Evaluation of CNTs and SiC Whiskers Effect on the Rheology and Mechanical Performance of Metakaolin-Based Geopolymers

Madeleing Taborda-Barraza; Francine Padilha; Laura Silvestro; Afonso Rangel Garcez de Azevedo; Philippe Jean Paul Gleize

doi:10.3390/ma15176099

Evaluation of CNTs and SiC Whiskers Effect on the Rheology and Mechanical Performance of Metakaolin-Based Geopolymers

Materials (Basel). 2022 Sep 2;15(17):6099. doi: 10.3390/ma15176099.

Authors

Madeleing Taborda-Barraza¹, Francine Padilha¹, Laura Silvestro², Afonso Rangel Garcez de Azevedo³, Philippe Jean Paul Gleize¹

Affiliations

¹ Laboratory of Application of Nanotechnology in Civil Construction (LabNANOTEC), Department of Civil Engineering, Federal University of Santa Catarina (UFSC), Florianópolis 88040-900, Brazil.
² Civil Engineering Coordination, Federal University of Technology-Paraná (UTFPR), Guarapuava 85053-525, Brazil.
³ LECIV-Civil Engineering Laboratory, UENF-State University of the Northern Rio de Janeiro, Campos dos Goytacazes 28013-602, Brazil.

Abstract

Despite geopolymers having emerged as a more sustainable alternative to Portland cement, their rheological properties still need to be thoroughly investigated, aiming at the material's applicability. Additionally, studies that evaluated the fresh state of geopolymer composites with nanomaterials are scarce. Thus, two metakaolin-based geopolymer systems were reinforced with nanomaterials with a similar geometry: carbon nanotubes (CNT) and silicon carbide whiskers (SCW). The nanomaterials incorporation was assessed by rotational rheometry (conducted up to 110 min), isothermal calorimetry, compressive strength after 7 and 28 days, and the microstructure was investigated using X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR). CNT and SCW incorporation (0.20 wt.%) did not significantly affect the yield stress and viscosity of the R2-group (based on metakaolin type 2), while increasing the rheological parameters up to 56.0% for the R1-group (based on metakaolin type 1). Both additions modified the reaction kinetics. Increments of up to 40.7% were observed in the compressive strength of geopolymer pastes with the incorporation of a SCW content of 0.2 wt.%. XRD and FTIR results suggest similar structural modifications between precursors. Nevertheless, R2 showed substantial transformations while the R1 group exhibited anhydrous material that can react over time. Overall, incorporating CNT and SCW contributed to higher mechanical increments on systems with average mechanical strength (R1) compared to systems with higher potential mechanical performance (R2).

Keywords: compressive strength; geopolymer; kinetics; metakaolin; nanomaterial; rotational rheometry; whiskers.

Grants and funding

This research was funded by INCT CEMtec, grant number CNPq Process No. 485340/2013-5. The participation of A.R.G.A. was sponsored by FAPERJ through the research fellowships proc. no: E-26/210.150/2019, E-26/211.194/2021, E-26/211.293/2021, E-26/201.310/2021 and by CNPq through the research fellowship PQ2 307592/2021-9.