Abstract
Warm mix asphalt (WMA) technologies allow significant lowering of the production and paving temperature of the conventional hot mix asphalt (HMA), which promise various benefits, e.g. lowering the greenhouse gas emissions, reduction of energy consumption, improved working conditions, better workability and compaction, etc. However, in order to reach widespread implementation of WMA, it is necessary to prove that it has the same or better mechanical characteristics and long-term performance as HMA. This article presents a laboratory study that has been conducted to evaluate two different WMA technologies – chemical (using Rediset WMX) and organic (using Sasobit) for the use with stone matrix asphalt (SMA). The properties of two types of bitumen after modification with two different dosages of each WMA additive have been tested by traditional empirical test methods and with the Dynamic Shear Rheometer for a wide temperature range. Asphalt testing has been performed for SMA11 type mixture. At first, the necessary changes in testing conditions were determined by means of asphalt stiffness – the results suggested that for adequate comparison with reference HMA, at least two hour asphalt aging is essential before preparing test specimens. The properties of asphalt were determined for specimens that were prepared at four different compaction temperatures by means of two compaction methods – Marshall hammer and gyratory compactor. The test results show that it is possible to reduce the compaction temperature of 155 °C for HMA to at least 125 °C for both WMA products with maintaining similar density and mechanical characteristics at intermediate to high temperatures.
Highlights
The modern warm mix asphalt (WMA) technologies have the potential to reduce production temperature by 20 °C up to 40...50 °C from the conventional hot mix asphalt (HMA) and have a potential to do this without affecting the performance of asphalt (Čygas et al 2009; Hurley, Prowell 2006)
Tasks of the research The aim of the research is to investigate the changes in bitumen consistency after modification with WMA additives, to determine the physical-mechanical properties of asphalt after reduction of compaction temperature and to compare the characteristics of WMA with those of conventional HMA
In order to determine the visco-elastic behaviour of bitumen after modification with WMA additives, testing has been performed with conventional testing methods and the Dynamic Shear Rheometer (DSR) according to the testing plan provided at Fig. 2
Summary
The modern warm mix asphalt (WMA) technologies have the potential to reduce production temperature by 20 °C up to 40...50 °C from the conventional hot mix asphalt (HMA) and have a potential to do this without affecting the performance of asphalt (Čygas et al 2009; Hurley, Prowell 2006). Not all of the techniques provide similar asphalt performance as for HMA, the WMA design process should involve empirical characterization of asphalt and a careful analysis of bitumen and the performance properties of asphalt at different temperatures. The test methods and evaluation criteria may require adjustment in some cases. This laboratory study has been conducted to evaluate Fischer-Tropsch wax and one of the available chemical additives
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