Effect of the Incorporation of Recycled Aggregate from Construction and Demolition Waste on the Mechanical Strength of Silty-Cement Soil

The present study aims to assess the effect of using recycled aggregates (RA) derived from construction and demolition waste (CDW) on the development of the unconfined compressive strength (UCS) of a silty-cement soil from the Guabirotuba Formation, located in the southern region of Brazil. Was considered the influence of various parameters, including RA content, compaction effort, maximum dry specific mass, and porosity/volume cement content (η/Civ). RA contents of 10%, 20%, and 30%, combined with 5% cement by dry soil weight, are studied at curing times of 0, 7, 14, and 28 days, using standard, intermediate, and modified compaction efforts. The results reveal that the addition of RA leads to an increase in the maximum dry specific mass, directly correlating with an increase in the rate of compressive strength gain over time. In the case of the modified compaction effort, the UCS value for the mixture with 30% RA at 28 days of curing reaches 2318 kPa, which is 35% higher compared to the mixture without RA, which has an RCS value of 1711 kPa. Equations establishing a relationship between η/Civ and UCS show that smaller η/Civ values result in greater UCS. Furthermore, a correlation between η/Civ and RA content with UCS suggests that η/Civ has a stronger influence on UCS than RA content. Lastly, Scanning Electron Microscopy (SEM) indicates that incorporating 30% RA reduces the number of pores as well as their size, which enhances the soil structure and its increases stability, resulting in a more compact structure.