Abstract
A novel ultra-high modulus carbon fibre reinforced polymer (CFRP) prestressing tendon made from coal tar pitch-based carbon fibres was characterized in terms of high temperature tensile strength (up to 570 °C) with a series of transient thermal and steady state temperature tensile tests. Digital image correlation was used to capture the high temperature strain development during thermal and mechanical loading. Complementary thermogravimetric (TGA) and dynamic mechanical thermal (DMTA) experiments were performed on the tendons to elucidate their high temperature thermal and mechanical behaviour. The novel CFRP tendons investigated in the present study showed an ambient temperature design tensile strength of 1400 MPa. Their failure temperature at a sustained prestress level of 50% of the design tensile strength was 409 °C, which is higher than the failure temperature of most fibre reinforced polymer rebars used in civil engineering applications at similar utilisation levels. This high-temperature tensile strength shows that there is potential to use the novel high modulus CFRP tendons in CFRP pretensioned concrete elements for building applications that fulfill the fire resistance criteria typically applied within the construction industry.
Highlights
In the last decade, the precast concrete industry has been progressively developing a range of advanced thin-walled concrete elements utilizing high-performance, self-consolidating concrete reinforced with high-strength, lightweight, and non-corroding carbon fibre reinforced polymer (CFRP) grids or tendons [1,2,3,4]
The novel ultra-high modulus (UHM) CFRP tendons investigated in the present study have a design tensile strength of 1400 MPa, and their failure temperature at a prestress of 50% of the design strength
A novel ultra-high modulus CFRP prestressing tendon made from coal tar pitch-based carbon fibres was characterized in terms of high-temperature tensile strength with a series of transient thermal and steady temperature tensile tests
Summary
The precast concrete industry has been progressively developing a range of advanced thin-walled concrete elements utilizing high-performance, self-consolidating concrete reinforced (or prestressed) with high-strength, lightweight, and non-corroding carbon fibre reinforced polymer (CFRP) grids or tendons [1,2,3,4]. Polymers 2016, 8, 446 between CFRP (transverse to fibre direction [1]) and high-performance concrete [5] One example of this trend is a new type of precast CFRP pretensioned concrete element intended as load-bearing panels for glass/concrete building facades [1]. Adequate fire resistance is a legitimate concern for these novel precast CFRP reinforced high strength concrete elements, since it is known that the tensile strength of CFRP and the bond strength between CFRP reinforcing tendons and concrete deteriorate comparatively quickly at elevated temperature [6,7]. The spalling behaviour of high-strength concrete can be effectively mitigated by advanced concrete mix design incorporating a suitable quantity and type of polypropylene microfibre [9]
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