Optimizing cement-treated recycled concrete aggregates for road bases using secondary additive

This study investigates the feasibility of a secondary additive treated recycled concrete aggregates (RCA) to reduce the required cement content for the construction of pavement base/subbase layers. The effectiveness of secondary additive was assessed based on extensive studies involving strength, durability and microstructural analysis considering different cement contents (2 %, 3 %, 4 %, and 5 % by weight of aggregates) and a silica-rich secondary additive (2 % and 4 %, by weight of cement). The addition of a secondary additive significantly reduced the required cement content (from 7 % to 5 %) to meet the minimum 7-day unconfined compressive strength criteria for base layers. Accordingly, 5 % cement content and 4 % additive contents are proposed in the study for base layer applications. The weight loss percentage of treated RCA specimens prepared with this optimal mix (3.1 %) is found to be less than the maximum permissible value (14 % after 12 wet-dry cycles). The 7-day cured specimens prepared with this mix showed a significantly high resilient modulus value (667 MPa). Additionally, the designed pavement section incorporating 5 % cement and 4 % additive-treated layers exhibited a 13 % reduction in pavement crust thickness compared to the non-treated pavement section. Treated RCA satisfied the requirements of pavement base/subbase layer in accordance with American, Australian, and Indian road standards and can be a viable solution towards sustainable road infrastructure. The findings demonstrate that secondary additive treated RCA can be effectively utilized in road pavement base/subbase layers with lower cement dosage and promoting sustainable road construction using recycled waste materials.