Novel precast concrete elements have been developed utilizing high-strength, self- consolidating concrete (fire resistant or expanding SCC) in which prestress is introduced by high-strength and modulus, lightweight, and non-corroding carbon fibre reinforced polymer tendons (UHM CFRP tendons). These precast FRP pretensioned HPSCC panels are intended as e.g. load-bearing panels for concrete building facades. lt is known that the bond strength between both steel and FRP reinforcing tendons and concrete deteriorates at elevated temperature and that high strength concrete tends to an explosive spalling failure mode when subjected to a fire. The bond strength reductions in fire, their impacts on the load-bearing capacity of prestressed concrete structures, and the spalling behaviour of high-strength concrete remain poorly understood and are the researched topics in this project.
The goals of this project are to improve the understanding of the fire behaviour of thin-walled CFRP self-prestressed SCC slabs and to define design criteria for fire performance to enable their application in building interiors.
The above objectives require the development of a spalling resistant expanding concrete. Accordingly, the first stage of the proposed thesis will be dedicated to understanding the spalling mechanisms of the current expanding SCC and the subsequent development of a spalling resistant expanding SCC of 75 MPa strength class or higher. Initial experiments have shown that Empa’s current expanding SCC spalls rapidly when centrally precompressed and subjected to an incident radiant heat flux representative of a compartment fire in a building. Therefore new spalling-resistant SCC mix designs will be studied using different admixtures and fibres. Thereafter, a series of self-prestressed SCC slabs will be studied for spalling. An experimental fire test series on thin-walled slabs will be performed at The University of Edinburgh.
A final stage will commence after satisfactory spalling resistance has been achieved by the used self-compacting concretes. Experiments will be designed to understand the high temperature bond behaviour between the UHM CFRP tendons and the novel prestressed SCCs.
This project may include annual multi-week research visits to EMPA Dubendorf; timescales, budget, and student interest allowing.
Further Information: fire.eng.ed.ac.uk
Tuition fees + stipend are available for Home/EU students (International students can apply, but the funding only covers the Home/EU fee rate)
Minimum entry qualification – an Honours degree at 2:1 or above (or International equivalent) in a relevant science or engineering discipline, possibly supported by an MSc Degree. Further information on English language requirements for EU/Overseas applicants
Applications are welcomed from self-funded students, or students who are applying for scholarships from the University of Edinburgh or elsewhere.
Informal enquiries should be sent to Prof. L Bisby at [email protected]
Application can be made directly online.