Residual cube strength and microstructural properties of fire-damaged biofibrous concrete with GEP-based prediction model

Abstract

Concrete under thermal loads is characterised by cracking and pore pressure build-up resulting in spalling and deterioration. Its retained strength is crucial to structural soundness and serviceability. Past findings indicate that some fibres could mitigate crack propagation and pore pressure in heated concrete. However, kenaf fibre-reinforced concrete (KFRC) is yet to be studied. This research presents an experimental report on kenaf fibre normal strength concrete (KFNSC) (grade 40), using an optimum volume (0.75 percent) and length (25 mm), heated frm 100 to 800 °C, sustained for 1, 2, and 3 h, and tested after cooling. The microstructure and thermal properties of treated fibre were examined using scanning electron microscope and thermogravimetry analysis. The residual compressive strength, microstructure, weight loss, and ultrasonic pulse velocity of KFRC were determined and compared with non-fibrous specimens. The test results revealed that KFNSC climaxed its compressive strength at 300 °C and was thermally stable up to 400 °C, compared with Plain normal strength concrete, with superior performance. However, both strengths declined, and the microstructure worsened with increased temperature and exposure duration. A Gene Expression Programming model was developed for prediction and gave a perfect correlation with empirical data. The research would offer technical information for biocomposite standards development and application strategy.