# Experimental Study on Physical and Rheological Properties of Trinidad Lake Asphalt Modified Binder
## 3 Results and Discussion  
### TLA Content Effect on Physical Properties of Modified Binders  
The physical properties determined for the TLA-modified binders are given in Table 3 and the following Figures 1-5. Generally, as expected, the test results presented in Table 3 show higher stiffness, higher softening temperature, and higher brittleness temperature obtained for all modified binders as compared to the base 35/50 bitumen. As shown in Figure 1, the penetration value depends on the TLA content; the base bitumen was stiffened by the addition of TLA. The penetration proportionally decreases with increasing TLA content to a level of less than 50%. The TLA concentration of more than 30% changes the grade of bitumen into 20/30 penetration. A 50.4% decrease of penetration was obtained for the 50% TLA-modified binder. The mixture Equation (1) was used to predict the penetration reduction of the modified binder. However, the calculated values were slightly lower than the measured values. Figure 1: Penetration of TLA-modified binders. Figure 3: Fraass breaking point of TLA-modified binders. Figure 2: Softening point of TLA-modified binders. Figure 2 shows that the softening point proportionally increases with increasing TLA content. For the 30% TLA-modified binder, the softening point is close to the upper limit of the service temperature under Polish climate conditions [43]; for higher TLA content, the softening point is above this limit. The softening point of TLA-modified binders was also determined by the mixture formula (2). The formula (2) does generally not fit measured values and the calculated values overestimate the measured ones. The softening point difference between calculated and measured values is proportional to the TLA content and increases with the TLA content. The Fraass breaking point for the modified binders is shown in Figure 3. It is in the range of \(-12\)\({}^{\circ}\)C to \(-8\)\({}^{\circ}\)C. The increase of the TLA content in base bitumen increases the Fraass breaking point accordingly. The only exception to that was the 20% content of TLA, where the Fraass breaking point is almost the same as the one with 10% TLA. The relationship between the Fraass breaking point temperature and the TLA content was established in the form of a quadratic equation with quite good correlation (R\({}^{2}\) = 0.975). The temperature plasticity range of the modified binders is in the range of 68.9 \({}^{\circ}\)C to 71.3 \({}^{\circ}\)C, which is only slightly higher than the range for the base bitumen (Figure 4). From these results, one can see that the TLA content has only a small effect on the plasticity range. All results are close to the most desired temperature range (about 80 \({}^{\circ}\)C), a conventional temperature range in which the binder exhibits the best viscoelastic behavior. However, the test results show higher softening temperature and higher brittleness temperature obtained for all modified binders as compared to base bitumen. The penetration index value was determined based on penetration at 25 \({}^{\circ}\)C and the softening point temperature. The IP values range from \(-0.39\) to \(-0.14\) (Figure 5). All of the tested binders have an IP value falling within the range recommended in the European  
Figure 4: Plasticity range of TLA-modified binders. Figure 5: Penetration index of TLA-modified binders. standard [25], i.e., from \(-1.5\) to \(0.7\). However, the binders modified with 10% and 20% of TLA content has an IP value slightly higher (\(-0.14\)) than the rest of the bitumen; they have an IP value in the range of \(-0.32\) to \(-0.40\), similar to the base bitumen. The addition of 10% to 20% of TLA by weight has a good effect on IP value because the increase of IP in the modified binder causes a decrease of temperature susceptibility of bitumen, which is beneficial in terms of deformation resistance of pavement.