Engineering Performance of Graphene Nanoplatelet-Modified Pumice-Based Lightweight Mortar

Abstract

Pumice-based lightweight mortars generally exhibit high porosity, which adversely affects their engineering performance. This study investigated the influence of graphene nanoplatelets (GNPs) on the fresh, physical, mechanical, and microstructural properties of pumice-based lightweight mortars. GNPs were incorporated at dosages of 0, 0.01, 0.03, 0.05, and 0.10 wt.% of cement, and the mortars were evaluated through flow diameter (FD), water absorption (WA), compressive strength (CS), flexural strength (FS), scanning electron microscopy (SEM), and ImageJ-based microstructural analysis. Increasing the GNP dosage from 0 to 0.10 wt.% reduced the FD from 207 to 186 mm, corresponding to a 10.1% decrease. Among the investigated mixtures, the mixture containing 0.03 wt.% GNP exhibited the best overall performance. At this dosage, WA decreased from 12.82% to 12.23%, representing a 4.60% reduction relative to the control mixture. The 28-day CS increased from 27.84 to 31.23 MPa, while the FS increased from 4.28 to 4.81 MPa, corresponding to improvements of 12.18% and 12.38%, respectively. ImageJ analysis showed that the two-dimensional void area decreased from 10.21% in the control mixture to 7.47% in the mixture containing 0.03 wt.% GNP, corresponding to a 26.84% reduction. SEM observations also indicated a denser and more homogeneous cementitious matrix at this dosage. Higher GNP dosages were associated with slight performance reductions and localized agglomeration of nanoplatelets. Overall, 0.03 wt.% GNP was the best-performing dosage among those investigated, improving the engineering performance and microstructural compactness of pumice-based lightweight mortars.