Effect of Degradation on Mechanical Strengths of Alkali-Activated Fines in Stabilized Construction and Demolition Waste Aggregates

Recent works have demonstrated that construction and demolition waste (CDW) aggregates for subbase road pavement applications can be stabilized via the alkali activation of their fine fraction (d<0.125 mm). Despite the promising results with this method, the durability of alkali-activated (AA) CDW fines (which act to stabilize CDW aggregate mixtures) need to be investigated. To this end, the effects on pavement materials of the typical degrading actions of water, deicing salts, and the freeze-thaw process were investigated. Samples of AA fines were subjected to water, deicing salt, and freeze-thaw treatments and assessed based on the variation in 28-day flexural and compressive strength values with respect to not-degraded materials. In addition to the fines normally present in CDW aggregate mixtures (i.e., the undivided fraction), samples with fines of the main CDW constituents (concrete, asphalt, bricks and tiles, aggregates and soil) were also prepared for comparison purposes. One set of specimens was cured at 20°C to replicate field conditions, and another was treated at 80°C to replicate optimal conditions for AA materials. Although 80°C heat-treated specimens achieved higher strength values, those values fell sharply following the degrading action of water and deicing salts. In contrast, the specimens cured at 20°C retained their mechanical property values even after exposure to water and deicing salt degradations.