Enhancing Recycled Aggregate Concrete Using a Three-Stage Mixed Coal Bottom Ash Slurry Coating

AbstractCoal bottom ash was pulverized into a fine powder and dispersed within a polycarboxylate-water solution to reinforce the interfacial transition zone and matrix of recycled aggregate concrete. The dispersion was used as part of a three-stage mixing sequence that included direct coating over recycled aggregate prior to, and immediately after, the application of a cement clinker coat to enhance the aggregate–cement clinker interface and the bulk matrix properties. The results suggest that when adequately dispersed, the bottom ash slurry enhances the performance of the recycled aggregate concrete system. The addition of a well-dispersed bottom ash slurry coating reinforces both the interfacial transition zone and the bulk matrix. The slurry decreases porosity and unhydrated clinker content and increases the presence of high-density Calcium-Silicate-Hydrate (C-S-H) near the interfacial transition zone. This leads to significant increases in both tensile and compressive strength and fracture toughness (∼12%).