scholarly journals Gessos pedra, usualmente empregados pelo cirurgião-dentista brasileiro, face a norma proposta pela Associação Dentária Americana

2021 ◽  
Vol 12 (1) ◽  
pp. 139-152
Author(s):  
Léo Werner Süffert ◽  
Airton Teixeira Brasil
Keyword(s):  
Setting Time ◽  
The Other ◽  
American Dental Association

The main objective of this research was to analyse four dental gypsum products by brazilian dentists, according to the proposed American Dental Association specification for Dental Gypsum Products. (Six Draft) Iuated: consistency, setting time, compressive strenght, setting expansion and reproduction of detail. Only one the products tested (products tested (product D) met all the requirements. The other three products, (A, B and C) althought and reproduction of detail requirements, failed with regard to setting time and setting expansion requirements.

scholarly journals Studi Pemanfaatan Limbah Padat Industri Pengolahan Minyak Kelapa Sawit Spent Bleaching Earth sebagai Pengganti Agregat pada Campuran Beton

2018 ◽  
Vol 15 (1) ◽  
pp. 7
Author(s):  
Denny Dermawan ◽  
Mochammad Luqman Ashari
Keyword(s):  
Heavy Metal ◽  
Compressive Strength ◽  
Palm Oil ◽  
Bleaching Earth ◽  
Setting Time ◽  
Chemical Compounds ◽  
Oil Refinery ◽  
The Other ◽  
Mix Design ◽  
Fine Aggregate

Palm oil refinery factory has solid waste by product  called Spent Bleaching Earth (SBE). SBE consists of some chemical compounds and one of them  is SiO2 up to 83,05%. SiO2 or silica fume can cause silicosis if it is exposed to the atmosphere and frequently inhaled by the workers.  On the other hand,  SiO2  is one of the material  composition of Portland cement. Thus, it is necessary to conduct a research about the utilization of SBE. as a concrete mixture. SBE is utilized as fine aggregate substitution by the composition of 0%, 10%, 20%, 30%, and 40% of the total amount of fine aggregate. The conducted tests are fineness modulus calculation, compressive strength, setting time, and TCLP. The method used for mix  design is SNI 03-2834-2000 with f’c 28,5 MPa and slump 12 ± 2 cm. This research  shows  that concretes with SBE substitution which achieve the planned compressive strength are 10% SBE with 34,16 MPa and 20% SBE with 29,06 MPa. Based on the TCLP test, the concentration of heavy metal substances in 10% SBE are below the standard. Thus, it is  scientifically proven to conclude that concrete with 10% SBE is technically proper and safe for the environment.

Effect of Structure of Polycarboxylate Superplasticizer on Hydration of Cement in Early Period

2012 ◽  
Vol 487 ◽  
pp. 24-28
Author(s):  
Jian Ping Duan ◽  
Sheng Hua Lv
Keyword(s):  
Cement Paste ◽  
Setting Time ◽  
Early Period ◽  
The Other ◽  
Side Chain ◽  
Carboxyl Groups ◽  
Structure Parameters ◽  
Polycarboxylate Superplasticizer ◽  
Hydrated Product ◽  
Effect Of Structure

Effect of polycarboxylate superplasticizer (PCs) with different bond between side chain and truck chain on hydration of cement in early period was studied. The performance of PCs in concrete was investigated by setting time, TGA and SEM. PC-based superplasticizer with ester bonding between side chain and truck chain. Although they had the proximate structure parameters in density of side chain and absorption group (carboxyl groups), the setting time of cement paste was significantly different when different PCs were employed in the preparation of cement. Decomposing of this bond in alkali environment may lead to a shorter setting time. On the other hand, same difference in hydration production was observed in early period hydration of cement paste when two different PCs was incorporated, which indicated that the different bond structure in PCs affected the hydration of cement in a different manner. The result of SEM indicated that the morphological phase of hydrated product was different when PC was applied, this may be related with the different result in the TG and TGA

scholarly journals Physicochemical Properties and Antibiofilm Activity of Tricalcium Silicate Cement and its Association with Cetrimide

2021 ◽  
pp. 333-341
Author(s):  
Giulia Bueno Rodrigues ◽  
Mario Tanomaru-Filho ◽  
Gisselle Moraima Chavez-Andrade ◽  
Fernanda Ferrari Esteves Torres ◽  
Juliane Maria Guerreiro-Tanomaru
Keyword(s):  
Physicochemical Properties ◽  
Zirconium Oxide ◽  
Setting Time ◽  
Mass Gain ◽  
Positive Control ◽  
Tricalcium Silicate ◽  
The Other ◽  
Antibiofilm Activity ◽  
Setting Times ◽  
Root Dentin

Cetrimide (CTR) is a cationic surfactant detergent with antimicrobial and antibiofilm activity. The aim of this study was to evaluate setting time, pH, solubility and antibiofilm activity of tricalcium silicate cement (TSC) with zirconium oxide (ZrO2) and its association with 0.2 and 0.4% cetrimide. Initial and final setting times (IST and FST) were assessed based on ISO-6876. pH was evaluated at periods of 1,3,7,14 and 21 days. Solubility was analyzed by weight loss. A modified direct contact test (MDCT) on the biofilm of Enterococcus faecalis formed on bovine root dentin blocks was performed, after 6 hours of manipulation and 15 hours of contact time. The analysis was performed by UFC mL ­¯¹ counting. The data were analyzed by ANOVA and Tukey’s tests (α=0.05). Higher IST was observed for TSC/ZrO2+CTR in both concentrations than for TSC/ZrO2 and lower FST for TSC/ZrO2+0.4% CTR (p<0.05). On day 1, TSC/ZrO2 showed lower pH than the associations with CTR (p<0.05). During the other periods, TSC/ZrO2 and associations promoted similar alkalinization (p>0.05). All materials exhibited increased mass. TSC/ZrO2+CTR 0.4% had lower mass gain than the other materials (p<0.05). The highest antibiofilm activity was observed for TSC/ZrO2+CTR in both concentrations, when compared with the positive control (p<0.05). In conclusion, CTR exhibited potential to promote greater antibiofilm activity to tricalcium silicate cement, without harming its physicochemical properties of setting time, pH and solubility.

scholarly journals Modifying composition of plastering mortar for the purpose of enhancing fire resistance of building structures by means of silicate additives

2019 ◽  
Vol 97 ◽  
pp. 03014
Author(s):  
Nikita Levashov ◽  
Marina Akulova ◽  
Yulia Sokolova
Keyword(s):  
Thermal Properties ◽  
Fire Resistance ◽  
Water Glass ◽  
Setting Time ◽  
The Other ◽  
Mechanical And Thermal Properties ◽  
Building Structures ◽  
Mixing Ratio ◽  
Optimum Choice ◽  
Cement Binder

The present paper deals with modifying composition of plastering mortar for the purpose of enhancing fire resistance of building structures by means of silicate additives. Interaction of soluble water glass with cement binder elongates the initiation of setting time and reduces the time of final setting that could be explained by the opposed action of each component. One of the components facilitates the increase in the mobility of the mortar while the other, as opposed, is fastening rapidly. The optimum choice of the mixing ratio in the mortar would enhance both physical-mechanical and thermal properties.

scholarly journals Physicochemical Properties of a Bioceramic Repair Material - BioMTA

2020 ◽  
Vol 31 (5) ◽  
pp. 511-515
Author(s):  
Hernán Coaguila-Llerena ◽  
Victor Manuel Ochoa-Rodriguez ◽  
Gabriela Mariana Castro-Núñez ◽  
Gisele Faria ◽  
Juliane Maria Guerreiro-Tanomaru ◽  
...  
Keyword(s):  
Physicochemical Properties ◽  
Setting Time ◽  
The Other ◽  
Repair Material ◽  
Alkaline Ph ◽  
Initial Setting Time ◽  
Significant Difference ◽  
Initial Setting ◽  
One Way Anova ◽  
Alkaline Material

Abstract This study aimed to assess the physicochemical properties of a repair material in the Brazilian market, BioMTA, in comparison to other two materials currently in use (Biodentine and MTA Angelus). The initial setting time was evaluated using Gillmore needle. The pH was measured with a pH-meter after 24 h, 3, 7, 14 and 21 days. The radiopacity was determined using the equivalence in millimeters of aluminum (mm Al) from digitized occlusal radiographs. Solubility was determined after immersion in water for 7 days. The data were analyzed by one-way ANOVA and Tukey tests (a=0.05). The BioMTA initial setting time (5.2 min) was lower than the other materials (p<0.05). All materials showed an alkaline pH at 21 days. At 24 h, BioMTA was the most alkaline material (p<0.05); and at 3, 7, 14 and 21 days there was no difference between BioMTA and Biodentine (p>0.05), both being more alkaline than MTA Angelus (p<0.05). The radiopacity of BioMTA (4.2 mm Al) was significantly higher compared to Biodentine (p<0.05) and lower than MTA Angelus (p<0.05). The solubility of the materials was -4.2%, -1.6% and 4.1% for BioMTA, MTA Angelus and Biodentine, respectively, with a significant difference between them (p<0.05). Therefore, it can be concluded that BioMTA displayed a shorter setting time, an alkaline pH, a higher radiopacity, and a gain in mass.

The Preparation and Performance of the Cement-Based Concrete 3D Printing Materials

2018 ◽  
Vol 932 ◽  
pp. 131-135
Author(s):  
Yun Zhu ◽  
Chao Kai Wen ◽  
Guo Dong Xu ◽  
Dong Liu ◽  
Jing Chen
Keyword(s):  
3D Printing ◽  
Cost Saving ◽  
Portland Cement ◽  
Ordinary Portland Cement ◽  
Setting Time ◽  
The Other ◽  
Mix Design ◽  
Mineral Powder ◽  
Concrete Materials ◽  
And Performance

To reach the goal that 3D printing equipment requires and cost saving, this study used the ordinary Portland cement, mineral powder, accelerating agent and the other compound admixtures to prepare the cement-based concrete materials. The mix design, the kind and amount of accelerating agent and the dosage of compound adjusting retarders were studied to research the workability, viscosity and plasticity of the cement-based concrete materials. Facts proved that its performance are all good. And the setting time of that is adjustable of gradient form, which the range of the initial is 10-40mins and the final is 15-80mins. And the material is used to print a few simple fancy goods, which looks good, for flowerpot with roundness and square, penta-five pentagon and so on. It reflects that the speed is so far and controlled, the appearance looks knitted and layered.

scholarly journals The Question of “Death” in Three Stories: A Comparative Study

2015 ◽  
Vol 6 (3) ◽  
pp. 5
Author(s):  
Ehsan Sadiq Mohammed Al Lawati
Keyword(s):  
Comparative Literature ◽  
Setting Time ◽  
Seventh Century ◽  
The Other ◽  
Human Beings ◽  
13Th Century ◽  
Artistic Vision ◽  
Different Cultures ◽  
Common Understanding ◽  
Historical Periods

ries representing two different cultures and two different historical periods. The first one is a story from Persia, dating back to the seventh Century AH (13th Century AD), by the well- known Iranian writer Sa’di Al-Shirazi. The other two were written by the two Arab writers; Yosuf Idrees and Abdu Salaam Al ‘Ojaily. The presence of “Death” as a theme in these three stories constitutes a distinctive and common feature that cuts across these three stories despite the differences among them in terms of setting, time, details and characters. This, in turn, vividly demonstrates that human beings have a common concern irrespective of differences. This, consequently, proves the prominent role played by comparative literature in enhancing, and cementing common understanding among human beings and, therefore, making it firmly rooted in them. The study also aims to focus on this theme at two levels; the implicit and the explicit. The main objective is to make the reader become fully acquainted with how these two concerted levels lead to a common artistic vision in the three stories in spite of their differences in terms of content and details (i.e. setting, time, character, etc.). 

Stromatoporoids from the Famennian (Devonian) Wabamun Formation, Normandville oilfield, north–central Alberta, Canada

1988 ◽  
Vol 62 (03) ◽  
pp. 411-419 ◽  
Author(s):  
Colin W. Stearn
Keyword(s):  
Patch Reef ◽  
Abundant Species ◽  
The Other ◽  
North Central ◽  
Biotic Crisis

Stromatoporoids are the principal framebuilding organisms in the patch reef that is part of the reservoir of the Normandville field. The reef is 10 m thick and 1.5 km2in area and demonstrates that stromatoporoids retained their ability to build reefal edifices into Famennian time despite the biotic crisis at the close of Frasnian time. The fauna is dominated by labechiids but includes three non-labechiid species. The most abundant species isStylostroma sinense(Dong) butLabechia palliseriStearn is also common. Both these species are highly variable and are described in terms of multiple phases that occur in a single skeleton. The other species described areClathrostromacf.C. jukkenseYavorsky,Gerronostromasp. (a columnar species), andStromatoporasp. The fauna belongs in Famennian/Strunian assemblage 2 as defined by Stearn et al. (1988).

D. The Line Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 207-244
Author(s):  
R. P. Kraft
Keyword(s):  
Variable Stars ◽  
The Other ◽  
Line Spectrum ◽  
Afternoon Session ◽  
Empirical Information ◽  
Pulsating Variable Stars ◽  
Almost Continuous ◽  
Informal Approach

(Ed. note:Encouraged by the success of the more informal approach in Christy's presentation, we tried an even more extreme experiment in this session, I-D. In essence, Kraft held the floor continuously all morning, and for the hour and a half afternoon session, serving as a combined Summary-Introductory speaker and a marathon-moderator of a running discussion on the line spectrum of cepheids. There was almost continuous interruption of his presentation; and most points raised from the floor were followed through in detail, no matter how digressive to the main presentation. This approach turned out to be much too extreme. It is wearing on the speaker, and the other members of the symposium feel more like an audience and less like participants in a dissective discussion. Because Kraft presented a compendious collection of empirical information, and, based on it, an exceedingly novel series of suggestions on the cepheid problem, these defects were probably aggravated by the first and alleviated by the second. I am much indebted to Kraft for working with me on a preliminary editing, to try to delete the side-excursions and to retain coherence about the main points. As usual, however, all responsibility for defects in final editing is wholly my own.)

C. The Continuous Spectrum of Pulsating Variable Stars

1967 ◽  
Vol 28 ◽  
pp. 177-206
Author(s):  
J. B. Oke ◽  
C. A. Whitney
Keyword(s):  
Continuous Spectrum ◽  
Variable Stars ◽  
Velocity Fields ◽  
The Other ◽  
Line Spectrum ◽  
Direct Information ◽  
Thermodynamic Structure ◽  
Diagnostic Interpretation ◽  
Pulsating Variable Stars ◽  
The Continuum

Pecker:The topic to be considered today is the continuous spectrum of certain stars, whose variability we attribute to a pulsation of some part of their structure. Obviously, this continuous spectrum provides a test of the pulsation theory to the extent that the continuum is completely and accurately observed and that we can analyse it to infer the structure of the star producing it. The continuum is one of the two possible spectral observations; the other is the line spectrum. It is obvious that from studies of the continuum alone, we obtain no direct information on the velocity fields in the star. We obtain information only on the thermodynamic structure of the photospheric layers of these stars–the photospheric layers being defined as those from which the observed continuum directly arises. So the problems arising in a study of the continuum are of two general kinds: completeness of observation, and adequacy of diagnostic interpretation. I will make a few comments on these, then turn the meeting over to Oke and Whitney.

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