Modelling mechanical behavior of cementitious material incorporating CNTs using design of experiments

- Effect of dispersion protocol when adding CNTs to cementitious materials is assessed.
- Design of experiments is used to perform the study and examine mechanical properties of blocks.
- Factors examined include wet mixing, sonication exposure time, whisking and CNTs concentration.
- Response surface methodology is used to model the experimentally determined compressive strength.
- The model can be used to determine the optimum methodology to disperse CNTs in cement composites.

One of the primary factors affecting the effectiveness of nanomaterials in enhancing cement composites properties is its ability to disperse efficiently without aggregation. To-date a number of methods have been proposed to increase the dispersion of CNTs in the mixes. Studies have shown that the response of cement-based materials to CNT addition can vary depending on the dispersion mechanism employed. Despite the need, there is no standardized methodology used to disperse CNTs, and consequently, it is hard to model the behavior. This study focused on using design of experiments (DOE) to assess the effect of dispersion protocol on the characteristics of cement-based composites. Experiments were carried out with different procedures to compare the effect of wet and dry mixing of CNTs, sonication exposure time, whisking and CNTs concentration on the mechanical properties of mortar blocks. Response Surface Methodology (RSM) was used to model the experimentally determined compressive strength. The model was further validated by comparing its predictions with other experimental scenarios. The model can be used to determine the optimum methodology to disperse CNTs in cement composites. To compare experimental data, there is a need to provide the exact details of all steps involved in a dispersion protocol that is captured by the proposed model. Following the suggested protocol for specimen preparation can ensure achieving a high level of dispersion and superior performance.