Optimizing mechanical properties of one-part alkali-activated mortar with recycled plastic and graphene nanoplatelets using response surface methodology

Abstract

This study aims to optimize the mechanical properties of one-part alkali-activated mortar (OPAAM) containing recycled plastic aggregates (RPA) and graphene nanoplatelets (GNP) using response surface methodology (RSM). Mixtures were prepared with RPA replacing fine aggregate in varying proportions from 0 % to 50 %, and GNP added in dosages ranging from 0.1 % to 0.4 % of the binder's weight. The results indicated that RPA substitution reduced the mechanical properties of OPAAM, with compressive strength decreasing by 27.5 % and 46.9 % for mixtures with 25 % and 50 % RPA, respectively, compared to the control mixture. However, the incorporation of GNP significantly improved the mechanical properties and microstructure of OPAAM, mitigating the negative effects of RPA. The maximum compressive strengths were 57 MPa, 38 MPa, and 31 MPa for mixtures containing 0 %, 25 %, and 50 % RPA, respectively, at 28 days, achieved with a 0.2 % addition of GNP. Predicted models were proposed based on RPA and GNP to estimate the strengths and water absorption of OPAAM. These models were found to be significant, with strong correlations in predicting the mechanical properties. The optimal OPAAM mixture was achieved with 10.7 % RPA and 0.2 % GNP. This result was validated experimentally, with the difference between predicted and experimental outcomes being less than 10 %.