Abstract—Bitumen emulsion in combination with Ordinary Portland cement is a commonly used additive in cold recycling applications. The current mix design approach for cold recycled mixes recommends the insertion of emulsion to a cement-reclaimed asphalt pavement material (RAPM)-water mixture and suggests the mixing to be completed within one to two minutes of adding water to the cement. The current study investigates the impact of different emulsion insertion times on cement hydration and the engineering properties of the mixes. Samples used in the study were prepared using RAPM, cationic slow-setting bitumen emulsion (SS-2 grade), and Grade 43 ordinary Portland cement. Mixes were prepared using a constant Water-to-Cement (W/C) ratio of 1.5. Emulsion-to-Cement (E/C) ratio used for preparing the mixes was varied along with the time of emulsion insertion to evaluate changes in physicochemical properties of the mixes. Changes in hydration and engineering properties of mixes were evaluated using isothermal conduction calorimetry, X-Ray Diffraction (XRD), Fourier Transform Infrared (FTIR) spectroscopy, and Indirect Tensile Strength (ITS) tests, respectively. Observations from the study suggest that an increase in E/C ratio extends the breaking time of emulsion and delays the rate of strength gain in these mixes. Observations also suggest that the time window recommended in the current mix design approach may not be effective when E/C ratio is higher than 1.5. An insertion time greater than one minute, but less than the time where initial setting of cement starts may be effective in providing a higher strength (ITS) to cold recycled mixtures

Keywords—bitumen cement interactions, delayed mixing of emulsion in cold recycled mixes, cement hydration, emulsion to cement ratio, bitumen emulsion, cement bitumen composite materials