Characterization of the Bonds Developed between Calcium Silicate Hydrate and Polycarboxylate-Based Superplasticizers with Silyl Functionalities.
Major developments in concrete technology have been achieved with the use of polycarboxylate-based superplasticizers (PCEs) to improve the concrete rheology without increasing the mix water content. Currently, it is possible to control the fluidity of the fresh concrete and obtain stronger and more durable structures. Therefore, there is a strong incentive to understand the interactions between PCEs and cement hydrates at the atomic scale to design new customized functional PCEs according to the ever-increasing requirements of the concrete industry. Here, the bonding types generated between a PCE with silyl functionalities (PCE-Sil) and a synthetic calcium silicate hydrate (C-S-H) are analyzed using XRD,29Si NMR spectroscopy, and synchrotron-based techniques, such as NEXAFS and EXAFS. The results indicated that the carboxylic groups present in PCE-Sil interact by a ligand-type bond with calcium, which modified not only the symmetry and coordination number of the calcium located at the surface of C-S-H but also the neighboring silicon atoms of the C-S-H. In addition, the silyl functionalities of the PCE-Sil generated covalent bonds through siloxane bridges between the silanol groups of PCE-Sil and the nonbonding oxygen located at the dimeric sites in C-S-H, forming new bridging silicon sites and subsequently increasing the silicate polymerization.
Department of Civil Engineering, University of California , Berkeley, California 94720 United States.|Research and Development Center, R&D Cementos Argos S.A , Medellin 050022, Colombia.
Carlos A
0000-0002-7965-6410
CA
Orozco
Grace Construction Products, W. R. Grace & Co. , Cambridge, Massachusetts 02140, United States.
Byong W
BW
Chun
Department of Civil Engineering, University of California , Berkeley, California 94720 United States.
Guoqing
G
Geng
NMR Core Lab, King Abdullah University of Science and Technology , Thuwal 23955, Saudi Arabia.
Abdul H
AH
Emwas
Department of Civil Engineering, University of California , Berkeley, California 94720 United States.
Paulo J M
0000-0002-6866-1783
PJ
Monteiro