Prediction of Tensile Strength of Cold Asphalt Emulsion Mixtures Using the Maturity Method

Abstract

Lack of universal design standards for CMA has led to the use of Laboratory-Field Curing Correlation techniques to predict the performance (strength) in CMA. Such techniques involve performance-based tests that were originally developed for hot mix asphalt. Laboratory-Field curing correlation techniques disregard the gradual strength gain in CMA, which is affected by curing time and temperature. Moreover, they have demonstrated considerable inconsistencies in the prediction of strength in CMA during curing. The main objective of this study was to predict the indirect tensile strength (ITS) of cold asphalt emulsion mixtures (CAEMs) produced using siliceous aggregates and a cationic bitumen emulsion. Materials characteristics were determined and mix designs were developed using virgin and recycled aggregates from Reclaimed Asphalt Pavement (RAP). The Marshall method was used to produce specimens of size 100 mm diameter and 63.5 mm thickness. Specimens were subjected to isothermal curing regimes at temperatures of 25, 40 and 60 ºC. The curing periods considered were 3, 8, 13, 18 and 23 days for each temperature. ITS was subsequently measured for each of those curing regimes. After 3 days of curing, the ITS of RAP mix cured at low temperature of 25 ºC was 47.04% lower than that of the virgin mix. However, for all temperature regimes, the difference in ITS of the virgin and RAP mix was 3% for specimens cured for 23 days and a maximum of 6% for specimens cured for 18 days. The temperature sensitivity factor (B) of the RAP mix was 94% higher than that of the virgin mix. This work determined that a linear-hyperbolic strength maturity function predicts the ITS of CAEMs produced using siliceous aggregates and a cationic bitumen emulsion with an accuracy of more than 95%. The study recommends the use of Maturity method to predict tensile strength of CAEMs during design and to monitor gradual strength gain in CAEMs during construction