The Reduction of Maximum Hydration Temperature in Cement Paste Using Calcium Silicate Hydrates and Glucose

Understanding the micro-mechanical properties and the microstructure of cement-based materials under the saline lake environment in western China can provide a scientific basis for the durability design. In this study, cement pastes ((w/c=0.35) and (w/c=0.53)) were prepared and soaked in brine solution to carry out the dry-wet cycle test, the chemical composition of which is similar to saline lake solution. The micrographs of corroded regions and corrosion products were observed and analyzed under scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). Micro-mechanical properties of different phases were tested by nanoindentation, and multi-peaks fitting was carried out for the experimental frequency distributions of the indentation modulus and indentation hardness by Gaussian function. In the meantime,the statistical distribution of micro-mechanical properties was summarized for the hydrates in corroded cement paste, which has included the low density calcium–silicate–hydrates (LD C-S-H gel), high density calcium–silicate–hydrates (HD C-S-H gel) and calcium hydroxide (CH). The results show that micro mechanical properties of each phase in cement paste after brine corrosion decreased significantly. In addition, the water-cement ratio has little effect on the micro mechanical properties, but much effect on volume fraction of each phase.

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Structure, Fractality, Mechanics and Durability of Calcium Silicate Hydrates

Fractal and Fractional ◽

10.3390/fractalfract5020047 ◽

2021 ◽

Vol 5 (2) ◽

pp. 47

Author(s):

Shengwen Tang ◽

Yang Wang ◽

Zhicheng Geng ◽

Xiaofei Xu ◽

Wenzhi Yu ◽

...

Keyword(s):

Mechanical Properties ◽

Cement Paste ◽

Calcium Silicate ◽

Preparation Method ◽

Point Of View ◽

Computational Point ◽

Calcium Silicate Hydrates ◽

Binding Phase ◽

Cement Based Materials ◽

Hydrated Products

Cement-based materials are widely utilized in infrastructure. The main product of hydrated products of cement-based materials is calcium silicate hydrate (C-S-H) gels that are considered as the binding phase of cement paste. C-S-H gels in Portland cement paste account for 60–70% of hydrated products by volume, which has profound influence on the mechanical properties and durability of cement-based materials. The preparation method of C-S-H gels has been well documented, but the quality of the prepared C-S-H affects experimental results; therefore, this review studies the preparation method of C-S-H under different conditions and materials. The progress related to C-S-H microstructure is explored from the theoretical and computational point of view. The fractality of C-S-H is discussed. An evaluation of the mechanical properties of C-S-H has also been included in this review. Finally, there is a discussion of the durability of C-S-H, with special reference to the carbonization and chloride/sulfate attacks.

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Microstructure-Based Evolution of Compressive Strength of Blended Mortars: A Continuum Micromechanics Approach

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.1144.121 ◽

2017 ◽

Vol 1144 ◽

pp. 121-127 ◽

Cited By ~ 1

Author(s):

Michal Hlobil

Keyword(s):

Compressive Strength ◽

Cement Paste ◽

Calcium Silicate ◽

Multiscale Model ◽

Elastic Stiffness ◽

Cementitious Materials ◽

Supplementary Cementitious Materials ◽

Successful Model ◽

Continuum Micromechanics ◽

Calcium Silicate Hydrates

The evolution of stiffness and strength belong to the most important properties of mortars. Motivated by an increasing demand for clinker substitution by supplementary cementitious materials (SCMs), this paper presents a multiscale model for prediction of elastic stiffness and compressive strength of blended mortars. Mortars are envisioned as hierarchically organized materials with microstructural phases spanning several orders of magnitude. On the scale of hundreds of nanometers, "CSH foam" consists of amorphous calcium silicate hydrates mixed with capillary pores which on the scale of hundreds of microns acts as a contiguous matrix reinforced by unhydrated clinker, SCM grains, and by crystalline hydration products forming "cement paste". The largest scale of observation describes mortar as quartz sand aggregate inclusions embedded into a contiguous cement paste matrix. Continuum micromechanics homogenization approach is used to upscale stiffness from calcium silicate hydrates, represented by needle-shaped ellipsoids, up to the scale of mortar. Macroscopic quasi-brittle failure of mortar is associated with a concentration of strain energy density-related microscopic stresses within a critically oriented needle-shaped hydrate in "CSH foam". Successful model validation on OPC-based and blended mortars provides strong evidence that continuum micromechanics is an efficient tool for quantification of stiffness and compressive strength.

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