The reasons for aging are internal and external causes. Internal cause refers to the nature of the material itself, mainly: the structure of the monomer, the internal nature of the polymer system, additives, and other external environmental factors, mainly sunlight, oxygen, heat, moisture, ph value, stress, industrial gases, seawater, salt mist, mold, bacteria and so on. The causes of aging are various, usually all kinds of factors work together, but the sun, water, oxygen and heat are the most important factors, this article mainly focuses on the discussion of these factors.
2 Aging Test
Aging test is to study the aging law of geotextile in a certain environment and to evaluate the aging performance of Geotextiles. Through aging test, the strength, elongation, elastic modulus and micropore structure of geotextiles were tested to be aged over time. The aging test mainly has three kinds of artificial accelerated aging test, natural environment aging test and actual application aging test.
1 Artificially accelerated aging test
The sample is placed in an aging box, according to the actual use of samples or related aging standards, set the parameters of the aging box, such as temperature and humidity, ultraviolet intensity, rain, condensation and so on. After a certain period of accelerated aging, the aging sample and the original is compared to estimate the aging performance of the sample. Accelerated aging is characterized by accelerated aging conditions, high comparability, short test cycle and good reproducibility.
The artificial accelerated aging test mainly includes: artificial accelerated ultraviolet aging test, artificial accelerated heat aging test, artificial accelerated oxygen aging test, artificial accelerated damp-heat aging test and so on.
2 Natural environment Aging test
The specimen is exposed to the natural environment to detect the aging of geotextile performance over time. The advantage of the natural environmental aging test is to use the real natural environment for the experiment, the result is true and reliable. Disadvantage is time-consuming and laborious, generally at least one year, many years, unable to new materials, new products, aging performance of rapid evaluation.
The natural environment aging test mainly includes: atmospheric aging test, underground burial test, seawater immersion test and underwater burial test. At present, more is the atmospheric aging test and underground burial test.
3 The actual application of aging test
This test is carried out in practical engineering application, sampling regularly at engineering site, testing intensity loss rate and related index, and understanding the aging degree of material in practical application. The actual application of the aging test is in the concrete construction environment sampling test, the data is true and reliable. The disadvantage is that the time period is long and the general applicability is poor.
In theory research, the correlation between artificially accelerated aging and natural environment aging is a relatively active field. Grey prediction of aging model was proposed, and the natural aging time was predicted by the results of artificial accelerated aging test. Grey prediction of aging model is a kind of forecasting method based on grey system theory, based on known data, a grey model of past extension to future is established to determine the future development trend of the system.