scholarly journals Description of the concrete carbonation process with adjusted depth-resolved thermogravimetric analysis

2021 ◽  
Author(s):  
Nico Vogler ◽  
Philipp Drabetzki ◽  
Mathias Lindemann ◽  
Hans-Carsten Kühne
Keyword(s):  
Calcium Hydroxide ◽  
Bound Water ◽  
Reference Method ◽  
Microscopic Analysis ◽  
Limestone Powder ◽  
Gravimetric Analysis ◽  
Sample Material ◽  
Accelerated Carbonation ◽  
Temperature Range ◽  
Carbonation Process

AbstractThe thermal gravimetric analysis (TG) is a common method for the examination of the carbonation progress of cement-based materials. Unfortunately, the thermal properties of some components complicate the evaluation of TG results. Various hydrate phases, such as ettringite (AFt), C–S–H and AFm, decompose almost simultaneously in the temperature range up to 200 °C. Additionally, physically bound water is released in the same temperature range. In the temperature range between 450 °C and 600 °C, the decomposition of calcium hydroxide and amorphous or weakly bound carbonates takes place simultaneously. Carbonates, like calcite, from limestone powder or other additives may be already contained in the noncarbonated sample material. For this research, an attempt was made to minimise the influence of these effects. Therefore, differential curves from DTG results of noncarbonated areas and areas with various states of carbonation of the same sample material were calculated and evaluated. Concretes based on three different types of cement were produced and stored under accelerated carbonation conditions (1% CO2 in air). The required sample material was obtained by cutting slices from various depths of previously CO2-treated specimen and subsequent grinding. During the sample preparation, a special attention was paid that no additional carbonation processes took place. As reference method for the determination of the carbonation depth, the sprayed application of phenolphthalein solution was carried out. Microscopic analysis was examined to confirm the assumptions made previously. Furthermore, the observed effect of encapsulation of calcium hydroxide by carbonates caused by the accelerated carbonation conditions was examined more closely.

Confocal laser scanning microscopic analysis of the penetration of an epoxy resin‐based sealer into dentinal tubules after calcium hydroxide dressing

2021 ◽  
Author(s):  
Manoel E.L. Machado ◽  
Virginia Natalia Veintimilla Lozada ◽  
Karol Jasmin Carrillo Rengifo ◽  
Raquel E.G. Guillén ◽  
Hector Caballero‐Flores ◽  
...  
Keyword(s):  
Epoxy Resin ◽  
Calcium Hydroxide ◽  
Laser Scanning ◽  
Microscopic Analysis ◽  
Confocal Laser Scanning ◽  
Confocal Laser ◽  
Dentinal Tubules

Dynamic Study on Vacuum Pyrolysis Reaction of Chinese Fir Sawdust Biomass

2012 ◽  
Vol 512-515 ◽  
pp. 375-378
Author(s):  
Su Wen Yang ◽  
Jian Min Yi ◽  
Ke Qiang Qiu ◽  
Xin Deng ◽  
Jian Shan Chen
Keyword(s):  
Heating Rate ◽  
Free Water ◽  
Chinese Fir ◽  
Peak Temperature ◽  
Gravimetric Analysis ◽  
Water Desorption ◽  
Exponential Factor ◽  
Pyrolysis Reaction ◽  
Temperature Range ◽  
Vacuum Pyrolysis

This thesis does thermal gravimetric analysis（TGA）studies on Chinese fir sawdust biomass by integrated thermal analyzer under vacuum conditions. Through the analysis on lostmass curve at different heating rate of 10, 15, 20 and 30°C/min, we found the process of Chinese fir sawdust vacuum pyrolysis can be mainly divided into three stages: evaporation of free water and combined water desorption, rapid lostmass of pyrolysis and slow decomposition of residues. The lostmass major temperature range is between 250 ~ 450°C, the peak temperature is between 365 ~ 400°C. When the pyrolysis temperature is 500°C, vacuum pyrolysis reaction of Chinese fir sawdust has basically completed. As the heating rate rises, the lostmass curve is moving to the right, the peak temperature is shifting to higher temperature, and the temperature range of thermal decomposition reaction widens significantly. According to experimental datas, we tried to obtain the vacuum pyrolysis dynamic parameters of Chinese fir sawdust, and the results are that the apparent activation energy of vacuum pyrolysis reaction of Chinese fir sawdust biomass is 128.34kJ/mol, with the pre-exponential factor being 6.42×109 and reaction order being 1.08, similar to first order reaction.

scholarly journals Effects of Nano-CaCO3/Limestone Composite Particles on the Hydration Products and Pore Structure of Cementitious Materials

2018 ◽  
Vol 2018 ◽  
pp. 1-8 ◽  
Author(s):  
Huashan Yang ◽  
Yujun Che
Keyword(s):  
Mechanical Properties ◽  
Pore Structure ◽  
Reaction System ◽  
Cementitious Materials ◽  
Limestone Powder ◽  
Composite Particles ◽  
Gravimetric Analysis ◽  
Hydration Products ◽  
Scanning Calorimetry ◽  
Necked Flask

The agglomeration of nano-CaCO3 (NC) is the largest bottleneck in applications in cementitious materials. If nano-CaCO3 modifies the surface of micron-scale limestone powder (LS), then it will form nano-CaCO3/limestone composite particles (NC/LS). It is known that micron-scale limestone is easily dispersed, and the “dispersion” of NC is governed by that of LS. Therefore, the dispersion of nano-CaCO3 can be improved by the NC/LS in cementitious materials. In this work, the preparation of NC/LS was carried out in a three-necked flask using the Ca(OH)2-H2O-CO2 reaction system. The morphology of NC/LS was observed by a field emission scanning electron microscope (FE-SEM). The effects of NC/LS on the hydration products and pore structure of cementitious materials are proposed. 5% NC/LS was added into cement paste and mortar, and the mechanical properties of the specimens were measured at a certain age. Differential scanning calorimetry (DSC), thermal gravimetric analysis (TG), and backscattered electron imaging (BSE) were conducted on the specimens to investigate the hydration products and pore structure. The properties of specimens with NC/LS were compared to that of control specimens (without NC/LS). The results revealed that NC/LS reduced the porosity and improved the mechanical properties of the cementitious materials.

Basic halides and related species of molybdenum(III). II. Spectroscopic and magnetic properties of MoOF(H2O)3 and MoOCl(H2O)3

1976 ◽  
Vol 29 (4) ◽  
pp. 717 ◽  
Author(s):  
DJ Stabb
Keyword(s):  
Magnetic Properties ◽  
Magnetic Susceptibility ◽  
Absorption Spectroscopy ◽  
Infrared Spectra ◽  
Electronic Spectra ◽  
Related Species ◽  
Bound Water ◽  
Temperature Range ◽  
Field Dependent

Two basic halides of molybdenum(111), namely MoOF(H2O)3 and MoOCl(H2O)3 (some samples containing additional loosely bound water), were investigated by absorption spectroscopy in the range 200-50000 cm-1, and by magnetic susceptibility measurements over a temperature range of 100-300 K. Infrared spectra showed bands at about 670 and 1600 cm-l, but not in the range 800-1100 cm-1. Electronic spectra showed poorly defined bands superimposed on strong general absorption. Very weak paramagnetism was observed: this was field dependent. The results are interpreted to show the compounds to be oxygen-bridged polymers [MOX(H2O)3O]n, rather than species containing Mo=O or Mo-0-H groups.

scholarly journals To what extent can aerosol water explain the discrepancy between model calculated and gravimetric PM<sub>10</sub> and PM<sub>2.5</sub>?

2005 ◽  
Vol 5 (2) ◽  
pp. 515-532 ◽  
Author(s):  
S. G. Tsyro
Keyword(s):  
Water Content ◽  
Bound Water ◽  
Chemical Characterization ◽  
Reference Method ◽  
Temporal Correlation ◽  
Monitoring And Evaluation ◽  
Model Calculations ◽  
Aerosol Model ◽  
Pm10 And Pm2.5 ◽  
Pm2.5 And Pm10

Abstract. Inter-comparisons of European air quality models show that regional transport models, including the EMEP (Co-operative Programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe) aerosol model, tend to underestimate the observed concentrations of PM10 and PM2.5. Obviously, an accurate representation of the individual aerosol constituents is a prerequisite for adequate calculation of PM concentrations. On the other hand, available measurements on the chemical characterization of ambient particles reveal that full chemical PM mass closure is rarely achieved. The fraction unaccounted for by chemical analysis can comprise as much as 30-40% of gravimetric PM10 or PM2.5 mass. The unaccounted PM mass can partly be due to non-C atoms in organic aerosols and/or due to sampling and measurement artefacts. Moreover, a part of the unaccounted PM mass is likely to consist of water associated with particles. Thus, the gravimetrically measured particle mass does not necessarily represent dry PM10 and PM2.5 mass. This is thought to be one of the reasons for models under-prediction of observed PM, if calculated dry PM10 and PM2.5 concentrations are compared with measurements. The EMEP aerosol model has been used to study to what extent particle-bound water can explain the chemically unidentified PM mass in filter-based particle samples. Water content of PM2.5 and PM10 has been estimated with the model for temperature 20°C and relative humidity 50%, which are conditions required for equilibration of dust-loaded filters according to the Reference method recommended by the European Committee for Standardization (CEN). Model calculations for Europe show that, depending on particle composition, particle-bound water constitutes 20-35% of the annual mean PM10 and PM2.5 concentrations, which is consistent with existing experimental estimates. At two Austrian sites, in Vienna and Streithofen, where daily measurements of PM2.5 mass and chemical composition are available, calculated PM2.5 water content is found to be about 75-80% of the undetermined PM2.5 mass and there is correlation between them. Furthermore, accounting for aerosol water has improved the agreement between modelled and measured daily PM2.5 concentrations, whilst model calculated dry PM2.5 concentrations appear to agree quite well with the total identified PM2.5 mass. No information on the composition of PM measured at EMEP sites is presently available. Given that PM10 and PM2.5 concentrations are measured at EMEP stations with gravimetric methods they are likely to contain water. We show that the levels of modelled PM10 and PM2.5 concentrations with aerosol water included agree with measurements better than dry PM concentrations. As expected, the spatial correlation has not changed significantly, whereas the temporal correlation of daily PM10 and PM2.5 with monitoring data has slightly improved at most of the EMEP sites. Our results suggest that aerosol water should be accounted for in modelled PM10 and PM2.5 when compared with filter-based gravimetric measurements.

scholarly journals To what extent can aerosol water explain the discrepancy between model calculated and gravimetric PM<sub>10</sub> and PM<sub>2.5</sub>?

2004 ◽  
Vol 4 (5) ◽  
pp. 6025-6066
Author(s):  
S. G. Tsyro
Keyword(s):  
Water Content ◽  
Bound Water ◽  
Chemical Characterization ◽  
Reference Method ◽  
Temporal Correlation ◽  
Monitoring And Evaluation ◽  
Model Calculations ◽  
Aerosol Model ◽  
Pm10 And Pm2.5 ◽  
Pm2.5 And Pm10

Abstract. Inter-comparisons of European air quality models show that regional transport models, including the EMEP (Co-operative Programme for monitoring and evaluation of the long-range transmission of air pollutants in Europe) aerosol model, tend to underestimate the observed concentrations of PM10 and PM2.5. Obviously, an accurate representation of the individual aerosol constituents is a prerequisite for adequate calculation of PM concentrations. On the other hand, available measurements on the chemical characterization of ambient particles reveal that full chemical PM mass closure is rarely achieved. The fraction unaccounted for by chemical analysis can comprise as much as 30–40% of gravimetric PM10 or PM2.5 mass. The unaccounted PM mass can partly be due to non-C atoms in organic aerosols and/or due to sampling and measurement artefacts. Moreover, a part of the unaccounted PM mass is likely to consist of water associated with particles. Thus, the gravimetrically measured particle mass does not necessarily represent dry PM10 and PM2.5 mass. This is thought to be one of the reasons for models under-prediction of observed PM, if calculated dry PM10 and PM2.5 concentrations are compared with measurements. The EMEP aerosol model has been used to study to what extent particle-bound water can explain the chemically unidentified PM mass in filter-based particle samples. Water content of PM2.5 and PM10 has been estimated with the model for temperature 20°C and relative humidity 50%, which are conditions required for equilibration of dust-loaded filters according to the Reference method recommended by the European Committee for Standardization (CEN). Model calculations for Europe show that, depending on particle composition, particle-bound water constitutes 20–35% of the annual mean PM10 and PM2.5 concentrations, which is consistent with existing experimental estimates. At two Austrian sites, in Vienna and Streithofen, where daily measurements of PM2.5 mass and chemical composition are available, calculated PM2.5 water content is found to be about 75–80% of the undetermined PM2.5 mass and there is correlation between them. Furthermore, accounting for aerosol water has improved the agreement between modelled and measured daily PM2.5 concentrations, whilst model calculated dry PM2.5 concentrations appear to agree quite well with the total identified PM2.5 mass. No information on the composition of PM measured at EMEP sites is presently available. Given that PM10 and PM2.5 concentrations are measured at EMEP stations with gravimetric methods they are likely to contain water. We show that the levels of modelled PM10 and PM2.5 concentrations with aerosol water included agree with measurements better than dry PM concentrations. As expected, the spatial correlation has not changed significantly, whereas the temporal correlation of daily PM10 and PM2.5 with monitoring data has slightly improved at most of the EMEP sites. Our results suggest that aerosol water should be accounted for in modelled PM10 and PM2.5 when compared with filter-based gravimetric measurements.

scholarly journals EVALUATION OF BOUND WATER FORMS IN CLAYS

2018 ◽  
Vol 13 (4-5) ◽  
pp. 52-61
Author(s):  
V. V. Seredin ◽  
N. A. Medvedeva ◽  
A. V. Anukhina
Keyword(s):  
Crystal Lattice ◽  
Water Mass ◽  
Bound Water ◽  
Physical Nature ◽  
Structural Elements ◽  
Kaolinite Clay ◽  
Temperature Range ◽  
Crystallite Surface ◽  
Montmorillonite Clays ◽  
Composition Structure

Clays during lithogenesis change the composition, structure and properties, including physicochemical. The result of the thermal analysis was thermograms, on which four peaks of loss of bound water mass were established. These peaks in the author's interpretation are presented as different types of bound water in clays. The obtained experimental data, from the position of the size of the structural elements, allowed to distinguish the following types of water: loosely bound and strongly bound water of the surface of colloids, water surface of crystallites (minerals) and the crystal lattice of minerals. It has been revealed that when the montmorillonite and kaolinite clays are heated, endo-effects are observed in the temperature range up to 900°C caused by the release of H2O and OH-, the source of which is adsorption water and crystal lattice water of minerals. For montmorillonite in the high-temperature range, endo-effects due to the release of CO and CO2 were also noted, which is due to the presence of calcite in its composition. The energy activity of the surfaces of the particles of montmorillonite and kaolinite clays is distributed in the following sequence: the crystallite surface > of the surface of the colloid > of the surface of the strongly bound water of the colloid, which does not contradict the physical nature of the formation of the clay particle. It has been revealed that in montmorillonite clay, the water of the surface of crystallites has the greatest strength of bonds between molecules, the smaller is the strongly bound water of the colloid and the least is loosely bound water of the colloid. In kaolinite clay, the greatest strength of the bonds between molecules is the water of the surface of crystallites, the smaller is the loosely bound water of the colloid and the least strongly bound water of the colloid. In kaolinite and montmorillonite clays, the temperature of the effect and the heat of dehydration of the studied forms of bound water determine the change in the loss of bound water mass in different directions. The results of the studies allowed to quantify various forms of water in clay minerals.

scholarly journals Effects of Carbonation on the Properties of Concrete

2019 ◽  
pp. 205-214
Author(s):  
Ikumapayi C. M. ◽  
Adeniji A. A. ◽  
Obisesan A. A. ◽  
Odeyemi O. ◽  
Ajayi J. A.
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Reinforced Concrete ◽  
Flexural Strength ◽  
Water Absorption ◽  
Research Work ◽  
Construction Materials ◽  
Accelerated Carbonation ◽  
Weight Changes ◽  
Carbonation Process

Concrete is one of the reliable, durable, economical and acceptable construction materials among the building and construction stakeholders worldwide. Performance of concrete could be threatened especially reinforced concrete by some processes such as corrosion, sulfate attack among others. Corrosion of reinforcement in reinforced concrete can be induced by carbonation process. Even though carbonation initiates corrosion, it has been gathered that carbonation could still be of immense benefits to building and construction industries if its mechanism of operation is understudied. This research work has therefore investigated the effect of carbonation on some selected mechanical properties of concrete such as compressive strength, flexural strength, water absorption and weight changes. Concrete cubes and beams of M15 grade with 0.5 % water-cement ratio were prepared and subjected to accelerated carbonation. Their compressive strength, flexural strength, water absorption and weight changes were determined in accordance with the relevant standards. The outcomes show that carbonation improves all the mechanical properties investigated. The use of carbonation can be positively explored in reinforced concrete provided there is adequate nominal cover.

AN X-RAY METHOD FOR THE STUDY OF "BOUND WATER" IN HYDROPHILIC COLLOIDS AT LOW TEMPERATURES

1935 ◽  
Vol 13b (4) ◽  
pp. 218-227 ◽  
Author(s):  
W. H. Barnes ◽  
W. F. Hampton
Keyword(s):  
Qualitative Study ◽  
Low Temperatures ◽  
Bound Water ◽  
New Method ◽  
Ray Method ◽  
X Ray ◽  
Temperature Range ◽  
Methods Of Analysis ◽  
Gelatin Gels ◽  
Ray Methods

A new method for the study of hydrophilic colloids by the application of X-ray methods of analysis to the frozen gels is described. The possibilities of the method and its limitations are shown by a qualitative study of the amount, and variation with temperature, of the so-called "bound" water in gelatin gels over the temperature range − 3° to − 50 °C.

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