Producing C-S-H gel by reaction between silica oligomers and portlandite: A promising approach to repair cementitious materials

Effect of Morphologically Controlled Hematite Nanoparticles on the Properties of Fly Ash Blended Cement

“…Case I ( Figure 11 a), the cementitious composites produce the C-S-H gel and capillary pores during hydration [ 51 ]. The added FA particles fill in the capillary pore of C-S-H gel structure to reduce the porosity in cement [ 52 , 53 ]. Meanwhile, as hydration progresses, the capillary pores create even more spacing that may decrease the strength of cement composites.…”

Advanced Materials in Cultural Heritage Conservation

“…The restoration of concrete-based materials is an emerging research field, given the number of historical monuments built in the last century using concrete that are in need of conservation interventions. To address the damages that affect these structures, two different approaches have been recently explored: (i) cement formulations enriched with inorganic admixtures, namely silica and benzotriazole-loaded halloysites, have been used to recover small damages, such as delaminations and cracks (<1 cm), and, at the same time, to address in an innovative way the problem of corrosion of steel rebars (see Figure 6 ) [ 74 ]; and (ii) silica oligomer based-impregnation treatments have been used to produce a C-S-H gel from the reaction between silanol groups from the silica-based products and Ca 2+ ions from original portlandite, resulting in a simple, compatible, and effective consolidation of degraded cements [ 75 ].…”

How Science Can Contribute to the Remedial Conservation of Cultural Heritage

“…The same type of reaction has been employed to have silica oligomers react with portlandite crystalline Ca(OH) 2 found in cement: the oligomers can penetrate cement, polymerize by sol-gel process, and form in situ a CSH gel that is incorporated in the existing CSH of cement, opening the way for simple repairs of contemporary concrete monuments. [24] Protection of artistic surfaces against recurring soiling and degradation is another type of remedial intervention where relevant contributions have been derived from colloids and materials science. Halloysite and other nanoclays can be incorporated into a polymer matrix (e. g., fluorinated or biopolymers) able to form protective films on stone and metals against atmospheric pollutants, corrosive agents, entomological attacks, and even graffiti vandalism.…”