scholarly journals Experimental Carbonation Study for a Durability Assessment of Novel Cementitious Materials

Materials ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 6253
Author(s):  
Lucija Hanžič ◽  
Sebastijan Robič ◽  
Alisa Machner ◽  
Marie Helene Bjørndal ◽  
Klaartje De Weerdt ◽  
...  
Keyword(s):  
Numerical Model ◽  
Moisture Transport ◽  
Gravimetric Method ◽  
Visual Assessment ◽  
Cementitious Materials ◽  
Accelerated Carbonation ◽  
Surface Layers ◽  
Carbonation Resistance ◽  
Durability Assessment ◽  
The Difference

Durability predictions of concrete structures are derived from experience-based requirements and descriptive exposure classes. To support durability predictions, a numerical model related to the carbonation resistance of concrete was developed. The model couples the rate of carbonation with the drying rate. This paper presents the accelerated carbonation and moisture transport experiments performed to calibrate and verify the numerical model. They were conducted on mortars with a water-cement ratio of either 0.6 or 0.5, incorporating either a novel cement CEM II/C (S-LL) (EnM group) or commercially available CEM II/A-S cement (RefM group). The carbonation rate was determined by visual assessment and thermogravimetric analysis (TGA). Moisture transport experiments, consisting of drying and resaturation, utilized the gravimetric method. Higher carbonation rates expressed in mm/day−0.5 were found in the EnM group than in the RefM group. However, the TGA showed that the initial portlandite (CH) content was lower in the EnM than in the RefM, which could explain the difference in carbonation rates. The resaturation experiments indicate an increase in the suction porosity in the carbonated specimens compared to the non-carbonated specimens. The study concludes that low clinker content causes lower resistance to carbonation, since less CH is available in the surface layers; thus, the carbonation front progresses more rapidly towards the core.

Carbonation of fly ash concrete: laboratory and field data

2010 ◽  
Vol 37 (12) ◽  
pp. 1535-1549 ◽  
Author(s):  
N. Bouzoubaâ ◽  
A. Bilodeau ◽  
B. Tamtsia ◽  
S. Foo
Keyword(s):  
Fly Ash ◽  
Cementitious Materials ◽  
Natural Environments ◽  
Type I ◽  
Accelerated Carbonation ◽  
Fly Ash Concrete ◽  
Concrete Mixtures ◽  
Carbonation Resistance ◽  
American Society ◽  
Indoor And Outdoor

The present study consists of investigating the carbonation resistance of two series of concrete mixtures designed for three classes of concrete (25, 35, and 45 MPa compressive strength at 28 d) and using American Society for Testing and Materials (ASTM) type I Portland cement and two commercially used fly ashes meeting the ASTM standards at the level of 20%, 35%, and 50% of the total weight of cementitious materials. The carbonation resistance was determined on samples moist cured for 3, 7, and 10 d and exposed to a CO2-enriched environment (3% CO2 at 23 °C and 65% relative humidity) for 140 d to accelerate the carbonation; it was also determined on samples moist cured for 7 d and exposed to an indoor and outdoor natural environments for 4 years. A mathematical model allowing the prediction of the depth of accelerated carbonation of fly ash concrete mixtures is presented.

Studies about the Initial Curing Conditions on the Carbonation Resistance of Fly-Ash Concrete

2011 ◽  
Vol 250-253 ◽  
pp. 920-924 ◽  
Author(s):  
En Li Lu ◽  
Guo Li ◽  
Ying Shu Yuan ◽  
Ou Geng ◽  
Jian Min Du
Keyword(s):  
Fly Ash ◽  
Curing Temperature ◽  
Accelerated Carbonation ◽  
Initial Water ◽  
Curing Conditions ◽  
Fly Ash Concrete ◽  
Concrete Carbonation ◽  
Carbonation Resistance ◽  
The Difference ◽  
C 30

Studies about the resistance of carbonation capability of fly-ash (FA) concrete at different initial curing regimes and exposure time through accelerated carbonation experiments were made. Firstly, 30% replacement ratio fly-ash concrete specimens were fabricated and cured in 20°C, 30°C and 40°C water for 3d, 7d, 14d and 28d respectively, and cured in a standard air environment (20±2°C, relative humidity ≥95% ) for 28d. As a comparison, ordinary Portland concrete (OPC) specimens were also made and cured in 30°C water for 7d, and standard curing for 28d. After the initial curing, all the specimens were taken out and placed indoor natural environment. When specimen age reach 30d, 60d and 120d, 2 weeks accelerated carbonation experiments were made and concrete carbonation depth were measured. In addition to this, hydration degrees of fly ash at different initial curing conditions were measured using the selective dissolve method. Results show that the initial curing conditions play an important role in the carbonation resistance of FA concrete. Initial water curing is beneficial to the development of carbonation resistance of FA and OPC concrete. Prolonging initial curing time and increasing curing temperature is beneficial for the carbonation resistance of FA concrete. For the same curing conditions, carbonation rate of FA concrete is usually higher than OPC concrete, but with the increase of initial curing temperature, the difference can be reduced.

Influence of Carbonation and Chemical Activity of Water on Coupled Moisture-Ion Transport in Cementitious Materials

2012 ◽  
Vol 323-325 ◽  
pp. 263-268 ◽  
Author(s):  
Xiao Meng Wang ◽  
Mickaël Thiéry ◽  
Véronique Baroghel-Bouny
Keyword(s):  
Numerical Model ◽  
Moisture Transport ◽  
Inverse Analysis ◽  
Gamma Ray ◽  
Cementitious Materials ◽  
Chemical Activity ◽  
Intrinsic Permeability ◽  
Transport Of Ions ◽  
Gamma Ray Attenuation ◽  
Moisture Profiles

The influence of the chemical activity effects on moisture transport in the presence of ions in cementitious materials is studied. Wetting-drying tests are carried out on various hardened concretes (sound and fully carbonated) with water. Moisture profiles are experimentally assessed by gamma-ray attenuation. A multispecies and multiphase numerical model, in which the Lin and Lee approach is applied to compute the chemical activity coefficients of water in presence of ions, is used to simulate the transport of ions and moisture. The drying kinetics is analyzed to assess the intrinsic permeability of the material by inverse analysis. Experimental profiles are compared to the simulations to illustrate the relevance of the modeling.

A Dynamic Model of III-V Ternary Semiconductor Alloys in the Epitaxial Growth

1994 ◽  
Vol 340 ◽  
Author(s):  
Bing-Lin Gu ◽  
Jing-Zhi Yu ◽  
Xiao Hu ◽  
Kaoru Ohno ◽  
Yoshiyuki Kawazoe
Keyword(s):  
Dynamic Model ◽  
Ground State ◽  
Wave Method ◽  
Semiconductor Alloys ◽  
Concentration Wave ◽  
Surface Layers ◽  
Ordered Structures ◽  
Effective Interactions ◽  
Ternary Semiconductor ◽  
The Difference

ABSTRACTA concentration wave method for several interpenetrating Bravais sublattices is presented by considering the intralayer and interlayer effective interactions and the difference between the surface layers and the deeper layers in III – V alloys. The ground state ordered structures of ternary III – V semiconductor alloys are deduced and a dynamic model is established.

Influences on the Hydrophobicity of Concrete Surfaces Treated with Alkyl Trialkoxysilanes

2014 ◽  
Vol 20 (6) ◽  
pp. 405-412
Author(s):  
U. Antons ◽  
M. Raupach ◽  
O. Weichold
Keyword(s):  
Uv Radiation ◽  
Cement Hydration ◽  
Alkaline Media ◽  
Water Repellent ◽  
Portland Cement Concrete ◽  
Accelerated Carbonation ◽  
Surface Layers ◽  
Hydrophobic Layer ◽  
Furnace Slag

Abstract The paper focuses on how alkaline media, UV radiation, and carbonation as well as on-going cement hydration affects hydrophobic treatments of concrete and influences the properties of these water-repellent layers. Single-sided nuclear magnetic resonance measurements show that layers formed by impregnating samples with alkyl trialkoxysilanes are stable even under long-term exposure to alkaline solution and UV radiation, with the damage of the latter being limited to the topmost surface layers. Microstructural changes during accelerated carbonation of blast furnace slag cement based concrete have a major impact on the hydrophobic layer properties, while the carbonation of Portland cement concrete has no influence. On-going hydration additionally influences the hydrophobic layer properties.

Numerical Simulation Research on the Shape of Top Coal Drawn-Body in Gently Inclined Seam

2012 ◽  
Vol 468-471 ◽  
pp. 2248-2254
Author(s):  
Qiang Li ◽  
Wan Kui Bu ◽  
Hui Xu ◽  
Xiao Bo Song
Keyword(s):  
Numerical Simulation ◽  
Numerical Model ◽  
Random Medium ◽  
Body Movement ◽  
The Other ◽  
Simulation Research ◽  
Research Results ◽  
Shape Equation ◽  
The Difference ◽  
Meso Scale

The numerical model of top coal drawing in gently inclined seam is built based on PFC2d software. By comparing with the theory of drawn-body movement law, it can be obtained that the shape of top coal drawn-body accords with the theory of random medium movement. The research results show that the form of the shape equation of top coal drawn-body is uniform while the top coal caving angle is different. On the other hand, with the difference of top coal caving angle and drawing height, the shape of top coal drawn-body is differential at the meso scale, which depends on the parameters of the shape equation of top coal drawn-body.

scholarly journals Influence of Dimethacrylate Monomer on the Polymerization Efficacy of Resin-Based Dental Cements—FTIR Analysis

Polymers ◽  
2022 ◽  
Vol 14 (2) ◽  
pp. 247
Author(s):  
Aleksandra Maletin ◽  
Ivan Ristic ◽  
Tanja Veljovic ◽  
Bojana Ramic ◽  
Tatjana Puskar ◽  
...  
Keyword(s):  
Spectral Analysis ◽  
Clinical Practice ◽  
Chemical Structure ◽  
Cementitious Materials ◽  
Degree Of Polymerization ◽  
Cementitious Material ◽  
Ftir Analysis ◽  
Dental Cement ◽  
Polymerization Mechanism ◽  
The Difference

The degree of polymerization for dimethacrylate resin-based materials (BisGMA, TEGDMA, UDMA, HEMA) ranges from 55 to 75%. Literature data indicate that polymerization efficacy depends, among other factors, on the type of methacrylate resin comprising the material. The aim of this study was to evaluate the polymerization efficacy of four dental cement materials characterized by different polymerization mechanisms using FTIR analysis. In the present study, the FTIR method was adopted to analyze the degree of polymerization efficacy of four resin-based dental cement materials, two of which were self-cured and two were dual-cured cements. The IR spectral analysis was performed 24 h after the polymerization of the cementitious material. RelyX ARC cement exhibits the lowest polymerization efficacy (61.3%), while that of Variolink II (85.8%) and Maxcem Elite is the highest (90.1%). Although the efficacy of self-cured cements appears to be superior, the difference is not statistically significant (p = 0.280). Polymerization efficacy largely depends on the chemical structure of the material in terms of the presence of a particular methacrylate resin and less on the polymerization mechanism itself, i.e., whether it is a self-cured or dually cured dental cement. Thus, in clinical practice, cementitious materials with a higher proportion of TEGDMA compared with BisGMA are recommended.

scholarly journals Durability of clinker reduced shotcrete: Ca2+ leaching, sintering, carbonation and chloride penetration

2021 ◽  
Vol 54 (2) ◽  
Author(s):  
Marlene Sakoparnig ◽  
Isabel Galan ◽  
Florian R. Steindl ◽  
Wolfgang Kusterle ◽  
Joachim Juhart ◽  
...  
Keyword(s):  
Binding Capacity ◽  
Cementitious Materials ◽  
Chloride Penetration ◽  
Supplementary Cementitious Materials ◽  
Conventional Concrete ◽  
Sprayed Concrete ◽  
Carbonation Resistance ◽  
Negative Environmental Impact ◽  
The Impact ◽  
Positive Effect

AbstractThe reduction of clinker use is mandatory to lower the negative environmental impact of concrete. In shotcrete mixes, similarly to the case of conventional concrete, the use of supplementary cementitious materials (SCMs) and proper mix design allow for the substitution of clinker without compromising the mechanical properties. However, the impact of the substitution on the durability of shotcrete needs to be further assessed and understood. The results from the present study, obtained from real-scale sprayed concrete applications, show a reduction of the Ca2+ leaching and sintering potential of clinker-reduced shotcrete mixes due to the presence of SCMs. This positive effect, crucial for low maintenance costs of tunnels, is mainly related to a reduced portlandite content, which on the other hand negatively affects the carbonation resistance of shotcrete. Additionally, the hydration of SCMs positively influences the chloride penetration resistance presumably due to a combination of microstructural changes and changes in the chloride binding capacity. Differences found in the pore size distribution of the various mixes have low impact on the determined durability parameters, in particular compared to the effect of inhomogeneities produced during shotcrete application.

Effects of Carbonation on the Specific Surface BET of Cement Mortar Measured by Two Different Methods: Nitrogen Adsorption and Water Adsorption

2014 ◽  
Vol 931-932 ◽  
pp. 421-425 ◽  
Author(s):  
Son Tung Pham ◽  
William Prince
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Water Adsorption ◽  
Cement Mortar ◽  
Nitrogen Adsorption ◽  
Accelerated Carbonation ◽  
Molecular Sizes ◽  
The Difference ◽  
Adsorption Desorption

The objective of this work was to examine the microstructural changes caused by the carbonation of normal mortar. Samples were prepared and subjected to accelerated carbonation at 20°C, 65% relative humidity and 20% CO2concentration. The evolutions of the pore size distribution and the specific surface area during carbonation were calculated from the adsorption - desorption isotherms of water vapour and nitrogen. Conflicts observed in the results showed that the porous domains explored by these two methods are not the same due to the difference in molecular sizes of nitrogen and water. These two techniques therefore help to complementarily evaluate the effects of carbonation. The study also helped to explain why results in the literature diverge greatly on the influence of carbonation on specific surface area.

Influence the Carbonation Resistance and Mechanical Properties of Shotcrete by Accelerated Carbonation Test

2014 ◽  
Vol 1065-1069 ◽  
pp. 1985-1989
Author(s):  
Jia Bin Wang ◽  
Di Tao Niu ◽  
Rui Ma ◽  
Ze Long Mi
Keyword(s):  
Mechanical Properties ◽  
Tensile Strength ◽  
Compressive Strength ◽  
Steel Fiber ◽  
Splitting Tensile Strength ◽  
Construction Technology ◽  
Accelerated Carbonation ◽  
Carbonation Depth ◽  
Normal Concrete ◽  
Carbonation Resistance

In order to investigate the carbonation resistance of shotcrete and the mechanical properties after carbonation, the accelerated carbonation test was carried out. The results indicate that the carbonation resistance of shotcrete is superior to that of normal concrete. With the increasing of carbonation depth, compressive strength and splitting tensile strength of shotcrete grew rapidly. The admixing of steel fiber can further improve the carbonation resistance, reduce the carbonation rate, and increase the splitting tensile strength of shotcrete greatly. Besides, based on analyzing the effects of construction technology and steel fiber of concrete for the carbonation resistance, a carbonation depth model for shotcrete was established. Key words: shotcrete; carbonation; steel fiber; mechanical properties

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