an analytical balance to accurately weigh each component (accuracy 0.001 g), and mix them strictly according to the R 3 method standard, and store them sealed after preparation.

[0105] 2. Test process

[0106] (1) Sample preparation: Mix the reagent and waste glass powder according to the standard ratio, control the temperature of the mixture at 23 ± 2 °C, and record the environmental parameters throughout the preparation process;

[0107] (2) Curing conditions: Maintain the temperature at 40 ± 0.5 °C, keep the relative humidity at 90 ± 5%, and the curing time is 7 days.

[0108] 3. Data comparison and analysis

[0109] (1) Result processing: Calculate the 7-day R 3 heat of evolution, compare it with the heat of hydration at 3 days, and analyze the correlation between the two methods;

[0110] (2) Comprehensive evaluation: Compare the advantages and disadvantages of the two methods, analyze the test efficiency and cost, and evaluate the engineering application value.

[0111] Table 3 R 3 Method verification results

[0112]

[0113]

[0114] By comparing with the R 3 test method, it can be found that the activity rankings obtained by the two rapid evaluation methods are exactly the same, and both are consistent with the 28-day activity index results. This further confirms the reliability of this method. Compared with the R 3 method, this method has the advantages of a short test period (3 days vs 7 days) and simple operation (no need to prepare complex chemical reagents).

[0115] Comprehensive analysis shows that the method of the present invention has the following characteristics:

[0116] First, this method has a wide range of applicability. For waste glass powders from different sources (activity index 72.0% - 84.2%), and waste glass powders treated differently (activity index 72.0% - 104.8%), it shows good evaluation effects. This indicates that this method has wide applicability.

[0117] Secondly, the evaluation results are accurate and reliable. The correlation coefficient R2 of the established relationship reaches 0.965, the error between the predicted result and the measured value does not exceed 1.5%, and it is consistent with the R 3 test result trend. This shows that this method has good accuracy and reliability.

[0118] Finally, this method has obvious practical value. The test period is short (3 days), the operation is simple, and there is no need to prepare complex chemical reagents, which can meet the needs of rapid evaluation in engineering practice. Especially when it is necessary to optimize the activation process of waste glass powder, this method can quickly obtain evaluation results and improve the R & D efficiency.

Claims

1. A method for rapid evaluation of the gelling activity of waste glass powder based on hydration heat, characterized in that: The following steps are involved: (1) Sample preparation: a) Ordinary Portland cement, waste glass powder and water are used; b) Prepare the mixture according to the mass ratio of waste glass powder to cement of 25:75-35:65 and the water-binder ratio of 0.45-0.55; c) Stir at low speed and then high speed at 20±2°C and 60±5% relative humidity; (2) Hydration heat test: Use an isothermal calorimeter with an accuracy of ±0.1℃; conduct continuous testing for 72 hours at 25±0.1℃, and the data collection interval during the test should not exceed 10 minutes; (3) Activity evaluation: a) Record the cumulative heat release Q72 (J / g) over 72 hours; b) The 28-day activity index was calculated by the relationship AI28=a×Q72+b, where a and b are fitting coefficients.

2. The evaluation method according to claim 1, characterized in that: The waste glass powder is waste glass powder with a specific surface area of ​​not less than 300m2 / kg and a moisture content of not more than 1%.

3. The evaluation method according to claim 1, characterized in that: In step b), the glue material in the water-binder ratio refers to the sum of the masses of waste glass powder and cement.

4. The evaluation method according to claim 1, characterized in that: In the sample preparation step c), the low-speed stirring time is 0.5 to 1.5 min; the high-speed stirring time is 1.5 to 2.5 min.

5. The evaluation method according to claim 1, characterized in that: The water is laboratory water that meets the requirements of JGJ63.

6. The evaluation method according to claim 1, characterized in that: The isothermal calorimeter has no less than 4 test channels.

7. The evaluation method according to claim 1, characterized in that: The error of parallel sample testing is no more than 5%.

8. The evaluation method according to claim 1, characterized in that: The waste glass powder is the product of any one of float glass, bottle glass or flat glass after ball milling.

9. The evaluation method according to claim 1, characterized in that: The waste glass powder is a product of activation treatment such as high-energy ball milling, silica fume co-milling or nano-silicon dioxide co-milling.

10. The evaluation method according to claim 1, characterized in that: The correlation coefficient R2 of the relationship is not less than 0.96.

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