Influencing factors on micromechanical properties of calcium (alumino) silicate hydrate C-(A-)S-H under nanoindentation experiment

Hay, Rotana; Li, Jiaqi; Çelik, Kemal

doi:10.1016/j.cemconres.2020.106088

Cited by 61 publications

(12 citation statements)

References 71 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Our measured H 2 O/Si ratios at various Ca/Si are within the range of common H 2 O/Si ratios of C−S− H summarized in a comprehensive data set, 20 confirming that the drying process was not excessive. To our knowledge, comparable basal spacings of C−S−H using different drying protocols in our published studies 29,30,37,56 of CaO−SiO 2 reacted C−S−H and in many unpublished studies were not found. Therefore, the comparable basal spacing of coprecipitated C−S−Hs at various Ca/Si is assigned to the strong interlayer CaOH +49 at low Ca/Si (caused by negative pH-Ca/ Si correlation in the coprecipitation method).…”

Section: ■ Experimental Sectionmentioning

confidence: 70%

Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate

Wenxin

Monteiro

2020

ACS Sustainable Chem. Eng.

Self Cite

View full text Add to dashboard Cite

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.

show abstract

Section: ■ Experimental Sectionmentioning

confidence: 70%

Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate

Wenxin

Monteiro

2020

ACS Sustainable Chem. Eng.

Self Cite

View full text Add to dashboard Cite

show abstract

“…The higher and stable value of elastic modulus of MK50 mix as compared to SF50 mix indicates the hydration products formed in MK50 mix could possess superior properties that aid in providing better mechanical and stiffness characteristics. Hay et al [44] demonstrated incorporation of aluminum in C-S-H, the major hydration product in PC, led to an increase in the elastic modulus and mechanical properties of the phase due to enhanced cross-linking and improved compactibility. An analogous result of the incorporation of aluminum in M-S-H could lead to an improvement of MgO binder performance containing MK.…”

Section: Concrete Mechanical Propertiesmentioning

confidence: 99%

Long-term performance of MgO–SiO2 binder

2022

View full text Add to dashboard Cite

Magnesium silicate hydrate (M–S–H) formed on reaction of MgO and reactive SiO2 imparts binding characteristics similar to Portland cement (PC). Limited knowledge is available on the long-term mechanical and durability performance of M–S–H binder systems. In this study, the performance of MgO–SiO2 binder was assessed up to 365 days. In addition to silica fume (SF), the most widely used silica source with MgO, calcined clay (CC) with kaolinite content of ~ 40–50% and industrial grade metakaolin (MK) were also investigated. Mortar specimens were prepared with all the three silica sources at three different proportion levels of MgO and silica source. Thermodynamic modelling was carried out to further understand the changes occurring in the phase assemblage during hydration for the adopted proportions. Concrete mixes comprising of MgO and MK or SF in a ratio of 1:1 and PC as a control mix were cast a water to binder ratio of 0.4. The compressive strength and porosity were measured at 7, 28, 90 and 365 days on mortar and concrete specimens. In addition, elastic modulus and electrical resistivity was also measured on the concrete samples at all the above-mentioned ages. MgO mixes with CC and MK showed a continual increase in compressive strength until 365 days whereas strength retrogression was observed in MgO–SF mixes after 90 days. The durability indicators for MgO–MK concrete showed better or similar performance as compared to PC. The aluminum present in the CC and MK helps to improve the overall characteristics of the MgO–SiO2 binder.

show abstract

“…Although the synthetic hydrates were compacted and finely polished, artifacts of compliance were present in the load-depth curves for basic indents, as well as modulus-depth plots for CSM indents. 20 Notably, Das et al used CSM indentation and the modulus-depth plot to ensure indent quality for SNI of an alkali-activated fly ash. Their results showed clearly defined data assignments for each phase, though this may also be attributed to the morphology of phases in the material's microstructure.…”

Section: F I G U R Ementioning

confidence: 99%

On the role of continuity in statistical nanoindentation of composite microstructures

2022

View full text Add to dashboard Cite

The validity of the statistical nanoindentation (SNI) technique for cementitious materials has been questioned by numerous researchers; however, it is still a commonly used method in literature. This study revisits assumptions pertaining to continuum mechanics of the method by using a well-established selective SNI method to evaluate continuity in the mechanical response of each indent. Ordinary portland cement (OPC) was investigated alongside a two-phase aluminosilicate ceramic (Al-Si). Filtering for continuity of indents eliminated a majority of indents in each sample. The indents meeting continuity requirements in the OPC sample had moduli values in the range of documented calcium silicate hydrates and portlandite-the predominant hydration phases in OPC. In the Al-Si sample, 73% of continuous indents were assigned to a mullite phase, although the chemical analysis showed only 42% mullite. This was attributed to the embedded morphology of the mullite phase, which made it more susceptible to structural compliance. These observations suggest that SNI may be ineffective for measuring the mechanical properties of individual phases in a microstructure if they are not prolific enough to exhibit a continuous indent response. Discontinuous indents due to microstructural interaction between phases were also shown to have a potential influence on the number of clusters (i.e., phases) suggested by the deconvolution algorithms.

show abstract

Influencing factors on micromechanical properties of calcium (alumino) silicate hydrate C-(A-)S-H under nanoindentation experiment

Cited by 61 publications

References 71 publications

Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate

Structure and Intrinsic Mechanical Properties of Nanocrystalline Calcium Silicate Hydrate

Long-term performance of MgO–SiO2 binder

On the role of continuity in statistical nanoindentation of composite microstructures

Contact Info

Product

Resources

About