Uso de suelos estabilizados con emulsión asfáltica como parte de la estructura vial en carreteras terciarias y vecinales

Abstract

The present investigation takes a closer look to the viability of the use of bitumen emulsion as a stabilizer in low traffic roads, which commonly contain a gravel and clay layer conforming the surface of the road. This study was developed in the province of Azuay and the data studied was handed by the province’s Prefecture. With the main goal of analyzing the viability of said technique of stabilization, two kinds of criteria were adopted. The first criteria focused on researching the state of art regarding emulsion stabilization; with studies of the stabilization, technical standards (norms) and real application cases of the technique in the region. The second criteria focused on rating the functional and structural performance of previously constructed roads in the province. In regard of the functional performance, the Pavement Condition Index (PCI) was chosen. In this test, distresses are identified visually and roads are rated with a number according to the condition of the pavement. Meanwhile, the structural test consisted in the measurement of deflections in the roads, using the Benkelman beam. To achieve this study, two roads were taken into consideration, one being the Ricaurte-Llacao road, and the other the Monay-El Valle road; the two of the roads were stabilized in early 2019. The results obtained with the application of the criteria showed some variety. According to bibliography studies, this technique has been used in the country and the region, especially in low traffic roads where by increasing the capacity of the granular layers, low thickness surface layers can be used. According to various standards, the use of some soils is restrained for its use in stabilization, especially in liquid limits with maximum values between 20 and 40, and plastic index with maximum values between 9 and 18. However this is a field where it is recommended to deeply analyze each case in order to find the real enhancement of the soil. According to the second criteria, results obtained in the performance assessments show that, in the functional evaluation, the Ricaurte-Llacao road’s PCI is 48, which is classified as “Fair”, and the Monay-El Valle road’s PCI is 60 corresponding to “Good”. By analyzing the type of distresses and its causes, it was found that most of the failures depended on other factors as the surface layer or an overload of traffic. The structural evaluation, in the other hand, showed that recoverable deflections were below the threshold of acceptable deflections exposed by various authors. Structural numbers of stabilized layers were calculated too. This gave a result of 1.17 for a layer thickness of 10 cm, and 1.77 for a layer thickness of 15 cm; these two higher numbers than the obtained with a normal base course layer. Finally, by applying an economic analysis, comparing the stabilized material and a base course layer, it was shown that the stabilized material offers a lower price comparing layer thicknesses that offer the same structural strength. Therefore, after studying all of the criteria, it can be concluded that the stabilization with bitumen emulsion is a good choice, but it is important to count with tests that help to quantify the enhancements achieved by the stabilization of the soil.