# Using Plastic Waste in a Circular Economy Approach to Improve the Properties of Bituminous Binders
## 2 Materials and Methods
### Methods
#### 2.2.4 Characterization of Bituminous Binders  
The consistency at an intermediate service temperature of binders (needle penetration, P) was evaluated following the NP EN 1426 [51] standard, at a temperature of 25 \({}^{\circ}\)C, under the action of a load of 100 g applied for 5 s. The test equipment used was a UTEST-UTAS-0120 (Ankara, Turkey).  
According to standard NP EN 1427 [52], consistency at an elevated service temperature of binders was evaluated through the softening point ring and ball method (obtaining the temperature, \(t_{RaB}\), at which \(P\) = 800 \(\times\) 0.1 mm), in a UTEST-UTAS-0130 (Ankara, Turkey) equipment. This test method and the penetration test are not sufficiently representative of PMB's properties.  
The penetration index (\(I_{p}\)) can be calculated to measure the temperature susceptibility of binders and is obtained from the penetration values at two different temperatures or from the penetration at 25 \({}^{\circ}\)C and softening point. Equation (1) [53] (developed by [PERSON] and [PERSON]) is used in the latter case.  
\[I_{p}=\frac{20\times t_{RaB}+500\times\log P-1951.55}{t_{RaB}-50\times\log P+ 120.15} \tag{1}\]  
where \(t_{RaB}\) is the softening point (\({}^{\circ}\)C) and \(\log P\) is the logarithm (base 10) of the penetration @ 25 \({}^{\circ}\)C (0.1 mm). A bitumen with \(P\) = 200 \(\times\) 0.1 mm (at 25 \({}^{\circ}\)C) and \(t_{RaB}\) = 40 \({}^{\circ}\)C has an \(I_{p}\) equal to zero. Naturally, this index is also not representative of the PMB's properties due to the uncertainty of the variables required in Equation (1). However, the \(I_{p}\) for PMB was established to have an indication of the thermal susceptibility of this binder and to be compared with the limits specified in the standards (Tables 1 and 2).  
The steady shear viscosity or dynamic viscosity (n) can be obtained by using a rotating spindle apparatus, according to the European standard EN 13302 [54]. A correct indication of the measurement geometry for cylindrical spindles is given in Figure 2c. The equipment used was a Selecta-ST-2020R rotational viscosimeter (Barcelona, Spain), Figure 2b. The previous wax \(\rightarrow\) bitumen mixing was performed using a suitable high-shear mixer, Figure 2a, at a temperature of \(\approx\)150 \({}^{\circ}\)C, with speeds of 800/1250 rpm and a duration of just \(\approx\)10 min (in order to minimize the ageing effects).  
Using a Dynamic Shear Rheometer (DSR), the bituminous binders' complex shear modulus (G\({}^{\bullet}\)) and phase angle (\(\delta\)) were obtained, over a range of test temperatures at a fixed frequency, according to the European standard EN 14770 [55]. This test was carried out in the region of linear viscoelastic behaviour of the binder. In [56] can be found several correlations between dynamic test parameters for binders (on a DSR, using a sinusoidal oscillatory mode) and permanent deformation behaviour of bituminous mixtures (for example, in wheel-tracking tests, WTT). The equipment used (Bohlin Instruments-DSR II10 INT, Texas City, TX, USA.) and the procedure followed are presented in Figure 3. During the tests, the binder samples were conditioned in water (with controlled temperature).  
The results achieved in each of the tests described in this Section 2.2 and their discussion and comparison with some results of similar research published by other authors, are presented in Section 3.