Title: Crack-Spacing-Based Flexural Capacity of Polymer Cement Mortar-Overlay Reinforced Concrete Beams at High Environmental Temperature

Author(s): Khuram Rashid, Minkwan Ju, Tamon Ueda, and Dawei Zhang

Publication: Structural Journal

Volume: 120

Issue: 4

Appears on pages(s): 57-71

Keywords: average crack spacing; environmental temperature; flexural strength prediction; polymer cement mortar (PCM)-overlay reinforced concrete beam (RCB); pullout force; strengthening

DOI: 10.14359/51738749

Date: 7/1/2023

Abstract:
Overlaying a reinforced concrete beam (RCB) with polymercement mortar (PCM) is a strengthening method that improvesflexural stiffness by the increasing sectional force. However, the reduction between bond strength and the reinforcement in PCM overlay at high temperatures results in an increase in flexural crack spacing. Therefore, the pullout force must be taken into account when estimating the flexural capacity of PCM-overlay RCBs. The experimental study aims to assess the flexural performance of PCM-overlay RCBs under three different environmental temperature conditions: 20, 40, and 60°C. Seventeen beams with varying reinforcement ratios in PCM are tested at the mentioned temperature levels. Experimental results indicate a decrease of approximately6 to 13% in strength at elevated temperatures, which canbe attributed to the reduction in bond strength of the reinforcement caused by the degradation of the PCM. Analytically, the strength reduction is calculated by determining the average crack spacing in the flexural zone. Therefore, the proposed average crack spacing method (CSM) predicts that the flexural strength is within ±10% limits of experimental observations. This method is more conservativethan the conventional sectional analysis method (SAM). Theaverage CSM can contribute to a safer design of PCM-overlayRCBs by preventing overestimated prediction of the ultimatestrength at high environmental temperatures.