**3. Effect of pyrolytic rejuvenator on non-aged and laboratory aged bitumen**

After selecting the appropriate pyrolytic rejuvenator, the focus of the study was to evaluate its effect on paving grade bitumen. When reclaimed asphalt (with aged bitumen) is added to the new asphalt mixture, stone aggregate and a calculated amount of fresh (non-aged) bitumen are also added at the same time. Consequently, researches on non-aged bitumen and on laboratory aged bitumen were conducted. The short term ageing, to which bitumen is subjected during mixing, transport and installation of asphalt, is in laboratory simulated by rolling thin film oven test (RTFOT) method according to EN 12607 [27]. According to this method, bitumen is aged under the influence of high temperatures and constant air flow. The ageing conditions are not exactly the same as in asphalt production, but the ageing results are comparable [28]. Ongoing ageing of bitumen during road use was simulated by the pressure ageing vessel (PAV) method according to EN 14769 [29]. PAV ageing at elevated pressure and temperature was performed on RTFOT aged bitumen. PAV simulates ageing according to climatic conditions (temperature, UV, etc.), but cannot take into account variables in the asphalt, such as the proportion of air voids, the type of aggregate and the absorbency of the aggregate.

Blends of non-aged bitumen and pyrolytic rejuvenator were laboratory prepared in different concentrations: 3%, 5%, 10% and 20% rejuvenator based on the mass of the reference bitumen (**Table 3**). All prepared samples and concentrations of the blends are presented in **Table 3**.

In addition to before mentioned standard test on samples, determination of the sample's consistency by needle penetration test according to the EN 1426 [30] at 25°C was also performed. The elastic recovery of the samples was determined according to the EN 13398 [31]. According to this standard, a specimen was first elongated to 20 cm and then cut in the middle to obtain two halves of the thread. After the predetermined time (30 minutes) for recovery has elapsed, the shortening of the half threads was measured and expressed as the percentage of the elongation length.

To check the possible phase separation in the blend of bitumen and pyrolytic products, a storage stability test according to EN 13399 [32] was performed only for the blend of pyrolytic product No. 14 and reference bitumen. In the test, the sample of the blend is maintained in the vertical vessel at 180°C for three days. After the sample is cooled down, it is cut into three equal parts. The two ends (top and bottom) are further analysed to evaluate possible differences in characteristics. The affinity between pyrolytic rejuvenator and stone aggregate (limestone) was checked by standard rolling bottle method according to EN 12697–11 [33] and compared with the affinity of reference bitumen (non-aged) and the blend.

The properties of samples in the low-temperature range were characterized with the bending beam rheometer (BBR) according to EN 14771 [34]. Bending tests are suitable for testing brittle materials when measurements at tensile load do not provide insight into the properties of the material or are not feasible. The stress relaxation in bitumen is significantly slower at low temperatures, which can lead to the formation of cracks in the asphalt and loss of binder functionality. During the BBR test a bitumen beam is bent under a constant load and deformation of bitumen is measured. The flexural creep stiffness Sm(t) is calculated at time t = 60 s. The characteristic parameter is also value m60, the slope of the curve S (t) at t = 60 s, which indicates the relaxation capacity of the bitumen stress. We presumed that the adequate quality of bitumen at low temperatures is ensured by the maximum value of S60 = 300 MPa and the minimum value of m60 = 0.300.

The results of softening point, Fraass breaking point and penetration of reference bitumen (non-aged, 'B 50/70' and laboratory aged, 'B\_PAV'), pyrolytic rejuvenator 'PR' and their blends are shown in **Table 3**. Comparison of penetration and Fraass breaking point between 'B 50/70' and pyrolytic rejuvenator 'PR' indicates on their different chemical composition. Pyrolytic rejuvenator shows a significantly lower value of softening point and Fraass breaking point and at the same time a much higher value of penetration.


**Table 3.** *Tested blends of pyrolytic rejuvenator (labels, RB and penetration) [21].*

### *Rejuvenator Obtained by Pyrolysis of Waste Tires for Use in Asphalt Mixtures with Added… DOI: http://dx.doi.org/10.5772/intechopen.99490*

Results on non-aged samples show the effect of the rejuvenator on the standard mechanical properties (penetration, softening point, Fraass breaking point) of bitumen. Penetration values increased, at the same time softening values decreased with increasing rejuvenator proportion. All added amounts of rejuvenator to nonaged bitumen decreased the values of the Fraass breaking point.

Original B 50/070 was RTFOT+PAV aged, simulating naturally aged bitumen in reclaimed asphalt. Then the same proportions of pyrolytic rejuvenator No. 14 (as in the case of non-aged bitumen) were added and the blends were tested.

A comparison of non-aged and aged bitumen blends shows the impact of laboratory ageing. Aged B 50/70 (B\_PAV) and all bitumen blends became stiffer since the penetration of aged bitumen decreased and the softening point increased. Unexpectedly, all proportions of rejuvenator which were added to RTFOT+PAV aged B 50/70 decreased the values of the Fraass breaking point. It should be noticed that the repeatability of the Fraass breaking point test is 3°C.

**Table 4** presents results of tensile properties of bitumen, pyrolytic rejuvenator and their blends. Non-aged bitumen and its blends with rejuvenator elongated to the maximum length (1500 mm). The elongation of aged bitumen was prolonged with the addition of a rejuvenator. When mixing materials such as bitumen, two consequences can be observed: the mixing effect (mostly linear change) and the structural-interaction effect (mostly nonlinear change) [21]. Maximum force decreased proportionally with the added rejuvenator indicating a linear change occurred. The effect of nonlinearity is not observed, as the elongation at maximum force, Fmax, is the same for all samples with non-aged bitumen, as well as for all samples with aged bitumen, regardless of the amount of rejuvenator added. The elongation of the non-aged bitumen was about 1.5 times greater than the elongation of the aged bitumen with rejuvenator, indicating that aged bitumen was not completely restored. The results show that due to the added rejuvenator, the mechanical properties of aged bitumen approached the values of non-aged bitumen, but a complete restoration was not achieved.


### **Table 4.**

*Tested blends of pyrolytic rejuvenator (ductility, elastic recovery) [21].*


### **Table 5.**

*Results of rheological tests [21].*

The elastic recovery did not change significantly for non-aged bitumen regardless of the amount of rejuvenator. In the case of aged bitumen, the elastic recovery decreases with the amount of rejuvenator and thus approached the value of the reference aged bitumen. The elastic recovery of the rejuvenator had a negative value, so the sample was stretching after the test, meaning that the rejuvenator had no elastic properties and all energy was lost. We expected that due to rubber content in car tires some elasticity will remain in our product, but it is evident that all rubber from tires decomposed during the pyrolytic process.

Mixing and compaction temperatures (**Table 5**) of aged bitumen were higher than temperatures of non-aged bitumen, and in both cases, the temperatures decreased with the increasing amount of added rejuvenator.

S60 and m60 are criteria that determine the lower limit of the bitumen application temperature. When the conditions: S60 ≤ 300 MPa and m60 ≥ 0.300 are met at the same time, the bitumen shows sufficient low temperature resistance. **Table 5** shows the results, i.e. the minimum temperatures for all samples. For non-aged bitumen, the critical temperature was determined by S60, while for aged bitumen the temperature at parameter m60 was decisive. With the addition of the rejuvenator, the critical temperature was lowered. Aged bitumen with the highest amount of rejuvenator additive achieved similarly low temperatures as the reference non-aged bitumen.

Storage stability was checked only on a blend with the highest amount of pyrolytic rejuvenator, B50/70\_50%. The test results showed that although an immense quantity of the rejuvenator was added to the reference bitumen, the blend remained homogeneous. This was evident from the very small changes in the penetration and softening values of the binder in the upper and lower parts of the tube (**Table 6**). Results also show that due to storage at high temperature the characteristics (pen, RB) did not change much.

The result of the affinity test (**Table 7**) shows that after the first 6 hours there was no difference between the tested samples. The binder detached only slightly from the aggregate (limestone) in all samples. After one day of testing in the rolling *Rejuvenator Obtained by Pyrolysis of Waste Tires for Use in Asphalt Mixtures with Added… DOI: http://dx.doi.org/10.5772/intechopen.99490*


### **Table 6.**

*Results of storage stability test [21].*


### **Table 7.**

*Results of affinity test.*

bottle, differences between the samples appeared more obvious. The pyrolytic rejuvenator had the best affinity with aggregate. After two days, the reference bitumen and rejuvenator covered the aggregate equally well, and after three days the aggregate was best covered with pyrolytic rejuvenator and worst with a mixture of reference bitumen and pyrolytic rejuvenator.

To verify the relationship between rheological and mechanical measured properties, presented in **Tables 3–5**, linear relationships between individual properties were examined. Linearity between properties was evaluated with statistical parameter R2 (**Table 8**). The results show that there is no linear relationship between BBR measurements and empirical mechanical tests. Correlation between the parameters S60 and m60 and the Fraass breaking point was expected since all measurements were performed in the low temperature range. Similarly, we expected a relationship between the properties measured in the medium and high temperature range. The softening point temperature was compared with the mixing and compaction temperatures. It turned out that there is no linear correlation for the samples of non-aged bitumen, and there is a good linear dependence for the samples of aged bitumen. There is also a good relationship between the results of the two most basic mechanical tests, penetration and softening point, for both non-aged and aged paving grade bitumen samples.


**Table 8.**

*The R2 values for various properties of non-aged and aged bitumen with rejuvenator.*
