Estudo do envelhecimento térmico e fotoquímico de cimento asfáltico de petróleo por técnicas analíticas

Abstract

The construction of roads and highways is an activity that has been going on since antiquity. Knowing the chemical composition of asphalt is relevant for the elaboration of materials with higher quality and durability. The first chapter of this work consists of a study of raw CAP, aged by RTFOT. After these aging methods, part of the samples were submitted to heating in an oven at 80 ºC for 5, 10 and 15 days and another group to ST aging also for 5, 10 and 15 days. It was possible to obtain a characterization of the samples and observe that oxidation reactions occur during aging. However, the oven times varying in 5, 10, and 15 days did not present linearity in the data obtained, showing that this study for raw samples would not be so recommended and possibly, the temperature of 80 ºC could not be high enough to visualize the aging reactions. For an isolated understanding of the transformations that occur in the molecules present in the CAP composition, a study was carried out involving the thermal aging of 15 patterns of compounds present in the CAP, representing the saturated fractions (hexatriacontane, 5-α-cholestane), aromatics (hexamethylbenzene, coronene, and benzo[a]anthracene), nitrogen compounds (acridine, carbazole, bis(dicarboximide)), indole sulfur and compounds N,N′-Bis(3-pentyl)perylene-3,4,9,10 ( 2-naphthalenethiol, 4,6 diethyldibenzothiophene, and NDT) and acids (stearic, pentadecanoic and sinapinic acid). The thermal aging of the samples occurred in two ways: i) fixed temperature of 80 ºC, varying the time from 0 to 60 days, and ii) temperature varying from 80 to 140 ºC for a fixed time of 15 days. Sample analyzes were performed by FT-ICR MS, GC/MS, and 1H and 13C NMR. With the temperature fixed at 80 ºC, of the 15 standards studied, only the indole sample showed the presence of products generated during aging, after 15 days. With the temperature fixed at 80 ºC, of the 15 standards studied, only the indole sample showed the presence of products generated during aging, after 15 days. With a study varying the temperature and setting the time, from 100 ºC, 6 of the 15 patterns began to show the presence of products generated in aging, this behavior is more aggravated at the temperature of 140 ºC, where 11 of the 15 patterns showed the presence of aging products. This work demonstrates the degradation reactions (hexatriacontane, coronene, stearic, pentadecanoic and sinapinic acids), oxidation (hexatriacontane, indole, N,N′-Bis(3-pentyl)perylene-3,4,9,10-bis( dicarboximide), 4,6-diethyldibenzothiophene), polymerization (hexatriacontane, 2 naphthalenethiol, stearic, pentadecanoic and sinapinic acids), dehydrogenation (5-α cholestane), in addition, to complete volatilization (5-α-cholestane and hexamethylbenzene). The acridine, NDT, carbazole, and benzo[a]anthracene samples did not show any form of thermal aging products in the analyzes performed. The third chapter consisted of the application of the study of patterns in real samples, using the CAP samples carried out in the study of the first chapter, virgin and aged by RTFOT and RTFOT+ST. Analyzes were performed by FTIR and FT-ICR MS and the results showed that all fractions (including saturated and aromatic) showed the presence of oxidation with increased C=O bands and the presence of oxygenated classes. From these results, it was possible to propose the oxidation mechanisms of all classes