Nanotechnology in Civil Infrastructure

pp 103-130

The Effect of SWCNT and Other Nanomaterials on Cement Hydration and Reinforcement

  • Jon MakarAffiliated withInstitute for Research in Construction, National Research Council Canada

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Additions of nanomaterials to cement pastes and concretes may have a significant effect on the performance of ordinary Portland cement (OPC), OPC blends and concrete. Due to the scale of these particles, they may not only modify the bulk behavior of the matrix in a manner similar to micro- and macroscopic additions, but also influence the formation and structure of the C-S-H and other products formed during hydration. Nanoscale additives also have the potential to add new capabilities to concrete. There is therefore growing interest in producing composite materials that include nanomaterials.

Single walled carbon nanotubes (SWCNT) are of particular interest due to their desirable properties as reinforcing materials. They have recently been shown to nucleate the formation of C-S-H during the hydration of ordinary Portland cement (OPC). A series of complementary studies are presented here. The effects of nanotitania, nano-calcium carbonate and nano-alumina dispersed by sonication with OPC on hydration are discussed and compared to the effect of SWCNT dispersed by the same method. The impact of dispersing the SWCNT in blends of admixture and mix water on the hydration of both tricalcium silicate and OPC are investigated. Fracture surfaces of OPC samples blended with all four nano-materials and hydrated for 7 days are analyzed. Classical reinforcing behaviour was identified in the SWCNT/OPC composite alone. A new, nanoscale reinforcing mechanism based on SWCNT bundle pull out is described. The experimental results are used to draw conclusions about the nucleation mechanism in SWCNT composites and on the impact of SWCNT dispersion method on the performance of those composites.