Análisis de Ciclo de Vida comparativo de pavimentos en la Ciudad de México

The objective of this thesis is to quantify and analyze the environmental impacts of three different rehabilitation methods proposed for the roads of Mexico City's (CDMX) primary network and compare them with the current procedure for determining the feasibility of introducing different rehabilitation alternatives based on a Life Cycle Assessment (LCA) approach, based on the ISO 14040 and 14044 methodologies. This objective seeks to improve the efficiency and environmental performance of construction processes in Mexico City, thus working towards the sustainable development objectives set by the United Nations and promoting the circular economy.
Each of the four different rehabilitation methods discussed in this document are called scenarios. The Base Scenario (zero) represents the current form of pavement preservation in Mexico City: partial milling (seven centimeters deep) and replacement of the surface course, while the other three scenarios propose alternative methods for replacing the current process. These three proposed scenarios consist of the following: Scenario 1: total milling and replacement of the surface course, considering a thickness of 15 centimeters as a representative thickness of the roads of the primary network of the CDMX. Scenario 2: Cold recycling (Full Depth Recycling) and Scenario 3: Hot in-place recycling and replacement of the surface course by means of heating panels by burning propane gas. The Functional Unit is defined as the conservation of the surface course of 1 km-lane of main road in Mexico City with 3.5 meters wide, without curves, exits or incorporations and during a study period of 30 years. The scope of the systems considers the entire Life Cycle of the rehabilitation of the surface course: from the first extraction of raw materials to the last removal and final disposal of the residual material 30 years later, taking as a starting point for all scenarios the previous existence of a road with damage to the entire depth of the surface course.
Of the four systems evaluated, it was observed that the Base Scenario achieved the worst environmental performance for all impact categories evaluated, mainly due to its short service life, because of the deep cracks that persist under the surface course when partial milling is performed. The scenario with the lowest environmental impacts turns out to be Scenario 3, Hot In-place Recycling, thanks to the highly specialized machinery that can unify several tasks into a single equipment. In addition, two sensitivity analyses are performed to evaluate the changes presented by the four scenarios, the first considering a partial recycling of the milled asphalt and the second to assess the environmental impact on the climate change impact category of Scenario 2: cold recycling, modifying the dosage of the quicklime used. These sensitivity analyses conclude that partial recycling significantly improves the environmental performance of the Base Scenario, and in less quantity to the other three scenarios evaluated. On the other hand, it was observed that the dosage of lime has a significant impact on the environmental performance of Scenario 2, without which its impact on the climate change category is cut in half. Finally, an economic analysis of the various alternatives was carried out, evaluated using the Life Cycle Cost Analysis methodology, using the procedure proposed by the United States Asphalt Pavement Association, which concludes that the scenario with the highest long-term costs is the Base Scenario, but is preferred by authorities since it has low short-term costs (less than 6 years).