Study on honeycombs in structural concrete elements

Abstract

Concrete structures are subjected to various types of surface defects such as honeycombs, surface voids, form streaking, etc. Proper understanding of the root causes of each type of defect is significant in preventing recurrence as well as applying remedies. An extensive field survey was conducted in connection with the construction sector of Sri Lanka to gather information on the current practices. It was found that the construction industry needs more awareness on correct practices. This study attempts to fill the gap between current field practices and standard practices. Poor workmanship in consolidation of fresh concrete leads to most of the defects, but this study shows how the understanding of technical background of each activity and the proper planning at initial stages contribute to effortless improvements in workmanship. Contradictions between codes of practices for design of reinforced concrete and codes of practices for consolidation of concrete were also discussed under this study. In order to identify the impact from reinforcement on UPV tests on concrete, a series of UPV tests (conventional approach) were done, and the drawbacks of that approach are highlighted under this study. As a modern approach, vibration pattern analysis of structural elements has emerged as a valuable technique for various purposes within the field of structural engineering. The analysis of vibrational patterns can be employed for different objectives, including damage detection, modal parameter identification, health monitoring, and structural integrity assessment. The presence of non-homogeneity in structural elements poses unique challenges in terms of analysing their behaviour, predicting their response to loads, and detecting damage or deterioration accurately. The straight-forward mathematical models based on first principles are for homogeneous elements having uniformly distributed mass and uniform distribution of stiffness. This study has developed a novel mathematical approach based on first principles for mode shapes of beams having deviated regions of mass and stiffness. This insight can help to identify key factors influencing the mode shapes and their variations. Furthermore, this study has done an extensive study on mode shape curvature analysis for identification of hidden honeycombs in concrete structures. The findings of this analysis fill research gaps in the study area. Moreover, the novelty of that approach is its extension to the analysis of portal frames. Consequently, a combination of conventional nondestructive tests and mode shape curvature analysis will provide a robust approach for hidden defect detection and assessment in structural concrete elements.