Effects of curing conditions on the evolution of coarse capillary pores in cement pastes

2004 ◽  
Author(s):  
S. Igarashi
Keyword(s):  
Cement Pastes ◽  
Curing Conditions

scholarly journals The Influence of Curing Regimes in Self-Healing of Nano-Modified Cement Pastes

Materials ◽  
2020 ◽  
Vol 13 (22) ◽  
pp. 5301
Author(s):  
Maria Stefanidou ◽  
Eirini-Chrysanthi Tsardaka ◽  
Aspasia Karozou
Keyword(s):  
Sem Analysis ◽  
Attenuated Total Reflectance ◽  
Self Healing ◽  
Nano Silica ◽  
Cement Pastes ◽  
Curing Conditions ◽  
Total Reflectance ◽  
Atr Spectroscopy ◽  
Curing Regimes ◽  
Early Healing

The present study proposes nano-calcium oxide (NC) and nano-silica (NS) particles as healing agents in cement pastes, taking into account the curing conditions. Two series of specimens were treated in water and under wetting-drying cycles. The addition of NC (1.5%wt of binder) triggered early healing since cracks were healed within 14 days in underwater immersion and before 28 days at wetting-drying cycles. Attenuated Total Reflectance (ATR) spectroscopy and SEM analysis revealed that the healing products were mainly aragonite and calcite in water conditions and more amorphous carbonates under wetting-drying cycles. The combination of NS and NC (3.0%wt in total) offered healing under both curing conditions before 28 days. The presence of NS assisted toward porosity refinement and NC increased the carbonates’ content. The newly formed material was dense, and its elemental analysis by SEM revealed the C-S-H compounds that were also verified by ATR.

scholarly journals Effect of Cellulose Nanocrystals on the Properties of Cement Paste

2019 ◽  
Vol 2019 ◽  
pp. 1-7
Author(s):  
Qiaoling Liu ◽  
Yujiao Peng ◽  
Long Liang ◽  
Xiaobin Dong ◽  
Hancai Li
Keyword(s):  
Cement Paste ◽  
Cellulose Nanocrystals ◽  
Nitrogen Adsorption ◽  
Cement Matrix ◽  
Size Distributions ◽  
Cement Pastes ◽  
Curing Conditions ◽  
X Ray ◽  
Pore Size Distributions ◽  
X Ray Computed

The effect of the addition of cellulose nanocrystals (CNCs) on the properties of cement pastes is studied herein. The compressive strength of CNC/cement paste was investigated under the curing conditions defined in this study. Two-dimensional micrographs and pore size distributions were obtained by scanning electron microscopy, X-ray computed tomography (XCT), and nitrogen adsorption. The addition of CNCs was found to significantly enhance the mechanical properties of cement pastes with a rapid decrease in temperature and humidity. XCT and nitrogen adsorption analyses show that the addition of CNCs leads to a refinement of the pore structure in the cement matrix. Almost no hydration products, including C-S-H, are formed in the cement matrix without CNCs under extreme conditions. This is in contrast with the results for the cement paste with 0.5% CNCs.

scholarly journals Review of NMR Studies for Oilwell Cements and Their Importance

2021 ◽  
Vol 5 (2) ◽  
pp. 18
Author(s):  
Fatemeh K. Saleh ◽  
Catalin Teodoriu ◽  
Carl Sondergeld
Keyword(s):  
Relaxation Times ◽  
Experimental Studies ◽  
Operating Characteristics ◽  
T2 Relaxation ◽  
Nmr Studies ◽  
Cement Pastes ◽  
Curing Conditions ◽  
Work Related ◽  
Data Comparison ◽  
Water Response

This paper summarizes experimental studies using Nuclear Magnetic Resonance (NMR) to evaluate cement porosity, pore size distribution, and other characteristics such as Calcium Silicate Hydrate (CSH) gel structure and morphology. The first known paper on NMR experiments to investigate cement pastes was published in 1978. Two main NMR parameters, the so-called longitudinal T1 and transverse T2 relaxation times, are commonly measured and analyzed, representing the water response which is trapped in the cement. The hydration process reported in this paper was found to be monitored from as low as 10 min to longer than 365 days. Other studies conducted experiments by using NMR, especially during the 1980s. These studies employed variations in methodologies and frequencies, making data comparison difficult. Additionally, different spectrometers and NMR concepts, as well as operating characteristics, were used. Therefore, it is challenging to reconcile results from previous NMR studies on cement. Other significant hurdles are different cement types, water/cement ratio, and curing conditions. One notable observation is that there has not been any comprehensive laboratory work related to NMR on oilfield cement types, including porosity and hydration. Two recent studies have presented NMR measurements on class G and class H cements.

scholarly journals Deformation of Alkali-Activated Materials at an Early Age Under Different Curing Conditions

2021 ◽  
Vol 9 ◽  
Author(s):  
Mark Češnovar ◽  
Katja Traven ◽  
Vilma Ducman
Keyword(s):  
Relative Humidity ◽  
Room Temperature ◽  
Standard Procedure ◽  
Autogenous Shrinkage ◽  
Drying Shrinkage ◽  
Mineral Wool ◽  
Cement Pastes ◽  
Curing Conditions ◽  
Material Sources ◽  
Alkali Activated

The production of alkali-activated materials (AAMs) is known for its environmentally friendly processing method, where several amorphous-rich aluminosilicate material sources combine with an alkali media solution to form solid, ceramic-like materials. In terms of the Si:Al, Na(K):Al, and Na(K):H2O ratios, the theory of AAM formation is quite well developed, but some open questions in the technology process remain, especially with regards to the means of curing, where the generation of defects can be persistent. Knowing that deformation is extremely high in the early ages, this study investigates the effects of temperature and moisture on shrinkage behavior within the first 72 h of AA pastes made from ladle (LS) and electric arc furnace (EAF) slag and activated by sodium silicate (Na2SiO3). The method to determine the deformation of alkali-activated slag-based materials, in terms of both autogenous and drying shrinkage, was based on the modified ASTM C1698-19 standard for the measurement of autogenous shrinkage in cement pastes. Autogenous deformation and strain were measured in four samples, using the standard procedure at room temperature, 40 and 60°C. Furthermore, using an adjusted method, nine samples were characterized for strain and partial surface pressure, while drying at room temperature, 40, or 60°C at a relative humidity of 30 or 90%. The results show that the highest rate of autogenous shrinkage occurred at a temperature of 60°C, followed by drying shrinkage at 60°C and 30% relative humidity, owing to the fact that the rate of evaporation was highest at this moisture content. The study aimed to provide guidance regarding selection of the optimal curing set in order to minimize deformations in slag-based alkali-activated materials. In the present case, curing at a temperature of around 40°C under lower moisture conditions for the first 24 h provided optimal mechanical properties for the slags investigated. The methodology might also be of use for other aluminosilicate sources such as metakaolin, fly ash, and mineral wool–based alkali-activated materials.

Composite Material Based on Cement and PVA: Evolution of Mechanical Properties during First 28 Days

2014 ◽  
Vol 1054 ◽  
pp. 215-220 ◽  
Author(s):  
Martin Lidmila ◽  
Pavel Tesárek ◽  
Tomáš Plachy ◽  
Zdeněk Prošek ◽  
Václav Nežerka ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Composite Material ◽  
Resonance Method ◽  
Cement Pastes ◽  
Shear Moduli ◽  
Curing Conditions ◽  
Laboratory Environment ◽  
Non Destructive ◽  
Common Laboratory

The aim of the presented study was to find a relationship between PVA concentration and properties of cement pastes. The PVA solution was added into fresh mortar in the amount equal to 1.4 and 2.8 % of cement weight. The produced samples were consequently stored in different curing conditions – exposed to air in common laboratory environment or submerged in water. The development of the dynamic Young’s and shear moduli was monitored using the non-destructive resonance method during first 28 days of hardening. The obtained data were compared to the measurements of a pure cement reference paste.

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