Experimental investigation on the effect of hydrated lime on mechanical properties of SMA

• Partial substitution of the filler with HL significantly improves the resistance indices of SMA.
• There is an optimum amount of hydrated lime in SMA mixture.
• Using HL as additive leads to superior performance comparing with partial substitution of HL.
• The HL modified SMA with 9.5 NMAS is much stronger against rutting compared to the SMA of 12.5 NMAS.

One of the most important and costly damages to the pavements, especially in high traffic areas is rutting. An optimal use of lime is significantly important with regard to expensive cost of the lime and its improving properties in stone matrix asphalt (SMA). In this paper, simple performance tests (i.e. dynamic modulus, dynamic creep, and static creep) were used based on NCHRP-465 report. In which the effect of directly added different percentages of hydrated lime filler to the mixture in dry state as a partial substitute of the aggregate materials in comparison with introducing it as an additive to the mixture on performance and mechanical properties of SMA was assessed. For this purpose, the SMA samples with two different aggregate gradation and different hydrated lime contents were prepared as a part of filler. The obtained results indicate that partial substitution of the filler with hydrated lime will cause an improvement in the resistance indices like flow number, flow time as well as rutting and fatigue cracking factors of SMA, while the permanent deformations of the asphalt decrease. Obviously, it indicates existence of an optimum amount of hydrated lime in mixture. The results obtained from this contribution can be used to design and implement asphalt mixtures in accordance with the requirements of the contractors, engineers and researchers.