calcium hydroxide
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2022 ◽  
Vol 112 ◽  
pp. 170-179
Author(s):  
Chutian Xu ◽  
Wei Yue ◽  
Peirong Sun ◽  
Shutong Chen ◽  
Zhengying Wu ◽  
...  
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Author(s):  
Caroline Anselmi ◽  
Igor Paulino Mendes Soares ◽  
Maria Luísa Leite ◽  
Fernanda Ali Kitagawa ◽  
Carlos Alberto de Souza Costa ◽  
...  

Author(s):  
Arminda Mamaní ◽  
Yolanda Maturano ◽  
Laura Herrero ◽  
Laura Montoro ◽  
Fabiana Sardella

Olive Tree Pruning (OTP) biomass can be considered a suitable source of fermentable sugars for the production of second-generation bioethanol. The present study proposes a remarkable alternative for the valorization of olive tree pruning residues. OTP biomass was processed using a sequential calcium hydroxide pretreatment/enzymatic hydrolysis. A 24–1 half fractional factorial design was adopted for the screening of process variables and a central composite design was used for the optimization stage. Temperature and lime loading resulted statistically significant. The following optimal conditions were obtained: 0.01 g of Ca(OH)2/g of dry material, 20 g of H2O/g of dry material at 160 °C for 2 h. The mathematical model that governs this alkaline pretreatment was obtained with a 76% adjusted determination coefficient, which means that it is a good representation of the process. Under optimal operating conditions, 13% of the cellulose and 88% of the hemicellulose was solubilized. Moreover, the fermentable sugar content increased 1800% compared with the initial conditions, obtaining 240 g of glucose per kg of OTP residue. The fermentable sugars obtained after the calcium hydroxide pretreatment and enzymatic hydrolysis of OTP biomass yielded 2.8 g of ethanol/100 g of raw material.


2022 ◽  
Vol 906 ◽  
pp. 47-52
Author(s):  
Maria Badalyan ◽  
Amalya Karapetyan ◽  
Hovsep Hoveyan

The possibility of using a clinker-free binder as an alternative to expensive and energy-intensive Portland cement is being considered. The pozzolanizing effect of volcanic rocks is presented, where along with the binding of calcium hydroxide by silica to hydrosilicates, the binding of calcium hydroxide by “free” alumina to hydroaluminates also takes place. In the process of hardening of the clinker-free binder, the phase mineralogical composition of the formed new formations differs from the new formations that are synthesized during hardening of traditional Portland cement, which explains the difference in their properties. The new formations that are formed during the hardening process of clinker-free cements are mainly low-basic hydrosilicates, and alkaline aluminosilicates give the cast-in-place stone water resistance, frost resistance, waterproofing, etc., in a word, durability. Physical and chemical studies of the hardening process of clinker-free lime-igneous cements have been carried out, which indicates the possibility of replacing the energy-intensive Portland cement with cheaper clinker-free cement.


2022 ◽  
Vol 25 (6) ◽  
pp. 773-781
Author(s):  
D. S. Aleshin ◽  
A. G. Krasheninin ◽  
P. V. Zaitseva ◽  
I. N. Tanutrov

This work aims to determine the conditions for the CaMoO4, CaSO4, Ca(ReO4)2 formation during oxidation of MoS2 and ReS2 in the presence of Ca(ОН)2. The concentrate from the Yuzhno-Shameyskoye deposit in the Sverdlovsk region, having 37% wt. Мо and 0.005% wt. Re, was selected as a feedstock for thermodynamic modelling of sweet roasting in the presence of Ca(OH)2. To determine the optimal amount of calcium-containing additives, the thermodynamic modelling was carried out using the following mass ratios: molybdenum concentrate: Ca(OH)2 = 1:0.8, 1:1, 1:1.2 and 1:1.5 in the temperature range of 100–800°С, with a step of 100°С, system pressure of 0.1 MPa in the air (molar ratio: molybdenum concentrate + Ca(OH)2: air = 1:5). The content of all sample components in moles was entered into the HSC 6.1 software package. The main reactions associated with the sweet roasting of molybdenum concentrate in the presence of calcium hydroxide were shown. It was established that the main phases formed as a result of roasting comprise CaSO4, CaSO3, MoO3, CaMoO4, CaMoO3 and CaReO4. The effect of temperature on the formation of the main gaseous products was studied under different mass ratios of molybdenum concentrate and Ca(OH)2. It was found that up to 600°C, with molybdenum concentrate to Ca(OH)2 ratio of 1:1, the concentrations of released sulphurous anhydride are lower than the maximum permissible concentrations. The calculated thermodynamic data was used for modelling the roasting process of molybdenum concentrate with calcium hydroxide. An optimal ratio necessary for the successful process operation was established: molybdenum concentrate: Ca(OH)2 = 1:1 by weight. Thermodynamic modelling showed that, in the temperature range of 100–600°С when using Ca(OH)2, no rhenium and molybdenum loss is observed, the release of sulfur is less than 10 mg/m3.


Materials ◽  
2022 ◽  
Vol 15 (1) ◽  
pp. 367
Author(s):  
Kira Weise ◽  
Neven Ukrainczyk ◽  
Aaron Duncan ◽  
Eduardus Koenders

This study aims to increase the pozzolanic reactivity of metakaolin (MK) in Portland cement (PC) blends by adding additional calcium hydroxide (CH_add) to the initial mixture. Cement paste samples were prepared with PC, MK and water with a water-to-binder ratio of 0.6. Cement replacement ratios were chosen from 5 to 40 wt.% MK. For higher replacement ratios, i.e., 20, 30 and 40 wt.% MK, CH_add was included in the mixture. CH_add-to-MK ratios of 0.1, 0.25 and 0.5 were investigated. Thermogravimetric analysis (TGA) was carried out to study the pozzolanic reactivity after 1, 7, 28 and 56 days of hydration. A modified mass balance approach was used to normalize thermogravimetric data and to calculate the calcium hydroxide (CH) consumption of samples with CH_add. Results showed that, without CH_add, a replacement ratio of 30 wt.% or higher results in the complete consumption of CH after 28 days at the latest. In these samples, the pozzolanic reaction of MK turned out to be restricted by the amount of CH available from the cement hydration. The increased amount of CH in the samples with CH_add resulted in an enhanced pozzolanic reaction of MK as confirmed by CH consumption measurements from TGA.


2022 ◽  
Vol 2152 (1) ◽  
pp. 012012
Author(s):  
Yang Shi ◽  
Wen Wang ◽  
Liujie Guo ◽  
Jiusu Li

Abstract In order to explore the rheological property and principles of modified room temperature biological asphalt made with petroleum asphalt, vegetable asphalt, and unsaturated fatty acids as raw materials, waste rubber powder as modifier, and calcium hydroxide powder as curing agent, this paper compared and tested the rheological properties and the original petroleum asphalt by using DSR and BBR, and the micro-properties of the asphalt were studied by using SEM. The PG classification of modified room temperature biological asphalt has been upgraded from PG58-28 of the original petroleum asphalt to PG82-28. Compared with the original petroleum asphalt, the high temperature rheological property of the modified room temperature biological asphalt has been greatly improved. Its low temperature rheological property is equivalent to the original one, but the possibility of cracking is lower. SEM test showed that the components of the modified room temperature biological asphalt are well combined. The calcium hydroxide curing agent reacts with fatty acid and the rubber particles cross link with each other to form a mesh package in the asphalt, which provides strength for the modified temperature biologic asphalt at room temperature.


2021 ◽  
Vol 71 (6) ◽  
pp. 2184-88
Author(s):  
Ajmal Yousaf ◽  
Fatima Ali ◽  
Afshan Bibi ◽  
Ahsan Masood Ahmed ◽  
Sana Ashfaq ◽  
...  

Objective: To find the effect of different combinations of Calcium Hydroxide for the management of post-operative pain in acute apical periodontitis. Study Design: Comparative cross-sectional study. Place and Duration of Study: Department of Operative Dentistry Armed Forces Institute of Dentistry, Rawalpindi. from Jun to Nov 2019. Methodology: A total of 282 patients presenting with acute apical periodontitis in their mandibular posterior teeth were selected for this study and were randomly divided into three equal groups with the help of scientific random number table. Group-A patients were given intracanal dressing of Calcium Hydroxide mixed with Chlorhexidine, group-B patients were given intracanal dressing of Calcium Hydroxide mixed with Saline and group-C patients were given intracanal dressing of Calcium Hydroxide mixed with Dexamethasone. Endodontic therapy was initiated after application of rubber dam, following pulpectomy and disinfection with frequent irrigation, canals were prepared and intra-canal dressings were placed according to the allotted group and the cavity was restored till the next appointment. Post-operative pain was recorded at 24 hours, 48 hours and one week using the visual analogue scale. Results: The three intra-canal combinations of Calcium Hydroxide used in the study were found to be equally effective in reducing pain. Overall, the result between the three groups after 24 hours proved to be insignificant (p=0.40), after 48 hours (p=0.84) and 1 week (p=0.45) were also insignificant. Conclusion: Calcium Hydroxide mixed with Saline, Chlorhexidine and Dexamethasone are all effective for pain reduction with dexamethasone being the most effective.


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