Laboratory evaluation of hard grade bitumen produced with PPA addition Sandeep Reddy Gottam a , Ramesh Adepu a *, Vinayaka Ram Vijayapuri b , Ramu Penki c a Department of Civil Engineering, VNR Vignana Jyothi Institute of Engineering and Technology, Hyderabad, Telangana, India b Department of Civil Engineering, BITS Pilani Hyderabad Campus, Hyderabad, Telangana, India c Department of Civil Engineering, GMR Institute of Technology, Rajam, Andhra Pradesh, India Received 16 March 2020; received in revised form 14 September 2020; accepted 3 October 2020 Abstract The present research deals with the development of poly phosphoric acid (PPA) based bituminous binder and investigating the corresponding changes happening with physical properties, chemical fractions, rheological properties, short term aging kinetics and surface morphology; when compared with virgin binder. During the current investigations, straight run VG-30 (AC-30) binder was modified with PPA from 0 to 4.5% with an incremental dosage of 0.75%. Rheological investigations were also carried out on the modified as well as unmodified binders using Antonpaar’s dynamic shea r rheometer (DSR). An increase in the dosage of PPA to straight binder has shown improved physical properties in terms of decreased penetration value and increased softening point. Asphaltenes fractions of binders were found to be increased with the increment in the PPA dosage. The aging kinetics of PPA modified binders was also improved when compared with the straight run binder. It was observed that a 4.5% PPA addition has resulted in high service temperature binder grade of PG 76 and 70V with a corresponding 23 dmm penetration levels. From the field emission scanning electron microscopy (FESEM) images, a clear morphological change was observed on the modified binders with the added PPA content, when compared with VG 30 bitumen. Thus, obtained results have shown that the addition of 4.5% PPA content was found to be optimum for the production of hard grade binder. Keywords: Poly phosphoric acid; High modulus asphalt binder; Fourier transforms infrared spectroscopy; Field emission scanning electron microscopy 1. Introduction Bituminous mixes prepared with base binders have shown tendency to fail prematurely under the influence of heavy vehicular loading and aggressive environmental conditions. It was felt imminent that the performance of mixes prepared with straight run binder should be enhanced with the use of high modulus asphalt concrete (HMAC) [1,2] to improve the performance of the pavements under the influence of ever increasing traffic loads and changing environmental conditions. HMAC was introduced in France during 1980s to prolong the effective service life of flexible pavements [3–5]. Apart from the hard grade binders produced at the refineries, gilsonite and polyolefin, novolac modified binders have also been tried as the high modulus asphalt binders (HMAB) during the recent past [6–10]. When the straight run bitumen is modified with the additives like gilsonite, polyolefin etc., the resultant binder is targeted to have the penetration in the range of 15/25 or 10/20 at 25°C [11]. * Corresponding author E-mail addresses: sandeepreddy974@gmail.com (Sandeep R. G.); ramesh_a@vnrvjiet.in (Ramesh A.); vinayak@hyderabad.bits- pilani.ac.in (V. Ram V.); abhiram.penki@gmail.com (Ramu P.). Peer review under responsibility of Chinese Society of Pavement Engineering. Majority of the reported studies have targeted to examine whether the modified binders are fulfilling the HMAB requirements or not. Not much has been studied about the aging behavior of these modified hard grade binders and hence, in the present study, the effect of aging on the modified hard grade binder is taken up. Since its initial patented attempt in 1973, the use of Poly Phosphoric Acid (PPA), as a modifier, has gone up substantially and hence this technique had provided an efficient option in developing HMAB [12–14]. Bitumen, modified with low dosages of PPA, has shown decreased penetration with the corresponding increase in softening point; strongly indicating its efficacy in introducing the hardening effect in the bitumen [15,16]. The same changes were found with the addition of 4 and 6% PPA to straight run binder [17,18]. Majority of the studies have reported that the PPA addition has resulted in increased asphaltenes content with the corresponding reduction of maltenes in the bitumen [16,19]. The aging kinetics of PPA modified binders was found substantially less when compared with the straight run binders [20]. Rheological study conducted on PPA modified binder has shown improved rheological performance in terms of increased high performance grade of binder without much lowering the low temperature grade [14,21]. Multiple stress creep recovery (MSCR) test carried on PPA modified binder has shown increased recovery and decreased non-recoverable creep compliance with the increase in dosage of PPA. [22]. ISSN: 1997-1400 DOI: https://doi.org/ 10.1007/s42947-020-0068-2 Chinese Society of Pavement Engineering. Production and hosting by Springer Nature International Journal of Pavement Research and Technology Journal homepage: www.springer.com/42947 Chinese Society of Pavement Engineering