Thermo-Mechanical Characterization of VGCF-Modified Adhesive for Bond between CFRP and Concrete Subjected to Combined Effect of Temperature and Humidity

Abstract

Adhesives are employed in external strengthening of concrete structures by Carbon Fibre Reinforced Polymer (CFRP). Carbon-based composites are currently the most common type used to increase the strength of concrete members. The application of Carbon Fibre fabrics (CF fabric) to concrete members involves the use of a compatible bonding agent, and it is the modification of such bonding agents that is investigated in this paper. The investigation involves examining the effects of adding different concentrations of vapour-grown carbon nanofibres (VGCF) (0.5 wt%, 1 wt%, 1.5 wt% and 2 wt%) on the thermal and mechanical properties of the bonding agent. The effect of modification on the glass transition temperature and heat flow of the modified adhesive was explored using Differential Scanning Calorimetry (DSC) technique. It was found that T_g reduces slightly or remains the same with the addition of VGCF to Part A of the adhesive and the highest reduction in T_g was found when Part A was reinforced with 2 wt % VGCF. Agglomaration of the fibres was observed when VGCF was introduced into MBrace® Saturant epoxy adhesive using the speed mixer and a random orientation for the fibres was noted within the epoxy matrix. Peeling-off of CF fabric was the common failure mode as the loaded CFRP/concrete system was subjected to the combined effect of temperature and humidity after short periods of exposure to such severe conditions.

Keywords

VGCF carbon nanofibers CFRP concrete modified adhesive durability

References

Al-Safy

Al–Mahaidi

and Simon

G.P.

(2009). “Bond performance of CFRP strengthening of Concrete Members using Nanoclay Modified Adhesives”. Proceedings of 09 PCI Annual Convention/Exhibition & National Bridge Conference, San Antonio, USA.

Al-Safy

Al-Mahaidi

, and Simon

G.P.

(2011). “Thermal and mechanical characterizations of nanomaterial-modified adhesive used in bonding CFRP to concrete”, The Journal of Adhesion, Vol. 87, No. 7–8, pp. 842–857.

Al-Safy

Al–Mahaidi

Simon

G.P.

and Habsuda

(2012). “Experimental investigation on the thermal and mechanical properties of nanoclay-modified adhesives used for bonding CFRP to concrete substrates”, Construction and Building Materials, Vol. 28, No. 1, pp. 769–778.

Choi

Y.K.

Sugimoto

Song

S.M.

Gotoh

Ohkoshi

and Endo

(2005). “Mechanical and physical properties of epoxy composites reinforced by vapor grown carbon nanofibers”, Carbon, Vol. 43, No. 10, pp. 2199–2208.

Hii

and Al-Mahaidi

(2006). “Experimental investigation on torsion behavior of solid and box- section RC beams strengthened with CFRP photogrammetry”, Journal of Composites for Construction, ASCE, Vol. 10, No. 4, pp. 321–329.

Lee

T.K.

and Al-Mahaidi

(2008). “An experimental investigation on shear behaviour of RC T-beams strengthened with CFRP using photogrammetry”, Composite Structures, Vol. 82, No. 2, pp. 185–193.

Park

J.S.

Kim

B.S.

Kim

J.B.

and Kim

T.W.

(2007). “Effect of VGCF addition to carbon fabric/Ep”, Key Engineering Materials, Vol. 334–335, pp. 741–744.

Patton

R.D.

Pittman

C.U.

Wang

and Hill

J.R.

(1999). “Vapor grown carbon fiber composites with epoxy and poly (phenylene sulfide) matrices”, Composites: Part A, Vol. 30, pp. 1081–1091.

Pham

and Al-Mahaidi

(2004a). “Assessment of available prediction models for the strength of FRP retrofitted RC beams”, Composites Structures, Vol. 66, No. 1–4, pp. 601–610.

10.

Pham

and Al-Mahaidi

(2004b). “Experimental investigation into flexural retrofitting of reinforced concrete bridge beams using FRP composites”, Composite Structures, Vol. 66, No. 1–4, pp. 617–625.

11.

Tibbetts

G.G.

(1992). “Growing carbon fibres with a linearly increasing temperature sweep: Experiments and modelling”, Carbon, Vol. 30, No. 3, pp. 399–406.

12.

Zeng

Q.H.

A.B.

G.Q.

and Paul

D.R.

(2005). “Clay- based polymer nanocomposites: Research and commercial development”, Journal of Nanoscience and Nanotechnology, Vol. 5, No. 10, pp. 1574–1592.

13.

Zhou

Pervin

and Jeelani

. (2007). “Effect vapour grown carbon nanofiber on thermal and mechanical properties of epoxy”, Journal of Materials Science, Vol. 42, No. 17, pp. 7544–7553.

14.

Al-Safy

R.A.

Al-Mahaidi

, and Simon

G.P.

(2013). “A study of the use of high functionality-based resin for bond between CFRP and concrete under harsh environmental conditions”, Composite Structures, Vol. 95, pp. 295–306.