Mechanical and moisture susceptibility properties of HMA containing ferrite for their use in magnetic asphalt

• The results proved the highly effective role of active fillers in HMA mix.
• Considering the small size and softness of ferrites, they can be used as fillers in asphalt mixes.
• Using ferrite as asphalt filler can lead to increase in resistant properties of asphalt mix and also increase in moisture durability.

Fillers have some properties which can have a great impact on the characteristics of asphalt concrete. Several physical and chemical transactions take place among fillers and binders, which affect asphalt mix performance. Ferrites are iron magnetic oxides with other metals such as barium, strontium, manganese, nickel, and zinc which can be grouped into two soft and hard groups. Considering the small size and softness of ferrites, they can be used as fillers in asphalt mixes. In this paper, mechanical properties and moisture susceptibility of the asphalt mix containing ferrite are studied in comparison with limestone and cement filler in different combinations. The necessary samples to conduct the experiments of the Marshal resistance, indirect tensile strength (ITS) and resilient modulus (Mr) were prepared as in filler segment of the specimen, ferrite with different percentages of 0%, 35%, 70%, and 100% of the total of fillers are placed in such manner that the remaining percent in each sample was replaced once with cement filler and once with limestone filler. And thus, the seven mixtures were obtained by three filler types. According to the results, adding ferrite increased the Marshal resistance and the sample with 100% ferrite filler increased the mix resistance by 11% and 35%, respectively, compared with the samples with cement and limestone by 100%. The largest amount of ITS was for the sample with 100% ferrite filler, which compared with the sample with limestone, increased the amount of ITS by about 39% in the unconditional state and by 62% in the conditional state, indicating its higher bonding with bitumen. This sample in combination with cement also showed higher resistance than limestone. These results proved the highly effective role of active fillers in HMA mix. The impact of ferrite on asphalt mix maintenance can be found at higher ferrite percentages. This impact was observable in the chart of toughness rate of the unconditional to conditional states in a way that increased with the increase in ferrite and its amount was 7% higher in the sample with 100% ferrite filler than the samples with 100% cement and limestone filler.