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CIR of surface courses : A Gap analysis of RAP gradation characteristics

Arling, Milan (2025) CIR of surface courses : A Gap analysis of RAP gradation characteristics.

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Abstract:Globally, the recycling of construction and demolition waste (CDW) has become an important element in the construction industry. The road industry, in particular, has adopted this element very well. In the Netherlands, recycling rates of up to 100% are reached regarding Reclaimed Asphalt Pavement (RAP). However, in the case of surface courses, this RAP material is mostly recycled in the form of Hot Mix Asphalt (HMA). This requires a considerable amount of energy compared to Cold Mix Asphalt (CMA), which is undesirable. However, partly due to the material properties of RAP, CMA’s with 100% RAP are unsuitable for surface courses. NTP, a Dutch innovative and sustainable operating company in the Grond-, Weg- en Waterbouw (GWW) sector wants to find a way to ensure that cold in-situ recycling (CIR) can be applied to surface courses and potentially be able to define what asphalt pavement surfaces are eligible for this rehabilitation treatment. This study focuses on improving the gradation characteristics of RAP material by performing a gap analysis. In this gap analysis, the state-of-practice regarding cold milling equipment and processes and their impact on RAP gradation is identified. This is done through a systematic literature review and a sieve analysis performed in accordance with NEN-EN 12697-2. This RAP gradation is then compared to the regulations defined in the NEN-Norms and the CROW Standaard RAW bepalingen 2020, to define the quality gap. Based on this quality gap, solutions for improving the RAP gradation and ultimately bridge the quality gap are identified. These solutions are then evaluated based on their potential effectiveness to bridge the quality gap. For the most suitable solution, an impact analysis was performed. In this study, it was found that the current cold milling equipment and process caused high RAP clustering, leading to the material being too coarse graded compared to the regulations. CIR can either be applied with a single-unit train or a multi-unit train, with solutions including optimizing travel speed and drum configuration (pick spacing and cutting direction) for the single-unit train, and adding a mobile crushing and screening unit for the multi-unit train. Additionally, two other hypothetical solutions were identified: Ultrasonic vibrations and steam induced asphalt-aggregate segregations. However, these solutions were not tested and developed sufficiently to be applied in the field. Of the other two options, optimizing the operating parameters and the drum configuration appeared to be the best option based on expert opinion and equipment availability. Reducing the travel speed and the pick spacing while ensuring a down-cutting motion of the milling drum, can result in a finer graded RAP material. In the impact analysis, it was concluded that if the assumptions for the effect of the travel speed and the pick spacing are accurate, the gradation of RAP material will be in accordance with the regulations in most scenarios. This suggests that this solution can potentially effectively reduce the effect of clustering and thereby improve the RAP gradation. To improve the accuracy of the results, the effect of the operating parameters and drum configuration has to be further researched. Additionally, it has to be determined if the resulting RAP gradations are of sufficient quality to create a CMA, which is in accordance with the required performance properties defined in the Standaard RAW bepalingen 2020.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Programme:Civil Engineering BSc (56952)
Link to this item:https://purl.utwente.nl/essays/106050
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