Chemical and Microstructural Properties of Designed Cohesive M-S-H Pastes

Materials

Charlotte Dewitte¹  Alexandre Dauzères¹  Mejdi Neji¹  Laurie Lacarrière²  Alexandra Bertron² 

[1] Institut de Radioprotection et de Sûreté Nucléaire (IRSN), PSE-ENV/SEDRE/LETIS, 92260 Fontenay-aux-Roses, France;LMDC (Laboratoire Matériaux et Durabilité des Constructions), Université de Toulouse, UPS, INSA, 135 Avenue de Rangueil, CEDEX 04, 31077 Toulouse, France;

关键词: magnesium silicate hydrates (M-S-H);    X-ray diffraction;    thermogravimetric analysis;    autoradiography;    physisorption;    mercury porosity;   

DOI  :  10.3390/ma15020547

来源: DOAJ

【 摘 要 】

Concretes can be exposed to a magnesium attack in several environments leading to the formation of magnesium silicate hydrates (M-S-H) and brucite (MH). The formation of M-S-H is likely to alter the properties of the cement matrix because it is linked to the decalcification of C-S-H. However, relatively few data on M-S-H exist in the literature. In order to characterize, physically and mechanically, the M-S-H phase, pure M-S-H cohesive pastes are needed. This work studies the formation of cohesive M-S-H pastes made with MgO-to-SiO₂ atomic ratios of 0.78, 1 and 1.3, from two types of silica (silica fume or colloidal silica) and under 20 °C and 50 °C thermal curing. X-ray diffraction and thermogravimetric analyses confirmed that the consumption of brucite and the formation of M-S-H were quicker with a 50 °C curing. Energy-dispersive X-ray spectroscopy and microtomography showed that colloidal silica enabled a better distribution of the particles than silica fume. Microstructural characterizations were conducted under the protocol with colloidal silica and 50 °C thermal curing. Porosity investigations allowed to describe the M-S-H pastes as highly porous materials with a low content of micropores in comparison with mesopores. The type of mixing influenced the mesopore size distribution.

【 授权许可】

Unknown