Effects of Nanosilica as Suspensions on the Hydration and the Microstructure of Hardened Cement Paste

2020 ◽  
pp. 036119812096795
Author(s):  
Dulani P. A. Kodippili ◽  
Robin A. L. Drew ◽  
Michelle R. Nokken
Keyword(s):  
Pore Size ◽  
Isothermal Calorimetry ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Production Methods ◽  
Beneficial Effects ◽  
Agglomeration Of Nanoparticles ◽  
Calorimetric Studies ◽  
Hydration Characteristics ◽  
Insight Into

Nanosilica (NS) has shown significant beneficial effects on concrete. However, the utilization of NS to achieve its maximum benefits is limited by the agglomeration of nanoparticles, which is associated with production methods and the method of NS dispersion in concrete. In this study, the effects of the utilization of NS as a suspension in calcium hydroxide (CH) on the hydration characteristics and the microstructure of the cement pastes were investigated with different levels of cement replacements (1%, 2%, 4%, and 6% NS) at 2, 7, and 28 days. The hydration of the cement pastes was investigated by isothermal calorimetry, and the measurement of CH content by thermogravimetry. The microstructures were analyzed by scanning electron microscopy and by energy dispersive X-ray spectroscopic mapping. The microstructure of the pastes was characterized by analyzing the pore size and the pore size distribution using mercury intrusion porosimetry (MIP). The calorimetric studies indicated that the replacing cement by NS derived by this method leads to faster hydration up to 4% replacement. The CH contents could be reduced by the incorporation of NS. The pore structures revealed that the pastes with NS had become comparably denser than the pastes without NS. A positive insight into the durability characteristics was shown by the results of the MIP when using NS as suspensions.

Pozzolanic Reactions in Cementitious Materials for Subsurface Applications

2014 ◽  
Author(s):  
Neven Ukrainczyk ◽  
Jure Zlopaša ◽  
Eduardus Koenders ◽  
Camila Aparecida Abelha Rocha ◽  
Romildo Dias Toledo Filho
Keyword(s):  
Silica Fume ◽  
Isothermal Calorimetry ◽  
Cementitious Materials ◽  
Microstructural Development ◽  
Oil Well ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
Beneficial Effects ◽  
Binder Ratio ◽  
Offshore Industry

Silica fume (SF) is used as a constituent to formulate cementitious materials for subsurface (oil-well) applications, e.g. by the offshore industry. Using green supplementary pozzolanic materials like silica fume could both improve the material’s performance and the footprint of the sustainable solution. X-ray diffraction and isothermal calorimetry were employed to investigate the evolution of cement paste hydration (water to binder ratio 0.44) after 14 h, 3, 7, and 28 days of curing. Experimental results are presented for both cement pastes made of Class G Portland cement and for a blended paste system where 8% of the Class G cement has been replaced by silica fume. The results indicate beneficial effects of SF on the microstructural development of the slurry.

scholarly journals New Approach for the Determination of Radiological Parameters on Hardened Cement Pastes with Coal Fly Ash

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 475
Author(s):  
Ana María Moreno de los Reyes ◽  
José Antonio Suárez-Navarro ◽  
Maria del Mar Alonso ◽  
Catalina Gascó ◽  
Isabel Sobrados ◽  
...  
Keyword(s):  
Fly Ash ◽  
Activity Concentration ◽  
Gamma Ray ◽  
Coal Fly Ash ◽  
Cementitious Materials ◽  
New Method ◽  
Supplementary Cementitious Materials ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Activity Concentrations

Supplementary cementitious materials (SCMs) in industrial waste and by-products are routinely used to mitigate the adverse environmental effects of, and lower the energy consumption associated with, ordinary Portland cement (OPC) manufacture. Many such SCMs, such as type F coal fly ash (FA), are naturally occurring radioactive materials (NORMs). 226Ra, 232Th and 40K radionuclide activity concentration, information needed to determine what is known as the gamma-ray activity concentration index (ACI), is normally collected from ground cement samples. The present study aims to validate a new method for calculating the ACI from measurements made on unground 5 cm cubic specimens. Mechanical, mineralogical and radiological characterisation of 28-day OPC + FA pastes (bearing up to 30 wt % FA) were characterised to determine their mechanical, mineralogical and radiological properties. The activity concentrations found for 226Ra, 212Pb, 232Th and 40K in hardened, intact 5 cm cubic specimens were also statistically equal to the theoretically calculated values and to the same materials when ground to a powder. These findings consequently validated the new method. The possibility of determining the activity concentrations needed to establish the ACI for cement-based materials on unground samples introduces a new field of radiological research on actual cement, mortar and concrete materials.

scholarly journals Effect of Some Acrylate—Poly(Ethylene Glycol) Copolymers as Superplasticizers on the Mechanical and Surface Properties of Portland Cement Pastes

2005 ◽  
Vol 23 (3) ◽  
pp. 245-254 ◽  
Author(s):  
S.A. Abo-El-Enein ◽  
S. Hanafi ◽  
F.I. El-Hosiny ◽  
El-Said H.M. El-Mosallamy ◽  
M.S. Amin
Keyword(s):  
Ethylene Glycol ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Mechanical Characteristics ◽  
Hardened Cement ◽  
Poly Ethylene Glycol ◽  
Cement Pastes ◽  
Surface Areas ◽  
Poly Ethylene ◽  
Hardened Cement Pastes

Ordinary Portland cement (OPC) pastes with added superplasticizer were made using water/cement weight ratios of standard consistency. Three types of superplasticizer based on acrylate—poly(ethylene glycol) copolymers were used. The pastes were hydrated for various time lengths and the mechanical characteristics of the hardened cement pastes were studied and related to their pore structures. It was found that the addition of the superplasticizers to OPC improved the mechanical properties of the hardened pastes for all hydration lengths. The addition of such superplasticizers to OPC resulted in a decrease in the specific surface areas and total pore volumes of the hardened superplasticized cement pastes relative to the corresponding hardened neat cement pastes.

Assessment of Anhydrous Ethanol Extraction to Determine the Ionic Concentration of Hardened Cement Pastes

2010 ◽  
Vol 177 ◽  
pp. 506-509 ◽  
Author(s):  
Man Jian Wu ◽  
Wu Yao ◽  
Wei Wang ◽  
Yong Qi Wei
Keyword(s):  
Pore Solution ◽  
Ph Value ◽  
Ionic Concentration ◽  
Anhydrous Ethanol ◽  
Hardened Cement ◽  
Cement Pastes ◽  
Ethanol Extraction ◽  
Alkali Ions ◽  
Ph Values ◽  
Hardened Cement Pastes

A new method involving the extraction of various ions from hardened cement pastes by anhydrous ethanol is presented to determine the pH value and ionic concentration during the first 28 days. The volume content of pore solution extracted by ethanol in the leachate reached 12% or above and the pH values calculated by alkali ions are more than 12, even up to 12.73. The results were compared with those from parallel, conventional pore water expression experiments. All of these comparisons verified the feasibility of the proposed method. However, the application of this method to pore solution analysis needs further improvement.

scholarly journals Mechanically activated mine tailings for use as supplementary cementitious materials

2021 ◽  
Vol 6 ◽  
pp. 61-69
Author(s):  
Sivakumar Ramanathan ◽  
Priyadarshini Perumal ◽  
Mirja Illikainen ◽  
Prannoy Suraneni
Keyword(s):  
Mine Tailings ◽  
Isothermal Calorimetry ◽  
Cementitious Materials ◽  
Supplementary Cementitious Materials ◽  
Strong Correlations ◽  
Negative Effects ◽  
Cement Pastes ◽  
Amorphous Content ◽  
Milling Duration ◽  
Median Particle

Two mine tailings are evaluated for their potential as supplementary cementitious materials. The mine tailings were milled using two different methods – ball milling for 30 minutes and disc milling for durations ranging from 1 to 15 minutes. The modified R3 test was carried out on the mine tailings to quantify their reactivity. The reactivity of the disc milled tailings is greater than those of the ball milled tailings. Strong correlations are obtained between milling duration, median particle size, amorphous content, dissolved aluminum and silicon, and reactivity of the mine tailings. The milling energy results in an increase in the fineness and the amorphous content, which do not appreciably increase beyond a disc milling duration of 8 minutes. The reactivity increases significantly beyond a certain threshold fineness and amorphous content. Cementitious pastes were prepared at 30% supplementary cementitious materials replacement level at a water-to-cementitious materials ratio of 0.40. No negative effects of the mine tailings were observed at early ages in cement pastes based on isothermal calorimetry and thermogravimetric analysis, demonstrating the potential for these materials to be used as supplementary cementitious materials.

scholarly journals Hydration characteristics and structure formation of cement pastes containing metakaolin

2018 ◽  
Vol 149 ◽  
pp. 01013 ◽  
Author(s):  
Leonid Dvorkin ◽  
Nataliya Lushnikova ◽  
Oleksandr Bezusyak ◽  
Mohammed Sonebi ◽  
Jamal Khatib
Keyword(s):  
Structure Formation ◽  
Cement Pastes ◽  
Hydration Characteristics
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