Foamed asphalt, also called expanded asphalt, is a cold water injected into the hot asphalt at certain normal temperature, causing it to expand and form a large amount of asphalt foam. After a short period of time, the asphalt foam burst.
When the foamed asphalt is in contact with aggregate, the asphalt foam is interchanged into tens of thousands of "small particles", dispersed on the surface of the fine aggregate, forming a fine material filling material with a large amount of asphalt. After mixing and compacting, these fine materials can fill the gap between coarse materials and form a mortar like function to make the mixture stable.
The waste road milling material can be used as a recycling material for foamed asphalt cold recycling mixture, and it will form a pavement structure layer with certain pavement performance under the pressure strength. Turn waste into treasure, so as to protect the environment and save resources; At the same time, the cold recycling technology of foamed asphalt can transform the traditional semi-rigid pavement structure into semi flexible base pavement structure, so as to optimize the pavement combination form and prolong the service life of pavement.
目前主要采用膨胀率和半衰期两个指标对沥青发泡特性进行评价。膨胀率是指沥青发泡膨胀时达到的最大体积与泡沫完全消失时的体积之比，反映泡沫沥青的黏度大小。半衰期是指泡沫沥青从最大体积降到最大体积的一半需要的时间，以 s 计，反映泡沫沥青的稳定性。
At present, the expansion rate and half-life are mainly used to evaluate the foaming characteristics of asphalt. The rate of expansion refers to the ratio between the maximum volume of asphalt expansion and the volume when the foam completely disappears, which reflects the viscosity of the foamed asphalt. The half-life is the time required to reduce the volume of foam asphalt from the maximum volume to the maximum volume. It reflects the stability of foamed asphalt in the form of S.
In order to fully mix foamed asphalt and normal temperature wet aggregate, the greater the expansion rate, the better, and the longer the half-life, so that foamed asphalt and aggregate can be mixed for a long time to improve the quality of foamed asphalt mixture. When evaluating the foaming effect of asphalt, the expansion rate and half-life are two inseparable indexes. The best foaming effect should make both values relatively large, but can not be controlled by one index alone. It is recommended that the expansion rate of foamed asphalt ≥ 10 times and the half-life ≥ 8s.