Zinc Waste as a Substitute for Portland Cement in Roller-Compacted Concrete Pavement Mixes Containing RAP Aggregates

Abstract

Owing to heavy toxic metal concentration such as copper, lead, zinc, sulfur, cadmium, and chromium, jarosite particles from the zinc industry are considered a hazardous waste material. Proper and safe disposal or converting this hazardous waste into nonhazardous material is vitally important. This study investigated the potential of utilizing jarosite as a substitute for portland cement in roller-compacted pavement (RCCP) mixes containing reclaimed asphalt pavement (RAP) material. Portland cement was partly replaced with jarosite in proportions of 5%, 10%, 15%, 20%, and 25% in mixes containing 50% RAP aggregates and tested for mechanical, durability, and microstructural properties. Based on test results and analyses, the incorporation of jarosite in RAP-RCCP mixes increased the fresh water demand owing to its hydrophilic nature, which in turn increased the porosity and water absorption and decreased the resistance to chemical attack. Jarosite incorporation level up to 5% may be recommended as the best mix because it exhibited 20% higher flexural strength than the recommended flexural strength of 3.67 MPa at 28 days for RCCP mixes, as well as enhanced abrasion resistance. Despite the inability to produce additional calcium silicate hydrate gels during the secondary pozzolanic reaction, the jarosite particles may have acted as a filler and resulted in a denser microstructure as revealed by scanning electron microscope images. Utilization of jarosite in RAP-RCCP mixes also would provide other ecological advantages, such as reduction of the burden on disposal landfills, lowering virgin aggregate and cement consumption, and lowering the carbon footprint.