Conference Papers
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Item Laboratory Evaluation on the Use of Natural Fibre in Gap-Graded Asphalt Mixtures(Springer Science and Business Media Deutschland GmbH, 2023) Chinnabhandar, R.K.; Ravi Shankar, A.U.; Sai Ganesh, V.; Cleetus, A.; Chourasia, S.Stone Matrix Asphalt (SMA) is a gap-graded mixture that consists of a high concentration of coarse aggregates, which imparts strength and rut resistance and a high binder content, making the mixture durable. The high binder content mortar consists of fine aggregates, filler, bitumen and stabilising additive. One of the limitations of SMA is it suffers from draindown of binder mortar which can be reduced by adding a mineral fibre, natural fibre or synthetic fibre. The addition of a stabilising additive not only controls the draindown but also improves the tensile strength because of the network of fibres in the mixture. In the present study, an attempt is made to determine the effect of Areca fibre, a natural fibre abundantly available in the southern Indian region. A comparison between two SMA mixtures prepared with and without stabilising additive is made. The Superpave mix design method was adopted, and tests such as draindown, fatigue, rutting and moisture-induced damage properties such as tensile strength ratio (TSR) were evaluated. The results indicate that the mixture with Areca fibre effectively controls the draindown and satisfies the volumetric and mix design criteria as per IRC SP 79. However, the performance of SMA without stabilising additive was better than the mixture with the stabilising additive with respect to resistance to rutting, fatigue and moisture-induced damage. © 2023, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.Item Unmodified Bitumen in SMA: A Sustainable and Cost-Effective Approach(Springer Science and Business Media Deutschland GmbH, 2025) Arun, U.; Chinnabhandar, R.K.; Talkeri, H.T.; Yatish, R.G.; Ravishankar, A.U.Stone Matrix Asphalt (SMA) is a Hot Mix Asphalt (HMA) mixture consisting of a discontinuous aggregate gradation characterised by a high coarse aggregate content (between 70 and 80%), a high percentage of binder (typically between 6 and 7%) and a filler content as high as about 10%. SMA has an aggregate skeleton which imparts high strength and rutting resistance to the mixture. The high binder content though provides the mixture with durability, it also drains through the void spaces in the aggregate skeleton during production, transportation and placement of the mixture in the field. Hence, to reduce the drainage of bitumen and bitumen mortar, the SMA guidelines suggest using a modified bitumen or pelletised cellulose fibres in the mixture when a conventional bitumen such as Viscosity Graded (VG 30) is used. However, the production of cellulose fibres is not only expensive but also requires trees to be cut since cellulose is obtained from plant sources leading to deforestation. Due to the high cost of Polymer Modified Bitumen (PMB), the SMA mixtures prepared with the modified bitumen are also expensive. Hence, the present study focuses on the laboratory evaluation of SMA mixes using a conventional Viscosity Graded bitumen (VG 40) without the use of pelletised cellulose fibres. The results indicated that the susceptibility of mixtures to drainage of binder and/or binder mortar was within the permissible limit of 0.3% by weight of the mixture. The mechanical and moisture susceptibility tests conducted on compacted specimens indicated that the performance is comparable to that of the mixtures prepared using PMB. Further, it was noted that only the grades of bitumen softer than VG 40 required cellulose fibres to reduce drain-down. The study also revealed a reduction in cost due to not using cellulose fibres with VG 40 bitumen or modified bitumen, which makes it more environmentally friendly and sustainable. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.