scholarly journals Effect of Ultrafine Additives on the Morphology of Cement Hydration Products

Crystals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1002
Author(s):  
Grigory Yakovlev ◽  
Rostislav Drochytka ◽  
Gintautas Skripkiunas ◽  
Larisa Urkhanova ◽  
Irina Polyanskikh ◽  
...  
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
Cement Hydration ◽  
Chemical Reactivity ◽  
Xrd Analysis ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
X Ray ◽  
Strong Adhesion

The present research is focused on the investigation of the influence of ultrafine additives on the structure formation of hardened cement paste and the establishment of the mechanisms of the morphological transformations, which determine the properties of hydrated products. In the course of the research, the modification of ordinary Portland cement was performed by the suspension of multi-walled carbon nanotubes (MWCNTs), carbon black (CB) paste, and silica fume (SF). Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD) analysis, thermal analysis, and Fourier-transform infrared (FTIR) spectroscopy were used to study cement hydration products. The morphology of hardened cement paste depends on the chemical reactivity of additives, their geometry, and their genesis. The action mechanism of the inert carbon-based additives and pozzolanic silica fume were considered. The cement hydration products formed in the process of modification by both types of ultrafine additives are described. In the case of the modification of cement paste by inert MWCNTs and CB paste, the formation of cement hydration products on their surface without strong adhesion was observed, whereas in the case of the addition of SF separately and together with MWCNTs, the strong adhesion of additives and cement hydration products was noted.

Thermodynamic Interpretation of Carbonation Process of Portland Cement Hydration Products

2013 ◽  
Vol 753-755 ◽  
pp. 543-557
Author(s):  
Yan Jun Liu ◽  
Bo Tian Chen ◽  
Yong Chao Zheng
Keyword(s):  
Carbon Dioxide ◽  
Free Energy ◽  
Gibbs Free Energy ◽  
Cement Paste ◽  
Cement Hydration ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Equilibrium Pressure ◽  
Carbonation Process

Cement hydration products carbonation is not only blamed for the carbonation-induced hardened cement paste or concrete cracking, also attributed to the pore water PH-value decrease, which causes the reinforcement corrosion under the existence of water and oxygen due to removal of oxide film passivating rebar surface, in hardened cement paste and concrete. Based on chemical thermodynamics, this paper presents the susceptibility of different cement hydration products to carbonation through calculating their Standard Gibbs Free Energy respectively, Gibbs free energy under temperature variation and the minimum equilibrium pressure of carbon dioxide triggering the carbonation process. The calculated results show that, under standard state (25°C, 100kpa), the minimum equilibrium pressure of carbon dioxide triggering carbonation process is significantly variable for different types of cement hydration products. For example, mono-sulfate sulfoferrite hydrates (3CaOFe2O3CaSO412H2O) is the most susceptible to carbonation, followed by mono-sulfate aluminate hydrates (3CaOAl2O3CaSO412H2O), while multi-sulfate sulfoaluminate hydrates (3CaOAl2O33CaSO432H2O) is the least vulnerable to carbonation, followed by silicate hydrates (5CaO6SiO25.5H2O). The findings in this paper are significant in understanding thermodynamic mechanism of cement hydrates carbonation and seeking the solution to prevent cement hydrates from carbonation-induced deterioration.

scholarly journals HYDRATION AND MICROSTRUCTURAL PROPERTIES OF CEMENT PASTE CONTAINING NANO AND MICROSILICA

2014 ◽  
Vol 1 (1) ◽  
Author(s):  
P. L. Chow ◽  
Salim Barbhuiya
Keyword(s):  
Cement Paste ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
Xrd Analysis ◽  
Hardened Cement ◽  
Microstructural Properties ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Final Setting Time ◽  
Binder Ratio

The influence of nano-and microsilica addition on ordinary Portland cement (OPC) pastes has been studied in terms of hydration and microstructural properties. Three different combinations of nano-and microsilica mixes were used. A constant water-binder ratio of 0.35 was maintained throughout the experiment. All samples were tested for initial and final setting time and compressive strengths were determined at the age of 3, 7, 28, and 90 days of hydration. The hydration products were examined by SDT and XRD analysis at various curing ages. The inclusion of nano-and microsilica reduced the initial and final setting time significantly, increased the compressive strength of hardened cement paste after 7 days of hydration, and reduced the amount of calcium hydroxide in the hardened paste compared to mixes without these nanoparticles.

The Combined Effect of the Plasticizer and Multi-Walled Carbon Nanotubes on the Cement Hydration Products

2018 ◽  
Vol 276 ◽  
pp. 21-26
Author(s):  
Gintautas Skripkiūnas ◽  
Grigory Ivanovich Yakovlev ◽  
Ekaterina Karpova ◽  
Anastasiia Gordina ◽  
Arina Shaybadullina
Keyword(s):  
Carbon Nanotubes ◽  
Cement Paste ◽  
Cement Hydration ◽  
Hardened Cement ◽  
Hydration Products ◽  
Hardened Cement Paste ◽  
Physico Chemical ◽  
Cement System ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

There are many research devoted to the influence of carbon nanotubes (CNT) on the structure and properties of cement systems. In the course of this research, the combined influence of of multi-walled carbon nanotubes (MWCNT) and polycarboxylate (PCE) plasticizer on the products of hydration and the properties of hardened cement paste was investigated. The strength characteristics of nanomodified hardened cement paste and the hydration products were determined by the usage of modern methods of physico-mechanical and physico-chemical analyses. Based on the physico-chemical investigations, it was concluded the necessity of additional experiments, associated primary with questions of uniform distribution of the nanostructures and their chemical interactions with another components of admixture and cement system.

scholarly journals COMPLEX ADMIXTURES FOR HIGH-STRENGTH CONCRETE

2002 ◽  
Vol 8 (4) ◽  
pp. 276-280 ◽  
Author(s):  
Gintautas Skripkiūnas ◽  
Žymantas Rudžionis ◽  
Vitoldas Vaitkevičius
Keyword(s):  
Silica Fume ◽  
Cement Paste ◽  
High Strength Concrete ◽  
Cement Hydration ◽  
High Strength ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
Strength Concrete ◽  
Concrete Production ◽  
Paste Properties

The influence of naphthalene formaldehyde superplasticizers (NFS), lignosulfonate plasticizers (LSP) and silica fume on cement paste properties and complex usage of these admixtures for high-strength concrete production are investigated in this research. These admixtures influence the cement hydration products morphology and properties of hardened cement paste. The degree of cement hydration and Ca(OH)2 content in hardened cement paste were determined for analysis of cement hydration process with admixtures. Mechanical properties and porosity of hardened cement paste with the admixtures were tested. Optimal dosages of plasticizing admixtures and silica fume were estimated and the most efficient method of silica fume adding to concrete mixture was proposed. The results of investigation have been used for high-strength concrete production.

Density mapping of hardened cement paste using ptychographic X-ray computed tomography

2013 ◽  
Vol 36 ◽  
pp. 71-77 ◽  
Author(s):  
Pavel Trtik ◽  
Ana Diaz ◽  
Manuel Guizar-Sicairos ◽  
Andreas Menzel ◽  
Oliver Bunk
Keyword(s):  
Computed Tomography ◽  
Cement Paste ◽  
Hardened Cement ◽  
Hardened Cement Paste ◽  
X Ray ◽  
Density Mapping ◽  
X Ray Computed

NMR T1–T2 correlation analysis of molecular absorption inside a hardened cement paste containing silanised silica fume

2018 ◽  
Vol 117 (7-8) ◽  
pp. 1000-1005 ◽  
Author(s):  
Calin Cadar ◽  
Andrea Cretu ◽  
Marioara Moldovan ◽  
Carlos Mattea ◽  
Siegfried Stapf ◽  
...  
Keyword(s):  
Correlation Analysis ◽  
Silica Fume ◽  
Cement Paste ◽  
Hardened Cement ◽  
Molecular Absorption ◽  
Hardened Cement Paste
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