Accelerated Moisture Transport through Local Weakness of High-Strength Concrete Exposed to High Temperature

Abstract

Spilling out of condensed liquid water from needle-like holes in high-strength concrete was experimentally observed under fire attack. The presence of these holes was found to prevent explosive spalling effectively in the vicinity of the holes during fire exposure tests. This spilling out occurred at about 10 to 30 minutes after the start of high temperature heating. These needle-like holes are defined herein as local weaknesses that may act as rapid paths of water permeation to reduce the risk of explosive spalling of cover concrete. The phase change of moisture from CSH solids to condensed liquid as well as free water in micro-pores was simulated by a multi-phase chemo-physics analysis of ultra-high-strength concrete. The prediction of the high-rate phenomena was experimentally proved by using embedded moisture sensor, and the high-rate discharge of condensed water though local weaknesses was analytically simulated.

Remaining Shear Capacity of Fire-Damaged High Strength RC Beams after Moist Curing

“…The authors have extended the scope of application of existing multi-scale analysis (Ishida and Maekawa 1999;Maekawa et al , 2008 to high temperature regions of about 1000°C (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2021. This analysis system (Fig.…”

“…This analysis system (Fig. 1) can take into account the loss of strength and stiffness caused by dehydration and crack propagation during heating, the rapid increase in internal temperature and loss of bond strength between reinforcement steel and concrete due to the spalling of the cover concrete, and the strength recovery due to post-fire re-curing (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2021.…”

“…Thus far, the authors have carried repeated upgrade and verification of the multi-scale platform (Ishida and Maekawa 1999;Maekawa et al , 2008 with a primary focus on material and structural behavior at high temperatures. The purpose of this study is to verify the accuracy and applicability of the upgraded multiscale platform (Iwama et al 2018(Iwama et al , 2019(Iwama et al , 2021 shown in Fig. 1, focusing on the behavior and remaining shear capacity after high temperature heating.…”