CN109443967B - Method for evaluating stability of steel slag aggregate - Google Patents
Method for evaluating stability of steel slag aggregate Download PDFInfo
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- CN109443967B CN109443967B CN201811532362.XA CN201811532362A CN109443967B CN 109443967 B CN109443967 B CN 109443967B CN 201811532362 A CN201811532362 A CN 201811532362A CN 109443967 B CN109443967 B CN 109443967B
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- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
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Abstract
The invention discloses an evaluation method of steel slag aggregate stability, which comprises the following steps: firstly, screening out a steel slag aggregate sample with the grain size range of 2.36-4.75mm according to the grain size; directly carrying out a los angeles abrasion test on the obtained steel slag aggregate sample to obtain a los angeles abrasion retention rate y%; calculating to obtain a reduction value x% of the loss rate of the los Angeles abrasion after the 9d constant-temperature water bath treatment by a fitting formula; and when the reduction value of the loss retention rate of the los Angeles in the steel slag aggregate sample is less than or equal to 5%, determining that the steel slag aggregate is stable, and when the reduction value of the loss retention rate of the los Angeles in the steel slag aggregate sample is more than 5%, determining that the steel slag aggregate is unstable. According to the method, various unstable components in the steel slag aggregate are not required to be respectively measured through the los Angeles abrasion test, the loss value of the los Angeles abrasion retention rate before and after treatment can be directly calculated through the untreated steel slag aggregate los Angeles abrasion retention rate, and the stability of the steel slag aggregate sample is judged.
Description
Technical Field
The invention belongs to the technical field of materials, and particularly relates to an evaluation method of aggregate stability of steel slag.
Background
With the rapid development of the steel industry in China, the production amount of the steel slag aggregate serving as a byproduct generated in the steel making process reaches more than 1 hundred million tons every year, however, the utilization rate of the steel slag aggregate in China is only 30%, the steel slag stacking amount is increased by thousands of tons every year, and the large accumulation of the steel slag causes serious pollution to the environment. If the steel slag is not processed and comprehensively utilized in time, more and more land is occupied, the environment is polluted, the waste of resources is caused, and the sustainable development of the steel industry is influenced.
Relevant studies at home and abroad show that the steel slag aggregate has good physical and mechanical properties, such as high hardness, high density, high strength, high polishing value, good graininess and the like. And the steel slag aggregate belongs to alkaline aggregate, and has good adhesion with asphalt. With the continuous improvement of the living standard of people driven by the high-speed development of national economy of China, the highway is rapidly developed as an important civil engineering. The requirement of paving asphalt concrete roads on aggregates is large, the aggregates used at present are mainly high-quality aggregates such as limestone, basalt and the like, however, the natural aggregates of non-renewable resources are in a state of short supply, and after the natural high-quality aggregates are replaced by the steel slag aggregates, the problem of shortage of high-quality natural aggregates in recent years can be well solved.
The main problem of limiting the use of steel slag aggregates at present is poor volume stability. During the steel-making process, lime is used as slag-forming material and is thrown into the steel-making furnace, in the initial smelting stage or low-alkaline slag, lime particles and acid oxide are combined into a stable mineral phase which floats on the surface of molten steel, so that the aim of removing impurities and improving the quality of the molten steel is achieved, along with the gradual trend of the solubility of the added lime towards saturation, excessive lime is thrown in the later stage of steel-making, and the primary lime which is not slagged and secondary lime which is crystallized in the liquid slag are both main sources for forming free calcium oxide in the steel slag aggregate. Wherein the part of f-CaO formed by the lime which is not fully dissolved is compact in structure and slow in hydration. The lime precipitated from the molten steel slag aggregate is C in the hot slag in the slow cooling process3S is extremely unstable and is converted into C at 1250 ℃ -1100 DEG C2S and f-CaO are mainly retained on the surface of the steel slag aggregate, and the f-CaO is a main reason for instability of the steel slag aggregate.
Due to the existence of unstable components in the steel slag aggregate, the volume of the steel slag aggregate is expanded by rain wash in the service process of a road surface, and meanwhile, the steel slag aggregate is further cracked and damaged due to the friction and impact action in the driving process of a vehicle, so that the stability of the steel slag aggregate needs to be evaluated before use. At present, two main evaluation methods for the volume stability of the steel slag aggregate in China exist, wherein one method is to evaluate by using the autoclaving pulverization rate index of the steel slag aggregate, and the other method is to evaluate by measuring the content of f-CaO contained in the steel slag aggregate. However, in the evaluation using the former method, the influence of friction and impact effect is not considered in the measurement of the autoclave pulverization rate. Also, when evaluated by the latter method, it is difficult to distinguish f-CaO from Ca (OH)2, resulting in a measured value larger than a true value.
Therefore, a method which can reflect the actual conditions of the service environment, simply, conveniently and quickly evaluate the stability of the steel slag aggregate is needed to be found, and the stability of the steel slag aggregate is accurately and effectively evaluated.
Disclosure of Invention
The invention aims to provide a method for simply, conveniently and quickly evaluating the stability of steel slag aggregate, so that the stability of the steel slag aggregate is more accurately and quickly determined, and the quality of the steel slag aggregate is effectively controlled.
In order to achieve the purpose, the technical scheme is as follows:
the method for evaluating the stability of the steel slag aggregate comprises the following steps:
1) firstly, screening out a steel slag aggregate sample with the grain size range of 2.36-4.75mm according to the grain size;
2) directly carrying out a los angeles abrasion test on the obtained steel slag aggregate sample to obtain a los angeles abrasion retention rate y%;
3) calculating to obtain the x% reduction value of the abrasion retention rate of the los angeles after 9d constant-temperature water bath treatment by fitting the formula of y to 120.66-5.7343 x;
4) and when the reduction value of the loss retention rate of the los Angeles in the steel slag aggregate sample is less than or equal to 5%, determining that the steel slag aggregate is stable, and when the reduction value of the loss retention rate of the los Angeles in the steel slag aggregate sample is more than 5%, determining that the steel slag aggregate is unstable.
According to the scheme, in the step 1, the steel slag aggregate sample to be tested with the particle size range of 2.36-4.75mm is screened out according to the requirements of relevant steps of T0302 in road engineering aggregate test protocol (JTGE 42-2005).
In the above protocol, step 2 was performed according to the requirements of the procedures related to T0317 in the road engineering aggregate test protocol (JTGE42-2005) for los Angeles abrasion test.
According to the scheme, the specific requirements of the los Angeles abrasion test are as follows: the mass of a steel slag aggregate sample is 2500 +/-10 g, the total mass of steel balls is 2500 +/-25 g, the number of rotation cycles of the los Angeles wearing machine is 500r, and the rotation rate is controlled to be 30 r/min-33 r/min.
According to the scheme, the specific heating temperature of the constant-temperature water bath is 70-80 ℃.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides an evaluation method of steel slag aggregate stability, which can directly calculate the reduction value of the loss retention rate of los Angeles abrasion before and after treatment of an untreated steel slag aggregate without respectively measuring various unstable components in the steel slag aggregate through the los Angeles abrasion test, and can judge the stability of a steel slag aggregate sample.
The invention provides an evaluation method of steel slag aggregate stability, which considers that the steel slag aggregate is unstable due to the weathering of rainwater in the use process of a road surface and simulates the influence of friction and impact action in the driving process of a vehicle.
Drawings
FIG. 1 shows the relationship between the retention rate of the abrasion of the slag aggregates of the los Angeles and the treatment time of the constant-temperature water bath
FIG. 2 is a linear fitting relationship for evaluating aggregate stability of steel slag
Detailed Description
The following examples further illustrate the technical solutions of the present invention, but should not be construed as limiting the scope of the present invention.
Taking steel slag aggregates from three different sources and different treatment processes as A, B and C respectively, wherein the chemical components are shown in the following table 1:
TABLE 1
The device adopts HHW21-600 type constant temperature water bath box and DM-II type los Angeles shelf board type abrasion tester.
Examples
According to the relevant steps of T0302 in Highway engineering aggregate test regulation (JTG E42-2005), a steel slag aggregate sample with the particle size range of 2.36-4.75mm is screened out from the steel slag aggregate by a standard square-hole sieve for standby.
(1) The following tests were conducted on group 1 steel slag aggregates: weighing 2 parts of each steel slag aggregate, wherein the mass of each part is 2500g, and performing a los Angeles abrasion test according to the requirements of relevant steps of T0317 in road engineering aggregate experimental regulation (JTG E42-2005). The parameters of the test are set specifically that the number of the machine rotation cycles is 500r, the revolution rate is controlled at 30r/min, and the mass of the added steel balls is 2500g and is about 4-5. After the los angeles abrasion test is finished, the steel slag aggregate needs to be screened again, screening data are recorded, and the loss retention rate of the steel slag aggregate los angeles is calculated.
The calculation formula is as follows:
wherein Pi is the steel slag aggregate los Angeles abrasion retention rate,%; mi is the mass on the sieve of the sieve pore with the grain diameter of the raw steel slag aggregate, g; m is the total mass, g, of the steel slag aggregate sample used in the experiment. The calculation results are shown in table 2. The experimental results represent the abrasion and impact resistance of the steel slag aggregate against vehicle loads.
(2) Carrying out constant-temperature water bath soaking treatment on the group 2 steel slag aggregate, wherein the specific heating conditions are as follows: the temperature is kept at 70-80 ℃ for 3, 6,9 and 12 days.
The steel slag aggregate after the soaking treatment in the constant-temperature water bath is heated to constant weight in a drying oven at 105 ℃.
Weighing 2 parts of each steel slag aggregate after different treatment durations, wherein the mass of each part is 2500g, and performing a los Angeles abrasion test according to the requirements of relevant steps T0317 in road engineering aggregate experimental regulation (JTG E42-2005). The test parameters are set as in group 1, after the los angeles abrasion test is finished, the steel slag aggregate needs to be screened again, screening data is recorded, the loss retention rate of the los angeles in the steel slag aggregate is calculated, and the calculation result is shown in table 2.
TABLE 2
Based on the data in Table 2, the results of plotting the los Angeles abrasion retention of the steel slag aggregates A, B, and C as a function of the treatment time in the constant temperature water bath are shown in FIG. 1. As can be seen from fig. 1: under the action of a constant-temperature water bath simulating natural weathering, the abrasion retention rate of the los angeles shows a gradually-decreasing trend along with the prolonging of the treatment time. The steel slag aggregate B processed by the constant-temperature water bath in the same time has the largest loss retention rate of los Angeles, and the steel slag aggregate A is the smallest after the steel slag aggregate C times. However, the abrasion retention rates of the los angeles of the three steel slag aggregates after being treated by the constant-temperature water bath for 6 to 12 days are not changed greatly, which shows that unstable components in the steel slag aggregates are basically digested, and the steel slag aggregates tend to be in a stable state. To ensure the accuracy of this evaluation method, the present invention selects the los Angeles abrasion retention at 9 days of thermostatic water bath treatment as the evaluation criterion. From table 2, it can be seen that the steel slag aggregates a, B and C after 9d had 73.09%, 88.21% and 78.98% respectively in terms of los angeles abrasion retention, which were reduced by 6.92%, 4.77% and 6.38% respectively compared to the untreated steel slag aggregates.
Because the abrasion retention values of the los angeles are different after different types of steel slag are treated by constant-temperature water bath for 9 days, the standards of the steel slag which tends to be stable are different, namely, a unified standard does not exist. However, it can be seen that there is an inverse correlation between the reduction value of the loss retention rate of los angeles abrasion after being treated with the constant temperature water bath for 9d and the loss retention rate of untreated steel slag los angeles abrasion, i.e. the higher the loss retention rate of los angeles abrasion of untreated steel slag aggregate is, the smaller the loss value of loss rate is when the loss retention rate of los angeles abrasion of untreated steel slag aggregate is stable. Therefore, the invention adopts the linear fitting relationship of the two to carry out the unified analysis on the loss retention rate of the los Angeles, thereby evaluating the stability of different types of steel slag aggregates through the loss test of the los Angeles. The linear fit relationship is shown in figure 2. Fitting the relation as formula (1):
y＝120.66-5.7343x R20.9683 (the closer the value to 1 indicates better fit and stronger correlation) for the linear relationship (1)
In the formula:
y-untreated slag los Angeles abrasion retention,%;
x-reduction value of abrasion retention rate of slag los Angeles after treatment in constant temperature water bath for 9d,%.
The higher the abrasion retention rate of the steel slag los Angeles, the better the stability of the steel slag aggregate, and the smaller the retention rate reduction value when the steel slag aggregate tends to be stable after being treated by the 9d constant-temperature water bath. The decrease in the los angeles abrasion retention (x) when it tends to stabilize can be determined by substituting the test untreated steel slag aggregate los angeles abrasion retention (y) into the fitting equation (1) above. As the steel slag aggregate is required to have the free calcium oxide content not higher than 3 percent when in use, the free calcium oxide content of the selected steel slag aggregate B is 2.91 percent and tends to be close to the stable and unstable critical value, and the steel slag aggregate A and the steel slag aggregate C are respectively 3.86 percent and 3.29 percent and are both higher than 3 percent. Therefore, the stability evaluation criteria was determined with reference to the 4.77% reduction in los angeles abrasion retention of steel slag aggregate B, where x is 5% in the present invention. Namely, the steel slag aggregate is judged to be unstable when the value of x is more than 5 percent, and the steel slag aggregate is judged to be stable when the value of x is less than or equal to 5 percent.
In conclusion, the invention provides the method for evaluating the stability of the steel slag aggregate, the stability of the steel slag aggregate sample can be judged by substituting the loss retention rate (y) of the los angeles into the formula (1) to calculate whether the x value is more than 5% after the loss test of the los angeles, various unstable components in the steel slag aggregate are not required to be respectively measured, the operation is simple, the data is reliable and convenient to analyze, and the friction and impact action in the vehicle driving process and the stability of different types of steel slag aggregates under the natural environment weathering action are simulated, so the method is suitable for popularization and application in actual production.
The above examples are merely illustrative of the theory of the invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (5)
1. The method for evaluating the stability of the steel slag aggregate is characterized by comprising the following steps of:
1) firstly, screening out a steel slag aggregate sample with the grain size range of 2.36-4.75mm according to the grain size;
2) directly carrying out a los angeles abrasion test on the obtained steel slag aggregate sample to obtain a los angeles abrasion retention rate y%;
3) calculating to obtain the x% reduction value of the abrasion retention rate of the los angeles after 9d constant-temperature water bath treatment by fitting the formula of y to 120.66-5.7343 x;
4) and when the reduction value of the loss retention rate of the los Angeles in the steel slag aggregate sample is less than or equal to 5%, determining that the steel slag aggregate is stable, and when the reduction value of the loss retention rate of the los Angeles in the steel slag aggregate sample is more than 5%, determining that the steel slag aggregate is unstable.
2. The method for evaluating the stability of steel slag aggregate according to claim 1, wherein the steel slag aggregate sample to be tested with the particle size range of 2.36-4.75mm is screened according to the requirements of relevant procedures of T0302 in Standard No. JTG E42-2005 Highway engineering aggregate test Specification.
3. The method for evaluating the stability of steel slag aggregate according to claim 1, wherein the los Angeles abrasion test is performed according to the requirements of the related procedures of T0317 in Standard No. JTG E42-2005 Highway engineering aggregate test Specification.
4. The method for evaluating the stability of the steel slag aggregate of claim 1, wherein the specific requirements of the los Angeles abrasion test are as follows: the mass of a steel slag aggregate sample is 2500 +/-10 g, the total mass of steel balls is 2500 +/-25 g, the number of rotation cycles of the los Angeles wearing machine is 500r, and the rotation rate is controlled to be 30 r/min-33 r/min.
5. The method for evaluating the stability of the steel slag aggregate according to claim 1, wherein the specific heating temperature of the constant-temperature water bath is 70-80 ℃.
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| CN113670764B (en) * | 2021-07-27 | 2024-03-15 | 宝武环科武汉金属资源有限责任公司 | Hydrothermal acceleration experiment method for safely detecting stability of steel slag particles in batches |
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| US5211750A (en) * | 1991-06-19 | 1993-05-18 | Conversion Systems, Inc. | Synthetic aggregate and landfill method |
| CN101216402B (en) * | 2007-01-05 | 2010-05-26 | 上海宝钢冶金技术服务有限公司 | Method for determining steel slag stability |
| CN103123310A (en) * | 2013-02-06 | 2013-05-29 | 西安建筑科技大学 | Method for rapidly detecting stability of steel slag fine aggregate |
| CN105300795B (en) * | 2014-06-18 | 2018-02-02 | 上海宝冶钢渣综合开发实业有限公司 | A kind of detection method of slag product stability |
| CN108627393A (en) * | 2018-02-02 | 2018-10-09 | 北京建筑大学 | A kind of water stability test method of macrovoid high molecular polymer mixture |
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