Effect of Sandy Soil Partial Replacement by Construction Waste on Mechanical Behavior and Microstructure of Cemented Mixtures

The large amounts of construction waste (CW) generated yearly and its high landfilled proportion worldwide motivate the search for sustainable solutions. Thus, the effect of sandy soil partial replacement for construction waste in cemented mixtures was assessed in the present work in terms of mechanical behavior and microstructure. Distinct cement contents, compaction efforts, and curing periods were evaluated from soil-waste proportion of S75W25, S50W50, and S25W75. Tests of unconfined compression strength (UCS), indirect tensile strength (ITS), ultrasonic pulse velocity, water absorption, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM) were conducted. The presence and increase in the amounts of cement and construction waste increase the optimum moisture content of the mixture. In contrast, only the CW content significantly affects maximum dry density. Both S75W25 and S50W50 mixtures resulted in similar UCS and ITS values, which was proven to be statistically equal by analysis of variance (ANOVA) at a 0.05 significance level, favoring CW replacing soil up to 50%. MIP and SEM results explained the sharp mechanical behavior transition obtained in 75% of CW. Cementation reactions resulted in macropores peak reduction and/or peak area translation to the left of the horizontal axis of the PSD curve, while its translation to the right indicates the cement mainly acting as filler, which was supported by SEM tests.