Evaluation of the rheological properties of recovered seal binders

Lingenfelder, Tanya (2022-04)

Thesis (MEng)--Stellenbosch University, 2022.

Thesis

ENGLISH ABSTRACT: Bitumen is a complex material that behaves differently depending on the temperature and loading conditions. The ageing of bitumen is an important consideration that influences the durability of a pavement structure. The South African pavement industry is currently transitioning towards a Performance Grade (PG) specification. The PG specifications were developed in the USA and only provide requirements for the evaluation of bitumen performance in asphalt layers. In South Africa, seals are used more frequently than asphalt. Therefore, there is a necessity to develop a seal binder recovery procedure, to gain insight regarding the rheology of South African seal binders and determine to what extent the PG requirements must be altered in order to be applied to seal binders. This study utilises a recommended seal binder recovery procedure and aim to evaluate the consistency of the rheological properties of the recovered seal binders The recommended seal binder recovery method was used to extract bitumen from in-situ seal samples. Various laboratory test, such as the Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), and Fourier-Transform Infrared Spectroscopy (FTIR), were performed to gain an understanding of the physical and chemical performance of the recovered binders. The precision values for penetration and softening point, provided in EN 12697-3 (2013), were used to compare the durability parameters (G-R, Gvet, Tvet, Tmax, and ΔTc) of binders recovered from the same seal. The durability parameters of younger binders (less than 6 years old) revealed that G-R and Tvet experienced the most variability and did not comply with the recommended specifications. The durability parameters of the older binders (6 years +) experienced less variability, since all complied with the recommended specifications. Where variability is present in the 8 mm DSR data, the G-R and Tvet did not comply with the proposed evaluation criteria. Similarly, variability in the 25 mm DSR and BBR data corresponded with inconsistencies in Tmax and ΔTc values, respectively. The FTIR absorbance revealed that all of the recovered binders had distinct peaks at two wave numbers (1030 cm-1 and 1460 cm-1). The peak areas at 1030 cm-1 appeared to correlate for both repeatability and reproducibility samples. The heights of the peaks at 1460 cm-1 varied, where binders recovered with a toluene-ethanol blend experienced a lower peak, while binders recovered with trichloroethylene, experienced higher peaks. Binders recovered with the toluene-ethanol blend experienced a peak at 1700 cm-1 and a more distinct peak at 1600 cm-1. The wave numbers where binders, recovered using trichloroethylene, experienced peaks varied between 1720 cm-1 and 1560 cm-1.

AFRIKAANSE OPSOMMING: Bitumen is 'n komplekse materiaal wat die vermoë het om verskillend op te tree, afhangende van die temperatuur en ladingstoestand waaraan die materiaal blootgestel is. Die veroudering van bitumen is 'n belangrike faktor wat die duursaamheid van 'n plaveiselstruktuur beïnvloed. Die Suid-Afrikaanse plaveiselbedryf is besig om oor te skakel na 'n Werksverrigtingspesifika- sies. Hierdie spesifikasies is in die VSA ontwikkel en verskaf slegs vereistes vir die evaluering van bitumenprestasie in asfaltlae. In Suid-Afrika word seëls meer gereeld as asfalt gebruik. Daarom is daar 'n noodsaaklikheid om 'n seëlbindmiddelherwinningsprosedure te ontwikkel om insig te verkry rakende die reologie van Suid-Afrikaanse seëlbinders en te bepaal tot watter mate die nuwe spesifikasie verander moet word sodat dit op seëlbinders toegepas kan word. Hierdie studie gebruik 'n aanbevole seëlbindmiddelherwinningsprosedure en het ten doel om die konsekwentheid van die reologiese eienskappe van herwonne seëlbinders te evalueer. Die aanbevole seëlbindmiddelherwinningsmetode is gebruik om bitumen uit in-situ seëlmonsters te onttrek. Verskeie laboratoriumtoetse, soos die Dynamic Shear Rheometer (DSR), Bending Beam Rheometer (BBR), en Fourier-Transform Infrared Spectroscopy (FTIR), is uitgevoer om 'n beter begrip van die fisiese en chemiese werkverrigting van die herwonne bindmiddels te verkry. Die evalueringskriteria vir penetrasie en versagtingspunt, soos verskaf in EN 12697-3 (2013), is gebruik om die duursaamheidsparameter (G-R, Gvet, Tvet, Tmax en ΔTc) van bindmiddels, wat van dieselfde seël herwin is, te vergelyk. Die duursaamheidsparameters van jonger bindmiddels (jonger as 6 jaar oud) toon aan dat G-R en Tvet die meeste variasie ervaar het en nie aan die aanbevole spesifikasies voldoen het nie. Dit blyk dat die duursaamheidsparameters van ouer bindmiddels (6 jaar +) minder variasie ervaar, aangesien al die duursaamheidsparameters aan die aanbevole spesifikasies voldoen het. Waar wisselvalligheid in die 8 mm DSR-data voorkom, het G-R en Tvet nie aan die aanbevole spesifikasie voldoen nie. Variasie in die 25 mm DSR data stem ooreen met verskille in Tmax, terwyl variasie in die BBR data korreleer met ΔTc wat nie aan die aanbevole spesifikasie voldoen nie. Die FTIR-absorbansie het aangedui dat al die herwonne bindmiddels duidelike pieke by twee golflengtes (1030 cm-1 en 1460 cm-1) ervaar. Die piekareas by 1030 cm-1 korreleer goed. Die hoogtes van die pieke by 1460 cm-1 varieer. Bindmiddels wat met 'n tolueen-etanolmengsel herwin is, ervaar laer pieke, terwyl bindmiddels wat met trichlooretileen herwin is, hoër pieke ervaar. Bindmiddels wat met die tolueen-etanolmengsel herwin is, het 'n piek by 1700 cm-1 en 'n meer duidelike piek by 1600 cm-1. Die golfgetalle waar bindmiddels wat met trichlooretileen herwin is, pieke ervaar, wissel tussen 1720 cm-1 en 1560 cm-1.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/124593
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