Christophe Labbez - The effect of polycations on early cement paste

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      Publication Details (including relevant citation   information):

      I. Pocharda, C. Labbeza, A.   Nonata, H. Vijab and B.   Jönssonc,   Cement and Concrete Research, (2010)   10.1016/j.cemconres.2010.06.002

      Abstract:

      This paper studies the possibility for improving the ductility of   cement  based materials by means of oligocationic additives.   Actually, the  setting of cement is due to ionic correlation   forces between highly  negatively charged C–S–H   nanoparticles throughout a calcium rich  solution. The main   drawback of this strong attraction is its very short  range   that results in low elastic deformation of hydrated   cementitious  materials. A way to enlarge the attraction   range between C–S–H particles  would be to add cationic   oligomers that would compete with calcium ions  modifying   the ionic correlation forces via a bridging mechanism of    longer range, which could lead to a more ductile material. The   studied  parameters were the polymerization degree, the   separation distance  between the charged monomers and the   balance between oligocations and  monovalent and divalent   cations in the solution. The results, both  experimental and   numerical by Monte Carlo (MC) simulations, demonstrate  that   cationic oligomers can compete with calcium cations as   counterions  to the C–S–H surface. The cohesive forces   between C–S–H surfaces,  calculated by MC simulations, show   an interesting behaviour where range  and magnitude can be   tuned with oligomer concentration, polymerization  degree   and line charge density. Thus, it seems possible to modulate   the  ductility and critical strain of cement by addition of   cationic  oligomers.

      Address (URL): http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6TWG-50CD24W-1&_user=4 92990&_coverDate=06%2F23%2F2010&_alid=1419506731&_rdoc=1&_fmt=high&_orig=search& _cdi=5562&_sort=r&_docanchor=&view=c&_ct=1&_acct=C000023918&_version=1&_urlVersi on=0&_userid=492990&md5=63abd584540d08cb6220d0cbd55008f2