SEM Analysis and Computer Modelling of Hydration of Portland Cement Particles

2009 ◽  
pp. 60-60-14 ◽  
Author(s):  
DP Bentz ◽  
PE Stutzman
Keyword(s):  
Portland Cement ◽  
Computer Modelling ◽  
Sem Analysis

Seawater Corrosion Resistance of Low Heat Portland Cement Concrete

2015 ◽  
Vol 814 ◽  
pp. 207-213
Author(s):  
Ning Wang ◽  
Xiao Wei Cheng ◽  
Yun Xia Yang
Keyword(s):  
Corrosion Resistance ◽  
Portland Cement ◽  
Test Specimen ◽  
Sem Analysis ◽  
Corrosion Mechanism ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Quality Change ◽  
Seawater Corrosion ◽  
Drying Test

With the analysis of the seawater corrosion effect on low-heat Portland cement concrete under wetting-drying test, the compressive strength and quality change of concrete test specimen were investigated for different test periods. According to the evaluation of seawater corrosion resistance, the low-heat Portland cement showed better corrosion resistance than that of ordinary Portland cement and moderate-heat Portland cement. Moreover, the corrosion mechanism was expounded through XRD and SEM analysis. It was found that lots of C2S in the low-heat Portland cement play an important role in corrosion resistance of cement concrete.

Accelerating the Setting of Portland Cement Based Dental Materials Using Calcium Sulphates

2007 ◽  
Vol 361-363 ◽  
pp. 343-346 ◽  
Author(s):  
J.L. O’Beirne ◽  
R.M. Shelton ◽  
P.J. Lumley ◽  
M.P. Hofmann
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Setting Time ◽  
Dental Materials ◽  
Testing Machine ◽  
Mineral Trioxide Aggregate ◽  
Calcium Sulphate ◽  
Sem Analysis ◽  
Initial Setting ◽  
Relative Porosity

Mineral trioxide aggregate (MTA) is a Portland cement (PC) based material used for sealing root canals however it has a long setting time which is undesirable for dental applications. This study investigated the effect of three different calcium sulphate additions for accelerating the initial setting of a PC based dental material, whilst attempting to maintain its high compressive strength and low relative porosity. Anhydrous calcium sulphate (CaS), Plaster of Paris, calcium sulphate hemihydrate (PoP) and Gypsum, calcium sulphate dihydrate (Gyp) were each added to PC at 5wt%, 10wt% and 20wt%. Initial setting times, compressive strengths and relative porosity were measured using the Gilmore Needles Test, a universal testing machine and a helium pycnometer respectively. Scanning electron microscopy (SEM) was used to observe any microstructural changes in cements. PoP and CaS had the most profound influence on the setting of PC. 20wt% CaS had the greatest effect on the setting time of PC (10min) although decreased the compressive strength by up to 40%, which may have arisen from the formation of microcracks, observed by SEM analysis. Additions of 10wt% PoP and CaS may have the potential to reduce the long setting time of PC based dental materials.

Effect of Active Magnesia on the Properties of Cementitious Binders

2012 ◽  
Vol 1488 ◽  
Author(s):  
Jing Zhu ◽  
Nan Ye ◽  
Jianwen Liu ◽  
Yalin Li ◽  
Jiakuan Yang
Keyword(s):  
Fly Ash ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Sem Analysis ◽  
Rapid Expansion ◽  
X Ray Diffraction ◽  
Initial Stage ◽  
Cementitious Binder ◽  
Negative Effect ◽  
The Dead

ABSTRACTReactive magnesium oxide (magnesia, MgO) was produced by calcining magnesite at comparatively low temperature, less than 800 ℃C. The reactive MgO and fly ash were used as additives to cementitious binder. The reactive MgO-ordinary Portland cement-fly ash is referred to as MgO-OPC-FA cement in further. The hydration expansion effect of active magnesia on the properties of cementitious binder in different mixing ratio was investigated. It is known that the “dead burnt” MgO reacts with water very slowly, which causes the expansion after the solidification of cement. Therefore, the MgO content in ordinary cement is commonly restricted to less than 5%. Effects of reactive MgO on the expansion properties of the cementitious binders were studied. Hydrated products of reactive MgO cements were investigated by X-ray diffraction (XRD) and Scanning electron microscope (SEM) analysis. The MgO-OPC-FA cement was sound, although the content of reactive MgO in cement was about 8 wt. %. Reactive MgO was hydrated at early age in 24 hours, thus causing rapid expansion. Mg(OH)2appeared on initial stage of cement hydration for active magnesia. The hydration rate of active magnesia was not equal to that of the dead burnt magnesia. The hydration of reactive MgO has a negative effect on the mechanical properties of reactive MgO-ordinary Portland cement-fly ash system, in spite of the inhibitive effect of the expansion of MgO hydration produced by fly ash. Our results shed light on the potential utilization of reactive MgO in the manufacturing of cementitious binders.

scholarly journals The Effect of Red Mud on Sintering Processes and Minerals of Portland Cement for Roads

Crystals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1267
Author(s):  
Xiao Wang ◽  
Ke Sun ◽  
Xin Li ◽  
Juntao Ma ◽  
Zhongtao Luo
Keyword(s):  
Portland Cement ◽  
Red Mud ◽  
Intermediate Phase ◽  
Sem Analysis ◽  
Raw Material ◽  
Cement Clinker ◽  
Silicate Phase ◽  
Alumina Industry ◽  
Storage Problem ◽  
Sintering Processes

As a solid waste generated in the alumina industry, red mud poses a significant environmental hazard and a storage problem. In this study, red mud was added to road cement clinker in order to utilize it. The sintering red mud was first de-alkalized, and then mixed with fly ash, clay, limestone, and sandstone, among other materials, to make Portland cement for road clinker. The effect of the addition of red mud on the thermal decomposition characteristics of Portland cement for roads was studied. The existent states of alkali and radioactive elements in Portland cement for road clinker were investigated by XRD and SEM analysis. The research results showed that the addition of red mud in Portland cement for road raw material significantly promoted the decomposition of carbonates in raw material. The major mineral phases of Portland cement for road clinker were C3S with a polyhedral morphology, quasi-sphericalC2S, and tubular C4AF. A small part of the alkali combined with the silicate phase to form a solid solution, and most of the alkali combined with S to form vermiform sulfate in the intermediate phase. The radionuclide 226Ra was mainly distributed in the silicate phase.232Th was mainly distributed in interstitial phases and then silicate phases, while 40Kwasmainly distributed in the interstitial phases.

Microstructure and Characterizations of Portland-Carbon Nanotubes Pastes

2008 ◽  
Vol 55-57 ◽  
pp. 549-552 ◽  
Author(s):  
T. Nochaiya ◽  
P. Tolkidtikul ◽  
Pisith Singjai ◽  
Arnon Chaipanich
Keyword(s):  
Carbon Nanotubes ◽  
Compressive Strength ◽  
Flexural Strength ◽  
Portland Cement ◽  
Aging Time ◽  
Sem Analysis ◽  
Cement Composites ◽  
Strength Tests ◽  
Tga Analysis

This research studied microstructure and characterizations of Portland cement with carbon nanotubes (CNTs) which were used as an additive material at 0 %, 0.5 % and 1 % by weight of cement. The compressive and flexural strength tests of mixes were conducted using water/cement ratios (w/c) of 0.5. Samples of mixes were selected for SEM analysis and then ground for TGA analysis. The results show that the compressive strength and flexural strength at all aging time of Portland-CNTs cement composites was higher than that of control mix. Microstructure results show that CNTs was filled in pores between matrix phases to show denser phase and TGA graphs show similar phases to PC mix.

Influence of Rubber Crumb Addition to Portland Cement Concrete

2011 ◽  
Vol 391-392 ◽  
pp. 600-605
Author(s):  
Hai Bo Zhang
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Coupling Agent ◽  
Sem Analysis ◽  
Cement Matrix ◽  
Rubber Crumb ◽  
Portland Cement Concrete ◽  
Cement Concrete ◽  
Polar Function ◽  
Rubber Concrete

In this paper, two kinds of rubber surface modifying methods were studied. One was bis[3-(triethoxysilyl) propyl] tetrasulfide (Si-69) silicon alkane coupling agent and the other was crylic acid coupling agent. The mechanical properties of cement concrete with modified rubber crumb and with non-modified rubber crumb were tested respectively. The results show that as the rubber crumb addition rises, the toughness of concrete with non-modified rubber crumb increases while the compressive strength decreases, and both thoughness and compressive strength of cement concrete with modified rubber crumb increase. The chloride impermeability of the rubber concrete are much better than that of the Portland cement concrete. After surface modification the chloride impermeability can be improved more. The thermoanalysis proves that the surface of modified rubber crumb is grafted by polar function groups, so the surface changes from hydrophobic to hydrophilic. The scanning electron microscopy (SEM) analysis confirms that the interface between rubber crumb and cement matrix is improved.

scholarly journals Characteristics of Ordinary Portland Cement Using the New Colloidal Nano-Silica Mixing Method

2019 ◽  
Vol 9 (20) ◽  
pp. 4358 ◽  
Author(s):  
Taewan Kim ◽  
Sungnam Hong ◽  
Ki-Young Seo ◽  
Choonghyun Kang
Keyword(s):  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
Sem Analysis ◽  
New Method ◽  
Nano Silica ◽  
Substitution Method ◽  
Replacement Method ◽  
Mechanical And Microstructural Properties ◽  
Mixing Water

This study applies a new method of mixing colloidal nano-silica (CNS). Previous studies have used powdered nano-silica or colloidal nano-silica and applied a binder weight substitution method. In this study, we tried to use ordinary Portland cement (OPC) as a binder and replace CNS with weight of mixing water. CNS was replaced by 10%, 20%, 30%, 40%, and 50% of the mixing water weight. The flow value, setting time, compressive strength, hydration reactant (X-ray diffractometer; XRD), pore structure (mercury intrusion porosimetry; MIP), thermal analysis, and scanning electron microscopy (SEM) analysis were performed. Experimental results show that the new substitution method improves the mechanical and microstructural properties through two effects. One is that the weight substitution of the mixing water shows a homogeneous dispersion effect of the nano-silica particles. The other is the effect of decreasing the w/b ratio when the CNS is substituted because the CNS is more dense than the mixing water. Therefore, we confirmed the applicability of mixing water weight replacement method as a new method of mixing CNS.

Calcined Kaolin Geopolymeric Powder: Influence of Water-to-Geopolymeric Powder Ratio

2012 ◽  
Vol 548 ◽  
pp. 48-53
Author(s):  
Y.M. Liew ◽  
H. Kamarudin ◽  
A.M. Mustafa Al Bakri ◽  
M. Binhussain ◽  
Luqman Musa ◽  
...  
Keyword(s):  
Compressive Strength ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
Sem Analysis ◽  
Cement Ratio ◽  
Water To Cement Ratio ◽  
Influence Of Water ◽  
Calcined Kaolin ◽  
Geopolymer Paste

This paper describes the synthesis of calcined kaolin geopolymeric powder from the alkaline activation of calcined kaolin followed by solidification and pulverizing process. The geopolymeric powder was used by just adding water to produce resulted geopolymer paste. In this paper, the effect of water-to-geopolymeric powder ratios on the properties of the resulted geopolymer paste was studied. This water-to-geopolymer powder ratio was similar to that of water-to-cement ratio in the case of ordinary Portland cement (OPC). However, the concept used here was based on geopolymerization process. The compressive strength, setting time and SEM analysis of the resulted geopolymer pastes were conducted. Highest strength was achieved at water-to-geopolymer powder ratio of 0.22. The resulted geopolymer paste could be handled up to 120 minutes and reached final setting after about 4 hours of setting. Microstructure showed the formation of geopolymeric gel after the addition of water to the geopolymeric powder.

SEM analysis of the change in the reaction rates with deposit structures in the copper-iron cementation system

1978 ◽  
Vol 36 (1) ◽  
pp. 456-457
Author(s):  
V. Annamalai ◽  
L.E. Murr
Keyword(s):  
Structural Characteristics ◽  
Secondary Electron Emission ◽  
Copper Deposit ◽  
Reaction Rates ◽  
Sem Analysis ◽  
Experimental Conditions ◽  
Major Drawback ◽  
Emission Mode ◽  
Scrap Iron ◽  
Image Position

Economical recovery of copper metal from leach liquors has been carried out by the simple process of cementing copper onto a suitable substrate metal, such as scrap-iron, since the 16th century. The process has, however, a major drawback of consuming more iron than stoichiometrically needed by the reaction.Therefore, many research groups started looking into the process more closely. Though it is accepted that the structural characteristics of the resultant copper deposit cause changes in reaction rates for various experimental conditions, not many systems have been systematically investigated. This paper examines the deposit structures and the kinetic data, and explains the correlations between them.A simple cementation cell along with rotating discs of pure iron (99.9%) were employed in this study to obtain the kinetic results The resultant copper deposits were studied in a Hitachi Perkin-Elmer HHS-2R scanning electron microscope operated at 25kV in the secondary electron emission mode.

SEM analysis of DC magnetron sputtered beryllium films

1988 ◽  
Vol 46 ◽  
pp. 960-961
Author(s):  
E. F. Lindsey ◽  
C. W. Price ◽  
E. L. Pierce ◽  
E. J. Hsieh
Keyword(s):  
Fine Structure ◽  
Electron Emission ◽  
Secondary Electron ◽  
Low Voltage ◽  
Ion Beam ◽  
Secondary Electron Emission ◽  
Sem Analysis ◽  
Fused Silica ◽  
Grain Structure ◽  
Silica Substrate

Columnar structures produced by DC magnetron sputtering can be altered by using RF biased sputtering or by exposing the film to nitrogen pulses during sputtering, and these techniques are being evaluated to refine the grain structure in sputtered beryllium films deposited on fused silica substrates. Beryllium is brittle, and fractures in sputtered beryllium films tend to be intergranular; therefore, a convenient technique to analyze grain structure in these films is to fracture the coated specimens and examine them in an SEM. However, fine structure in sputtered deposits is difficult to image in an SEM, and both the low density and the low secondary electron emission coefficient of beryllium seriously compound this problem. Secondary electron emission can be improved by coating beryllium with Au or Au-Pd, and coating also was required to overcome severe charging of the fused silica substrate even at low voltage. The coating structure can obliterate much of the fine structure in beryllium films, but reasonable results were obtained by using the high-resolution capability of an Hitachi S-800 SEM and either ion-beam coating with Au-Pd or carbon coating by thermal evaporation.

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