Micro Computed tomography (Micro-CT) employs X-ray radiation emitted from a source towards an object, enabling the generation of two-dimensional (2D) images of the object being examined in a non-destructive manner. The utilization of this technique has become increasingly prevalent in various industrial and engineering domains, including the field of Civil Engineering, being extensively employed for analytical purposes.
Civil engineering is the integrated application of physical and scientific principles for the design, development, and maintenance of both man-made and natural structures. Such broad discipline encompasses a wide array of infrastructure, including but not limited to airports, railways, and roads to buildings, power plants, sewage systems, and various other components.
Civil engineering is the second oldest branch of engineering as a successor to military engineering. Civil engineering emerged to separate engineering for civilian purposes from that of military objectives. With a history dating back to more than 4000 years ago, Civil engineering can be broken down into numerous subdisciplines such as construction, earthquake, environmental, hydraulic, structural, transportation, urban, and more. Notably, material engineering is also regarded as a subfield within the vast spectrum of civil engineering.
The need to study the microstructure of materials used in construction, such as concrete, asphalt, and soil is an inseparable part of civil engineering. Microstructure of a material is analyzed to observe the mechanical parameters responsible for the behaviors of such materials. This can include air void volumes or the distribution of additives in said materials. Consequently, micro-CT emerges as an advanced imaging tool with tremendous capabilities to fulfill such tasks facilitating a deeper understanding of materials and their properties and performance.
Micro-CT, much like clinical CT, is an X-ray imaging technique capable of providing 2D and 3D visualization of the inner structures of the material. Micro-CT holds the great advantage of its non-destructive nature over other imaging and analysis techniques. This distinctive attribute empowers researchers to repeatedly employ the same sample for analysis while ensuring its intactness.
Here we will explain some applications of the micro-CT in the field of Civil engineering:
Concrete is undeniably one of the major construction materials in civil engineering due to its one-of-a-kind characteristics, including high compressive strength and low relative cost. Concrete is composed of cement, water, and a mixture of fine and coarse aggregates such as gravel, sand, crushed rock, etc. Furthermore, many new materials such as fibers in macro, micro, or nano-scale are being incorporated into the mixture above to enhance the mechanical properties of concrete.
The addition of such components to concrete necessitates a detailed analysis of the concrete microstructure. These analyses include but are not limited to, porosity analysis, air voids and their size distribution analysis, carbonation effects, observation of sulfate attacks in cement paste, and damage and crack analysis after loading.
Soil exhibits a complex composition, where sand, clay, silt, and underground water come together. The behavior of soil is highly influenced when the contents of this mixture change. Water is a vital factor in different geotechnical designs due to its significant effect on soil strength and behavior. Offering cost and time-effective facilities in water distribution assessments, micro-CT has become a widely used technique in the field.
Pore structure analysis is another vital component in soil evaluation as it can determine pore diameters which can impact flows and contaminant movements. Micro-CT is often the preferred imaging technique for this application, offering high-resolution 3D images of the soil's internal structure. These images can be processed and analyzed to extract quantitative data on pore sizes, volumes, and connectivity.
Asphalt is a bituminous mixture of different materials, possessing advanced mechanical properties like strength and durability, making it a great choice for road pavement. Additionally, when asphalt cement and fine and coarse aggregates are mixed, they form asphalt concrete, expanding its application to airport paving and highways.
The evaluation of morphological properties such as texture, angularity, and shape are essential for the assessment of asphalt or asphalt concrete. Additionally, Moisture distribution, as a vital factor in the durability of the asphalt, needs to be closely examined. Micro-CT offers a thorough range of tools for conducting these evaluations, enabling the field to shift from qualitative to quantitative analysis.
With its exceptional capabilities in non-destructive analysis in microscale resolution, micro-CT has become the modality of choice for many researchers within the realm of civil engineering.
The list below provides a summary of applications of micro-CT in civil engineering: