Browsing by Author "Baartman, Quinton"

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    Factors contributing to stripping and stone loss of ultra-thin friction courses, and their remedy.
    (Stellenbosch : Stellenbosch University, 2024-03) Baartman, Quinton; Jenkins, Kim J.; Stellenbosch University. Faculty of Engineering. Dept. of Civil Engineering.
    ENGLISH ABSTRACT: Asphalt surfacings are versatile and durable materials and gives a smooth and robust layer. These surfacings are commonly used in road construction, parking lots, and driveways. It provides a cost-effective solution with good resistance to wear and weathering. An ultra-thin friction course (UTFC) is an example of a functional surfacing. The functional requirements of UTFCs include providing a wearing surface, reduction in noise, increased wet skid resistance, and in-layer drainage. UTFCs can be opened to traffic faster than conventional hot-mix asphalt (HMA) and can accommodate high speed traffic better than conventional HMA. UTFCs are paved with a special self-priming paver. Asphalt mixtures would typically have voids percentages that range from 3- 5%. UTFCs are designed to be permeable with an increased percentage of voids, that can range from 12- to 20%. UTFCs are designed to last for 5 – 8 years. There are currently no guidelines on how to perform maintenance on UTFCs once it has come to the end of its life. This is the gap that this research is attempting to fill. The primary goal of this research was to establish whether it is worthwhile to perform maintenance on an open structure such as UTFCs. This research also aims to provide some guidance for UTFC maintenance. An arterial road in Gauteng was paved with an UTFC and premature failures of stripping and ravelling was observed. These failures are moisture induced. Moisture has a degrading impact on asphalt and causes the gradual breakdown of the mix integrity. The road was divided into five different sections (Sections A to E) and each section was treated with a different method. Three cores were taken from each section before the application of treatment as well as after treatment was applied. The applied treatment options were: • Section A: Ralumac used for rut filling (7 mm NMAS) followed by Ralumac overlay (5 mm NMAS) • Section B: Fogspray (0.5 l/m2) followed by Ralumac overlay (5 mm NMAS) • Section C: Fogspray (1 l/m2) • Section D: Onyx (2 x 1.1 l/m2) • Section E: Solvent based rejuvenator (0.34 l/m2) The primary testing method used in this research is permeability. The permeability testing involved, air-, Marvil-, and high-pressure permeability testing. The Marvil test, which is an in-field permeability test, was modified for laboratory environment. It was modified to only test for vertical permeability and to test horizontal and vertical permeability at the same time. The high-pressure permeameter (HPP) was developed by Stellenbosch University in 2016. The typical testing are pressures of 100- and 150 kPa. Computed Tomography (CT) scanning also formed part of this research, where void- and permeability analysis was performed. CT analysis aided in understanding the inner nature for the cores as well permeability correlations. Binder was extracted and recovered from the treated cores of Sections C, D, and E. Rheological testing of the binder was conducted using the bending beam rheometer (BBR) and the dynamic shear rheometer (DSR) and master curves were created. FTIR of the recovered binder was performed as well. These binder tests were included to investigate how rejuvenation methods impact binder performance and aging. The UTFCs were found to be more permeable horizontally as opposed to the vertically. In some cases, the samples were 100% of the flow contributed to horizontal permeability. Little to no permeability in the vertical direction speaks to the sealing off capability of the bond coat. The results mainly found that the Ralumac applications in Section A and B led to the most significant reductions in permeability, followed by Section C and D. Section E mainly caused slight to major increases in permeability. It was also found that the Ralumac treatment can be applied in the long-term maintenance of UTFCs, where stone loss has been initiated. This can then serve as a substrate for future overlays. The sprays in Sections C and D were found to be more useful in the short to medium term maintenance of UTFCs.