Abstract
In this paper, a method for the evaluation of the influence of different polymer suspensions and environmental conditions on adhesion between an impregnated carbon fibre heavy tow and concrete for reinforcement will be proposed. For this purpose, the impregnation material itself was investigated as a polymer film before and after incubation in water and aqueous suspensions, such as NaOH and a cementitious solution, in terms of its thermal properties, swelling behaviour and morphology. Thin polymer films were manufactured and subsequently investigated with quantification of the swelling for 28 d by thermal and scanning electron microscope analysis. The effect of pull-out shear stress was evaluated to investigate parameters such as high temperature and moisture on adhesion to concrete. Contact angle measurements were used to determine the surface energy of the polymer films. All incubated polymer films yielded a change in both surface morphology and specific residues on the polymer film surface, e.g. in the form of calcium carbonate, but no change in glass-transition temperature. A high correlation between glass-transition temperature and measured shear stress was shown during single yarn pull-out tests. Furthermore, the water treatment of pull-out samples strengthened the influence for the glass-transition temperature during the adhesion test. No influence of the surface energy of the used polymer impregnation for carbon fibres on the pull-out test was detected.
Highlights
Textile reinforcements for concrete structures have been more and more accepted in the building industry since they offer several advantages over conventional steel reinforcement [1] [2]
A further swelling in different solutions was observed, which concurs with residues or crystal growth verified via SEM images
A distinct relationship between the maximum shear stress measured in the yarn pull-out test and the glass-transition temperature and its swelling could be observed
Summary
Textile reinforcements for concrete structures have been more and more accepted in the building industry since they offer several advantages over conventional steel reinforcement [1] [2]. A composite made of concrete and textile is typically named Textile Reinforced Concrete (TRC) This textile reinforcement consists of high-performance fibres such as alkali-resistant glass, aramid, or carbon fibres (CF). CF are not corrosive in an alkaline environment, have a high tensile strength and modulus of elasticity in the longitudinal direction of the fibre, they are largely suitable for use as structural reinforcement in concrete elements or for the strengthening of concrete structures [3] [4] [5] Due to their superior mechanical and chemical properties, CF increasingly replace alkali-resistant glass fibres, which have been used in concrete for decades. Depending on the geometry of concrete elements and the loading of carbon reinforcement, CF can be shaped to rebars, biaxial grids, or multi-axial warp knitted fabrics [6]
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