scholarly journals The Expansion Cracks of Dolomitic Aggregates Cured in TMAH Solution Caused by Alkali–Carbonate Reaction

Materials ◽  
2019 ◽  
Vol 12 (8) ◽  
pp. 1228 ◽  
Author(s):  
Xiaoxiao Chen ◽  
Bin Yang ◽  
Zhongyang Mao ◽  
Min Deng
Keyword(s):  
Electron Microscopy ◽  
Energy Dispersive Spectrometry ◽  
Alkali Silica Reaction ◽  
Polarizing Microscopy ◽  
Alkali Carbonate ◽  
Area Expansion ◽  
Carbonate Reaction ◽  
Tmah Solution ◽  
Scanning Electron ◽  
Curing Age

In this study, concrete microbars and rock prisms made of dolomitic aggregates were cured in a 1-mol/L tetramethylammonium hydroxide (TMAH) solution at 80 °C to avoid the effect of alkali–silica reaction (ASR) on expansion. The expansion of specimens was only caused by the alkali–carbonate reaction (ACR). The reason that self-made cement was used in this work was to ensure that the Mg2+ contained in the brucite originated only from dolomite. Expansion of concrete microbars and rock prisms was measured, the expansion cracks were systematically observed by orthogonal polarizing microscopy, and the products of ACR were analyzed by scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results showed that the dolomite crystals in the dolomitic aggregates reacted with the TMAH solution and resulted in ACR, which formed calcite and brucite and led to cracking of the specimens. The source of the expansion was the dolomite crystals of the dolomite enrichment area. Expansion cracks either extended inside the rock or into the cement phase and eventually disappeared. The alkali–carbonate reaction significantly contributed to the expansion of dolomitic aggregates cured in TMAH solution at a later curing age.

scholarly journals Effects of Recycled Fine Glass Aggregates on Alkali Silica Reaction and Thermo-Mechanical Behavior of Modified Concrete

2021 ◽  
Vol 11 (19) ◽  
pp. 9045
Author(s):  
Ibtissam Abalouch ◽  
Siham Sakami ◽  
Fatima-Ezzahra Elabbassi ◽  
Lahcen Boukhattem
Keyword(s):  
Electron Microscopy ◽  
Thermal Effusivity ◽  
Maximum Size ◽  
Pozzolanic Reaction ◽  
Alkali Silica Reaction ◽  
Natural Sand ◽  
Fine Glass ◽  
Recycled Waste ◽  
Scanning Electron ◽  
Curing Age

The objective of this work is to develop a new composite material by substituting sand with recycled waste glass (RWG). Different volume percentages of RWG varying from 0 to 50% were incorporated into concrete, with maximum size that did not exceed 1.25 mm. The microscopic characterization by scanning electron microscopy SEM-EDS and optical microscopic test, as well as the durability against alkali silica reaction (ASR) test, were performed respectively to visualize the morphology and assess the damage caused by ASR. Furthermore, the mechanical and thermophysical properties measurements were carried out. The results of microscopic characterization showed the presence of cracks inside a minority of glass particles due to ASR, and ASR test indicated that expansion activity remained well below the limit expansion value of 0.15%. The obtained results also showed that, at 28 and 90 days of curing, compressive strength increased respectively by up to 1.63% and 29% for 20% of the incorporated RWG volume rate in concrete; however, beyond this rate it diminished receptively by 30% and 3.2%. This improvement with curing age was attributed to pozzolanic reaction. Regarding density, it reduced by around 5%. Furthermore, thermal conductivity and thermal effusivity decreased respectively by 36% and 8.06% at dry state and they dropped respectively by 44% and 21.28% at saturated state, related to reference concrete RC. It is therefore feasible to substitute high amount of natural sand with RWG to obtain new composite that may be successfully used as structural material in construction building.

scholarly journals Analytical study of Buddha sculptures in Jingyin temple of Taiyuan, China

2021 ◽  
Vol 9 (1) ◽  
Author(s):  
Xiaojian Bai ◽  
Chen Jia ◽  
Zhigen Chen ◽  
Yuxuan Gong ◽  
Huwei Cheng ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Analytical Study ◽  
Energy Dispersive Spectrometry ◽  
Analytical Techniques ◽  
X Ray Diffraction ◽  
Ancient China ◽  
X Ray ◽  
Unique Style ◽  
Scanning Electron

AbstractWith exquisite design and unique style, the painted sculptures of Tutang Buddha and two attendants Buddha in Jingyin Temple are precious cultural heritages of China. The sculpture of Tutang Buddha, which was carved from a mound and painted by ancient craftsmen, was rarely found in ancient China. However, due to natural and human factors, the sculptures were severely damaged. Obviously, they require urgent and appropriate protection and restoration. In this study, samples taken from the sculptures were analysed through multiple analytical techniques, including scanning electron microscopy with energy dispersive spectrometry (SEM–EDS), Raman spectroscopy, X-ray diffraction (XRD), optical microscopy (OM) and granulometry. The analysis results enable us to infer the techniques used by the craftsmen in making the sculptures and provide a reliable evidence for the conservation and future protection of these and similar sculptures.

Geochemistry of halloysite-7Å formation from plagioclase in trachyandesite rocks from Limnos Island, Greece

Clay Minerals ◽  
2014 ◽  
Vol 49 (1) ◽  
pp. 75-89 ◽  
Author(s):  
D. Papoulis ◽  
S. Komarneni ◽  
D. Panagiotaras
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Chemical Analysis ◽  
Geochemical Data ◽  
X Ray Diffraction ◽  
Polarizing Microscopy ◽  
X Ray ◽  
Geochemical Evaluation ◽  
Scanning Electron ◽  
Southwest Part

AbstractTrachyandesite rocks, occurring over an area of about 1 km2in the southwest part of Limnos Island, Greece, are altered mainly to halloysite. The samples were collected and analysed by polarizing microscopy, powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and chemical analysis. The alteration of plagioclase to halloysite follows seven discrete stages that are described in detail. The geochemical evaluation of the data shows enrichment of the lightREE(LREE) over heavyREE(HREE) as expressed by the (La/Yb)n ratio. TheΣLREErange from 206.44 to 272.30, while the sum ofHREEvaries from 11.01 to 26.26. The (La/Yb)n ratio ranges from 9.72 to 27.64. Fractionation amongLREEexpressed as (La/Sm)n and between middleREE(MREE) andHREEis shown as (Tb/Yb)n ratios. The most altered rocks close to the fault zone have high (Tb/Yb)n ratios and low (La/Sm)n and Eu/Eu* ratios. Although mineralogy and clay mineral textures indicate hydrothermal genesis of halloysite, the geochemical data are not conclusive due to a secondary weathering effect.

Tribocorrosion Behaviors of D40 Steel in Artificial Seawater

2017 ◽  
Vol 898 ◽  
pp. 840-848
Author(s):  
Liang Shi ◽  
Shao Peng Qu ◽  
Hai Yan Chen ◽  
Yan Sheng Yin ◽  
Li Jing Yang
Keyword(s):  
Electron Microscopy ◽  
Oxygen Diffusion ◽  
Energy Dispersive Spectrometry ◽  
Diffusion Rate ◽  
Corrosion Process ◽  
Ion Adsorption ◽  
White Light Interferometry ◽  
Friction Process ◽  
Surface Morphologies ◽  
Scanning Electron

The friction, corrosion and tribocorrosion experiments were carried out to study the tribocorrosion characteristics of the D40 steel. Friction process was undertaken using a TriboLab. The electrochemical property of D40 steel was studied using an electrochemical workstation. The surface morphologies of the D40 steel after experiments were characterized by white light interferometry, scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The results indicated that both the tribocorrosion and corrosion process of D40 steel under the condition of seawater were controlled by the cathodic oxygen diffusion. The diffusion rate of oxygen in the solution was accelerated by the friction. The phenomenon of Cl ion adsorption was more obvious for the D40 steel during tribocorrosion test, and the corrosion resistance was significantly reduced due to the promotion of friction.

Homogenization Treatment to Optimize the Microstructures of the Al-3.5Cu-1.5Li Alloy and Analysis of Al3Zr Precipitates

2018 ◽  
Vol 921 ◽  
pp. 195-201 ◽  
Author(s):  
Jin Jun Xu ◽  
Mang Jiang
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Energy Dispersive Spectrometry ◽  
Single Step ◽  
Experimental Alloy ◽  
Composition Distribution ◽  
Double Step ◽  
Homogenization Treatment ◽  
Transmission Electron ◽  
Scanning Electron

The microstructure evolution and composition distribution of the cast Al-3.5Cu-1.5Li-0.11Zr alloy during single-step and double-step homogenization were studied with the help of the optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive spectrometry (EDS) and transmission electron microscopy (TEM) methods. The results show that severe dendrite segregation exists in the experimental alloy. Six different homogenization treatments, conventional one-stage homogenization and double-stage homogenization are carried out, and the best homogenization treatment of the experimental alloys was achieved. Moreover, the precipitation of Al3Zr particles was significantly different after two kinds of homogenization in the experimental alloy. Compared with the single-stage homogenization, a finer particle size and distribution more diffuse of Al3Zr particles can be obtained in the double-stage homogenization treatment.

scholarly journals Effect of lithium nitrate on the reaction between opal aggregate and sodium and potassium hydroxides in concrete over a long period of time

2017 ◽  
Vol 65 (6) ◽  
pp. 773-778 ◽  
Author(s):  
J. Zapała-Sławeta ◽  
Z. Owsiak
Keyword(s):  
Electron Microscopy ◽  
Pore Solution ◽  
Alkali Silica Reaction ◽  
Lithium Nitrate ◽  
X Ray ◽  
Long Period ◽  
Chemical Admixtures ◽  
Mortar Bar ◽  
Sodium And Potassium ◽  
Scanning Electron

AbstractAlkali-silica reaction (ASR) is a reaction between amorphous or poorly crystallized siliceous phase, present in aggregates, and sodium and potassium hydroxides in the pore solution of concrete. Chemical admixtures such as lithium compounds are known to have high potential of inhibiting ASR. The aim of this study was to determine the effect of lithium nitrate on ASR in mortars containing high reactive opal aggregate over a long period of time. Mortar bar expansion tests were performed and microstructures of mortar bars were observed by scanning electron microscopy coupled with an energy dispersive X-ray microanalyser. Results from this study showed that effectiveness of lithium nitrate in mitigating ASR was limited over a long period of time. A larger amount of ASR gel which was formed in the presence of lithium nitrate indicated that the deterioration processes intensify within longer periods of time, which so far has not been observed in literature. Microscopic observation confirmed the presence of alkali-silica gel and delayed ettringite in mortars with lithium nitrate.

The Microstructure of AlSi7Mg Alloy in as Cast Condition

2015 ◽  
Vol 229 ◽  
pp. 3-10 ◽  
Author(s):  
Bartłomiej Dybowski ◽  
Bogusława Adamczyk-Cieślak ◽  
Kinga Rodak ◽  
Iwona Bednarczyk ◽  
Andrzej Kiełbus ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Chemical Composition ◽  
Energy Dispersive Spectrometry ◽  
Intermetallic Phases ◽  
Transmission Electron ◽  
Alloy Microstructure ◽  
Cast Condition ◽  
Scanning Electron

The complex microstructure of as-cast AlSi7Mg alloy has been investigated. Microstructure observations were done using light microscopy, scanning electron microscopy and transmission electron microscopy. Chemical composition of the microstructure constituents was investigated by means of energy dispersive spectrometry, conducted both during SEM and STEM investigations. Selected area diffraction was used to identify the phases in the alloy. Microstructure of the alloy in the as-cast condition consists of Al-Si eutectic and intermetallic phases in the interdendritic regions. These are: Mg2Si, α-AlFeMnS, β-AlFeSi and π-AlFeSiMg phases. What is more, number of fine precipitates were found within the α-Al dendrites. Only the occurrence of U1 (MgAl2Si2) phase has been confirmed.

Sign in / Sign up

Export Citation Format

Share Document