Spalling mitigation techniques for high-performance concrete at elevated temperature

Abstract

High-performance concrete (HPC) is highly susceptible to temperature-induced spalling, which unveils severe damage of HPC structural members. Therefore, this research work is aimed at developing spalling mitigation techniques for HPC and experimentally assessing spalling behaviour at transient heating conditions up to 1000 °C for a 4-hour fire resistance rating. A total of four HPC mixes were comprised for spalling behaviour evaluation, in which Mix H1 was designed only using main binder ordinary Portland cement (OPC), whereas Mix-H2, Mix-H3, and Mix-H4 were designed by partial replacement of OPC with three different supplementary cementitious materials (SCMs), i.e., fly ash (FA), silica fume (SF), ground granulated blast furnace slag (GGBS) one at a time as a binary composite system. Polypropylene (PP) fibres and steel (ST) fibres one at a time from a range of 0.00, 0.62, 1.24, 1.86, and 2.48 kg/m3 and ST fibres range of 0.00,12.43, 24.87, 37.30, and 49.74 kg/m3 were incorporated into HPC mixes for evaluating spalling mitigation behaviour at elevated temperature. For each HPC mix, a total of three standard cylindrical specimens (100 mm diameter × 200 mm height) were exposed to transit temperature 1000 °C for up to 4 h to assess spalling behaviour. It is observed that Mix-H1 content only OPC does not reveal any severe damage and spalling behaviour, whereas Mix-H2, Mix-H3, and Mix-H4 comprising SCMs revealed very severe damage and spalling behaviour. This result indicates that the highly dense microstructure with a highly durable HPC matrix using SCMs does not allow any moisture movement/migration from the inherent concrete binding matrix to the outer exposed surface of cylinder specimens and resulting in explosive-type spalling of HPC. However, using 1.86 kg/m3 of PP fibres and 37.30 kg/m3 of ST fibres in HPC binary systems has a positive impact on mitigating spalling of HPC at elevated temperatures.