It is really necessary for investigating the influencing factors in tropical countries on roads constructed with asphalt mixtures and to know the sensitivity of this mixture in semi-warmed areas. Layers shall be constructed in bituminous mixtures containing asphalt with an acceptable degree of hardness to increase resistance to permanent deformation or rutting. When the existing asphalt is not hard enough, the solution is to modify the asphalt with gilsonite. This paper presents laboratory results from tests conducted on samples of hot asphalt mixes modified with gilsonite in both wet and dry processes Gilsonite increases the hardness and workability of unused bitumen at high temperatures. In addition, gilsonite-modified hot asphalt mixtures provide improved strength and stiffness under uniform and dynamic loading. According to Saganom (1999), natural asphalts are solid-state bituminous materials, containing high molecular weight hydrocarbons in layers ranging from a few centimeters to tens of meters in thickness. 
These materials exhibit a variety of hardness properties, such that their melting points can range from 100°C to more than 300°C. Natural asphalts exhibit high softening points (above 90°C) and are internationally recognized as asphalt treatment materials due to their high content of asphalt. One of the most commonly used natural asphalts for modifying hot mix asphalt properties is Trinity Lake Asphalt (TLA). According to Kim et al. (2013), TLA is a high viscosity asphalt that offers high resistance against permanent deformation and provides durability by using asphalt mixtures as one of its components. The first documented use on roads appears in Port, Spain, in 1815, and the material was used as an asphalt binder for the paving of several roads in the United States. For example, tropical South America has a tropical climate. Roads with asphalt layers in these countries should be constructed with asphaltic bituminous mixtures strong enough to increase resistance against permanent deformations, i.e. despite this requirement for rutting, the highest strength asphalt cement (AC) used in Colombia and other countries is AC 60–70 [performance grade (PG). This asphalt is not strong enough to withstand the occurrence of rutting in high temperature regions. Another way to improve asphalt stability is to modify the asphalt with the help of gilsonite (G).
Colombia has several natural deposits of gilsonite-type asphalt. The deposits occur chiefly in the divisions of Boyacá, Caqueta, Caldas, Cundinamarca, Tolima, Santander, and Caesar. Gilsonite is one of the highest purity natural asphalts and has low fixed carbon and low sulfur content. Rond´on and Reyes used this material to fabricate an asphalt-concrete mix and evaluated its properties under monotonic dynamic loading. The results in their study showed that asphalt mixes modified with gilsonite using a wet process, i.e. adding gilsonite to asphalt cement, produced stronger asphalt concrete mixes, leading to the conclusion that these mixes would do better in warmer climates Stability and Marshall hardness values of the modified mixtures were higher for all percentages of asphalt and gilsonite than the reference mixture, that is, without gilsonite. Resistivity units of modified mixes were better than parameters found for reference mixes, larger increases were obtained on increasing test temperature These results indicated that gilsonite, as asphalt modifier, can be used to improve stiffness characteristics and resistance to permanent deformation of mixes used in hot climates prepared Alaskan asphalt cement with gilsonite using the wet process with percentages between 12% reported similar findings.
Esfeh found that the addition of gilsonite to asphalt helps increase viscosity, reduce penetration and strengthen bonding. Amery and his friends. (2011), based on rheological characterization tests, reported that in terms of mass of asphalt, from the modification of two asphalts (PG 58-22 and PG 64-22) with gilsonite at percentages of 4, 8, and 12% , the performance grade of the two asphalts at the improved higher service temperature; however, these additional factors reduced the low-temperature performance range. Since gilsonite-modified asphalt exhibits brittle behavior at low service temperatures, crack generation can occur. Anderson et al. (1999) reported a similar phenomenon. Yilmaz and his colleagues. (2013) reported a significant increase in stiffness under cyclic loading, resistance against permanent deformations, and fatigue resistance of hot mix asphalts when 3% gilsonite was added in terms of mix load, although it reduced a plus brittle and causes elastic character to show . In this study, gilsonite replaced part of the filler mineral. Through rheological characterization tests on styrene-butadiene-styrene (SBS) modified asphalt, Köket al. (2011) reported that gilsonite can be used to reduce the manufacturing cost and strength of asphalt mixtures. In addition, based on the Marshall test method, dynamic modulus test, indirect tensile strength test, and dynamic creep test applied to gilsonite-modified hot mix asphalts, Kök et al also increased stiffness under cyclic loading with resistance to moisture with reported damage and freeze-thaw cycles and permanent deformation resistance.
In addition, these researchers found that gilsonite-modified mixes reduced the optimum asphalt content in mix formulation by 1%, reduced asphalt mix production costs Strength and durability of road, bridge, and tunnel structures built with TLA-modified asphalt layers Through the analysis of Charles and Grimaldi (1997) concluded that the larger thicknesses required less maintenance of these structures when applying this technique and offered the possibility of reducing the design. Cholewinska and Ivanski prepared asphalt with 50–70 (0.1 mm) penetration with 5, 10, and 15% percentages of gilsonite in terms of total mass of asphalt These authors significant decrease in penetration and viscosity of modified asphalt due to increasing gilsonite content reported an increase in and an increase in softening point.
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