Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate

Abstract

Nanocrystalline calcium silicate hydrate (C–S–H) is the binding phase of many low-CO2 cements. Understanding its structure–mechanical properties relationship is critical in designing sustainable concrete. For the first time, a similar basal spacing (only 0.17 Å variation) of C–S–Hs at Ca/Si ratios of 0.8–1.5 is prepared via coprecipitation. The C–S–H nanostructure is determined using X-ray absorption spectroscopy, and the intrinsic nanomechanical properties of C–S–H at various Ca/Si are measured using high-pressure X-ray diffraction. For the first time, the influence of basal spacing on the nanomechanical properties is eliminated. At similar basal spacing, the ab-planar incompressibility remains independent of Ca/Si and silicate chain length, while the c-axis incompressibility is governed by the interlayer density (i.e., interlayer Ca content). The bulk modulus of C–S–H is governed by the interlayer densitymore interlayer Ca yields higher bulk modulus at comparable basal spacings. Our results show that coprecipitated C–S–Hs at higher Ca/Si have higher mechanical properties. The results have implications in designing green cement/concrete using bottom-up approaches by providing property inputs for multiscale simulation and references for validating computational methods/parameters.

Fly ash derived calcium silicate hydrate as a highly efficient and fast adsorbent for Cu(ii) ions: role of copolymer functionalization

“…1b, the CSH has a layer-stacked structure composed of intralayer Ca and wollastonite type Si chains. 22,23 When the molar Ca/Si ratio is 1, there are some distorted interlayer Ca atoms between layers, 23 which prefer to react with CO 2 in desilication solution and form by-product CaCO 3 . 17 While, in the presence of Acumer2000, the carboxyl groups can recognize and chelate to Ca( ii ) ions, and its carbon chains with sulfonic groups can give rise to steric and electrostatic repulsion.…”

Identification of Chemical Bonds and Microstructure of Hydrated Tricalcium Silicate (C3S) by a Coupled Micro-Raman/BSE-EDS Evaluation

“…This phenomenon can be confirmed by the formation of Ca-OH bonds in the C-S-H. M.J. Abdolhosseini Qomi [ 26 ] found that more Ca-OH bonds formed through water molecules dissociated and condensed into silica chains when the Ca/Si ratios increased from 1.1 to 2.0. This Ca-OH bond was pH dependently [ 27 ]. The other possible explanation is that outer C-S-H can grow on the surface of nano-CH particles [ 28 ].…”

Municipal Solid Waste Incineration Ash-Incorporated Concrete: One Step towards Environmental Justice

“…Figure 2 shows the approximate compositions of PC, MSWI ash, and industrial byproducts (coal fly ash, silica fume, and ground granulated blast-furnace slag (GGBFS)). [61,[64][65][66]). C-S-H is mesoporous with high surface areas.…”

“…Figure 1. Schematic diagrams of concrete at different scales (derived from[61,[64][65][66]). C-S-H is mesoporous with high surface areas.…”