Microstructures and mechanical property of post-fire grouting sleeve connections considering concrete cover

Abstract

The performances of grouting sleeves for connections (GSCs) were critical for safety of prefabricated concrete structures especially after building fire. The consideration of concrete cover around sleeves was insufficient in previous studies which was essential for predicting the properties of GSCs in actual engineering. This study simulated the building fire, and the properties of post-fire GSCs with different concrete covers were explored. The influences of peak temperature (200 °C-800 °C) and the thickness of concrete cover (15 mm, 25 mm) on the strength of grouting materials and the anchorage performance of GSCs were analyzed. TG, MIP and SEM were used to reveal the deterioration of hydration products and microstructures of post-fire grouting materials. The failure mode, load–displacement relation and internal damage phenomenon of post-fire GSCs were tested, the prediction formula of bonding strength and peak temperatures was established. Furthermore, the prediction formula of bearing capacity of post-fire GSCs were recommended in condition of two kinds of concrete cover. The results showed that the peak temperature of 600 °C was upper limit of acceptability for GSCs under the protection of concrete cover. Increasing the thickness of concrete cover could slightly relieve the decomposition of hydration products and deterioration of microstructures of grouting materials, and then improve the bearing capacities of GSCs.