Experimental investigation on the thermal and mechanical properties of nanoclay-modified adhesives used for bonding CFRP to concrete substrates

In this paper we investigate the thermal and mechanical properties of nanoclay-modified adhesives for use in civil engineering applications, in particular in relation to the strengthening of concrete members with carbon fibre reinforced polymer (CFRP). In this paper, the effect of the addition of different percentages of a layered silicate nanoclay, Nanomer I.30E (0, 1, 2.5, 5, and 7.5 wt%), to an epoxy adhesive used to bond CFRP to concrete members was explored. Differential Scanning Calorimetry (DSC), X-ray diffraction (XRD) and Transmission Electron Microscopy (TEM) were used to characterize the adhesive structure. The glass transition temperature (Tg), measured by DSC, was found to decrease with nanoclay addition. Measurements from XRD and TEM identified an intercalated/exfoliated structure of the nanoclay, Nanomer I.30E in the epoxy matrix. The adhesive tensile strength showed a reduction with the addition of nanoclay at elevated temperatures, however, improvement in tensile modulus was found for all nanoclay addition. The bond-loss temperature of CFRP/concrete systems with modified adhesive was observed to be lower than for the control (0% NC) using adhesion (pull-off) tests at elevated temperatures.