In this study, the strength of hot and warm asphalt mixtures containing 3% Sasobite in cold regions has been investigated using the principles of fracture mechanics. The effect of temperature and loading modes (tensile and shear) on the fracture toughness of the mixture was investigated using a semicircular samples with an edge crack under three-point bending. The coefficient of critical stress intensity was determined from the results of the fracture test and the shape coefficients were determined from finite element analysis in ABACUS software. In hot and warm asphalt mixtures containing 3% Sasobite, with decreasing temperature, the critical stress intensity coefficient increased in tensile and shear modes. The results showed that the hot asphalt mixture at temperatures of 0, -10 and -20 °C presents significant fracture resistance compared to the warm asphalt mixture in all loading modes. As the temperature decreases, the fracture toughness of both types of both asphalt mixtures increases.

In the past few decades, warm mix asphalt (WMA) has been used as advanced technology alternative to hot mix asphalt (HMA) due to the relatively low temperatures required heating the asphalt in the production and application process, reducing environmental damage while providing benefits. Asphalt maintains the hot mix, it is noticeable. However, low manufacturing and processing temperatures may result in asphalt deterioration from moisture. The aim of this study was to evaluate the characteristics of asphalt containing natural zeolite and compare it with synthetic zeolite and WMA organic and chemical additives against deterioration against moisture. Resistance properties of samples against moisture sensitivity using tests.

Compared to typical hot-mix asphalt (HMA), Warm-mix asphalt (WMA) is produced at a lower temperature; therefore, it can be a good alternative for pavement located in cold climates. On the other hand, the low-temperature cracking is one of the main concerns of highways agencies in cold climates. Many different additives including fibers have been used for improving hot-mix asphalt performance; however, a few types of research have been conducted to investigate the effects of fibers on warm-mix asphalt performance. In this paper, warm-mix asphalt containing Sasobit and different percentages of natural and synthesis fibers (0.7%, 0.5% and 0.3% by weight of the total warm mix asphalt) were prepared by gyratory compactor. The cylinder specimens were cut to prepare semi-circular bending (SCB) specimens to determine the critical intensity factor (fracture toughness) of the warm-mix asphalt specimens. Using ABAQUS software the finite element analysis was conducted to determine the geometry factors and crack positions for pure tension (mode I), pure shear (mode II) and mixed modes (I/II). The cracked specimens were loaded at a constant rate (3 mm/min) at 0 oC, -10 oC and -20 oC until they were fractured; then the fracture toughness of each specimen was calculated. Analysis of testr esults indicated that the fracture toughness of warm-mix asphalt specimens containing natural or synthesis fibers increased when the temperature test decreased. In addition, the tests results showed that fracture toughness of warm mix specimens containing natural or synthesis fibers in mixed mode (with the same portion of tension and shear) and pure tension mode are higher than that of the control asphalt mixtures. However, this trend was not observed for loading modes with the higher portion of shear, especially for specimens containing natural fibers. Furthermore, in the same percentages of fibers, the effect of synthesis fibers to improve the fracture toughness of the mixtures was higher than that of the natural fibers.

The current study examined the properties of warm mixture asphalt (WMA), which contains nano- and polypropylene polymer (PP) polymers. Unmodified WMA and modified WMA both include 3% PP and NS (2–5%) by weight of asphalt respectively. The tests used to assess performance include the tests for fatigue resistance, rutting resistance, and moisture resistance. The results show that adding Nano-silica and Polypropylene enhances WMA performance. The results also show that adding polypropylene and nano-silica to asphalt as modifiers increases the asphalt's performance and durability.

The performance properties of bitumen and asphalt mixtures can be improved by using several modifiers, including: poly phosphoric acid (PPA1), semi-hot asphalt mixture modifiers (WMA2) and styrene butadiene rubber (SBR3). The present study evaluated the effect of PPA and WMA contents on the functional properties of SMA4 mixture. The modified SBR / PPA and SBR / PPA / WMA mixtures were subjected to indirect tensile strength tests (ITS5), dynamic creep, elastic modulus (Mr6), wheel path and four-point beam fatigue (FPB7). Two-factor analysis of variance (ANOVA8) was used to analyze the data. According to the results, the use of SBR and PPA increases the properties of Mr, grooved, ITS, FE and fatigue behavior of the samples. As the percentage of PPA increases, caries and fatigue behavior increase. While reducing Mr and IT’S of modified mixtures. Among hot additives, Sasobit has a better effect on increasing the performance of bitumen and mixtures.

The performance properties of bitumen can be improved by using several modifiers, including: polyphosphoric acid (PPA), semi-hot asphalt mixers (WMA) and styrene butadiene rubber (SBR). The present study evaluated the effect of PPA and WMA additives on the rheological behavior of SBR modified bitumen. Modified SBR / PPA and SBR / PPA / WMA bitumen were subjected to rotational viscosity, dynamic shear rheometer, multiple stress and creep recovery (MSCR) and linear slope sweep (LAS) tests. Based on the results of MSCR test at both stress levels, modification of the base bitumen by SBR, PPA and WMA additives improves the permanent deformation performance of the main bitumen. The results of LAS test showed that the use of SBR and WMA additives improves the fatigue life of bitumen. Also, by adding PPA, the fatigue life of SBR modified bitumen is increased. While the fatigue life is longer than the original bitumen. Among warm additives, Sasobit has a better effect on increasing the performance of bitumen.

Warm-mix asphalt (WMA), which reduces the production temperatures (mixing and compaction), while maintaining the advantages of hot-mix asphalt (HMA), is becoming an attractive paving material. In this study, rheological properties of two commonly used performance grade (PG) binders (PG 64-22 and PG 70-28) were evaluated, with and without Sasobit and Aspha-Min additives. For PG 64-22, 2%, 3%, and 4% Sasobit additive reduced the mixing temperature of the pure binder from 163°C to 147°C (i.e., by 16°C). In case of the PG 70-28, the reductions are 10°C, 12°C and 13°C, respectively, for 2%, 3%, and 4% Sasobit additive. No significant decrease in mixing temperature by the Aspha-Min additive was observed in using the rotational viscometer. Evaluation of the binders on the basis of G*/sin () demonstrates no negative effect on high-temperature grading due to high-temperature viscosity reduction. With the addition of 4% Sasobit additive, the high-temperature binder grading of PG 64 (actually PG 65) increases to PG 69, while 4% Sasobit additive improves the PG 70 (actually PG 75) to PG 80. No significant changes in grading were observed with the addition of the Aspha-Min additive. In fact, reduction in binder viscosity and improvement in binder grading with- out increasing the viscosity indicate two-way reductions (both direct and indirect) in production temperatures by the Sasobit additive. Finally, the Sasobit additive is found to decrease the asphalt pavement analyzer rut depths significantly, and these rut depths correlate well with the rutting factor G*/sin(). It was also observed that rutting potential decreases with decreasing mixing and compaction temperatures. Comparatively, a smaller reduction in rut depths was observed by adding the Aspha-Min additive.

The use of Reclaimed Asphalt Pavement (RAP) helps us save our natural resources and money. Of the different types of asphalt pavements that can be built, HMA pavements are considered the best in the terms of strength and durability. But the production temperature limits the amount of RAP used in the new mixture because this production`s high temperature requirement causes the deterioration of the aged binder of RAP and increases greemhouse gas emission. In the recent years there has been much focus on Warm Mix Asphalt (WMA) technology, because the aim of this approach is to reduce the production temperature by using additives which increase the workability of the binder at a lower temperature. The use of WMA additives helps us reduce the temperature while preserving the desired workability, thus enables HMA to contain higher percentages of RAP. The purpose of this experimental study was to evaluate the effect of production temperature reduction by using WMA additives on the performance properties of asphalt mixture containing 100% RAP. To reach this goal, five mixes were prepared and tested: a control mix (100% RAP-mixing temperature 150°C), three mixes with Sasobit, Rheofalt and without additives (mixing temperature of 130°C), and one virgin mix with extracted aggregate (mixing temperature of 160°C). The performance properties of the mixtures were evaluated based on indirect tensile strength, resilient module, four point beam fatigue test, and dynamic creep test etc. The results showed that the mixtures with WMA additives had better performance according to their moisture susceptibility and rutting potential, but the control mix had better performance in fatigue and low temperature cracking.

Half warm mix asphalt (H-WMA) is one of the alternatives to conventional asphalt due to its special production conditions.  Half warm mix asphalt (H-WMA) manufactured with high proportions of reclaimed asphalt pavement (RAP). Half warm mix asphalt (H-WMA) are produced and compacted at the temperature range of 60-100 ° C, which requires less temperature for production process of hot mix asphalt (HMA) for example cold mix asphalt (CMA) manufactured at a temperature lower than 60 ° C; (ii) half warm mix asphalt (H-WMA) manufactured at less than 100 ° C, normally at 60-100 ° C; (iii) warm mix asphalt (WMA) manufactured at temperatures of 100-140 ° C. The aim of this study is to investigate the effects of high percentages of reclaimed asphalt pavement (RAP) on the volumetric and mechanical properties of Half warm mix asphalt (H-WMA) mixtures. In this research, bitumen emulsion (CSS-1) and conventional bitumen 60/70 were used. The siliceous aggregates were obtained from a mine near Tehran and reclaimed asphalt pavement (RAP) were obtained from an asphalt plant and its granulation before and after extraction was done according to report number 234.  Generally speaking, in H-WMA, aggregates are heated to temperatures of 100-110 ° C and then mixed with emulsion, which has previously been heated to 60-80 ° C and RAP are heated to 90-100 ° C. To determine the most suitable mixing time in the tests, the coating was visually analyzed after mixing times of 1 and 2 min and the mixing temperature was 95-85 ° C. Thus, a laboratory analysis was carried out in which the behavior of half warm mix asphalt (H-WMA) manufactured with 100%, 70% and 0% reclaimed asphalt pavement (RAP) was compared with that of a control mix, Hot mix asphalt (HMA). Optimum bitumen content for hot asphalt mixture (HMA) and optimum bitumen emulsion content for half warm mix asphalt (H-WMA) were calculated. Then indirect tensile tests (IDT) (at 25° C), moisture damage (TSR) and Semi-Circular Bending (SCB) Tests (at 25° C and -20° C) were performed on half warm mix asphalt (H-WMA) and hot mix asphalt (HWA). indirect tensile tests (IDT) yielded acceptable results, the IDT resistance increased with increasing the reclaimed asphalt pavement (RAP) content. Following this, the moisture damage (TSR) of half warm mix asphalt (H-WMA) improves by increasing the reclaimed asphalt pavement (RAP) content, which can be due to the complete covering of the surface of the aggregates with aged bitumen and the high adhesion force between the aged bitumen and the aggregates and the lack of moisture penetration into the aggregates. emulsified bitumen exhibited proper volumetric (e.g., air voids and density) and mechanical behavior in terms of moisture damage and IDT. On the other hand, the results of SCB tests at medium and low temperatures showed that by increasing the RAP content the samples become brittle, which means that resistance to crack propagation reduced, and it may be the reason for fracture energy reduction. These findings encourage greater confidence in promoting the use of these sustainable asphalt mixes for their use in road pavements or urban streets.

To protect environment and reduce the consumption of energy, warm asphalt technology has been used widely in recent years. There are different technology to produce warm mix asphalt. In this research Zycotherm nano material and Sasobit, which are respectively chemical and organic additives, as two sorts of warm mix asphalt construction trends were investigated. Although having many advantages, moisture susceptibility and rutting performance are two major concerns about warm mix asphalt that was investigated in this study. The functional characterization of the base bitumen with and without Zycotherm was analyzed by means of Fourier Transform Infrared Spectroscopy (FTIR). Overall, fifty four hot and warm mix asphalt mixtures were made. In order to check moisture susceptibility, Indirect Tensile Strength and resilience modulus tests, and to evaluate rutting potential of the mixtures, dynamic creep test were conducted. Results showed that Zychoterm nano material, in addition to the reduction it causes in mixing and compaction temperature, also improves moisture susceptibility of mixtures compared to control mix and the mixture with Sasobit. On the other hand, Mixtures with Zycotherm nano material had lower flow number than HMA and Sasobit mixtures, Generally reduction in temperature leads to less oxidative and subsequently to less rutting resistance, however, as it was expected because of the stiffer Sasobit modified binder, WMA mixtures containing Sasobit had significantly higher resistance to rutting than other mixtures.