The impact of cement contents on the properties of asphalt emulsion stabilized cold recycling mixtures

This paper studied how the content of Portland cement in emulsion stabilized cold recycling (CR-Emulsion) mixtures impacts the properties of asphalt. The properties (i.e., the rate of increase in initial strength, moisture susceptibility, rut resistance, and crack resistance) of asphalt CR-Emulsion mixtures with varying cement content and different curing histories were tested using indirect tensile strength (ITS) tests, bending beam tests at -10°C, and dynamic stability rutting tests at 60°C. The test results showed that ITS values linearly increased as the cement content and curing time increased. Increasing the cement content lead to better moisture resistant properties and the strength increased at a higher rate. Specimens with a cement content lower than 0.5% by weight exhibited relatively poor water resistance properties and a poor rate of increase in initial strength. The ITS values of the wet condition samples (ITS_wet) were more significantly affected by cement content than the ITS values of the dry condition samples (ITS_dry). Specimens with 1.5% cement by weight exhibited better rut resistance properties than specimens with 0%, 0.5%, and 2.5% cement content. As the cement content increased, the maximum bending strength at -10°C increased, whereas the maximum bending strain at -10°C decreased. The cement in CR-Emulsion mixtures requires a certain amount of curing time to improve the mixture properties; thus, curing methods that use an accelerated process cannot reflect the real conditions of CR-Emulsion mixtures. It was concluded that Portland cement is necessary to enhance the rate of increase in initial strength and to improve both the moisture resistance properties and high temperature properties of CR-Emulsion mixtures. However, too high of a cement content leads to brittleness at low temperatures. The optimal cement content for CR-Emulsion mixture was suggested to be around 1.5%.