Microcracking of reinforcing bars used in informal housing construction: Riobamba case study

Abstract

This study investigates the relationship between the method used to bend reinforcing bars and the initiation of microcracks in reinforcing steel used in informal housing in the city of Riobamba, Ecuador. Two bending techniques were compared: the traditional method and the method carried out in accordance with Standard NTE INEN 2167. Field surveys were used to identify the most commonly used rebar diameters and bending practices. Twenty samples of 10 mm and 12 mm diameter rebars were analyzed, including straight sections and rebars bent at 180°, using metallographic tests and scanning electron microscopy (SEM). The results show the absence of microcracks in the unbent samples and in those bent with a semi-automatic machine under standard conditions, while traditional bending generates microcracks located in the inner area of the bend, associated with stress concentrations in the longitudinal ridges. Analysis of the cumulative length of microcracks indicates that the diameter of the bar has a significant influence on the level of microcracking under the conditions studied. The findings highlight the importance of complying with standard bending procedures to preserve the ductility of reinforcing steel and improve the performance of reinforced concrete structures under cyclic loads in informal construction contexts.