Impact of Element Size on Rebar-Concrete Interface Microstructure Using X-ray Computed Tomography
Milena Kucharska1, Piotr Dybeł1
1Faculty of Civil Engineering and Resource Management, AGH University of Krakow, Al. A. Mickiewicza 30, 30-059 Krakow, Poland.
Materials (Basel, Switzerland)
|August 10, 2024
Summary
The microstructure of the steel-concrete interface in self-compacting concrete (SCC) is affected by element size and rebar depth. Deterioration of the interface is linked to proximity to the top surface, not element type.
Area of Science:
- Materials Science
- Civil Engineering
- Construction Materials
Background:
- The steel-concrete interface is critical for reinforced concrete structures.
- Self-compacting concrete (SCC) offers advantages in placement but requires understanding its fresh state behavior.
- The microstructure at the rebar-concrete interface influences bond strength and durability.
Purpose of the Study:
- To investigate the impact of element size on the steel-concrete interface microstructure in SCC.
- To analyze the influence of rebar position and casting method on interface properties.
- To evaluate the relevance of current design standards for bond conditions based on rebar depth.
Main Methods:
- Experiments using deep beam and wall elements cast with SCC.
- X-ray computed tomography (CT) for 3D microstructural analysis of the rebar-concrete interface.
- Analysis of core samples to assess interface characteristics.
Main Results:
- Interface microstructure is influenced by distance from the casting point and vertical position.
- Bleeding, air-pore entrapment, and plastic settlement occurred under top rebars.
- Interface deterioration correlated with distance from the element's top surface, irrespective of element type.
Conclusions:
- The study elucidates fresh state phenomena affecting bond properties in SCC.
- Current standards differentiating bond based on rebar depth may be overly strict.
- Findings provide guidance for reinforced concrete construction and design practices.
Keywords:
X-ray computed tomographyair voidsself-compacting concretesettlementsteel–concrete interfaceMore Related Videos
11:07Preparation of Aligned Steel Fiber Reinforced Cementitious Composite and Its Flexural Behavior
Published on: June 27, 2018
11.1K
10:10Three-Dimensional Particle Shape Analysis Using X-ray Computed Tomography: Experimental Procedure and Analysis Algorithms for Metal Powders
Published on: December 4, 2020
1.8K
Related Concept Videos
01:25Reinforcements in Concrete
81
Reinforced concrete is a composite material used extensively in construction, combining the compressive strength of concrete with the tensile strength of steel. This synergy is essential as concrete, while excellent at resisting compression, is weak under tension. Steel bars, or rebars, are embedded in the concrete to handle these tensile forces. The choice of steel is strategic; it shares a similar coefficient of thermal expansion with concrete, which ensures uniformity in response to...
81
01:20Microcracking in Concrete
114
Microcracking in concrete refers to the tiny cracks that can form within the material even before any external load is applied. These microcracks typically occur at the interface between the coarse aggregate and the hydrated cement paste, often as a result of differential volume changes prompted by variations in stress-strain behavior, as well as thermal and moisture movement. Initially, these microcracks remain stable and do not grow substantially until the concrete is stressed to about 30...
114
01:22Design Example: Distributing Reinforcements in Concrete Sections
84
The topic explores the practical aspects of adjusting steel reinforcements within a concrete beam section to meet specific design requirements. When designing a reinforced concrete beam, it is essential to distribute the steel reinforcements properly to ensure structural integrity and efficiency. The example provided details a scenario where a beam requires a total steel cross-section of 4 square inches. The engineer identifies that the available steel bars have a nominal diameter of 1.693...
84
01:16Tensile Strength Considerations of Concrete
119
Considering the tensile strength of concrete involves recognizing that the theoretical strength of cement paste can be up to a thousand times higher than what is observed in practical applications. This significant discrepancy is largely attributed to the presence of microscopic cracks within the concrete. These cracks tend to amplify stress at their tips when a load is applied, a phenomenon explained by Griffith's theory of brittle fracture.
The dimensions and shape of a concrete specimen...
The dimensions and shape of a concrete specimen...
119
01:27Shrinkage in Concrete
89
Shrinkage in concrete is primarily due to water loss from evaporation, hydration of cement, or carbonation, leading to a reduction in volume. The volumetric contraction results in volumetric strain in concrete. However, in practice, shrinkage is measured as linear strain, which is one-third of the volumetric strain.
When concrete is still in its plastic state, it can undergo a decrease in volume by about 1% of its absolute volume. This decrease is known as plastic shrinkage. It arises either...
When concrete is still in its plastic state, it can undergo a decrease in volume by about 1% of its absolute volume. This decrease is known as plastic shrinkage. It arises either...
89
01:22Fiber Reinforced Concrete
71
Fiber-reinforced concrete significantly enhances the structural and nonstructural properties of traditional concrete by incorporating fibers like steel, glass, and polymers. These fibers, varying from natural ones such as sisal and cellulose to manufactured ones like polypropylene and Kevlar, are mixed into hydraulic cement with aggregates. Steel fibers, often preferred for their robustness, contribute to improved ductility, toughness, and post-cracking performance. The concrete is classified...
71