Abstract

A structure–property assessment of coating plaster reinforced with a low dosage (0.01 wt%) of graphene oxide (GO) was investigated to address the intrinsic mechanical and thermal limitations of gypsum in civil construction. Nanocomposite specimens were characterized in terms of hydration kinetics (setting time), wettability (water contact angle), and compressive behavior across a range of post-fabrication thermal treatments at 200 °C, 250 °C, and 300 °C. Although the incorporation of 0.01 wt% GO maintained the ultimate compressive strength of the matrix (~13.8 MPa), it fundamentally transformed the pre-yield behavior, doubling the initial structural stiffness (slope) from 8.7 to 18.7 MPa·mm−1. This mechanical enhancement suggests the role of GO as a structural anchor capable of bridging micro-voids and restricting microcrack propagation. Beyond 200 °C, phase transformation via gypsum dehydration into basanite and anhydrite phases, validated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), led to a severe reduction in compressive strength for both neat and reinforced matrices. Crucially, however, the GO-reinforced composites retained a 76% higher structural stiffness compared to the neat plaster within this post-thermal regime. Additionally, thermal activation at 200 °C induced a critical surface modification, elevating the water contact angle to 68.1° because of partial GO thermal reduction, as confirmed by coupled TG/FTIR analysis. These findings demonstrate that while GO does not suppress the intrinsic chemical dehydration of the calcium sulfate matrix, it provides vital mechanical stabilization to the crystalline network, significantly enhancing rigidity and deformation resistance under severe thermal stress.

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