Determination of atomistic deformation of tricalcium silicate paste with high‐volume fly ash

Abstract

Supplementary cementitious materials (SCMs), such as blast-furnace slag, 1 fly ash (FA), 2 natural pozzolans, 3 calcined clays, 4 and silica fumes, 5 have been investigated as partial replacements for Portland cement (PC) in concrete mixes. FA, a by-product of coal, is one of the main SCMs, and has been studied extensively. 6 Using FA as a partial replacement for PC allows for recycling of the industrial by-products, effectively reduces carbon emissions from cement production, and confers durability to concrete. 7 According to ASTM C618, there are two types of FA, namely Class F and Class C, which are defined based on their contents of silicates and CaO. While Class F is the main type of FA currently produced, it does not possess cementitious characteristics. 8 However, the siliceous and

Temperature effects on local structure, phase transformation, and mechanical properties of calcium silicate hydrates

“…Recently, PDF analysis has proven a powerful analytical tool for understanding the structure of amorphous phases (e.g., silica fume, fly ash, alkali silica reaction gel, and geopolymers) over a wide range of length scales 11 . Our previous studies confirmed the nanostructural deformation of C–S–H in C 3 S paste 16,49 and C 3 S paste with high‐volume fly ash 30 via PDF analysis. In our work, the PDF analysis was based on the isotropic assumption.…”

“…In our work, the PDF analysis was based on the isotropic assumption. Although it is clear that the structural anisotropy strain under uniaxial loading should be considered, 50 the difference between isotropic and anisotropic analyses is negligible for metallic glasses 30,51 . In addition, it is still controversial whether C–S–H possesses intrinsically anisotropic properties or transversely isotropic properties owing to its imperfect structure 52 .…”

“…However, the intrinsic mechanical properties of the C–S–H phases differ with varying Ca/Si ratios. Recent studies have presented two hypotheses for the elastic modulus of C–S–H: one is that a higher Ca/Si should have a higher elastic modulus, 72 and the other is that lower Ca/Si should have a higher elastic modulus 30 . Therefore, in‐situ X‐ray scattering experiments should be conducted on pure synthetic C–S–H pastes with varying Ca/Si to provide new insight into the kinetics of dehydration, decomposition, and recrystallization due to heating.…”

“…During the X‐ray scattering experiments, compression testing was conducted using a 5‐kN compression stage (MicroTest, Deben, Bury St. Edmunds, UK) to investigate the changes in the macromechanical/nanomechanical properties of C–S–H after heating. Furthermore, two foil strain gauges were attached to the surfaces of four samples to measure the macroscopic uniaxial strain during compression testing at intervals of 0.4 MPa, and a loading rate of 0.01 mm/min 30 . The stress–strain curves were then obtained using the average values of stress and strain.…”

Synthesis of Highly-Dispersed Graphene Oxide Nanoribbons–Functionalized Carbon Nanotubes–Graphene Oxide (GNFG) Complex and Its Application in Enhancing the Mechanical Properties of Cementitious Composites

“…In general, XRD is used to determine the CH content instead of the C–S–H content because CH has a hexagonal crystal structure that can be easily detected by XRD. In contrast, the C–S–H phase forms a semi-crystalline or amorphous phase, which limits the use of XRD as a detection technique [ 47 , 99 , 100 , 101 ]. In the crystallization patterns ( Figure 17 ), the diffraction peaks of CH were observed at 2θ = 17.9°, 28.6°, 34.1°, 47.1°, and 50.1° [ 47 ].…”