scholarly journals Microstructure and Relative Humidity Effects on Long-Term Indentation Creep Properties of Calcium Carbonate Cement

2018 ◽  
Author(s):  
Jesús Rodríguez-Sánchez ◽  
Qing Zhang ◽  
Dag Kristian Dysthe
Keyword(s):  
Elastic Modulus ◽  
Calcium Carbonate ◽  
Relative Humidity ◽  
Indentation Creep ◽  
Amorphous Calcium Carbonate ◽  
Creep Properties ◽  
Carbonate Cement ◽  
Creep Modulus ◽  
Term Creep

This paper addresses the effect of both microstructure and relative humidity on the long-term creep properties of sustainable calcium carbonate (CaCO3) cements. Those can be prepared by mixing amorphous calcium carbonate and vaterite with water. A larger starting amount of vaterite, XV, within the mixture design gives a higher elasticity and resistance to the specimens due to the larger overall bridging area within the newly formed calcite crystals. Regarding creep properties for a given relative humidity, the amplitude of creep strain decreases with XV, and makes the relation between the elastic modulus, E, and hardness, H, of the samples to be linear with the contact creep modulus, C. On the other hand, for a given composition, the amplitude of creep increases with the relative humidity, making the contact creep modulus, Ci, to rise exponentially with the elastic modulus, E, and hardness, H, of the specimens. The most probable creep mechanisms for this kind of cement seem to be a combination of microcraking in the early stages and dissolution and reprecipitation of calcite in the long-term (also known as pressure solution theory). The presence of water in pores with increasing relative humidity might enhance the local dissolution of calcite, and hence the creep amplitude.

Prediction of Long-Term Creep Properties of Zirconium-2.5 % Niobium Alloy Using Wilshire Method

2021 ◽  
Vol 10 (2) ◽  
pp. 20200146
Author(s):  
Vivek Patel ◽  
R. N. Singh ◽  
Madangopal Krishnan
Keyword(s):  
Niobium Alloy ◽  
Creep Properties ◽  
Term Creep

Grades 92 and 23: Weldability Assessment and Long-Term Performances for Power Generation Applications

2008 ◽  
Vol 580-582 ◽  
pp. 383-388
Author(s):  
Emmanuel Bauné ◽  
E. Galand ◽  
B. Leduey ◽  
G. Liberati ◽  
G. Cumino ◽  
...  
Keyword(s):  
Creep Strength ◽  
Welded Joints ◽  
Power Plants ◽  
Product Family ◽  
Base Material ◽  
Advanced Materials ◽  
Creep Properties ◽  
Steam Parameters ◽  
Term Creep

Increased efficiency and emission reduction in modern power plants lead to the use of new advanced materials with enhanced creep strength, with the objective to increase the steam parameters of power plants. With over ten years on market and wide experience related to its use, ASTM Grade 92 is becoming one of the most required materials when high service temperatures are reached (max. 610°C). Its composition, with 9%Cr and 1.5%W, gives rise to martensitic microstructures which offer very high creep strength and long term stability. The improved weldability and creep-strength between 500 and 580°C of the low alloy ASTM Grade 23, as well as a cost advantage over higher Cr materials in this temperature range, make it one of the possible candidates to meet the stringent requirements of modern power plants. Air Liquide Welding (ALW) has optimized and distributes a complete product family for the welding of Grades 23 and 92. TenarisDalmine (TD) focused on the development of Grade 23 tubes and pipes and is working on the development of Grade 92. A deep characterization work of the microstructural evolution and long term creep performances of these high temperature resistant materials was thus undertaken by ALW and TD, in collaboration with the Centro Sviluppo Materiali (CSM). The joint characterization program consisted in the assessment of welded joints creep properties. Welded joints were produced using the gas tungsten (GTAW), shielded metal (SMAW) and submerged arc welding (SAW) processes. Mechanical and creep properties of weldments were measured both in the as welded and post weld heat treated conditions and proper WPS’s were designed in a manner such that industrial production needs were satisfied. Short term creep resistance of cross weld specimens was measured to be within the base material acceptance criteria. Long term base material and cross weld creep performance evaluation are now in progress.

Microstructure and Creep Properties of AISI 316LN Steels with Niobium Additions

2005 ◽  
Vol 482 ◽  
pp. 275-278 ◽  
Author(s):  
Vlastimil Vodárek ◽  
Gabriela Rožnovská ◽  
Jaromír Sobotka
Keyword(s):  
S Phase ◽  
Creep Life ◽  
Creep Ductility ◽  
Niobium Content ◽  
Creep Properties ◽  
Size Refinement ◽  
Tertiary Stage ◽  
Type Aisi ◽  
Term Creep

The long-term creep rupture tests have been carried out on three casts of a type AISI 316LN steel at 600 and 650°C. Two of the casts investigated contained additions of 0.1 and 0.3 wt.% of niobium. The growing niobium content strongly reduced the minimum creep rate and prolonged the time to the onset of the tertiary stage of creep and also shortened this stage. The enhanced creep resistance of niobium containing steels is not accompanied by the longer creep life that might have been expected. At both temperatures of creep exposure the niobium-bearing casts displayed an inferior creep ductility. Microstructural investigations revealed that niobium provoked significant grain size refinement and the formation of Z-phase. Particles of this phase were considerably dimensionally stable. Furthermore, niobium accelerated the formation and coarsening of s-phase, h-Laves and M6(C,N). The coarse intergranular particles facilitated the formation of cavities which resulted in intergranular failure mode.

Building amorphous calcium carbonate into geochemical biomineralisation models

2020 ◽  
Author(s):  
David Evans ◽  
William Gray ◽  
James Rae ◽  
Rosanna Greenop ◽  
Paul Webb ◽  
...  
Keyword(s):  
Calcium Carbonate ◽  
Isotope Fractionation ◽  
Planktonic Foraminifera ◽  
Transformation Process ◽  
Geochemical Data ◽  
Amorphous Calcium Carbonate ◽  
Carbonate System ◽  
Precursor Phase ◽  
Shell Geochemistry

<p>Amorphous calcium carbonate (ACC) has been observed, or inferred to exist, in the majority of the major phyla of marine calcifying organisms. The CaCO<sub>3</sub> produced by these organisms represents one of the largest long-term carbon sinks on Earth’s surface, such that identifying how calcification will respond to anthropogenic climate change is an urgent priority. A substantial portion of our knowledge of the biomineralisation process of these organisms is derived from inferences based on skeletal geochemical data, yet such models typically do not include an ACC component because little is known about trace element and isotope fractionation into ACC. In order to address this, we present, to our knowledge, the first structural and geochemical data of ACC precipitated from seawater under varying carbonate system conditions, seawater Mg/Ca ratios, and in the presence of three of the most common intracrystalline amino acids (aspartic acid, glutamic acid, and glycine). Based on these data we identify the carbonate system conditions necessary to produce ACC from seawater [Evans <em>et al</em>., 2019], and identify the dominant controls on ACC geochemistry. As an example, we utilise these data to build a simple biomineralisation model for the low-Mg (e.g. planktonic) foraminifera, based on precipitation of low-Mg calcite through an ACC precursor phase in a semi-enclosed pool. This exercise demonstrates that the observed shell geochemistry of this group of organisms can be fully reconciled with a model that includes an ACC component, and moreover that constraints can be placed on the degree of ACC utilisation and the ACC-calcite transformation process. More broadly, the exercise demonstrates that knowledge of the characteristics and geochemistry of ACC is important in the development of a process-based understanding of marine calcification.</p><p>Evans, D., Webb, P., Penkman, K. Kröger, R., & Allison, N. [2019] The Characteristics and Biological Relevance of Inorganic Amorphous Calcium Carbonate (ACC) Precipitated from Seawater. <em>Crystal Growth & Design</em> <strong>19</strong>: 4300.</p>

scholarly journals Influence of Heat Treatment on Long Term Creep Properties of 9Cr–W–Mo–V–Nb Steel

2010 ◽  
Vol 96 (4) ◽  
pp. 172-181
Author(s):  
Satoshi Obara ◽  
Takashi Wakai ◽  
Tai Asayama ◽  
Yoshiyuki Yamada ◽  
Takanori Nakazawa ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Creep Properties ◽  
Term Creep

Basic Study on Creep Properties of Eucalyptus Wood

2014 ◽  
Vol 911 ◽  
pp. 232-237
Author(s):  
Yuan Rong Ma ◽  
Xian Jun Li ◽  
Biao Deng ◽  
Ying She Luo
Keyword(s):  
Model Parameters ◽  
Short Term ◽  
Basic Study ◽  
Burger Model ◽  
Creep Properties ◽  
Eucalyptus Plantation ◽  
Moisture Contents ◽  
Creep Curves ◽  
Term Creep

The study tested the short-term bending creep curves of Eucalyptus Plantation Wood under different loads, moisture contents and temperatures, analyzed the influence of load, moisture content and temperature on creep of Eucalyptus. Guided by the rheological theory, the study adopted the Burger rheological model to do the curve fitting and solved the model parameters. A defect found from Burger model in simulating long-term creep properties of wood was preliminary discussed and remedied. The equivalence of creep test and relaxation one was discussed.

scholarly journals Long-Term Creep Properties of Hastelloy XR in Simulated High-Temperature Gas-Cooled Reactor Helium

1995 ◽  
Vol 32 (11) ◽  
pp. 1108-1117 ◽  
Author(s):  
Yuji KURATA ◽  
Yutaka OGAWA ◽  
Tomio SUZUKI ◽  
Masami SHINDO ◽  
Hajime NAKAJIMA ◽  
...  
Keyword(s):  
High Temperature ◽  
Creep Properties ◽  
Term Creep ◽  
High Temperature Gas

Prediction of Long – Term Creep Properties of Kenaf Fiber Unsaturated Polyester Composites

2014 ◽  
Vol 974 ◽  
pp. 9-14
Author(s):  
Saad A. Mutasher ◽  
Ekhlas A. Osman
Keyword(s):  
Curve Fitting ◽  
Linear Time ◽  
Unsaturated Polyester ◽  
Kenaf Fiber ◽  
Creep Properties ◽  
Polyester Composite ◽  
Term Creep ◽  
Long Term Behavior ◽  
Fitting Model

This research focuses on predicting long-term behavior of unsaturated polyester resin (UP) and kenaf unsaturated polyester composite. The objectives of these tests are to establish a relationship between stress, strain and time at constant loading and temperature. The results obtained from these tests are used in predicting the life and strength of the polymer material. Based on the 1,000 hours experimental data, curve fitting and Findley Power Law models are employed to predict long-term behavior of the material. The results showed that curve fitting model accurately predicted the non-linear time dependent creep deformation of these materials with acceptable accuracy.

scholarly journals Mechanisms of Phase Transformation and Creating Mechanical Strength in a Sustainable Calcium Carbonate Cement

2018 ◽  
Author(s):  
Jesús Rodríguez-Sánchez ◽  
Teresa Liberto ◽  
Catherine Barentin ◽  
Dag Kristian Dysthe
Keyword(s):  
Calcium Carbonate ◽  
Mechanical Strength ◽  
Energy Difference ◽  
Amorphous Calcium Carbonate ◽  
Carbonate Cement ◽  
In Situ Xrd ◽  
Carbonate Cements ◽  
Size Evolution ◽  
Bulk Free Energy ◽  
Delta G

Calcium carbonate cements have been synthesized by mixing amorphous calcium carbonate and vaterite powders with water to unravel the mechanisms of creating mechanical strength during the setting reaction. In-situ XRD was used to monitor the transformation of ACC and vaterite phases into calcite. Unlike this transformation of crystals suspended in a stirred solution, the transformation in the cement is controlled by vaterite dissolution. The supersaturation within the cement paste, Ω, depends not only on the bulk free energy difference of the phases, ΔG, but also on the grain size evolution. Among the strengthening mechanisms, an initial geometric reorganization of CaCO3 particles has been identified by rheological measurements; followed by the formation of an interconnected network of calcite crystals that increases in strength as the crystals grow and form bridges among them. All compositions yield microporous calcite structures with diverse transformation history, crystal bridging efficiency, and hence final mechanical properties.

Corelation of Results of Creep and Micro-Indentation Creep for PP-Copo

2014 ◽  
Vol 606 ◽  
pp. 233-236
Author(s):  
Martin Reznicek ◽  
Martin Ovsik ◽  
David Manas ◽  
Adam Skrobak ◽  
Michal Stanek ◽  
...  
Keyword(s):  
Material Properties ◽  
Test Material ◽  
Indentation Creep ◽  
Comparison Of Methods ◽  
Depth Sensing ◽  
Indentation Method ◽  
Material Development ◽  
Term Creep ◽  
Micro Indentation

This article deals with the comparison of methods for measuring the creep behavior of filled polypropylene. Creep was measured by two methods, using the micro-indentation method (Depth Sensing Indentation - DSI) and the standard long-term creep test at elevated temperature. Results of this article show the feasibility of these two methods to replace each other and thus shorten the length of the testing material development with evaluation whether the test material is better or worse than the previous. Using the DSI method we can evaluated other material properties at the same time, which may be an important contributor in determining an appropriate application of the material. Mixtures of polypropylene with different kinds and levels of filling were selected for the comparison.

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