Avaliação dos procedimentos para determinação de teor de ligante e granulometria em concretos asfálticos de diferentes faixas granulométricas e origens mineralógicas

Abstract

The verification of binder content and granulometry of asphalt mixtures are of great importance in the technological control of the construction process. These ensure a good performance of the pavement in its useful life. In order to obtain the binder content, the bitumen extraction test standard DNER ME 053/94, which is a low cost and simple procedure, is carried out. A more accurate alternative is the ignition method, with no current brazilian standard, with american standards ASTM D 6307:2010 where ignition furnaces are used. The granulometric analysis has the brazilian standard DNER-ME 083/98, and can be carried out with final samples of binder extraction. Rocks of different mineralogical origins of Rio Grande do Sul were used. CAP 50-70 was used for the mixtures in all the rocks, besides one using PMB 60/85. For each one of the 6 rocks, 30 samples were prepared for the ignition method and 30 samples for the centrifugal extraction using two DNIT granulometric ranges, B and C, with 15 samples for each range, 5 for each variation of binder content: a trace with design content and 2 more traces with greater and lesser amount of binder in relation to the designed. After each extraction, the granulometric analysis of each sample was performed. The convection ignition furnace presented good results in its two standardized methodologies, A and B. The calibration factor used was confirmed as a fundamental part to guarantee the accuracy of its results with the current methodology. The CF factor compensates the loss of mass of the aggregate during the process of burning the sample in the furnace, where each aggregate has a distinct need for correction due to mineralogical differences. It was indicated in the research an alternative to the current methodology, composed of equations obtained by linear regression of the raw data of binder content of the ignition furnace, being independent of the calibration phase. The results of binder content and granulometry showed greater dependence of the mineralogical origin of the aggregate used in the mixture. Samples with CAP 50-70 and AMP 60/85 differed in the CF values in the oven data, with values lower than those of the mixtures with the conventional binder. In the case of the centrifuge, mixtures with AMP 60/85 showed a drop in efficiency compared to CAP 50-70. The ignition furnace data showed good response to variations in binder content in the mixes. The binder content obtained with the centrifuge did not present a good response in the different variations of the mixtures imposed on the research, with low accuracy and also low precision. Incomplete extraction of the binder from the centrifuge caused a direct change in the binder content and distortion in the grain size curves provided by the post-extraction samples. In the data of the centrifuge neither patterns nor results were observed that point to the absorption as a preponderant factor in the data of binder content and granulometry. The variation of binder content in the mixtures had a great influence on the data obtained in binder content and granulometry of the centrifuge: mixtures with low binder content showed values above the design content and mixtures with binder addition presented results below the design content. The ignition furnace is indicated as a great alternative to the method that uses the centrifuge because it presented data with high accuracy and precision in obtaining binder content and granulometric analysis.