Microstructural changes of globules in calcium–silicate–hydrate gels with and without additives determined by small-angle neutron and X-ray scattering

Abstract

a b s t r a c tThe microstructure of calcium-silicate-hydrate (CÀSÀH) gel, a major hydrated phase of Ordinary Portland Cement, with and without polycarboxylic ether (PCE) additives is investigated by combined analyses of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) data. The results show that these comb-shaped polymers tend to increase the size of the disk-like globules but have little influence on the thickness of the water and calcium silicate layers within the globules. As a result, the fractal packing of the globules becomes more open in the range of a few hundred nanometers, in the sense that the mass fractal dimension diminishes, since the PCE adsorption on the globules increases the repulsive force between and polydispersity of the CÀSÀH units. Moreover, scanning electron microscope (SEM) study of the synthesized CÀSÀH gels in the micrometer range shows that the PCEs depress the formation of fibrils while enhancing the foil-like morphology.

The application of thermal analysis, XRD and SEM to study the hydration behavior of tricalcium silicate in the presence of a polycarboxylate superplasticizer

“…Similar results concerning this effect have been reported by other authors for C-S-H [12,13] and also other types of superplasticizers like polycondensates [9]. In particular, Chiang et al [12] found the microstructure of C-S-H was modified by PC. The C-S-H formed in the presence of PC is foil-like morphology rather than fibril, which was more compact and interconnected.…”

“…In another paper, the microstructural evolution of C-S-H in the presence of PCs was investigated by combined analyses of small-angle X-ray scattering (SAXS) and small-angle neutron scattering (SANS) data. Chiang et al [12] showed that the addition of PCs to C 3 S pastes modified both the structure of the C-S-H basic globules and the overall microstructural arrangement. Recently, the C-S-H microstructure during C 3 S hydration has been studied [13] by means of low-temperature differential scanning calorimetry (LT-DSC).…”

“…The determination of the change in Ca (OH) 2 phase during cement hydration represents one of the way to trace the development of the hydration process. Although systematic work has been done on the hydration kinetics of C 3 S as well as on C-S-H microstructure [12,14,15], the formation of Ca (OH) 2 during C 3 S hydration and morphology change of Ca(OH) 2 in the presence of PC is poorly investigated. In this study, pure C 3 S phase was synthesized and the interaction between C 3 S and PC were carefully studied.…”

Multi-scale Review for Possible Mechanisms of Natural Frequency Change of Reinforced Concrete Structures under an Ordinary Drying Condition

“…Small angle scattering profiles (Chiang et al 2012(Chiang et al , 2013Nicoleau et al 2013;Trapote-Barreira et al 2015) and 1 H-NMR relaxometry (Korb 2009;McDonald et al 2010;Muller et al 2012Muller et al , 2013Muller et al , 2015Valori et al 2013) give insights on this topic. An example of elaboration to explain the relationships between C-S-H microstructure change under the first drying and physical properties is shown in the references (Maruyama et al 2014a(Maruyama et al , 2016a.…”

Recent studies of cements and concretes by synchrotron radiation crystallographic and cognate methods

“…[110] The changes in the microstructures due to the use of cement additives have also been investigated by SAXS and SANS (see Figure 10). [111] The reported results showed that the used PCE tends to increase the size of the disk-like C-S-H globules but has little influence on the thickness of the water and calcium silicate layers within the globules. It must also be noted in importance of SANS studies.…”