The flexural creep and freeze-thaw splitting properties of asphalt are important indicators to evaluate its durability in road engineering. Through standardized testing methods, the performance of asphalt under different environmental conditions can be effectively analyzed to ensure its reliability and stability during use. These tests provide a scientific basis for optimizing road design and construction, thereby improving the overall quality and service life of roads, which has important implications for traffic safety and economic efficiency.
Flexure creep test
Purpose and Scope of Application
The flexure creep test is designed to evaluate the deformation properties of a hot-mix asphalt mixture. The deformation characteristics of the asphalt mixture are evaluated by measuring the strain rate under defined temperature and loading conditions. The test is suitable for prismatic specimens with a length of 250mm, a width of 30mm and a height of 35mm, with a span of 200mm, and the loading temperature can be selected according to the test requirements, usually the low temperature test is 0 °C, and the high temperature test is 30~40 °C.
Instrument and material requirements
This test requires the use of an electro-hydraulic servo-hydraulic universal material testing machine or a lever creep testing machine, equipped with auxiliary equipment such as LVDT displacement sensors, data acquisition systems, and Thermostatic Water Baths. The test instrument should be temperature controlled with a high accuracy (±0.1°C) and the accuracy should be ensured by the use of a testing machine capable of constant loading.
Test procedure
1. Preparation of specimens - the specimens formed by wheels are cut into prismatic bodies that meet the dimensional requirements.
2. Measure and record the size and physical indexes of the specimen, and put the specimen into the constant temperature Water Tank for pretreatment for 1 hour.
3. Carry out the flexure test, and 10% of the loading failure load is used as the creep test load.
4. A constant load is applied to the testing machine while the LVDT sensor is used to record the change in mid-span deflection until the specimen enters the stabilization period.
5. The flexural creep compliance and creep rate of the specimen are calculated by reading the time of the stabilization period and the change in deflection in the span.
Calculations & Reporting
According to the recorded load and deflection data, the parameters such as flexural creep flexibility and flexural tensile stress are calculated by formula. The test results were taken as the average value of the three specimens, and the test conditions and loading rate were recorded.
Freeze-thaw splitting test
Purpose and Scope of Application
The freeze-thaw splitting test is used to evaluate the water stability of asphalt mixtures after freeze-thaw cycles. The splitting strength ratio of the mixture specimen before and after water damage was determined to reflect its water resistance. The test temperature is usually 25°C, the loading rate is 50mm/min, and it is suitable for specimens with a maximum particle size of 26.5mm.
Instrument and material requirements
The test uses a cylindrical specimen formed by the Marshall compaction method and uses a materials testing machine or a Marshall Tester. The temperature control of the thermostatic refrigerator is required to be within ±2°C, and the accuracy of the thermostatic sink is ±0.5°C.
Test procedure
1. Prepare cylindrical specimens to ensure that the formed specimens meet the size and density requirements.
2. Put the specimen into a constant temperature freezer for freeze-thaw cycle.
3. The treated specimen is preheated in a constant temperature Water Tank to test its splitting strength.
4. Record the failure load of the specimen before and after damage, and calculate the splitting strength ratio.
Calculations & Reporting
Based on the measured splitting strength, the strength ratio before and after freezing and thawing is calculated, and the water stability of the asphalt mixture is evaluated accordingly. The test report should indicate the conditions such as the specimen forming method, loading rate and temperature.
summary
The flexural creep and freeze-thaw splitting performance tests of asphalt are the key links to evaluate its application effect in road engineering. The quality of these properties directly affects the durability and service life of asphalt, which in turn is related to the safety and economy of the road. Through scientific testing methods, it can provide a strong basis for the selection of asphalt materials and road design, so as to achieve high-quality road construction and maintenance, and ensure the smooth and safe transportation.
