Title:
Fundamental Interactions between Multi-Walled Carbon Nanotubes (MWCNT), Ca2+ and Polycarboxylate Superplasticizers in Cementitious Systems
Author(s):
Ilina Kondofersky-Mintova and Johann Plank
Publication:
Symposium Paper
Volume:
288
Issue:
Appears on pages(s):
1-12
Keywords:
Carbon nanotubes, concrete, strength, polycarboxylate
DOI:
10.14359/51684245
Date:
9/14/2012
Abstract:
The fundamental interactions between polycarboxylate superplasticizers (PCEs), multi-walled carbon nanotubes (MWCNTs), Ca2+ ions and cement were investigated. Two commercial samples of MWCNTs were characterized by SEM and TEM imaging. It was found that only one sample contained mostly individual, non-agglomerated CNTs which were used in further tests. The MWCNT sample reduced cement paste flowability, but increased 28 day compressive strength by ~ 20% and tensile strength by 26%. The rela¬tively modest increase can be attributed to agglomeration of individual CNTs into large bundles (Ø ~ 900 nm, 3.51 × 10–5 in.). Agglomeration is caused by adsorption of Ca2+ ions onto the initially negatively charged surfaces of CNTs. This way, Ca2+ ions present in every cement pore solution impede maximal dispersion of CNTs in the cementitious matrix, thus limiting their potential application as nano reinforcement for concrete.