Laboratory performance of Recycled Asphalt Mixes containing wax and chemical based Warm Mix Additives using Semi Circular Bending and Tensile Strength Ratio tests

Abstract

Durability and sustainability are two major requirements of the asphaltic pavement structure. Durability aspect may involve performance parameters such as fracture property, moisture sensitivity etc., whereas, sustainability aspect may involve utilization of Recycled Asphalt Pavement (RAP) and Warm Mix Additive (WMA) in the conventional asphaltic mixture. Though improvement in high temperature performance may be expected with the addition of RAP due to its stiffer nature, it may degrade intermediate temperature performance. Additionally, RAP utilization may also increase the mixing and compaction temperature during the construction phase. Therefore, researchers have recommended using different WMA additives to decrease production temperature of mixes containing RAP. Though the use of WMA additives with RAP may decrease mixing and compaction temperature, their effects on various performance parameters of the asphaltic mixture must be evaluated. Sufficient research works have been reported on the performance of RAP and WMA mixes at high temperature, however, so far, limited work is available on understanding effects of RAP and WMA additives on fatigue and moisture sensitivity of asphalt mixture. Therefore, the present research work aimed at evaluating intermediate temperature fracture properties and moisture sensitivity of asphaltic mixture containing RAP and WMA. Five different RAP contents (0%, 10%, 20%, 30%, and 40%), two different types of WMA additives (2% wax based “Sasobit” and 0.5% chemical based “Evotherm”) and one without WMA additive (Control mixture) were considered. Fracture properties of different asphaltic mixture combinations were evaluated using Semi Circular Bending (SCB) test. Improvement in fracture property of Control mixture was observed with increase in RAP content, however, the addition of wax based and chemical based WMA additives showed an overall reduction in fractured resistance. Further, the asphaltic mixture containing wax based WMA additive showed better fracture performance compared to the corresponding mixture containing chemical based WMA additive. Similarly, moisture sensitivity of asphaltic mixtures was evaluated using Tensile Strength Ratio (TSR) approach. Addition of both WMA additives resulted in lowered Indirect Tensile Strength (ITS) under dry as well as wet condition. Though the addition of WMA additive showed a negative impact on moisture sensitivity, all mixture considered in the present research work passed the minimum TSR requirement. Therefore, wax and chemical based WMA additive may deem acceptable from moisture sensitivity point of view.