Uso de agregado reciclado de resíduos de construção e demolição na estabilização de um solo siltoso melhorado com cimento para aplicação em base de pavimentos urbanos

Abstract

The present study aims to evaluate the use of recycled aggregate (RA) from construction and demolition waste (CDW) in the performance of a silty soil from the Guabirotuba Formation improved with cement and to analyze its use in the base layer of urban pavements. Unconfined compressive strength (UCS) tests were performed with RA contents of 10%, 20% and 30%, combined with 5% cement by dry weight of soil, at curing times of 0, 7, 14 and 28 days, and with different compaction efforts. Several parameters, such as RA content, compaction effort, maximum dry specific mass (ρd max) and porosity/cement volume (η/Ciυ) were considered. Scanning Electron Microscopy (SEM) tests were performed to complement the analyses. Furthermore, the study analyzed the resilient behavior and permanent deformation (PD) of silty soil stabilized with cement and RA. Finally, the use of these materials as a base layer for urban pavements was analyzed by means of dimensioning using the MeDiNa method. The results showed that the addition of RA resulted in an increase in the maximum dry specific mass, directly correlating with the increase in UCS over time. In particular, for the modified compaction effort, the mixture with 30% RA reached UCS of approximately 2.300 kPa at 28 days, which represents a value 35% higher than the mixture without RS, which presented RCS in the order of 1.700 kPa. Equations establishing the relationship between η/Ciυ and RCS indicated that lower values of η/Ciυ result in higher RCS values, with η/Ciυ having a greater influence than the RA content. Scanning Electron Microscopy (SEM) revealed that the incorporation of 30% RA improved the soil structure, increasing its stability. The results indicate that the mixture showed a significant increase in the resilient modulus compared to pure soil. For the highest pair of stresses tested, at the modified effort, the RM of the mixture (70% soil-30% RS) + 5% cement (627 MPa) is approximately 47% higher than that of the mixture soil + 5% cement (437 MPa) and 825% higher compared to pure soil (76 MPa). Furthermore, low PD values and favorable accommodation behavior were observed for all tested materials, suggesting that they are suitable for use in pavement layers regarding this parameter. In terms of urban pavement design, the mixture with 30% RS and 5% cement was the most suitable, meeting the established design criteria. Thus, the use of RA in conjunction with cement proved to be viable from a technicaland environmental point of view for the base layer of urban pavements, contributing to the sustainability and efficiency of urban infrastructures.