Influence of MWCNT/surfactant dispersions on the rheology of Portland cement pastes

This work studies the effect of MWCNT/surfactant aqueous dispersions on the rheology of cement paste. Three types of surfactants (sodium dodecyl sulfate, cetylpyridinium chloride and triton TX-100) were used to prepare cement pastes with and without MWCNT. Three rheological parameters were determined for each sample: static yield stress, yield stress, and viscosity. The first was measured directly, while the other two were obtained by fitting a Bingham model to the descending portion of a flow curve. Additionally, X-ray diffraction and isothermal calorimetry were used to follow the hydration reaction of cement during the first hour. It was found that the MWCNT/surfactant dispersions generate an overall shift to higher yield stress values while maintaining viscosity, suggesting a modification of the interparticle attraction. It was concluded that the triple interaction MWCNT-surfactant-cement governs the rheology of cement pastes. © 2018 Elsevier Lt

Reinforcing Effect of Carbon Nanotubes/Surfactant Dispersions in Portland Cement Pastes

Decoupling the individual effects of multiwalled carbon nanotubes (MWCNTs) and surfactants when used as reinforcement materials in cement-based composites is aimed in this study. Powder MWCNTs were dispersed in deionized water using different types of surfactants as chemical dispersing agents and an ultrasonic tip processor. Cement pastes with carbon nanotubes additions of 0.15% by mass of cement were produced in two steps: first, the MWCNT/surfactant dispersions were combined with the mixing water, and then, cement was added and mixed until a homogeneous paste was obtained. Mechanical properties of the pastes cured at 7 days were measured, and their fracture behavior was characterized using the linear elastic finite element analysis. It was found that the reinforcing effect of MWCNT was masked by the negative effect of surfactants in the cement matrix; nevertheless, nanotubes were capable of increasing both stress and strain capacity of the composite by controlling the crack propagation process at the tip of the crack. © 2018 Oscar A. Mendoza Reales et al