Simple molding method of test piece for testing dynamic modulus of basalt fiber asphalt mixture and result optimization method

Abstract

The application discloses a simple forming method of a test piece for testing the dynamic resilient modulus of basalt fiber asphalt mixture and a result optimization method, and comprises the following steps: S1, a Marshall compaction dynamic modulus test piece mold is designed and manufactured, the inner diameter of the mold is 101.6mm±0.2mm, the cylindrical metal cylinder is 165mm high, the base plate is 12.7mm thick and has a diameter of about 120.6mm; S2, a multi-stage interface hot fusion forming process, (1) the first stage, base forming, (2) the second stage, heightening forming, (3) the third stage, final forming; the application has the advantages that the interlayer overall stability of the high test piece is effectively guaranteed, and the dynamic modulus test piece can be formed by replacing the rotary compaction method; the minimum stable sample size of the Marshall compaction is proposed, and the result is compared, analyzed and corrected with the result of the rotary compaction, so that the stability and reliability of the Marshall method for testing the dynamic resilient modulus of the asphalt mixture are ensured.

Description

Technical Field

[0001] This invention relates to the field of dynamic resilient modulus testing technology for basalt fiber asphalt mixtures, specifically to a simplified specimen molding method and result optimization method for testing the dynamic resilient modulus of basalt fiber asphalt mixtures. Background Technology

[0002] In asphalt pavement structural calculations, the dynamic elastic modulus is a key parameter characterizing the mechanical properties of asphalt mixtures. To accurately measure this index, industry standards require the use of cylindrical specimens with a diameter of 101.6 mm and a height of 150 mm. Currently, the preparation of such standard large-size specimens mainly relies on rotary compactors. While rotary compactors can produce high-quality specimens, the equipment is expensive, bulky, complex to operate, and requires a high-quality laboratory environment, making it difficult to widely adopt in construction sites or base course laboratories. This results in the inaccurate acquisition of this parameter in asphalt pavement design.

[0003] However, the inexpensive Marshall compaction equipment has a standard specimen molding size of φ101.6mm×63.5mm, which means that the Marshall compaction equipment cannot replace the rotary compactor to obtain the key parameter of dynamic elastic modulus. Summary of the Invention

[0004] In view of the above problems, the purpose of this invention is to provide a simplified molding method and result optimization method for testing the dynamic resilient modulus of basalt fiber asphalt mixtures. By improving the mold and sleeve of the Marshall compaction test apparatus, layered compaction molding is achieved, realizing the molding of specimens using conventional equipment. Furthermore, statistical analysis was conducted on the dynamic resilient modulus results of two molding methods: the Marshall compactor method and the rotary compaction method. A result optimization method with corrected parameters for the simplified molding method is provided to overcome the shortcomings of the prior art.

[0005] This invention provides a simplified molding method for testing the dynamic resilient modulus of basalt fiber asphalt mixtures, comprising the following steps: Step S1: First, design and fabricate a mold for the Marshall compacted dynamic modulus specimen. The mold's inner diameter is 101.6 mm ± 0.2 mm, the cylindrical metal tube is 165 mm high, the base plate is 12.7 mm thick, and its diameter is approximately 120.6 mm. The base plate thickness is consistent with the requirements of the standard test method. Step S2: Multi-stage interface thermal fusion molding process, (1) First stage, matrix forming: Cylindrical asphalt mixture specimens are compacted on both sides 75 times to form standard Marshall specimens (φ101.6mm×63.5mm); standard Marshall specimens with a diameter of about 100mm and a height of 63.5mm±2mm are formed. The upper interface of the standard Marshall specimen is marked as interface A and the lower interface is marked as interface B. (2) Second stage, height increase molding: Then, interface A is heated to 150°C and roughened. Cylindrical asphalt mixture is added to the side of interface A and compacted on one side 75 times to achieve height increase. A cylindrical specimen with a diameter of 100mm ± 0.2mm and a height of 107mm ± 2mm is formed. (3) Third stage, final molding: Finally, the interface B is heated to 150℃ and roughened. Cylindrical asphalt mixture is added to the side of interface B and compacted 75 times on one side to achieve height increase. After the secondary height increase and interface fusion are completed, the cylindrical asphalt mixture specimen is finally molded into a cylindrical dynamic modulus specimen with a diameter of 100±2mm and a height of 150±2mm.

[0006] The second objective of this invention is to provide a method for optimizing the dynamic modulus of a cylindrical specimen formed using a simplified specimen molding method, comprising the following steps: Step S1: Perform dynamic modulus tests on the standard specimen formed by rotary compaction using a rotary compactor and the cylindrical dynamic modulus specimen formed by a simplified specimen forming method. Step S2: Based on the test results of the rotary compaction molding and the simplified specimen molding method obtained in Step 1, determine the reasonable number of specimens for the rotary compaction molding and the simplified specimen molding method. Step S3: The results of the Marshall molding method were corrected to obtain the accurate dynamic modulus value using the Marshall molding method.

[0007] As a preferred embodiment of the present invention, step S1 further includes the following step: Step S11: Rotary compaction molding method, A set of eight standard specimens for dynamic modulus testing were formed using a rotary compactor. Dynamic modulus tests were then conducted on each specimen. From the eight test results, the number of valid specimens was randomly extracted. Data was analyzed using the rotary compaction method (SGC data processing). Based on the determined valid test data, the representative value of the dynamic modulus was calculated using the distribution method. The specific calculation formula and the relationship between the number of valid specimens and the value are as follows: In the formula, is the representative value of the dynamic modulus (MPa), is the average value of the measured dynamic modulus of a set of specimens (MPa), is the standard deviation of the measured values ​​of a set of specimens (MPa), is the number of valid specimens in a set of standard specimens, and is a coefficient that varies with the guarantee rate. The guarantee rate is 95% for expressways and Class I highways, and 90% for other grades of highways. Step S12: Marshall molding process, A set of 12 cylindrical dynamic modulus specimens were fabricated using a simplified specimen molding method, and dynamic modulus tests were conducted on each specimen. From the obtained 12 test results, the number of valid specimens was randomly extracted, and the data were analyzed using the rotational compaction method (SGC data processing). Based on the determined valid test data, the representative value of the dynamic modulus was calculated using the distribution method. The specific calculation formula and the relationship between the number of valid specimens and the value are as follows: In the formula, represents the number of valid specimens in a set of cylindrical dynamic modulus specimens.

[0008] As a preferred embodiment of the present invention, step S2 further includes the following step: Step S21: In the rotary compaction molding method of step S11, the average value of the calculated representative value of dynamic modulus is used as the evaluation benchmark, and 1% is used as the deviation range to determine the effective number of specimens for the dynamic modulus test. Through calculation and analysis of the data processing of the rotary compaction method, it is determined that if the nominal maximum particle size is ≤16mm, 4 specimens are selected; if the nominal maximum particle size is >16mm, 5 specimens are selected. Step S22: In the Marshall molding method of step S12, the average value of the representative value of the dynamic modulus calculated by the group is used as the evaluation benchmark, and 5% is used as the deviation range to determine the effective number of specimens for the dynamic modulus test. Through the calculation and analysis of the Marshall compaction molding method, it is found that if the nominal maximum particle size is ≤16mm, 6 specimens are selected; if the nominal maximum particle size is >16mm, 7 specimens are selected.

[0009] As a preferred embodiment of the present invention, step S3 further includes the following step: Step S31: Based on the two sets of test data obtained in step S2, the dynamic resilient modulus value measured by the Marshall compaction method is calculated and corrected using the least squares regression analysis method, so as to be used for asphalt pavement structure calculation. In the formula, is the maximum nominal particle size of the asphalt mixture.

[0010] The beneficial effects of this invention are as follows: it effectively ensures the overall interlayer stability of high-strength specimens and can replace the rotary compaction method for forming dynamic modulus specimens. It proposes a minimum stable sample size for Marshall compaction and compares and corrects the results with those of rotary compaction, ensuring the stability and reliability of the Marshall method for testing the dynamic resilient modulus of asphalt mixtures. Attached Figure Description

[0011] Other objects and results of the invention will become more apparent and readily understood with reference to the following description taken in conjunction with the accompanying drawings. In the drawings: Figure 1 This is a schematic diagram of the Marshall compacted dynamic modulus specimen of Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the test results of the standard specimen formed by rotational compaction in Embodiment 2 of the present invention; Figure 3 This is a schematic diagram of the test results of the dynamic modulus specimen of a cylinder formed by the Marshall molding method in Embodiment 2 of the present invention. Detailed Implementation

[0012] Example 1

[0013] See Figure 1 The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0014] This invention provides a simplified molding method for testing the dynamic resilient modulus of basalt fiber asphalt mixtures, comprising the following steps: Step S1: First, design and fabricate a mold for the Marshall compacted dynamic modulus specimen. The mold's inner diameter is 101.6 mm ± 0.2 mm, the cylindrical metal tube is 165 mm high, the base plate is 12.7 mm thick, and its diameter is approximately 120.6 mm. The base plate thickness is consistent with the requirements of the standard test method. Step S2: Multi-stage interface thermal fusion molding process, (1) First stage, matrix forming: Cylindrical asphalt mixture specimens are compacted on both sides 75 times to form standard Marshall specimens (φ101.6mm×63.5mm); standard Marshall specimens with a diameter of about 100mm and a height of 63.5mm±2mm are formed. The upper interface of the standard Marshall specimen is marked as interface A and the lower interface is marked as interface B. (2) Second stage, height increase molding: Then, interface A is heated to 150°C and roughened. Cylindrical asphalt mixture is added to the side of interface A and compacted on one side 75 times to achieve height increase. A cylindrical specimen with a diameter of 100mm ± 0.2mm and a height of 107mm ± 2mm is formed. (3) Third stage, final molding: Finally, the interface B is heated to 150℃ and roughened. Cylindrical asphalt mixture is added to the side of interface B and compacted 75 times on one side to achieve height increase. After the secondary height increase and interface fusion are completed, the cylindrical asphalt mixture specimen is finally molded into a cylindrical dynamic modulus specimen with a diameter of 100±2mm and a height of 150±2mm.

[0015] Example 2

[0016] This invention provides a method for optimizing the dynamic modulus of a cylindrical specimen formed using a simplified specimen molding method, comprising the following steps: Step S1: Perform dynamic modulus tests on the standard specimen formed by rotary compaction using a rotary compactor and the cylindrical dynamic modulus specimen formed by a simplified specimen forming method. Step S11: Rotary compaction molding method, A set of eight standard specimens for dynamic modulus testing were formed using a rotary compactor. Dynamic modulus tests were then conducted on each specimen. From the eight test results, the number of valid specimens was randomly extracted. Data was analyzed using the rotary compaction method (SGC data processing). Based on the determined valid test data, the representative value of the dynamic modulus was calculated using the distribution method. The specific calculation formula and the relationship between the number of valid specimens and the value are as follows: In the formula, is the representative value of the dynamic modulus (MPa), is the average value of the measured dynamic modulus of a set of specimens (MPa), is the standard deviation of the measured values ​​of a set of specimens (MPa), is the number of valid specimens in a set of standard specimens, and is a coefficient that varies with the guarantee rate. The guarantee rate is 95% for expressways and Class I highways, and 90% for other grades of highways. Step S12: Marshall molding process, A set of 12 cylindrical dynamic modulus specimens were fabricated using a simplified specimen molding method, and dynamic modulus tests were conducted on each specimen. From the obtained 12 test results, the number of valid specimens was randomly extracted, and the data were analyzed using the rotational compaction method (SGC data processing). Based on the determined valid test data, the representative value of the dynamic modulus was calculated using the distribution method. The specific calculation formula and the relationship between the number of valid specimens and the value are as follows: In the formula, represents the number of valid specimens in a set of cylindrical dynamic modulus specimens.

[0017] Step S2: Based on the test results of the rotary compaction molding and the simplified specimen molding method obtained in Step 1, determine the reasonable number of specimens for the rotary compaction molding and the simplified specimen molding method. Step S21: In the rotary compaction molding method of step S11, the average value of the calculated representative value of dynamic modulus is used as the evaluation benchmark, and 1% is used as the deviation range to determine the effective number of specimens for the dynamic modulus test. Through calculation and analysis of the data processing of the rotary compaction method, it is determined that if the nominal maximum particle size is ≤16mm, 4 specimens are selected; if the nominal maximum particle size is >16mm, 5 specimens are selected. Step S22: In the Marshall molding method of step S12, the average value of the representative value of the dynamic modulus calculated by the group is used as the evaluation benchmark, and 5% is used as the deviation range to determine the effective number of specimens for the dynamic modulus test. Through the calculation and analysis of the Marshall compaction molding method, it is found that if the nominal maximum particle size is ≤16mm, 6 specimens are selected; if the nominal maximum particle size is >16mm, 7 specimens are selected.

[0018] Step S3: The results of the Marshall molding method were corrected to obtain the accurate dynamic modulus value using the Marshall molding method; Step S31: Based on the two sets of test data obtained in step S2, the dynamic resilient modulus value measured by the Marshall compaction method is calculated and corrected using the least squares regression analysis method, so as to be used for asphalt pavement structure calculation. In the formula, is the maximum nominal particle size of the asphalt mixture.

[0019] In this embodiment, the representative value of rotary compaction is as follows: Figure 2 As shown, although there is some vertical dispersion when the sample size is small, the point cloud exhibits rapid convergence as the sample size increases, achieving a high level of stability even with a small sample size. The vast majority of representative point clouds remain within a ±1% bandwidth range in their respective intervals, reflecting good repeatability and controllability of the rotary compaction test results. Due to differences between mixtures with different maximum nominal particle sizes, the compaction effect deviates during molding, resulting in relatively slow point cloud convergence for BFAC-20, with significant deviations in its original samples. As n increases, this effect is averaged, leading to enhanced convergence. The results indicate that the recommended sample size for the rotary compaction dynamic modulus test is 4 for BFAC-13 / 16 and 5 for BFAC-20.

[0020] In this embodiment, the representative value of the Marshall compaction is as follows: Figure 3 As shown, the point cloud exhibits rapid convergence with increasing size, achieving a high level of stability even with a small sample size. Most representative point clouds remain within the median ± 5% bandwidth range in their respective intervals, reflecting good repeatability and controllability of representative values ​​under Marshall compaction molding conditions. Differences between mixtures with different maximum nominal particle sizes lead to deviations in compaction effect and interlayer fusion uniformity during molding. The results indicate that the recommended sample size for the Marshall compaction dynamic modulus test is 6 for BFAC-13, 6 for BFAC-16, and 7 for BFAC-20.

[0021] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A simplified molding method for testing the dynamic resilient modulus of basalt fiber asphalt mixture, characterized in that, Includes the following steps: Step S1: First, design and fabricate a test mold for the Marshall compacted dynamic modulus specimen. The mold's inner diameter is 101.6mm ± 0.2mm, the cylindrical metal tube is 165mm high, and the base plate is 12.7mm thick with a diameter of approximately 120.6mm. Step S2: Multi-stage interface thermal fusion molding process, (1) First stage, matrix forming: the cylindrical asphalt mixture specimens are compacted on both sides 75 times to form standard Marshall specimens; the standard Marshall specimens with a diameter of about 100 mm and a height of 63.5 mm ± 2 mm are formed. The upper interface of the standard Marshall specimen is marked as interface A and the lower interface is marked as interface B. (2) Second stage, height increase molding: Then, interface A is heated to 150°C and roughened. Cylindrical asphalt mixture is added to the side of interface A and compacted on one side 75 times to achieve height increase. A cylindrical specimen with a diameter of 100mm ± 0.2mm and a height of 107mm ± 2mm is formed. (3) Third stage, final molding: Finally, the interface B is heated to 150℃ and roughened. Cylindrical asphalt mixture is added to the side of interface B and compacted 75 times on one side to achieve height increase. After the secondary height increase and interface fusion are completed, the cylindrical asphalt mixture specimen is finally molded into a cylindrical dynamic modulus specimen with a diameter of 100±2mm and a height of 150±2mm.

2. The method for optimizing the results of the cylindrical dynamic modulus specimen formed according to claim 1, characterized in that, Includes the following steps: Step S1: Perform dynamic modulus tests on the standard specimen formed by rotary compaction using a rotary compactor and the cylindrical dynamic modulus specimen formed by a simplified specimen forming method. Step S2: Based on the test results of the rotary compaction molding and the simplified specimen molding method obtained in Step 1, determine the reasonable number of specimens for the rotary compaction molding and the simplified specimen molding method. Step S3: The results of the Marshall molding method were corrected to obtain the accurate dynamic modulus value using the Marshall molding method.

3. The result optimization method according to claim 2 is characterized in that, Step S1 also includes the following steps: Step S11: Rotary compaction molding method, A set of eight standard specimens for dynamic modulus testing were formed using a rotary compactor. Dynamic modulus tests were then conducted on each specimen. From the eight test results, the number of valid specimens was randomly extracted. The data was analyzed using the rotary compaction method. Based on the determined valid test data, the representative value of the dynamic modulus was calculated using the distribution method. The specific calculation formula and the relationship between the number of valid specimens and the value are as follows: In the formula, is the representative value of the dynamic modulus, is the average value of the measured dynamic modulus of a set of specimens, is the standard deviation of the measured values ​​of a set of specimens, is the effective number of specimens in a set of standard specimens, and is a coefficient that varies with the guarantee rate. Step S12: Marshall molding process, A set of 12 cylindrical dynamic modulus specimens were fabricated using a simplified specimen molding method, and dynamic modulus tests were conducted on each specimen. From the obtained test results, the number of valid specimens was randomly extracted, and the data were analyzed using the rotary compaction method. Based on the determined valid test data, the representative value of the dynamic modulus was calculated using the distribution method. The specific calculation formula and the relationship between the number of valid specimens and the value are as follows: In the formula, represents the effective number of a set of cylindrical dynamic modulus specimens.

4. The result optimization method according to claim 2, characterized in that, Step S2 also includes the following steps: Step S21: In the rotary compaction molding method of step S11, the average value of the calculated representative value of dynamic modulus is used as the evaluation benchmark, and 1% is used as the deviation range to determine the effective number of specimens for the dynamic modulus test. Through calculation and analysis of the data processing of the rotary compaction method, it is determined that if the nominal maximum particle size is ≤16mm, 4 specimens are selected; if the nominal maximum particle size is >16mm, 5 specimens are selected. Step S22: In the Marshall molding method of step S12, the average value of the representative value of the dynamic modulus calculated by the group is used as the evaluation benchmark, and 5% is used as the deviation range to determine the effective number of specimens for the dynamic modulus test. Through the calculation and analysis of the Marshall compaction molding method, it is found that if the nominal maximum particle size is ≤16mm, 6 specimens are selected; if the nominal maximum particle size is >16mm, 7 specimens are selected.

5. The result optimization method according to claim 4 is characterized in that, Step S3 also includes the following steps: Step S31: Based on the two sets of test data obtained in step S2, the dynamic resilient modulus value measured by the Marshall compaction method is calculated and corrected using the least squares regression analysis method, so as to be used for asphalt pavement structure calculation. In the formula, is the maximum nominal particle size of the asphalt mixture.

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