A review on the chemical, mechanical and microstructural characterization of carbon nanotubes-cement based composites

- The mechanisms by which CNT's interact with cement are not fully understood.
- Characterization techniques must be adapted to better understand the composites.
- Specific testing standardization is needed to develop the CNT's-cement technology.

It is known that carbon nanotubes (CNT's) modify the properties of cement based composites in fresh and hardened state; it is also known that these modifications are positive when appropriate dispersion of CNT's within the matrix is achieved. Traditional experimental approaches used for fiber reinforced composites have been widely applied to study CNT's-cement composites; nevertheless, high statistical dispersions and conflicting reports have been found to be a common issue due to the nanometric nature of CNT's. This review presents a critical analysis of the most commonly used techniques to test CNT's-cement composites, opening the discussion of the necessity of specific testing standardization for the development of the technology. Topics such as CNT's dispersion and measurement of mechanical performance, electromagnetic properties and durability of CNT's-cement composites are addressed.It is concluded that the benefits of CNT's in cement composites have been fairly identified, but the mechanisms by which nanotubes maintain dispersion within the matrix, interact with hydrating cement, and modify properties of composites are not yet fully understood. Understanding these mechanisms is considered of most importance to identify the limitations of CNT's-cement composites and define which applications are achievable with the use of CNT's. Better characterization of the interaction between CNT's and hydration products at the nanoscale is required to develop more efficient composites, targeting the enhancement of multiple properties at the same time.