Desempenho mecânico de uma mistura composta por solo e cinza têxtil para fins de uso na pavimentação

Abstract

Industrial solid waste, especially that generated by the textile industry, represents a serious environmental problem due to its high volume and inadequate final disposal, which often occurs through landfilling. This accumulation negatively impacts the environment and wastes a material that could be reused in engineering applications. In this context, it becomes necessary to seek alternatives for the reuse of such waste, combining sustainability with technical efficiency. At the same time, the increasing demand for materials used in pavement construction, together with the scarcity of high-quality natural resources near construction sites, has encouraged the search for technical and environmentally sustainable solutions. Within this framework, this research aimed to analyze the technical feasibility of using a soil–textile ash mixture as an alternative material for pavement layers by evaluating its physical, chemical, and mechanical properties when incorporated into sandy soil. The ash used originated from combustion in ceramic kilns at Cerâmica do Liro in Russas, Ceará, Brazil, while the soil was collected from a rural road in the same municipality. The methodology included the application of the Modified Andreasen particle packing model in order to optimize the granulometric curve of the mixture, in addition to laboratory tests for characterization and performance evaluation. Different waste incorporation contents were also tested, and the method was used to determine the optimum content. Hygroscopic moisture, Atterberg limits, particle size distribution by sieving and sedimentation, specific gravity of grains, compaction, and California Bearing Ratio (CBR) tests were performed. The proposed optimized mixture consisted of 70% sandy soil and 30% textile ash, a proportion defined based on the theoretical particle packing curve. The results indicated that both the soil and the ash exhibited non-plastic behavior, low hygroscopic moisture content, and were classified as silty sand (SM) according to the Unified Soil Classification System (USCS). The specific gravity of the grains of the mixture was 2,720 kg/m3, a value considered satisfactory for geotechnical applications. In the compaction tests, the soil–ash mixture presented a maximum dry unit weight of 19.14 kN/m3 and an optimum moisture content of 8.60%, demonstrating good compactability with low moisture content. The CBR values of the samples ranged from 46% to 83%, all exceeding the minimum requirement established by DNIT standards (≥ 20%) for subbase layers. The expansion by immersion ranged from 0.0% to 0.2%, indicating volumetric stability. Therefore, it is concluded that the soil–ash mixture, particularly at the proportion of 30% ash, represents a technically and environmentally suitable alternative, promoting the reuse of industrial waste, contributing to the circular economy, and reducing environmental impacts associated with the improper disposal of textile ash.