Description
This is a recorded webinar from April 5, 2016.
Concrete, the most ubiquitous material, is a nano-structured, multi-phase, composite material that ages over time. It is composed of an amorphous phase, nanometer to micrometer size crystals, bound water and wide range of porosity. The properties of concrete exist in, and the degradation mechanisms occur across, multiple length scales (nano to micro to macro) where the properties of each scale derive from those of the next smaller scale. The amorphous phase, calcium-silicate-hydrate (C–S–H) is the “glue” that holds concrete together and is itself a nanomaterial. Viewed from the bottom-up, at the nanoscale concrete is a composite of molecular assemblages, surfaces (aggregates, fibers), and chemical bonds that interact through local chemical reactions, intermolecular forces, and intraphase diffusion. There is strong evidence that the processes occurring at the nanoscale ultimately affect the engineering properties and performance of the bulk material.
Nano-engineering employs the manipulation of the structure at the nanometer scale to develop a new generation of tailored, multifunctional, cementitious composites with superior mechanical performance and durability potentially having a range of novel properties such as: low electrical resistivity, self-sensing capabilities, self-cleaning, self-healing, high ductility, and self-control of cracks. Concrete can be nano-engineered by the incorporation of nano-sized building blocks or objects (e.g., nanoparticles and nanotubes) to control material behavior and to add novel properties, or by the grafting of molecules onto cement particles, cement phases, aggregates, and additives (including nano-sized additives) to provide surface functionality, which can be adjusted to promote specific interfacial interactions. At the same time, this new nano-engineered concrete should be sustainable, cost and energy effective—in essence, exhibiting the qualities modern society demands.
Cement-based materials with nano-sized particles such as nano-silica and nano-Al2O3 demonstrate enhanced workability, strength and durability. Incorporation of nano-sized TiO2 particles introduces new characteristics such as self-cleaning, due to their photocatalytic properties. Nano-fibers such as multi-wall carbon nano-tubes and carbon nano-fibers alter the fracture properties of cement composites enabling to produce smart and ductile concrete composites.
Nanotechnology has changed our vision, expectations, and abilities to control the material world. These developments will greatly affect modern construction and the field of cement-based materials. In spite these developments, the nanotechnology is still in its pre-exploration stage; it is just emerging from fundamental research onto the industrial floor; thus the full-scale applications in concrete are still limited. Yet, the tremendous potential of nanotechnology to improve the performance of concrete is most promising.
Table of Contents
Learning objectives:
1. Recognize the opportunities with new nano-engineered concrete.
2. Identify appropriate production methods and suitable applications for concrete with nanoparticles / nanofibers.
3. Compare the performance of nanoparticles /nanofibers in concrete.
4. Analyze the assumptions and common misconceptions related to nanotechnology of concrete.
5. Recognize the environmental issues related to application of nanomaterials in concrete.
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