Method for determining the dry suction rate of the saturated surface of a concrete coarse aggregate

Abstract

The application provides a method for measuring the saturated surface dry water absorption rate of concrete coarse aggregate, which mainly uses an oven, a metal mesh basket, a beaker, an electronic balance and other tools, constructs a quantitative relationship model of relevant parameters according to the mass change of the coarse aggregate before and after being soaked in different liquids, and calculates the saturated surface dry water absorption rate of the concrete coarse aggregate. The application is based on the pore structure characteristics and capillary adsorption characteristics of the coarse aggregate, uses the difference in the absorption capacity of the coarse aggregate for different liquids, and the difference in the density and the viscous coefficient of different liquids, and designs the method for measuring the saturated surface dry water absorption rate of the concrete coarse aggregate. The method has the characteristics of simple steps, low cost, reliable test, stable data, easy popularization and the like, overcomes the defects of the traditional method, such as large human operation error and serious subjective experience influence, and can be used for the research and development of automatic equipment and the design of software algorithm, and has good popularization and application value.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of hydraulic engineering, and particularly relates to a method for measuring saturated surface dry water absorption rate of coarse aggregate of concrete. BACKGROUND

[0002] Coarse aggregate is also called coarse aggregate, which mainly refers to gravel in raw materials of concrete, including artificial gravel and natural pebbles. According to different particle sizes, gravel is further divided into small stones (5mm-20mm), medium stones (20mm-40mm), large stones (40mm-80mm) and extra-large stones (80mm-150mm or 120mm). The saturated surface dry water absorption rate is one of the main performance indicators of coarse aggregate, which reflects the maximum amount of water that can be absorbed by coarse aggregate when it is fully saturated from the absolute dry state without water. The saturated surface dry state is a state in which the coarse aggregate is saturated inside and has no water outside, that is, the coarse aggregate is in a critical state of water absorption and water release balance.

[0003] When the coarse aggregate is in the saturated surface dry state, it neither absorbs water from the surrounding environment nor releases water to the surrounding environment, so it does not affect the free water content of the concrete mixture. Therefore, the “Design Specification for Mixing Proportion of Hydraulic Concrete” (DL / T 5330-2015) clearly requires that “the design and test of concrete mixing proportion should be based on the saturated surface dry aggregate”, and the saturated surface dry water absorption rate is also an important basis for adjusting the water quantity and correcting the coarse aggregate quantity in the actual mixing process. However, when some projects mix concrete according to the recommended mixing proportion, problems such as non-compliance of fluidity and large fluctuation of actual strength still occur, which is also related to inaccurate determination of the saturated surface dry water absorption rate.

[0004] The traditional method for determining the saturated surface dry water absorption rate of coarse aggregate has many human factors and high degree of subjective experience influence. The method for determining the saturated surface dry water absorption rate of gravel provided by the “Test Specification for Hydraulic Concrete” (SL / T352-2020) is to use a porcelain plate and a wet towel to determine the “saturated surface dry state” by absorbing excess water on the surface of the sample with a wrung wet towel. However, the technical experience of the tester has a great influence on the accuracy and stability of the data results in actual operation, and the test results of different testers differ significantly, especially in the determination of water marks, traces and water stains, which are obviously influenced by human subjective factors. Therefore, engineers and technical workers urgently need a more objective and reliable method for determining the saturated surface dry water absorption rate.

[0005] To explore more accurate saturated surface dry water absorption determination method, researchers from the aggregate water absorption law, saturated particle packing characteristics and other aspects of a large number of exploration. Kong Xiangzhi et al. by fine recording after the fine aggregate fully watered in the drying process, the change characteristics of water evaporation rate, the indirect calculation of fine aggregate saturated surface dry water absorption. Sun Renjuan et al. according to the change of fine aggregate drying process, the particle natural angle of repose, put forward a kind of based on the angle of repose of fine aggregate saturated surface dry state quantitative determination method. But these methods are only effective for small particle size of fine aggregate, and for large particle size of coarse aggregate, still lack of effective saturated surface dry water absorption test method. SUMMARY

[0006] The present application provides a method for determining the saturated surface dry water absorption of coarse aggregate, which can significantly improve the reliability and objectivity of the test results, eliminate the influence of human factors and subjective experience, without increasing the cost of new test equipment or test, and is convenient for engineering site use, providing a new way for the water absorption performance characterization of coarse aggregate.

[0007] In order to achieve the above technical purpose, the present application provides a method for determining the saturated surface dry water absorption of coarse aggregate, which comprises the following steps:

[0008] (1) take mg natural state of coarse aggregate for drying, control the drying temperature is 105-110℃, during the period of multiple weighing sample quality, and calculate the moisture content of the sample, until the difference between the two moisture contents is not more than 0.2%, then stop drying, and store in a moisture-proof state after natural cooling, the moisture content of the sample, the difference between the two moisture contents is calculated as follows:

[0009]

[0010] Δq=q j -q j-1 (j=2·N) ②

[0011] In the formula: m0 is the mass of the natural state of coarse aggregate before drying, g;

[0012] m i is the mass of the sample in the i-th weighing during the drying process, g;

[0013] q i , q j , q j-1 are the moisture contents calculated in the i-th, j-th and j-1-th time, respectively, %;

[0014] Δq is the difference between the two moisture contents, %;

[0015] N is the total number of sample mass weighing during the drying process;

[0016] i is the number of weighing of the aggregate sample mass;

[0017] j is the number of aggregate sample moisture content calculation;

[0018] (2) The dried aggregate sample is evenly divided into two parts, numbered A and B respectively, and the mass of sample A is weighed using an electronic balance m A , and the mass of sample B is m B ; ready for use;

[0019] (3) Take two beakers and two metal mesh baskets, the beakers are numbered 1# and 2# respectively, and the metal mesh baskets are numbered 3# and 4# respectively, then pour distilled water into 1# beaker, weigh the total mass of beaker and distilled water m 10 ; pour machine oil into 2# beaker, weigh the total mass of beaker and machine oil m 20 ;

[0020] (4) Soak 3# metal mesh basket in 1# beaker, keep it raised but still submerged below the liquid surface, weigh the total mass of beaker and distilled water m 11 ; then completely lift and remove the metal mesh basket, weigh the total mass of 1# beaker and distilled water again m 12 ;

[0021] (5) Soak 4# metal mesh basket in 2# beaker, keep it raised but still submerged below the liquid surface, weigh the total mass of beaker and machine oil m 21 ; then completely lift and remove the metal mesh basket, weigh the total mass of 2# beaker and machine oil again m 22 ;

[0022] (6) Put sample A into 3# metal mesh basket and sample B into 4# metal mesh basket, then soak 3# metal mesh basket with sample A in 1# beaker for sufficient soaking, and soak 4# metal mesh basket with sample B in 2# beaker;

[0023] (7) Lift the metal mesh baskets but keep them submerged in distilled water and machine oil, weigh the total mass of 1# beaker and distilled water again m 13 , weigh the total mass of 2# beaker and machine oil again m 23 , and calculate the saturated surface dry water absorption rate P of coarse aggregate according to the following formula:

[0024] Δm1 = m 13 -m 12 -m 11 +m 10 ③

[0025] Δm2 = m 23 -m22 -m 21 +m 20 ④

[0026]

[0027]

[0028] P = saturated surface dry water absorption of coarse aggregate, %;

[0029] ρ c = density of machine oil, g / cm 3 ;

[0030] Δm1 = force of aggregate sample in distilled water, g;

[0031] Δm2 = force of aggregate sample in machine oil, g;

[0032] k = mass ratio of dried aggregate sample A and dried aggregate sample B.

[0033] The preferred technical scheme of the present application: the water content difference Δq in the step (1) refers to the difference of water content of two adjacent times, and the time interval of sample weighing of two adjacent times is 1.5-2.0h.

[0034] The preferred technical scheme of the present application: the viscosity number of the machine oil in the step (3) is 30-50, and different viscosity numbers of machine oil can be mixed, and the density ρ c of the mixed machine oil needs to be calculated. c The calculation method of the density ρ i of the mixed machine oil is as follows:

[0035]

[0036] M i = mass proportion of the i-th machine oil in the mixed machine oil, %;

[0037] ρ i and ρ j = density of the i-th and j-th machine oil in the mixed machine oil, g / cm 3 ;

[0038] n = total number of different viscosity numbers of machine oil.

[0039] The preferred technical scheme of the present application: the soaking time in the step (6) is 24-30h, and the sample B does not need to be soaked.

[0040] The preferred technical scheme of the present application: the operation steps are all carried out in the environment of 20-22℃ temperature and 80%-85% humidity.

[0041] Since the concrete aggregate surface has micro cracks and pores, it can form a channel for the penetration of external liquid, but the amount of liquid penetration, penetration rate and aggregate pore structure characteristics, crack width, environmental temperature, viscosity coefficient and other factors are related. According to the principle of similarity and compatibility, the aggregate and water are inorganic materials, and the aggregate has good absorption performance for water, but the absorption performance of the aggregate for organic solvents is poor, and the difference in absorption characteristics of the aggregate for different liquids can be used to calculate the saturated water absorption of the aggregate.

[0042] The inventors of the present application found that the absorption characteristics of the aggregate for organic solvents are related to the viscosity coefficient of the organic solvent. The organic solvent with lower viscosity coefficient is more likely to invade the pores and micro cracks of the aggregate, and the organic solvent with higher viscosity coefficient has limited penetration amount and penetration rate due to the strong adhesion between the aggregate surface and the solvent. Therefore, the present application considers using an organic solvent with a certain viscosity coefficient requirement as a comparison sample. The selection of the organic solvent should consider the factors such as the convenience of purchase, the safety of use, the environmental protection after use and the like. Although the chemical solvent has high purity and good effect, it is difficult to purchase on the construction site, and the operator has certain health risks, and after the end of the test, the material processing also faces the problem of pollution. Therefore, by comparing common materials such as machine oil, hydraulic oil, cooling oil and heavy oil, considering the absorption characteristics of common aggregate, test error and influence degree and other factors, the present application finally selects machine oil as a comparison sample. The viscosity grade of machine oil reflects the viscosity characteristics of machine oil, and the viscosity characteristics of machine oil are directly related to the penetration amount and penetration rate. In the early test process, it is found that using machine oil with small viscosity grade can cause large penetration amount and high result error; and using machine oil with large viscosity grade can cause large adhesion amount on the surface of the metal mesh basket and the aggregate, increase the material loss amount, and reduce the economy of the method. Therefore, the present application selects machine oil with a specific viscosity grade for testing in combination with the characteristics of common aggregate such as basalt, granite, sandstone and gneiss in engineering, and the production characteristics of sandstone processing system, considering the result deviation and data stability requirement.

[0043] Since the viscosity of the liquid is related to the ambient temperature. Generally, the viscosity coefficient decreases with the increase of the ambient temperature, and the increase of the viscosity coefficient will lead to the increase of the aggregate penetration amount and the penetration rate. Considering the change characteristics of the viscosity of the engine oil with the ambient temperature and the influence degree of the change of the viscosity of the engine oil on the test results, the ambient temperature is set to 20-22°C in the application. There is a phenomenon of moisture absorption in the storage process of the aggregate, and the greater the environmental humidity, the more obvious the moisture absorption phenomenon of the aggregate, and too low environmental humidity also puts strict requirements on the test conditions. At the same time, during the soaking process of the aggregate, the water in the beaker also has a phenomenon of evaporation, and the loss of water will lead to the lower test results. In fact, the water evaporation rate is related to the environmental humidity. The lower the environmental humidity, the faster the water evaporation rate; and the higher the environmental humidity, the smaller the water evaporation rate. Considering the influence of the field environmental conditions, the humidity range of the conventional laboratory, the water evaporation rate under different humidity and the moisture absorption characteristics of the aggregate, the environmental humidity is limited to 80%-85% in the application.

[0044] In the application, according to the water absorption kinetics characteristics of the material, the water absorption rate of the aggregate is fast at the beginning of the soaking, but the water absorption rate of the aggregate continues to decrease with the extension of the soaking time. The purpose of sufficient soaking is to ensure that the water absorption of the aggregate reaches stability, and to improve the accuracy and reliability of the test results. The applicant's previous test shows that the water absorption rate of the aggregate changes greatly within 1h after the soaking begins, and basically stabilizes after 24h. Therefore, the water absorption time of the aggregate is set to 24-30h in the application. Since the oil absorption capacity of the aggregate is limited, and in order to reduce the influence of the soaking time in the oil on the results, the sample B does not need to be soaked sufficiently. The drying of the aggregate is a slow process, and the water loss rate of the aggregate is large at the beginning of the drying, and the water content changes fast; and the water loss rate of the aggregate is small at the later stage of the drying, and the water content changes slowly. The weighing time interval of the sample mass before and after the weighing is mainly to avoid the false appearance of the water content meeting the requirements due to the short interval, and the time interval of the two weighings needs to be set.

[0045] In the application, the metal mesh is "kept raised but still immersed below the liquid surface" to ensure the stability of the test results and avoid errors caused by human factors. The force of the metal mesh basket in the liquid mainly includes the lifting force, the buoyancy and the gravity. In the completely immersed condition, the buoyancy of the metal mesh basket is not related to the relative position, the immersion depth and other factors, so that the overall mass is relatively stable, and the error caused by human factors is avoided

[0046] The saturated surface dry water absorption rate is one of the main technical indexes of coarse aggregate, and is also an important parameter for determining the actual water consumption and coarse aggregate consumption before mixing. Based on the pore structure characteristics of the coarse aggregate and the capillary adsorption principle, combined with the viscosity characteristics of the liquid at different temperatures, the differences in the absorption capacity of the coarse aggregate for different liquids, and the differences in the viscosity coefficients of different liquids, a method for determining the saturated surface dry water absorption rate of the concrete coarse aggregate is provided by comparing the mass changes of the coarse aggregate in different media. Compared with the existing means and technologies, the present application has the following advantages:

[0047] (1) The test results of the method are more objective, the influence of human factors is reduced, and the problems such as strong subjectivity and serious dependence on operation experience existing in the traditional means are overcome.

[0048] (2) The method can be carried out with the existing equipment and devices, without the need to purchase or increase new test instruments, with low economic investment, low technical requirements for personnel, and convenient for the popularization and application of the method.

[0049] (3) The test results of the method have good stability and repeatability, the test results of different batches are less different, the dispersion degree of the data is reduced, the fluctuation range of the data is improved, and the method can be used for the research and development of automatic equipment and the design of software algorithm.

[0050] The present application has the characteristics of simple steps, low cost, high test reliability, good data stability, easy popularization and the like, significantly improves the reliability and objectivity of the test results, eliminates the influence of human factors and subjective experience, and does not need to increase new test equipment or test cost, has good popularization and application value, and is convenient for engineering site use. BRIEF DESCRIPTION OF DRAWINGS

[0051] Figure 1 is a variation curve diagram of the viscosity coefficient of the machine oil under different environmental temperatures;

[0052] Figure 2 is a curve diagram of the absorption of the aggregate to kerosene and machine oil under different viscosity coefficients;

[0053] Figure 3 is a view of the pebble sample in the water and electricity engineering in example 1;

[0054] Figure 4 is a view of the artificial crushed stone in the water and electricity engineering in example 2;

[0055] Figure 5 is a view of the artificial crushed stone in the water and electricity engineering in example 3. DETAILED DESCRIPTION

[0056] The present application will be further described below in combination with the drawings and examples. The present application is described in detail below. Figures 1 to 5For the purpose of clarity and conciseness, the drawings of the embodiments are drawn in a simplified manner. The technical solutions shown in the drawings are specific schemes of the embodiments of the present application, and are not intended to limit the scope of the claimed application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor fall within the scope of the present application.

[0057] The present application provides a method for determining the saturated surface dry water absorption rate of concrete coarse aggregate, specifically comprising the following steps, all of the following operation steps are carried out in a temperature of 20-22℃ and a humidity of 80%-85%, and the specific steps are as follows:

[0058] (1) Take mg of coarse aggregate in a natural state for drying, control the drying temperature to be 105-110℃, weigh the sample mass multiple times during the drying process, and calculate the water content of the sample, until the difference between the water contents of the previous and subsequent times is not more than 0.2%, then stop the drying, and after natural cooling, store in a moisture-proof manner, the calculation formulae of the water content of the sample and the difference between the water contents are as follows:

[0059]

[0060] Δq=q j -q j-1 (j=2·N) ②

[0061] In the formula, m0 is the mass of the coarse aggregate in a natural state before drying, g;

[0062] m i is the mass of the sample weighed at the ith time during the drying process, g;

[0063] q i , q j , and q j-1 are the water contents calculated at the ith time, the jth time, and the (j-1)th time, respectively, %;

[0064] Δq is the difference between the water contents of the previous and subsequent times, %;

[0065] N is the total number of times of weighing the sample mass during the drying process;

[0066] i is the number of times of weighing the mass of the aggregate sample;

[0067] j is the number of times of calculating the water content of the aggregate sample;

[0068] The aggregate drying process is necessary, and the fully dried aggregate can further carry out the subsequent water absorption test. The water content is a parameter for characterizing the drying condition of the aggregate, which refers to the percentage of water contained in the aggregate under natural conditions. The water content is 0, indicating that the aggregate is in a fully dried state. The stable water content indicates that the water content in the aggregate is basically unchanged. Formulas ① and ② are mathematical formulas constructed according to the physical meaning of the water content. The determination of the water content limit considers the water loss characteristics, drying efficiency, test period and result accuracy of common aggregates, etc. Under the condition that the error fluctuation of the saturated surface dry water absorption rate of the aggregate sample does not exceed 0.2%, the accuracy requirement is met.

[0069] (2) The dried coarse aggregate sample is evenly divided into two parts for testing, numbered A and B, and the mass of sample A is measured by an electronic balance as m A , and the mass of sample B is m B ; standby;

[0070] (3) Take two beakers and two metal mesh baskets, and the numbers of the beakers are 1# and 2#, and the numbers of the metal mesh baskets are 3# and 4#. Then pour an appropriate amount of distilled water into the 1# beaker, and measure the total mass of the beaker and the distilled water as m 10 ; pour an appropriate amount of machine oil into the 2# beaker, and measure the total mass of the beaker and the machine oil as m 20 ; the viscosity number of the machine oil is 30-50, and different viscosity numbers of the machine oil can also be mixed, and the density of the mixed machine oil ρ c needs to be calculated when used. The filtered machine oil can be reused, and the calculation method of the density of the mixed machine oil ρ c is as follows:

[0071]

[0072] In the formula, M i is the mass proportion of the i-th machine oil in the mixed machine oil, %;

[0073] ρ i and ρ j are the densities of the i-th and j-th machine oils in the mixed machine oil;

[0074] n is the total number of different viscosity numbers of the machine oils.

[0075] Formula ⑦ is a mathematical formula constructed by considering the mass proportion of different viscosity numbers of the machine oils and the density of each viscosity number of the machine oil, which is used to calculate the density of the mixed machine oil. In the calculation, it is assumed that there is no mutual solubility between the machine oil components, that is, the overall volume is compounded and added, and the density of the mixed machine oil is:

[0076]

[0077] After rearrangement, it is:

[0078]

[0079] After further refinement and deformation, we have:

[0080]

[0081] Therefore, the density of the mixed engine oil is:

[0082]

[0083] Using mixed oils can improve material utilization, solve the problem of insufficient oil reserves of specific viscosity grades at engineering sites, and improve the economic efficiency of the method.

[0084] (4) Immerse the No. 3 metal mesh basket in the No. 1 beaker, keeping it raised but still submerged below the liquid surface, and weigh the total mass m of the beaker and distilled water. 11 Then, completely lift and remove the metal mesh basket, and weigh the total mass m of beaker #1 and distilled water again. 12 ;

[0085] (5) Immerse the No. 4 metal mesh basket in the No. 2 beaker, keeping it raised but still submerged below the liquid surface, and weigh the total mass m of the beaker and the oil. 21 Then, completely lift and remove the metal mesh basket, and weigh the total mass m of beaker #2 and the engine oil again. 22 ;

[0086] (6) Put sample A into a No. 3 metal mesh basket and sample B into a No. 4 metal mesh basket. Then immerse the No. 3 metal mesh basket containing sample A into a No. 1 beaker for full immersion. Immerse the No. 4 metal mesh basket containing sample B into a No. 2 beaker. Full immersion means that the immersion time is 24-30 hours, while sample B does not need to be fully immersed.

[0087] (7) Lift the metal mesh basket but keep it submerged in the distilled water and oil, and weigh the total mass m of beaker #1 and distilled water again. 13 Weigh the total mass m of beaker #2 and engine oil. 23 The saturated surface-dry water absorption rate P of the coarse aggregate is calculated according to the following formula:

[0088] Δm1=m 13 -m 12 -m 11 +m 10 ③

[0089] Δm2=m 23 -m 22 -m 21 +m 20 ④

[0090]

[0091]

[0092] Where: P is the saturated surface-dry water absorption rate of coarse aggregate, %;

[0093] ρ c The density of the engine oil is expressed in g / cm³. 3 ;

[0094] Δm1 represents the force exerted on the aggregate sample in distilled water, in grams;

[0095] Δm2 is the force exerted on the aggregate sample in the engine oil, in grams;

[0096] k is the mass ratio of dried aggregate sample A to dried aggregate sample B.

[0097] Immersing the aggregate sample and metal basket in a liquid will cause a change in the overall stress state. This change is related to both the liquid density and the volume of the aggregate sample. Macroscopically, this change manifests as fluctuations in the total mass of the beaker and the liquid. By accurately measuring these fluctuations and considering the absorption characteristics of the aggregate sample to different liquids, the saturated surface-dry water absorption rate of the aggregate sample can be calculated. Formulas ③, ④, and ⑤ calculate the overall mass change. Formula ⑥ is a model derived from physical modeling and mathematical derivation, based on the mass change of different liquids and the differences in the adsorption characteristics of aggregates to different liquids at room temperature. The calculation process for Formula ⑥ is as follows:

[0098] Based on the water absorption and stress of the aggregate sample in water, the changes in mass of the beaker and distilled water are as follows:

[0099]

[0100] Based on the stress conditions of the aggregate sample in the engine oil, the changes in the mass of the beaker and the engine oil are as follows:

[0101]

[0102] After organizing public statement ⑨ and substituting it into public statement ⑧, we obtain formula ⑥:

[0103]

[0104] The selection of organic solvents in the present application is based on the absorption characteristics of stones in different liquids, and the selection of liquid types is based on the absorption characteristics of aggregates in different solvents, as well as the safety, volatility, and stability of different solvents. In view of the selection process, the inventors of the present application conducted the following tests, in which the solvents commonly used in concrete laboratories were selected as shown in Table 1. Among them, anhydrous ethanol, acetone, machine oil and kerosene are commonly used, but acetone is toxic and has a fast evaporation rate, so it is generally not used.

[0105] Table 1: Common solvents in concrete laboratory

[0106]

[0107]

[0108] The inventors of the present application selected anhydrous ethanol, machine oil and kerosene for comparison and testing, analyzed the absorption of dry aggregates in these solvents, and the viscosity coefficient and evaporation rate of each solvent at different temperatures, and the test results are shown in Tables 2 to 4. Among them, the absorption rate of aggregates in different solvents is shown in Table 2:

[0109] Table 2: Absorption rate of aggregates in different solvents

[0110]

[0111] From the absorption rate of different solvents in Table 2, it can be seen that the absorption of aggregates in water and anhydrous ethanol is similar, which is consistent with the characteristics of alcohol and ethanol being mutually soluble. From the absorption rate in Table 2, anhydrous ethanol can be excluded, and the applicant further selects machine oil and kerosene.

[0112] Table 3 shows the evaporation characteristics of different solvents. Combined with the previous selection results of anhydrous ethanol, the flash point in Table 3 represents the volatility of the reagent, and the ignition temperature represents the safety of the reagent. In general, the stability and safety of machine oil are higher than those of kerosene, but further comparison and analysis are needed for reagent selection, especially the absorption of aggregates in machine oil and kerosene.

[0113] Table 3: Physical property parameters of different solvents

[0114]

[0115] Comparing the absorption characteristics of aggregates in machine oil and kerosene in Table 2, it can be seen that the absorption capacity of aggregates in kerosene and machine oil is much weaker than that in water and anhydrous ethanol, with a difference of about 100 times. At the same time, the absorption capacity of aggregates in machine oil is slightly less than that in kerosene, and the absorption amount of aggregates in machine oil is 0.01% lower than that in kerosene after 30h immersion. Using error analysis, it can be seen that:

[0116]

[0117] wherein δ is the absorption rate of the aggregate sample to the oil or kerosene;

[0118] The total error of the test results is:

[0119]

[0120] The density of kerosene and oil is 0.85-0.98 g / cm 3 The application finds that the absorption rate of the aggregate sample to kerosene is 0.02%-0.04%, and the saturated surface dry water absorption error caused by the absorption of kerosene by the aggregate is 0.02%-0.05%. At the same time, the application finds that the absorption rate of the aggregate sample to oil is 0.01%-0.03%, and the saturated surface dry water absorption error caused by the absorption of oil by the aggregate is 0.01%-0.03%. This shows that the test results using oil have higher precision.

[0121] Viscosity coefficients (mPa·S) of various solvents at different temperatures

[0122]

[0123] The stability of oil and kerosene at different temperatures is also an important factor considered by the application. The reason why the environmental temperature causes the change in the absorption rate of the aggregate to oil and kerosene is mainly related to the fluctuation of the viscosity coefficient of the reagent. The viscosity coefficients of various solvents at different temperatures are shown in Table 4. Figure 1 is the change in the viscosity coefficient of oil at different environmental temperatures, Figure 2 is the absorption of kerosene and oil by the aggregate at different viscosity coefficients. Overall, the thermal stability of oil is much higher than that of kerosene. From the change in the viscosity coefficient and the absorption rate, the application uses oil better.

[0124] Using error analysis method, when the environmental temperature is set at 20-25℃ for testing, the change range of the viscosity coefficient of oil is 0.05 mPa·S, which causes the change range of the absorption rate to be 0.01%, and the corresponding error range is 0.02%. At the same time, further considering the measurement accuracy of the thermometer, the application limits the environmental temperature to 20-22℃. In fact, error analysis should also consider the influence of weighing error and the amplification effect of error accumulation, and these factors are comprehensively considered in the method design.

[0125] From the above part of the test data can be seen, the aggregate absorption capacity of water and alcohol is much higher than that of oil and kerosene, and the fluctuation range of oil viscosity is also smaller than that of kerosene. At the same time, the flash point of oil is much higher than that of kerosene and anhydrous ethanol, which indicates that the volatility of oil is much smaller than that of kerosene. Therefore, the oil is selected as the comparative solvent in the present application, and the temperature characteristics of different oil grades are further studied, so as to select the appropriate range.

[0126] In addition to the above tests, the method also analyzes the influence of environmental temperature and humidity on the test results, evaluates the fluctuation range of the test results, and limits the test conditions. In the present application, the oven, metal mesh basket, beaker and electronic balance are used, and according to the mass change of the coarse aggregate before and after soaking in different liquids, combined with the principle of Archimedes buoyancy, the relationship between the saturated surface dry water absorption rate of the coarse aggregate and the related mass parameters is constructed, and the saturated surface dry water absorption rate of the coarse aggregate is calculated, so as to realize the accurate determination of the saturated surface dry water absorption rate of the stone.

[0127] The present application is further described below in combination with specific examples.

[0128] Example 1 is for the determination of the saturated surface dry water absorption rate of pebble samples of a certain hydropower engineering in Jilin City, Jilin Province. The sample in Example 1 is shown in Table 1, and the test temperature is 20℃ and the humidity is 80%. Figure 3

[0129] The sample in the natural state is weighed to 10314.6g for drying treatment, and the drying temperature is controlled to be 105℃. After 10h of continuous drying, the sample mass is weighed to be 10263.4g for the first time, and the corresponding water content q1 is 0.50%. The sample mass is weighed to be 10254.7g for the second time, and the corresponding water content q2 is 0.58%. The time interval between the two weighings is 1.5h, and the water content difference Δq is 0.08%. The requirement of Δq≤0.2% is met, which can be used for further test. 2-1

[0130] The dried coarse aggregate is evenly divided into 4 parts, and 2 parts are selected for test, numbered A and B. The sample mass m A of numbered A is 2467.5g, and the sample mass m B of numbered B is 2531.2g, and the k value is 0.975. Then two beakers with a capacity of 5000mL are taken, numbered 1# and 2#. Distilled water with a mass of 2467.5g is poured into the 1# beaker, and oil with a mass of 2531.2g is poured into the 2# beaker. The oil viscosity grade is 30, and the density is 0.946g / cm 3 . Then the total mass m 10 of the 1# beaker and the distilled water is weighed to be 2812.9g, and the total mass m 20 of the 2# beaker and the oil is weighed to be 2873.8g.​​

[0131] Take two metal mesh baskets, numbered 3# and 4# respectively; immerse the 3# metal mesh basket in the distilled water in the 1# beaker and the 4# metal mesh basket in the engine oil in the 2# beaker, keep the metal mesh basket lifted and the top end below the liquid surface, weigh the total mass m of the 1# beaker and the distilled water 11 2818.1 g, the total mass m of the 2# beaker and the engine oil 21 2878.1 g; then take out the metal mesh basket from the distilled water and the engine oil, weigh the total mass m of the 1# beaker and the distilled water again 12 2807.5 g, the total mass m of the 2# beaker and the engine oil 22 2869.9 g;

[0132] After the metal mesh basket is cleaned, sample A is loaded into the 3# metal mesh basket and sample B is loaded into the 4# metal mesh basket, then the 3# metal mesh basket is immersed in the 1# beaker, after 24 hours of immersion, the metal mesh basket is lifted and kept below the liquid surface; the 4# metal mesh basket is immersed in the 2# beaker, the metal mesh basket is lifted and kept below the liquid surface; the mass of the 1# beaker and the distilled water is weighed as 3682.7 g, and the mass of the 2# beaker and the engine oil is weighed as 3747.0 g.

[0133] According to the mass parameters in the above test process, the saturated surface dry water absorption rate P of the sample is calculated as 1.19%. The results of repeated tests are shown in Table 5, the average value of the results is 1.19%, the standard deviation is 0.02%, and the variation coefficient is 0.01. The saturated surface dry water absorption rate of the sample measured by the traditional method is shown in Table 6, the average value of the results is 1.26%, the standard deviation is 0.07%, and the variation coefficient is 0.06.

[0134] Table 5 Test results of the saturated surface dry water absorption rate of the aggregate of a power plant project in Jilin City, Jilin Province

[0135] Number of tests 1 2 3 4 5 6 7 8 9 10 Test results 1.19 1.16 1.16 1.18 1.21 1.20 1.19 1.18 1.19 1.20

[0136] Table 6 Test results measured by the traditional method of a power plant project in Jilin City, Jilin Province

[0137] Number of tests 1 2 3 4 5 6 7 8 9 10 Test results 1.12 1.26 1.34 1.28 1.18 1.29 1.19 1.27 1.3 1.32

[0138] It can be seen from the comparison of the above tables that the results of the present method are smaller than those of the traditional method, the data fluctuation range is smaller than that of the traditional method, which can prove that the stability of the results in the present application is higher and the discrete degree is smaller.

[0139] Example 2 Determination of the saturated surface dry water absorption rate of the artificial gravel sample of a hydropower project in Chengde City, Hebei Province, the sample is shown in Table 7. Figure 4 The test temperature is 21℃ and the humidity is 83%.

[0140] Take 12460.3 g of the sample in natural state for drying treatment, control the drying temperature at 110°C, and continuously dry for 12 h. The first time, the sample mass is 12320.6 g, the corresponding water content q1 is 1.12%, the second time, the sample mass is 12281.8 g, the corresponding water content q2 is 1.43%, the time interval between the two times of weighing is 1.7 h, the water content difference Δq 2-1 is 0.31%, which does not meet the requirement of Δq≤0.2%. The sample is continuously dried for 2 h, the third time, the sample mass is 12276.2 g, the corresponding water content q3 is 1.48%, the water content difference Δq 3-2 is 0.05%, which meets the requirement of Δq≤0.2%, and can be used for further test.

[0141] Divide the dried coarse aggregate into 4 parts, and optionally take 2 parts for test, numbered as A and B. The sample mass m A of sample numbered A is 2983.7 g, and the sample mass m B of sample numbered B is 3011.6 g, and k value is 0.991. Then take two metal buckets with a capacity of 5000 mL, numbered as 1# and 2#. Pour 2088.6 g of distilled water into 1# beaker, and pour 2108.1 g of machine oil into 2# beaker, the machine oil has a viscosity grade of 40 and a density of 0.966 g / cm 3 . Then weigh the total mass m 10 of 1# beaker and distilled water, which is 2434.0 g, and the total mass m 20 of 2# beaker and machine oil, which is 2450.7 g.

[0142] Take two metal mesh baskets, numbered as 3# and 4#. Submerge 3# metal mesh basket in the distilled water in 1# beaker, and submerge 4# metal mesh basket in the machine oil in 2# beaker, and keep the metal mesh basket lifted and the top end below the liquid surface. Weigh the total mass m 11 of 1# beaker and distilled water, which is 2439.2 g, and the total mass m 21 of 2# beaker and machine oil, which is 2455.0 g. Then take out the metal mesh baskets from the distilled water and machine oil, and weigh the total mass m 12 of 1# beaker and distilled water, which is 2428.6 g, and the total mass m 22 of 2# beaker and machine oil, which is 2446.8 g.

[0143] After the metal mesh basket is cleaned, sample A is loaded into a 3# metal mesh basket and sample B is loaded into a 4# metal mesh basket. Then the 3# metal mesh basket is immersed in a 1# beaker, and after 26h of immersion, the metal mesh basket is lifted and kept below the liquid level. The 4# metal mesh basket is immersed in a 2# beaker, and the metal mesh basket is lifted and kept below the liquid level. The mass of the 1# beaker and distilled water is 3469.9g, and the mass of the 2# beaker and engine oil is 3512.5g.

[0144] According to the quality parameters in the above test process, the saturated surface dry water absorption rate P of the sample is 1.76%. The results of repeated tests are shown in Table 7, and the average value of the results is 1.78%, the standard deviation is 0.03%, and the coefficient of variation is 0.01. The saturated surface dry water absorption rate of the sample measured manually using the traditional method is shown in Table 8, and the average value of the results is 1.84%, the standard deviation is 0.26%, and the coefficient of variation is 0.14.

[0145] Table 7 Test results of the saturated surface dry water absorption rate of the aggregate of a hydropower project in Chengde City, Hebei Province

[0146] Number of tests 1 2 3 4 5 6 7 8 9 10 Test results 1.81 1.79 1.76 1.75 1.79 1.74 1.76 1.79 1.8 1.75

[0147] Table 8 Test results measured using the traditional method of a hydropower project in Chengde City, Hebei Province

[0148] Number of tests 1 2 3 4 5 6 7 8 9 10 Test results 1.53 2.11 1.97 2.26 1.67 1.53 1.61 1.94 2.06 1.69

[0149] As can be seen from the above table comparison, the results of the present method are smaller than those of the traditional method, and the data fluctuation range is smaller than that of the traditional method, which can prove that the stability of the results in the present application is higher and the dispersion degree is smaller.

[0150] In Example 3, the saturated surface dry water absorption rate of a sample of artificial gravel of a hydropower project in Fukang City, Xinjiang is determined, and the sample is as shown in Table 9. Figure 5 The test temperature is 22℃ and the humidity is 85%.

[0151] A sample in a natural state weighing 15527.4g is dried, and the drying temperature is controlled at 108℃. After 9h of continuous drying, the sample is weighed for the first time and the mass is 15477.2g, and the corresponding water content q1 is 0.32%. The sample is weighed for the second time and the mass is 15469.3g, and the corresponding water content q2 is 0.37%. The time interval between the two weighings is 2h, the water content difference Δq is 0.05%, which meets the requirement of Δq≤0.2% and can be used for further testing. 2-1

[0152] The dried coarse aggregate is evenly divided into 4 parts, and 2 parts are selected for testing, numbered A and B. The mass of sample No. A m A is 3288.6g, and the mass of sample No. B m B ​The mass is 3197.1g, and the k value is 1.029. Then, take two deep concave plastic basins, numbered 1# and 2#. Pour 4932.9g of distilled water into beaker 1#, and pour 4795.7g of machine oil into beaker 2#. The machine oil is a mixture of two types of machine oil with viscosity grades of 30 and 50, with a mass ratio of m... 30 :m 50 =40%:60%, the density of grade 30 engine oil is 0.946 g / cm³. 3 The density of grade 50 engine oil is 0.987 g / cm³. 3 The density of the mixed engine oil is 0.970 g / cm³. 3 Then weigh the total mass m of beaker #1 and distilled water. 10 The total mass of beaker #2 and engine oil is 5278.3g. 20 It is 5138.3g.

[0153] Take two metal mesh baskets, numbered 3# and 4#. Immerse metal mesh basket #3 in the distilled water in beaker #1, and immerse metal mesh basket #4 in the machine oil in beaker #2, keeping the metal mesh baskets raised with their tops below the liquid surface. Weigh the total mass m of beaker #1 and the distilled water at this point. 11 The total mass of beaker #2 and engine oil is 5283.5g. 21 The mass was 5142.6g; then the metal mesh basket was removed from the distilled water and machine oil, and the total mass m of beaker #1 and distilled water was weighed again. 12 The total mass of beaker #2 and engine oil is 5272.9g. 22 It weighs 5134.4g;

[0154] After wiping the metal mesh baskets clean, sample A was placed in metal mesh basket #3 and sample B in metal mesh basket #4. Then, metal mesh basket #3 was immersed in beaker #1 for 30 hours. After immersion, the metal mesh basket was lifted and kept below the liquid level. Metal mesh basket #4 was immersed in beaker #2 and lifted and kept below the liquid level. The mass of beaker #1 and distilled water was 6432.1 g, and the mass of beaker #2 and machine oil was 6270.5 g.

[0155] Based on the quality parameters in the above experimental process, the saturated surface-dry water absorption rate P of the sample can be calculated to be 1.40%. The results obtained from repeated experiments are shown in Table 9, with an average value of 1.43%, a standard deviation of 0.07%, and a coefficient of variation of 0.05. The saturated surface-dry water absorption rate of the sample determined manually using traditional methods is shown in Table 10, with an average value of 1.56%, a standard deviation of 0.15%, and a coefficient of variation of 0.09.

[0156] Table 9. Test results of saturated surface-dry water absorption rate of aggregates in a hydropower project in Fukang City, Xinjiang.

[0157] Number of tests 1 2 3 4 5 6 7 8 9 10 Test results 1.46 1.28 1.37 1.43 1.48 1.51 1.42 1.43 1.44 1.48

[0158] Table 10 Test results of a certain hydropower project in Fukang City, Xinjiang using traditional method

[0159] Number of tests 1 2 3 4 5 6 7 8 9 10 Test results 1.53 1.59 1.61 1.67 1.22 1.67 1.53 1.72 1.42 1.59

[0160] Through the comparison of the above table, it can be seen that the results of the present method are smaller than those of the traditional method, and the data fluctuation amplitude is smaller than that of the traditional method, which can prove that the stability of the results in the present application is higher and the discrete degree is smaller.

Claims

1. A method of determining the saturated surface dry water absorption of a concrete coarse aggregate, characterized by The method comprises the following steps: (1) taking the natural state of coarse aggregate mg drying, control drying temperature is 105-110 ℃, during multiple weighing sample quality, and calculate the moisture content of the sample, until the difference between the two moisture contents is not more than 0.2%, then stop drying, after natural cooling and moisture storage, the moisture content of the sample, the difference between the moisture content is calculated as follows: Δq = q j -q j-1 (j = 2 · N) ② In the formula: m0 is the mass of the natural state of coarse aggregate before drying, g; m i m is the mass of the sample at the i-th weighing during the drying process, g; q i , q j , q j-1 are the moisture content, % calculated at the i-th, j-th and j-1-th time, respectively. Δq is the difference between the two moisture contents, %; N is the total number of sample mass weighing during drying; i is the number of times of weighing the mass of the aggregate sample; j is the number of times of calculating the moisture content of the aggregate sample; (2) The dried aggregate sample is evenly divided into two parts, numbered A and B respectively, and the mass of sample A is m A , and the mass of sample B is m B ; standby; (3) Take 2 beakers and 2 metal mesh baskets, wherein the numbers of the beakers are 1# and 2# respectively, the numbers of the metal mesh baskets are 3# and 4# respectively, then pour distilled water into the 1# beaker, and measure the total mass m of the beaker and the distilled water 10 ; pour machine oil into the 2# beaker, and measure the total mass m of the beaker and the machine oil 20 ; (4) Immerse the 3# metal mesh basket in the 1# beaker, keeping it raised but still submerged below the liquid surface, and weigh the total mass m of the beaker and distilled water 11 ; then completely raise and remove the metal mesh basket, and weigh the total mass m of the 1# beaker and distilled water again 12 ; (5) immerse the 4# metal mesh basket in the 2# beaker, keeping it raised but still submerged below the liquid surface, weigh the total mass m of the beaker and the oil 21 ; then completely raise and remove the metal mesh basket, weigh the total mass m of the 2# beaker and the oil again 22 ; (6) sample A is loaded into 3# metal mesh basket, sample B is loaded into 4# metal mesh basket, then 3# metal mesh basket with sample A is immersed in 1# beaker, and 4# metal mesh basket with sample B is immersed in 2# beaker; (7) The metal mesh basket is lifted but kept immersed in distilled water and machine oil, and the total mass m of the 1# beaker and distilled water is weighed again 13 The total mass m of the 2# beaker and machine oil is weighed 23 And the saturated surface dry water absorption rate P of the coarse aggregate is calculated according to the following formula: Δm1 = m 13 -m 12 -m 11 +m 10 ③ Δm2 = m 23 -m 22 -m 21 +m 20 ④ In the formula: P is the saturated surface dry water absorption of coarse aggregate, %; p c p is the density of the oil, g / cm 3 ; Δm1 is the force of the aggregate sample in distilled water, g; Δm2 is the force of the aggregate sample in oil, g; k is the mass ratio of dried aggregate sample A and dried aggregate sample B; p 水 is the density of water, 1.0 g / cm 3 .

2. The method for determining the saturated surface dry water absorption of a coarse aggregate according to claim 1, characterized in that: The moisture content difference Δq in step (1) refers to the difference between the two adjacent moisture contents, and the time interval between the two adjacent sample weighings is 1.5-2.0 h.

3. The method for determining the saturated surface dry water absorption of a coarse aggregate according to claim 1, wherein: The viscosity grade of the engine oil in step (3) is 30-50, and engine oils of different grades can be mixed, and the density of the mixed engine oil should be calculated c The engine oil can be reused after filtration, and the density of the mixed engine oil should be calculated c ​ wherein: M i is the mass proportion of the i-th engine oil in the mixture, %; ρ i and ρ j are the densities of the i-th and j-th oil in the blend, g / cm 3 ; n is the total number of different types of oil.

4. The method for determining the saturated surface dry water absorption of a coarse aggregate of concrete according to claim 1, characterized in that: In step (6), the full immersion refers to the immersion time of 24-30 h, and sample B does not need to be fully immersed.

5. The method for determining the saturated surface dry water absorption of a coarse aggregate according to claim 1, wherein The operation steps are carried out in an environment of 20-22 ℃ temperature and 80%-85% humidity.

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