Characterization of Calcium Silicate Hydrate Gels with Different Calcium to Silica Ratios and Polymer Modifications

Abstract

Calcium silicate hydrate (CSH) gels, the main binding phases of hydrated cement, are the most widely utilized synthetic materials. To understand the influences of composition and polymers on the reaction kinetics and phase formation, CSH gels with varying Ca/Si ratios and amounts of poly (acrylamide-co-acrylic acid) partial sodium salt (PAAm-co-PAA) were synthesized via a direct method. The CSH gels were characterized through isothermal calorimetry, thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Raman spectroscopy at different ages. By increasing the Ca/Si ratio from 0.8 to 1.0, the formation of CSH was enhanced with a 5.4% lower activation energy, whereas the incorporation of PAAm-co-PAA increased the temperature sensitivity of the reactions with an 83.3% higher activation energy. In the presence of PAAm-co-PAA, the reaction rate was retarded at an early age and the negative impact faded over time. The results of an XRD analysis indicated the formation of tobermorite as the main phase of the CSH gels, while the addition of PAAm-co-PAA resulted in a postponed calcium hydroxide consumption and CSH formation, which was confirmed by the decreased FTIR intensity of the C=O bond, Si–O stretching and Si–O bonds. The increased Raman vibrations of Si–O–Si bending Q2, Ca–O bonds, O–Si–O and asymmetric bending vibrations of SiO4 tetrahedra in the presence of PAAm-co-PAA indicate the intercalation of the polymeric phase and internal deformation of CSH gels.

Carbonation Curing and Kinetics of Wood-Sodium Silicate Composites

“…These peaks were due to the evaporation of chemically bound water and the degradation of silicate gel hydrates, which occurred at a higher temperature for the 105 °C cured samples. The intensity and the late degradation of the samples cured at 105 °C show a high initial reaction rate and better crosslinking . Liu et al observed a similar DTG peak temperature between 150 and 200 °C in the study of effects of additives and fillers on properties of SS wood adhesive modified with poly(vinyl alcohol) .…”

“…The intensity and the late degradation of the samples cured at 105 °C show a high initial reaction rate and better crosslinking. 72 Liu et al observed a similar DTG peak temperature between 150 and 200 °C in the study of effects of additives and fillers on properties of SS wood adhesive modified with poly(vinyl alcohol). 33 For the carbonated SS samples, DTG peaks (Figure 5d,f) below 600 °C were seen between 139 °C and 179 °C for samples postcured at 60 °C and between 136 °C and 284 °C for samples postcured at 105 °C.…”

“…The intensity of 105 °C post-cured SS-CO 2 samples was lower than 60 °C post-cured samples indicating better reactivity and increased thermal stability. 72 DTG peaks of the SS-CO 2 composites below 600 °C generally shifted to lower temperatures with an increase in CO 2 reaction time owing to increased formation of SiO 2 and Na 2 CO 3 , which had more mass loss at lower temperatures. There were also shifts in the DTG peak temperatures to lower values with an increase in CO 2 pressure from 7 to 138 kPa (Table S5) due to probable reactions that yielded more NaHCO 3 formation.…”

A Study on the Cement Gel Formation Process during the Creation of Nanomodified High-Performance Concrete Based on Nanosilica

“…The addition of CSH nanoparticles as nuclei has been successfully used to accelerate the process of the hydration and settling of binder phases in both conventional Portland cement and alternative binders [ 17 , 37 ]. In addition, CSH gels are known as the most widely used synthetic materials [ 38 ].…”

The Investigation of Compacting Cement Systems for Studying the Fundamental Process of Cement Gel Formation

“…At the same time, the importance of the gel/space ratio for the compressive strength of cement composites is noted [ 27 , 28 , 29 ]. The study of the microstructure of calcium silicate hydrate (CSH) gels from theoretical and computational points of view, as well as the fractality of CSH and the evaluation of the mechanical properties and durability of CSH—with particular reference to carbonization and chloride/sulfate exposure—are also important in influencing the mechanical properties and durability of cement-based materials [ 30 , 31 ]. The most recent works of authors who studied the formation of the structure of cement pastes from the point of view of the mechanisms of gel formation and hardening are primarily aimed at the microstructural component of these processes and mechanisms [ 32 , 33 , 34 , 35 , 36 ].…”