Self-sensing concrete is a smart concrete technology that can sense the stress, strain, and damage in itself. It is also called as self-monitoring or piezoresistive or pressure-sensitive or intrinsically smart concrete.
The composition and significance of self-sensing concrete are explained briefly in this article.
Composition of Self-Sensing Concrete
The composition of self-sensing concrete is similar to conventional concrete with the addition of functional fillers. The functional fillers used can be steel fibers, carbon fibers or carbon nanotubes, nickel powder, etc. The presence of functional fibers provides the concrete to have a conductive network that gives values for electric resistance, conductance, and impedance when current is allowed to pass through it.
Self-Sensing Property of Self-Sensing Concrete
The self-sensing property of smart concrete is based on the arrangement of the functional fibers in the concrete. The functional fibers are well dispersed in the concrete matrix, based on which the concrete matrix has a unique and extensive conductive network.
When the concrete is subjected to any form of deformation or stress, the conductive network is disturbed. It changes the electrical parameters of the concrete matrix. The electrical parameters studied are capacitance, electric resistance, and impedance of the material. The measurement of these electrical parameters determines the strain, stress, and damage caused to the concrete under static and dynamic conditions. The strain is measured by determining the electrical resistance.
Structure of Self-Sensing Concrete
The self-sensing concrete has a complex structure. It is a multiphase and multiscale composite.
The figure-1 below shows the structure of self-sensing concrete at the macroscopic level. It is a combination of two-phase material, in which the functional fillers are dispersed in the concrete matrix. The functional fillers can exist in any of the following forms:
- Fiber
- Particle
- Hybrid of fiber and Particle
The distribution of these fillers forms the conductive network for the concrete.
The self-sensing concrete structure at the microscopic level does not have a homogeneous structure. At the microscopic level, the self-sensing concrete is distributed in three levels:
- The distribution of functional fillers in binders
- The binder distributed with functional fillers among fine aggregates
- The fine aggregates distributed with binder and functional fillers among course aggregates.
The distribution of functional fibers within the concrete matrix is dependent on :
- The geometrical shape of the functional filler
- The processing methods
- The concentration of the functional filler
Significance of Self-Sensing Concrete
Among all the functional fillers used in self-sensing concrete, the carbon fiber provides a unique benefit to the self-sensing property of the concrete. This combination can detect the stress or strain in the concrete structures before they fail.
The self-sensing concrete can detect even small structural flaws. This application is significant in studying the internal conditions of the structures subjected to earthquakes.
Composite and Conventional concrete structures undergo cracks when subjected to unexpected loadings. Embedding sensors within the structures usually evaluate these unexpected deformations. A sensor is highly expensive and costs even more for its installation. It is when the application of smart concrete finds its place as self-healing concrete is far cheaper compared to sensors.
With the growth of the smart buildings market, the application of smart concrete is encouraged. Its primary function is to detect minor cracks and arresting the progress of cracks to make a more reliable mix.
Smart concrete requires a lot of external force to bend even in smaller amounts. It can store more energy before fracture.
The significance of smart concrete is not restricted to building structures alone. It is used for detecting the position, speed, and weight of the vehicles.
Important Highlights
Self-sensing concrete is a smart concrete technology that can sense the stress, strain, and damage in itself. It is also called as self-monitoring concrete or piezoresistive or pressure-sensitive or intrinsically smart concrete.
The concrete subjected to deformation or stress makes the conductive network disturbed. It changes the electrical parameters of the concrete matrix. The electrical parameters studied are capacitance, electric resistance, and impedance of the material. The measurement of these electrical parameters determines the strain, stress, and damage caused to the concrete under static and dynamic conditions. The strain is measured by determining the electrical resistance.
The composition of self -sensing concrete is similar to conventional concrete with an extra addition of functional fillers. The functional fillers used can be steel fibers, carbon fibers or carbon nanotubes, nickel powder, etc. The presence of functional fibers provides the concrete to have a conductive network
In highway road construction, smart concrete can be used for detecting the position, speed, and weight of the vehicles.
The important applications of self-sensing concrete are:
a). To detect the flaws and cracks in structure before its failure
b). To determine the movement characteristics of vehicles on roads.
c). To arrest the progress of cracks utilizing fibers (functional fillers)
d). To analyze the structure after subjected to dynamic loads
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