A method for determining the specific surface area of concrete continuously graded aggregates
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- CHANGJIANG RIVER SCI RES INST CHANGJIANG WATER RESOURCES COMMISSION
- Filing Date
- 2022-12-28
- Publication Date
- 2026-07-10
Smart Images
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Abstract
Description
Technical Field
[0001] This invention relates to the field of water conservancy engineering, and in particular to a method for determining the specific surface area of continuously graded aggregates in concrete. Background Technology
[0002] Concrete is currently the most widely used man-made building material, with global annual consumption exceeding 6 billion tons. This massive consumption not only generates substantial energy and material demands but also leads to a serious construction waste problem. Therefore, the development of high-performance, high-durability, and high-quality concrete has become a broad consensus in the engineering and academic communities.
[0003] Mix design optimization is a crucial approach to achieving concrete performance design and control, and water content and water-cement ratio are key indicators affecting the mechanical strength and durability of concrete. Especially with the continuous development of water-reducing agents and superplasticizers, minimizing water content and achieving a low water-cement ratio have become primary principles of mix design optimization. In fact, the flowability of concrete mixtures is closely related to water content. Mixing water forms a lubricating water film on the particle surfaces and also free water that disperses between particles. By minimizing the free water content while ensuring the thickness of the water film on the particle surfaces, the goal of minimizing water content in concrete can be achieved.
[0004] The thickness of the water film on the particle surface is related to both adsorption characteristics and specific surface area. The specific surface area of concrete raw materials varies considerably; for example, the specific surface area of silica fume can reach 20,000 m². 2 / kg, the specific surface area of ultrafine slag and ultrafine fly ash is 600m². 2 / kg-1000m 2 / kg, the specific surface area of general fly ash and common slag is 300m². 2 / kg-500m 2 / kg, the specific surface area of cement is usually 300m² 2 / kg-400m 2 / kg, while the specific surface area of gravel is 20m². 2 / kg-150m 2 / kg. Overall, test results from different researchers vary, and there is a lack of research on aggregate specific surface area, which leads to difficulties in engineering applications.
[0005] Commonly used methods for measuring specific surface area include the Blaine method and the BET method, but effective means for determining the specific surface area of aggregates are still lacking. Yin Yuejiang et al., based on fractal theory and Image-Pro plus software, calculated the specific surface area of aggregates with particle sizes of 80mm-150mm, 40mm-80mm, 20mm-40mm, and 5mm-20mm, with results of 22.57mm². 2 / g, 30.75mm 2 / g, 60.44mm 2 / g, 150.06mm 2 / g, but this method has high technical requirements and is difficult to promote.
[0006] Liu Tianjie et al. used the grout coating method and the principle of specific surface area calculation to estimate the specific surface area of the concrete cube specimen to be 0.26 cm² based on the mass of cement grout coating the aggregate surface. 2 The specific surface area of recycled aggregate with a diameter of 4.75mm-9.5mm is 5.98cm² / g. 2 / g, while the specific surface area of 9.50mm-19.00mm recycled aggregate is 4.19cm². 2 / g, but there are problems with the calculation of slurry thickness in this method, and the mass of slurry remaining in the aggregate voids is not taken into account.
[0007] Jiang Zhengwu et al. disclosed a method and procedure for testing the specific surface area of irregular aggregates based on random cross-sections. The method includes sample preparation, image acquisition, Image Pro software processing, reading the number of aggregate pixels, and calculating the specific surface area. The implementation involves cutting and grinding the aggregates, converting the color image to grayscale, and performing binarization. However, this method requires precise operation and high technical skills, making its widespread application difficult.
[0008] Ke Guojun et al., based on Image Pro Plus software and quantitative stereoscopic principles, used a digital camera to study the specific surface area of aggregates. The specific process included image acquisition, image denoising, size calibration, region selection, binarization, and calculation of the specific surface area. The results showed that the specific surface area of crushed stone was 186.83 mm². 2 / g, the specific surface area of the broken pebbles is 174.77mm². 2 The specific surface area of the mixed pebbles is 143.09 mm² / g. 2 / g. However, this method is difficult to apply in practice, and the requirements for field test conditions are relatively high.
[0009] Zhou Yunlin calculated the specific surface area based on the aggregate particle size distribution and proposed a wax impregnation method for testing specific surface area. The particle size distribution calculation assumes the aggregate is a sphere of equivalent diameter and uses the sphere area formula. The wax impregnation method involves scraping a paraffin sample from the aggregate surface after the paraffin has cooled, accurately measuring the paraffin thickness, and then calculating the specific surface area of the aggregate based on the paraffin coating quality and average thickness. The specific surface area of the 5mm-40mm aggregate tested was 0.89 cm². 2 / g-0.92cm 2 / g. However, the basic principles and main steps of this method are consistent with the coating method of other scholars.
[0010] Wang Qing et al. addressed the shortcomings of existing slurry-coating and wax-coating methods by proposing a method for calculating the specific surface area of coarse aggregate based on sieving curves. This method includes steps such as particle sieving, quartering sampling, slurry-coating method for determining specific surface area, computer image processing, disc sample preparation, and sieving curve fitting. However, this method suffers from cumbersome procedures and limited practicality.
[0011] In summary, the main testing methods for aggregate specific surface area include the slurry coating method, the wax coating method, and the image analysis method. However, the slurry coating method and the wax coating method have drawbacks such as the need for drying, hardening, and long waiting times. Furthermore, the thickness of the slurry and paraffin requires statistical analysis, and it is impossible to avoid errors caused by uneven thickness. Additionally, residual slurry and paraffin in the pores can also affect the results. The image method suffers from high technical requirements, complex procedures, difficult data post-processing, and insufficient practicality. Summary of the Invention
[0012] To address the shortcomings of the existing technologies, this invention provides a method for determining the specific surface area of continuously graded aggregates in concrete, which has advantages such as short time cycle, simple steps, low technical requirements, high result stability, and ease of promotion. Specifically, it is implemented through the following techniques.
[0013] A method for determining the specific surface area of continuously graded aggregates in concrete includes the following steps:
[0014] S1. Weigh the aggregate sample and standard balls and dry them at 100-105℃. During the process, weigh the aggregate sample and standard balls multiple times and calculate the corresponding moisture content until the difference between the two moisture contents does not exceed 0.1%.
[0015] S2. Weigh out 100 parts of cement, (40-45) parts of water, (0.15-0.25) parts of borax, and (0.10-0.20) parts of sodium carboxymethyl cellulose in the following order by weight, mix them as raw materials to make cement slurry, and pour the cement slurry into a metal bucket for later use.
[0016] S3. Take two metal mesh baskets and label them A and B respectively. Weigh the two metal mesh baskets. Then, immerse the two metal mesh baskets in cement slurry and quickly lift them out. Weigh the changes in mass of metal mesh baskets A and B immediately after lifting them out and 60 minutes later. Calculate the slurry coating rate of metal mesh baskets A and B using the following formula:
[0017]
[0018] In the formula η A / B m1 is the coating percentage of the metal mesh basket A (or B) at the moment of lifting or 60 minutes after lifting, in %; m1 is the mass of the metal mesh basket at the moment of lifting or 60 minutes after lifting, in g; m A / BLet A or B be the mass of the metal mesh basket, in grams.
[0019] S4. Clean metal mesh baskets A and B thoroughly. Then, place the standard ball into metal mesh basket A and the aggregate sample into metal mesh basket B. Weigh the two metal mesh baskets and calculate the mass m of the standard ball. 标 and aggregate sample mass m 骨 ;
[0020] S5. Immerse metal mesh baskets A and B in the cement slurry again until the cement slurry covers the standard balls and aggregate samples. Then, quickly lift metal mesh baskets A and B, and weigh the changes in mass of metal mesh baskets A and B immediately after lifting and 60 minutes later. Calculate the slurry coating rate of the standard balls and aggregate samples using the following formula:
[0021]
[0022] In the formula η 标 / 骨 m2 represents the slurry coating rate of the standard ball (or aggregate sample) immediately after lifting or 60 minutes after lifting, in %; m2 represents the mass of the standard ball (or aggregate sample) and the metal mesh basket immediately after lifting or 60 minutes after lifting, in g; m 标 / 骨 The mass of a standard ball or aggregate sample, in grams;
[0023] S6. Based on the standard ball coating ratio and the aggregate sample coating ratio, calculate the specific surface area of the aggregate sample using the following formula:
[0024]
[0025]
[0026] In the formula S 骨 The specific surface area of the aggregate is m. 2 / kg; R 标 Let be the radius of a standard sphere, in meters (m). For calculation constants; Parameters related to aggregate samples; ρ 标 The density of a standard sphere, kg / m³ 3 ;ρ 骨、表 The apparent density of the aggregate sample is kg / m³. 3 ;ρ 骨、振 The compacted density of the aggregate sample is given in kg / m³. 3 η 标0 η 骨0 The coating percentage (%) of the standard ball and aggregate sample at the moment of lifting are shown in η. 标60 η 骨60 The percentages (%) are the slurry coating rate of standard balls and aggregate samples after 60 minutes of lifting.
[0027] The formula described in S6 is derived through theoretical analysis, mathematical modeling, and experimental correction, taking into account factors such as aggregate packing state, density influence, and adhesion between slurry and aggregate, using a standard sphere as a reference.
[0028] Furthermore, the drying time for the aggregate samples and standard balls mentioned in S1 is 8h-12h; the formula for calculating the moisture content is:
[0029]
[0030] In the formula, m0 is the mass before drying, in g; m i Let q be the mass measured during the i-th weighing process, in g; i The moisture content, %, is calculated based on the mass of the i-th weighing; Δq is the difference in moisture content between the (j-1)-th and j-th aggregate samples, %; n is the number of weighings.
[0031] Furthermore, the aggregate sample mentioned in S1 is gravel with a particle size range of 5mm-20mm or 20mm-40mm, or a combination of both;
[0032] Furthermore, the standard sphere described in S1 is made of granite or basalt, with a radius R. 标 The thickness is 0.005m-0.010m, and the density is ρ. 标 2800 kg / m 3 -3300kg / m 3 .
[0033] Furthermore, the cement mentioned in S2 is silicate cement, including one of ordinary silicate cement (code PO), medium-heat silicate cement (code PMH), and low-heat silicate cement (code PLH).
[0034] Furthermore, in S2, the stirring speed is 40-50 rpm, and the stirring time is 3-4 minutes.
[0035] Furthermore, the metal basket described in S3 is a barrel-shaped container with a closed circumference, a hollow top, and a metal mesh at the bottom. The aperture of the bottom metal mesh is smaller than the particle size of the aggregate sample and the diameter of the standard ball.
[0036] Furthermore, the ambient temperature during the test was 20℃-25℃, and the relative humidity was 80%-85%.
[0037] Compared with the prior art, the advantages of the present invention are:
[0038] 1. The method of the present invention has simple steps and a short test cycle; it only includes steps such as sample drying, slurry preparation, mass weighing, and data calculation, and does not involve the coagulation and hardening of the slurry, nor does it involve statistical analysis of the slurry thickness. The test cycle is greatly shortened compared with the existing image method and slurry coating method.
[0039] 2. The method of this invention is easy to operate and has low technical requirements; it utilizes common materials found on engineering sites, such as cement and granite, as well as devices such as metal buckets and metal mesh baskets for testing, eliminating the need to purchase new equipment and reducing testing costs. Each test step only involves weighing and calculation, resulting in a low technical threshold and facilitating the promotion of the method.
[0040] 3. The method of the present invention has high reproducibility and good data stability; it mainly calculates the specific surface area through data such as mass and time, without involving statistical analysis of coating thickness, grayscale processing of sample images, threshold setting, etc., thus avoiding errors caused by subjective factors such as the operator's experience and technical level, and the results are stable. Detailed Implementation
[0041] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0042] Example 1
[0043] The aggregate used in a concrete construction project in Shannan City, Tibet Autonomous Region, has a particle size range of 5mm-40mm. The apparent density ρ of the aggregate is... 骨、表 2750kg / m 3 tap density ρ 骨、振 1840 kg / m 3 ,parameter The value is 0.260, parameter The value was 0.331, the test temperature was 20℃, and the relative humidity was 80%.
[0044] A standard granite sphere with radius R was selected for the experiment. 标 The value is 0.005m, and the density is ρ. 标 2810 kg / m 3 Weigh 4963.3g of aggregate sample in its natural state and 4964.2g of standard balls and dry them at a temperature of 102℃.
[0045] After drying for 8 hours, the mass m of the stone sample was weighed for the first time. 样1 The weight is 4952.6g, and the corresponding moisture content is q. 样1 It is 0.22%; the standard ball mass m 球1 The weight is 4957.3g, and the corresponding moisture content is q. 球1 The content was 0.14%; after drying for another 10 hours, the mass of the stone sample was weighed a second time. 样2 The weight is 4948.6g, and the corresponding moisture content is q.样2 It is 0.30%; the standard ball mass m 球2 The weight is 4956.4g, and the corresponding moisture content is q. 球2 The value is 0.16%. The difference in moisture content Δq between two tests on the gravel sample is... 样 The difference Δq between the moisture content of the standard sphere and the moisture content of the two samples is 0.08%. 球 The value is 0.02%, which meets the requirement that the difference in function rates should not exceed 0.1%, and can be used for subsequent experiments.
[0046] Ordinary Portland cement (PO) was used to prepare the slurry, with a mix ratio of 100 parts cement, 40 parts water, 0.15 parts borax, and 0.1 parts sodium carboxymethyl cellulose. The mixer speed was controlled at 40 rpm, and the mixing time was continuously for 3 minutes. The slurry was then poured into a metal bucket for later use.
[0047] Take two metal mesh baskets and label them A and B respectively. Weigh the metal mesh basket A and measure its mass m. A The mass m of the metal mesh basket B is 313.4g. B The mass of the metal basket A is 320.7g; then, the metal basket is immersed in cement slurry and then quickly lifted out, and the mass m of the metal basket A at the moment of lifting is measured. 1(A0) It is 337.6g, and the coating rate η A0 The mass m of the metal basket B at the moment of lifting is 7.72%. 1(B0) It is 345.1g, with a coating rate η. B0 The percentage was 7.61%; the mass m of the metal basket A after 60 minutes of lifting was... 1(A60) The weight is 318.2g, and the coating rate η is... A60 The percentage was 1.53%; the mass m of the metal basket B after 60 minutes of lifting was... 1(B60) The weight is 326.2g, and the coating rate η is... B60 It is 1.71%.
[0048] Clean metal mesh baskets A and B thoroughly. Then, place the standard ball into metal mesh basket A and the aggregate sample into metal mesh basket B. Weigh the mass m of metal mesh basket A. A标 The mass m of the metal mesh basket B is 5270.4g. B骨 The mass is 5269.9g; calculate the mass m of the standard ball. 标 The aggregate sample mass was 4957.0g. 骨 The mass is 4949.2g. The standard sphere and metal basket A, along with the aggregate sample and metal basket B, are simultaneously immersed in cement slurry and then quickly lifted out. The mass m of the standard sphere and metal basket A at the moment of lifting is measured. 2(A0) The mass m of the aggregate sample and the metal basket B at the moment of lifting was 5749.2g. 2(B0) The mass m of the standard ball and metal basket A after being lifted for 60 minutes is 5806.9g. 2(A60)The mass of the aggregate sample and the mass of the metal mesh basket B after 60 minutes of lifting were 5377.1g. 2(B60) The weight was 5388.4g; the coating rate η of the standard ball at the moment of lifting was... 标0 The coating rate η after lifting for 60 minutes was 9.17%. 标60 The percentage was 2.06%; the slurry coating rate η at the moment the aggregate sample was lifted was... 骨0 The coating rate η after lifting for 60 minutes was 10.36%. 骨60 It is 2.28%.
[0049] Based on the above results, the specific surface area S of the aggregate was calculated. 骨 It is 19.2m 2 / kg.
[0050] To compare the fluctuations in test results among different operators, 10 operators with varying levels of skill were simultaneously recruited on-site. After brief training, they conducted the tests according to the procedures, and the results are shown in Table 1. The average value of the test results from all operators was 19.1m. 2 / kg, standard deviation is 0.6m 2 / kg indicates that the method has good stability and high reproducibility.
[0051] Table 1. Fluctuations in test results for different operators in the Shannan City, Tibet project.
[0052] Operator 1 2 3 4 5 6 7 8 9 10 <![CDATA[S 骨 ]]> 19.7 19.5 18.8 19.2 18.9 19.4 18.9 18.7 19.0 19.1
[0053] Example 2
[0054] The aggregate used in a concrete construction project in Anqing City, Anhui Province, has a particle size range of 5mm-20mm. What is the apparent density ρ of the aggregate? 骨、表 2680 kg / m 3 tap density ρ 骨、振 1790kg / m 3 ,parameter The value is 0.260, parameter The value was 0.332, the test temperature was 22℃, and the relative humidity was 83%.
[0055] A standard sphere made of basalt was selected for the experiment, with a radius R of the standard sphere. 标 The value is 0.010m, and the density is ρ. 标 3150kg / m 3 Weigh 5127.4g of aggregate sample in its natural state and 5132.7g of standard balls and dry them at a temperature of 105℃.
[0056] After drying for 10 hours, the mass m of the stone sample was weighed for the first time. 样1 The weight is 5079.3g, and the corresponding moisture content is q. 样1It is 0.94%; the standard ball mass m 球1 The weight is 5091.5g, and the corresponding moisture content is q. 球1 The content was 0.80%; after drying for another 12 hours, the mass m of the stone sample was weighed a second time. 样2 The weight is 5075.7g, and the corresponding moisture content is q. 样2 It is 1.01%; the standard ball mass m 球2 The weight is 5089.4g, and the corresponding moisture content is q. 球2 The value is 0.84%. The difference in moisture content Δq between two tests on the gravel sample is... 样 The difference in moisture content Δq between two standard sphere tests is 0.07%. 球 The value is 0.04%, which meets the requirement that the difference in function rates should not exceed 0.1%, and can be used for subsequent experiments.
[0057] The slurry was prepared using medium-heat silicate cement (PMH) with a mix ratio of 100 parts cement, 42 parts water, 0.20 parts borax, and 0.15 parts sodium carboxymethyl cellulose. The mixer speed was controlled at 45 rpm, and the mixing time was continuously 3.5 minutes. The slurry was then poured into a metal container for later use.
[0058] Take two metal mesh baskets and label them A and B respectively. The mass of metal mesh basket A is m. A The mass m of the metal mesh basket B is 319.2g. B The mass of the metal basket A was 316.9g. The basket was then submerged in cement slurry and quickly lifted. The mass m of the metal basket A at the moment of lifting was measured. 1(A0) The weight is 345.3g, and the coating rate η is... A0 The mass m of the metal basket B at the moment of lifting is 8.18%. 1(B0) The weight is 351.7g, and the coating rate η is... B0 The percentage was 10.98%; the mass m of the metal basket A after 60 minutes of lifting was... 1(A60) It weighs 325.9g, with a coating rate η. A60 The percentage is 2.10%; the mass m of the metal basket B after 60 minutes of lifting is... 1(B60) It weighs 324.7g, with a coating rate η. B60 It is 2.46%.
[0059] Clean metal mesh baskets A and B thoroughly. Then, place the standard ball into metal mesh basket A and the aggregate sample into metal mesh basket B. Weigh the mass m of metal mesh basket A. A标 The mass m of the metal mesh basket B is 5409.2g. B骨 The mass is 5393.2g; the mass m of the standard ball is calculated. 标 The aggregate sample mass is 5090.0g. 骨The mass is 5076.3g. The standard sphere and metal basket A, along with the aggregate sample and metal basket B, are simultaneously immersed in cement slurry and then quickly lifted out. The mass m of the standard sphere and metal basket A at the moment of lifting is measured. 2(A0) The mass m of the aggregate sample and the metal basket B at the moment of lifting is 6363.2g. 2(B0) The mass m of the standard ball and metal basket A after being lifted for 60 minutes is 10561.2g. 2(A60) The mass m of the aggregate sample and the metal mesh basket B after being lifted for 60 minutes was 5683.5g. 2(B60) The weight is 5873.4g; the coating rate η of the standard ball at the moment of lifting is... 标0 The coating rate η after lifting for 60 minutes was 18.23%. 标60 The percentage was 5.26%; the slurry coating rate η at the moment the aggregate sample was lifted was... 骨0 The coating rate η after lifting for 60 minutes was 101.12%. 骨60 It is 9.31%.
[0060] Based on the above results, the specific surface area S of the aggregate was calculated. 骨 It is 24.2 m2 / kg.
[0061] To compare the fluctuations in test results among different operators, 10 operators with varying levels of skill were simultaneously recruited on-site. After brief training, they conducted the tests according to the procedures, and the results are shown in Table 2. The average value of the test results from each operator was 24.2 m² / kg, and the standard deviation was 0.5 m² / kg, indicating that the method has good stability and high reproducibility.
[0062] Table 2. Fluctuations in test results for different operators in the Anqing, Anhui project.
[0063] Operator 1 2 3 4 5 6 7 8 9 10 <![CDATA[S 骨 ]]> 23.8 24.6 24.2 24.1 24.5 23.9 24.2 23.8 24.3 24.5
[0064] Example 3
[0065] The concrete aggregate for a project in Zhaoqing City, Guangdong Province, consists of two particle sizes: 5mm-20mm and 20mm-40mm, with a mass ratio of 50%:50%. The apparent density ρ of the aggregate... 骨、表 2730kg / m 3 tap density ρ 骨、振 1850 kg / m 3 ,parameter The value is 0.260, parameter The value was 0.322, the test temperature was 25℃, and the relative humidity was 85%.
[0066] A standard granite sphere with radius R was selected for the experiment. 标 The value is 0.008m, and the density is ρ. 标3050kg / m 3 Weigh 5206.7g of aggregate sample in its natural state and 5206.8g of standard balls and dry them at a temperature of 103℃.
[0067] After drying for 8 hours, the mass m of the stone sample was weighed for the first time. 样1 The weight is 5096.5g, and the corresponding moisture content is q. 样1 It is 2.12%; the standard ball mass m 球1 The weight is 5189.2g, and the corresponding moisture content is q. 球1 The content was 0.34%; after drying for another 10 hours, the mass of the stone sample was weighed a second time. 样2 The weight is 5074.5g, and the corresponding moisture content is q. 样2 It is 2.54%; the standard ball mass m 球2 The weight is 5184.3g, and the corresponding moisture content is q. 球2 The value is 0.43%. The difference in moisture content Δq between two tests on the gravel sample is... 样 The difference in moisture content Δq between two standard sphere tests is 0.42%. 球 The content was 0.09%; after drying for another 12 hours, the mass m of the stone sample was weighed for the third time. 样3 The weight is 5071.6g, and the corresponding moisture content is q. 样3 It is 2.59%; the standard ball mass m 球3 The weight is 5183.8g, and the corresponding moisture content is q. 球3 The value is 0.44%. The difference in moisture content Δq between two tests on the gravel sample is... 样 The difference Δq between the moisture content of the standard sphere and the moisture content of the two samples is 0.06%. 球 The value is 0.01%, which meets the requirement that the difference in function rates should not exceed 0.1%, and can be used for subsequent experiments.
[0068] Low-heat silicate cement (PLH) was used to prepare the slurry, with a mix ratio of 100 parts cement, 45 parts water, 0.25 parts borax, and 0.20 parts sodium carboxymethyl cellulose. The mixer speed was controlled at 50 rpm, and the mixing time was continuously for 4 minutes. The slurry was then poured into a metal bucket for later use.
[0069] Take two metal mesh baskets and label them A and B respectively. Weigh the metal mesh basket A and measure its mass m. A The mass m of the metal mesh basket B is 323.5g. B The mass of the metal basket A is 314.9g; then, the metal basket is immersed in cement slurry and then quickly lifted out, and the mass m of the metal basket A at the moment of lifting is measured. 1(A0) The weight is 341.8g, and the coating rate η is... A0 The percentage is 5.66%; the mass m of the metal basket B at the moment of lifting is... 1(B0) It weighs 334.7g, with a coating rate η. B0The percentage was 6.29%; the mass m of the metal basket A after 60 minutes of lifting was... 1(A60) The weight is 330.8g, and the coating rate η is... A60 The percentage was 2.26%; the mass m of the metal basket B after 60 minutes of lifting was... 1(B60) The weight is 321.1g, and the coating rate η is 100%. B60 It is 1.97%.
[0070] Clean metal mesh baskets A and B thoroughly. Then, place the standard ball into metal mesh basket A and the aggregate sample into metal mesh basket B. Weigh the mass m of metal mesh basket A. A标 The mass m of the metal mesh basket B is 5507.9g. B骨 The mass is 5387.1g; calculate the mass m of the standard ball. 标 The aggregate sample mass was 5184.4g, and the mass m of the aggregate sample was... 骨 The mass is 5072.2g. The standard sphere and metal basket A, along with the aggregate sample and metal basket B, are simultaneously immersed in cement slurry and then quickly lifted out. The mass m of the standard sphere and metal basket A at the moment of lifting is measured. 2(A0) The mass m of the aggregate sample and the metal basket B at the moment of lifting is 6609.3g. 2(B0) The mass m of the standard ball and metal basket A after being lifted for 60 minutes is 8649.2g. 2(A60) The mass of the aggregate sample and the metal mesh basket B after being lifted for 60 minutes was 5671.4g. 2(B60) The weight was 5749.2g; the coating rate η of the standard ball at the moment of lifting was... 标0 The coating rate η after lifting for 60 minutes was 20.89%. 标60 The percentage was 3.01%; the slurry coating rate η at the moment the aggregate sample was lifted was... 骨0 The coating rate η after lifting for 60 minutes was 63.92%. 骨60 It is 7.02%.
[0071] Based on the above results, the specific surface area S of the aggregate was calculated. 骨 It is 18.3m 2 / kg.
[0072] To compare the fluctuations in test results among different operators, 10 operators with varying levels of skill were simultaneously recruited on-site. After brief training, they conducted the tests according to the procedures, and the results are shown in Table 3. The average value of the test results from all operators was 18.1m. 2 / kg, standard deviation is 0.5m 2 / kg indicates that the method has good stability and high reproducibility.
[0073] Table 3. Fluctuations in test results for different operators in the Zhaoqing, Guangdong project.
[0074] Operator 1 2 3 4 5 6 7 8 9 10 <![CDATA[S 骨 ]]> 17.9 18.1 18.5 17.9 18.2 18 17.8 18.3 18.5 18.1
[0075] Example 4
[0076] The concrete aggregate used in a construction project in Fukang City, Xinjiang, has a particle size of 20mm-40mm. The apparent density ρ of the aggregate... 骨、表 The tap density is 2760 kg / m³, and the tap density is ρ. 骨、振 1720kg / m 3 ,parameter The value is 0.260, parameter The value was 0.377, the test temperature was 23℃, and the relative humidity was 80%.
[0077] A standard sphere made of basalt was selected for the experiment, with a radius R of the standard sphere. 标 The value is 0.010m, and the density is ρ. 标 3300 kg / m 3 Weigh 4866.7g of aggregate sample in its natural state and 4879.5g of standard balls and dry them at a temperature of 105℃.
[0078] After drying for 8 hours, the mass m of the stone sample was weighed for the first time. 样1 The weight is 4853.1g, and the corresponding moisture content is q. 样1 It is 0.28%; the standard ball mass m 球1 The weight is 4871.6g, and the corresponding moisture content is q. 球1 The content was 0.16%; after drying for another 10 hours, the mass m of the stone sample was weighed a second time. 样2 The weight is 4848.3g, and the corresponding moisture content is q. 样2 It is 0.38%; the standard ball mass m 球2 The weight is 4868.5g, and the corresponding moisture content is q. 球2 The value is 0.23%. The difference in moisture content Δq between two tests for the stone sample is... 样 The difference Δq between the moisture content of the standard sphere and the moisture content of the two samples is 0.10%. 球 The content was 0.06%; after drying for another 11 hours, the mass m of the stone sample was weighed for the third time. 样3 The weight is 4846.7g, and the corresponding moisture content is q. 样3 It is 0.41%; the standard ball mass m 球3 The weight is 4867.9g, and the corresponding moisture content is q. 球3 The value is 0.24%. The difference in moisture content Δq between two separate tests of the gravel sample is... 样 The difference Δq between the moisture content of the standard sphere and the moisture content of the two samples is 0.03%. 球 The value is 0.01%, which meets the requirement that the difference in function rates should not exceed 0.1%, and can be used for subsequent experiments.
[0079] Low-heat silicate cement (PLH) was used to prepare the slurry, with a mix ratio of 100 parts cement, 43 parts water, 0.22 parts borax, and 0.19 parts sodium carboxymethyl cellulose. The mixer speed was controlled at 40 rpm, and the mixing time was continuously 3.5 minutes. The slurry was then poured into a metal bucket for later use.
[0080] Take two metal mesh baskets and label them A and B respectively. Weigh the metal mesh basket A and measure its mass m. A The mass m of the metal mesh basket B is 326.7g. B The mass is 322.4g; then the metal basket is immersed in cement slurry and then quickly lifted out, and the mass m of the metal basket A at the moment of lifting is measured. 1(A0) The weight is 338.3g, and the coating rate η is... A0 The mass m of the metal basket B at the moment of lifting is 3.55%. 1(B0) It is 335.5g, and the coating rate η B0 The percentage was 4.06%; the mass m of the metal basket A after 60 minutes of lifting was... 1(A60) The weight is 332.4g, and the coating rate η is... A60 The percentage was 1.74%; the mass m of the metal basket B after 60 minutes of lifting was... 1(B60) It is 327.6g, and the coating rate η B60 It is 1.61%.
[0081] Clean metal mesh baskets A and B thoroughly. Then, place the standard ball into metal mesh basket A and the aggregate sample into metal mesh basket B. Weigh the mass m of metal mesh basket A. A标 The mass m of the metal mesh basket B is 5195.2g. B骨 The mass is 5169.7g; the mass m of the standard ball is calculated. 标 The aggregate sample mass was 4868.5g. 骨 The mass is 4847.3g. The standard sphere and metal basket A, along with the aggregate sample and metal basket B, are simultaneously immersed in cement slurry and then quickly lifted out. The mass m of the standard sphere and metal basket A at the moment of lifting is measured. 2(A0) The mass m of the aggregate sample and the metal basket B at the moment of lifting was 6329.4g. 2(B0) The mass m of the standard ball and metal basket A after being lifted for 60 minutes is 6019.7g. 2(A60) The mass m of the aggregate sample and the metal mesh basket B after being lifted for 60 minutes was 5706.3g. 2(B60) The weight is 5611.8g; the coating rate η of the standard ball at the moment of lifting is... 标0 The coating rate η after lifting for 60 minutes was 23.06%. 标60 The slurry coating rate η at the moment the aggregate sample is lifted is 10.38%. 骨0 The coating rate η after lifting for 60 minutes was 17.27%. 骨60 It is 9.01%.
[0082] Based on the above results, the specific surface area S of the aggregate was calculated. 骨 It is 9.1m 2 / kg.
[0083] To compare the fluctuations in test results among different operators, 10 operators with varying levels of skill were simultaneously recruited on-site. After brief training, they conducted the tests according to the procedures, and the results are shown in Table 4. The average value of the test results from all operators was 9.1m. 2 / kg, standard deviation is 0.4m 2 / kg indicates that the method has good stability and high reproducibility.
[0084] Table 4. Fluctuations in test results for different operators in a project in Fukang City, Xinjiang.
[0085] Operator 1 2 3 4 5 6 7 8 9 10 <![CDATA[S 骨 ]]> 9.4 8.9 9.3 9.1 8.8 9.2 9.3 8.9 9.1 9.2
[0086] The above detailed embodiments describe the implementation of the present invention; however, the present invention is not limited to the specific details described in the above embodiments. Within the scope of the claims and technical concept of the present invention, various simple modifications and changes can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.
Claims
1. A method for determining the specific surface area of continuously graded aggregates in concrete, characterized in that, Includes the following steps: S1. Weigh the aggregate sample and standard balls and dry them at 100-105℃. During the drying process, weigh the aggregate sample and standard balls multiple times and calculate the corresponding moisture content until the difference between the two moisture contents does not exceed 0.1%. S2. Weigh out 100 parts of cement, (40-45) parts of water, (0.15-0.25) parts of borax, and (0.10-0.20) parts of sodium carboxymethyl cellulose in the following order by weight, mix them as raw materials to make cement slurry, and pour the cement slurry into a metal bucket for later use. S3. Take two metal wire mesh baskets and label them A and B respectively. Weigh the two metal wire mesh baskets. Then, immerse the two metal wire mesh baskets in cement slurry and quickly lift them out. Weigh the changes in mass of metal wire mesh baskets A and B immediately after lifting them out and 60 minutes later. Calculate the slurry coating rate of metal wire mesh baskets A and B according to the following formula: ； In the formula η A / B The coating rate of metal mesh basket A or B at the moment of lifting or 60 minutes after lifting, % m 1 represents the mass of the metal basket at the moment of lifting or 60 minutes after lifting, in grams; m A / B Let A or B be the mass of the metal mesh basket, in grams. S4. Clean metal mesh baskets A and B thoroughly. Then, place the standard ball into metal mesh basket A and the aggregate sample into metal mesh basket B. Weigh the two metal mesh baskets and calculate the mass of the standard ball. m 标 and the quality of aggregate samples m 骨 ; S5. Immerse metal baskets A and B in the cement slurry again until the slurry covers the standard balls and aggregate samples. Then, quickly lift metal baskets A and B, and weigh them immediately after lifting and 60 minutes later. Calculate the slurry coating rate of the standard balls and aggregate samples using the following formula: ； In the formula η 标 / 骨 The percentage of slurry coating on a standard ball or aggregate sample immediately after lifting or 60 minutes after lifting, expressed as %. m 2 represents the mass of the standard ball or aggregate sample and the metal basket at the moment of lifting or 60 minutes after lifting, in grams; m 标 / 骨 The mass of a standard ball or aggregate sample, in grams; S6. Based on the standard ball coating ratio and the aggregate sample coating ratio, calculate the specific surface area of the aggregate sample using the following formula: ； ； In the formula S 骨 The specific surface area of the aggregate is m. 2 / kg; R 标 Let be the radius of a standard sphere, in meters (m). φ 1 is a calculation constant; φ 2 represents the parameters related to the aggregate sample; ρ 标 The density of a standard sphere, kg / m³ 3 ; ρ 骨、表 The apparent density of the aggregate sample is kg / m³. 3 ; ρ 骨、振 The compacted density of the aggregate sample is given in kg / m³. 3 ; η 标0 , η 骨0 The coating rates of the standard ball and aggregate sample at the moment of lifting are respectively the coating rates of the aggregate sample. η 标60 , η 骨60 The percentages are the slurry coating rates of standard balls and aggregate samples after 60 minutes of lifting.
2. The method for determining the specific surface area of continuously graded aggregates in concrete according to claim 1, characterized in that, In step 1, the drying time for the aggregate samples and standard balls is 8-12 hours; the formula for calculating the moisture content is: ； In the formula m 0 represents the mass before drying, in grams; m i For the first step in the drying process i The mass of the next weighing, in grams; q i According to the i Moisture content calculated from the mass of the first weighing, % ∆ q For the first j-1 Second and third j The difference in moisture content of the secondary aggregate samples, %; n is the number of times the mass is weighed.
3. The method for determining the specific surface area of continuously graded aggregates in concrete according to claim 1, characterized in that, The aggregate sample mentioned in step 1 is gravel with a particle size range of 5mm-20mm or 20mm-40mm, or a combination of both.
4. The method for determining the specific surface area of continuously graded aggregates in concrete according to claim 1, characterized in that, The standard sphere mentioned in step 1 is made of granite or basalt, and has a radius of... R 标 Its thickness is 0.005m-0.010m, and its density is... ρ 标 2800 kg / m 3 -3300kg / m 3 .
5. The method for determining the specific surface area of continuously graded aggregates in concrete according to claim 1, characterized in that, In step 2, the stirring speed is 40-50 rpm and the stirring time is 3-4 minutes.
6. The method for determining the specific surface area of continuously graded aggregates in concrete according to claim 1, characterized in that, The metal basket mentioned in step 3 is a barrel-shaped container with a closed circumference, a hollow top, and a metal mesh at the bottom. The aperture of the bottom metal mesh is smaller than the particle size of the aggregate sample and the diameter of the standard ball.
7. The method for determining the specific surface area of continuously graded aggregates in concrete according to claim 1, characterized in that, The ambient temperature during the test was 20℃-25℃, and the relative humidity was 80%-85%.