Comparing the effects of nano-silica and hydrated lime on the properties of asphalt concrete

In this study, the effects of nano-silica (NS) and hydrated lime (HL) were investigated on some engineering properties of asphalt concrete. The unconditioned indirect tensile strength (ITS) and that after subjecting to one, three and five freeze-thaw cycles; resilient modulus at 5, 25, and 45 degrees C; and stress-controlled fatigue cracking behavior of the mixtures modified by different percentages of each additive were examined. Results showed that the both additives improved the ITS of the mixture. The ITS of the mixture modified by 6% of NS was approximately 10% higher than that of the mixture containing 2.5% of HL. However, NS was more effective than lime in improving the resistance against freeze-thaw cycles. Moreover, it was shown that 20 and 26.7% of ITS was lost after five freeze-thaw cycles in the mixtures containing 6% of NS and 2.5% of HL, respectively. The both additives improved the resilient modulus and resistance against the fatigue cracking of the mixture with a slightly higher improvement for NS. The fatigue life of the mixture modified by 6% of NS was approximately 5.8% higher than that of the mixture containing 2.5% of HL. The results also showed that, in general, the temperature sensitivity of the resilient modulus of the mixtures modified with lime and NS was lower than that of the control mixture, with higher sensitivity for the mixtures modified with NS. Moreover, the sensitivity decreased with increasing the modifier content and decreasing the temperature. (C) 2019 Elsevier Ltd. All rights reserved.