Carbon-Based and Silicon-Based Nanomaterials for Enhanced Structural Adhesives

Various carbon-based (i.e., carbon nanofibres (CNF), cellulose nanocrystals and graphite nanoparticles) and silicon-based nanomaterials (i.e., silica and MMT clay nanoparticles) were incorporated into neat structural epoxy adhesive (NE) (Sikadur®-30) at 0.5, 1.0 and 1.5 wt.% by means of a simple and cost-effective mixing method to produce the nanomaterial-modified epoxy adhesives (NMEAs). The performance of the NMEAs in regard with the bond characteristics and strength of cement paste (CP)-adhesive joints was investigated through conducting lap-shear test. Results showed that loading epoxy with 0.5 and 1.0 wt.% of carbon-based nanofillers, except in the case of adding 1.0 wt.% CNF, contributed to a significant enhancement in the joints’ strength, but a strength reduction the of the joints, even below those of the NE-bonded joints, was observed upon a further loading (i.e., at 1.5 wt.%). While all the joints bonded with epoxy loaded with silicon-based nanofillers at all wt.% showed a strength increase over the unfilled epoxy. The joints’ strength was found to decrease with the wt.% of the nanofillers due to particles’ agglomerations. All joints failed in a mixed cohesive and adhesive mode.