scholarly journals Influence of the Heating Temperature and Fineness on the Hydration and Mechanical Property of Recycled Gypsum Plaster

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Zhixin Li ◽  
Kaidong Xu ◽  
Jiahui Peng ◽  
Jina Wang ◽  
Jianwu Zhang ◽  
...  
Keyword(s):  
Mechanical Property ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Heating Temperature ◽  
Setting Time ◽  
High Strength ◽  
Initial Setting Time ◽  
Gypsum Plaster ◽  
Recycled Gypsum

Influence of the heating temperature and fineness on the hydration and mechanical property of recycled gypsum plaster was investigated to find the suitable heating temperature and fineness. According to the results, the setting time of recycled gypsum plaster increased with the increase of heating temperature, and the mechanical strength increased first and then decreased at a temperature of 165°C. Therefore, the suitable heating temperature was 165°C, and at this time, the initial setting time and final setting time were 8 min and 12.5 min, respectively, which met the requirements of the Chinese standard of GB/T 9776-2008. The strength of recycled gypsum plaster increased with the increase of specific surface area, and the low water to plaster ratio and high strength were achieved when the specific surface area was 1526 m2/kg. Therefore, it can be concluded that the suitable heating temperature was 165°C and the suitable specific surface area was 1526 m2/kg considering the properties and economics of recycled gypsum plaster.

scholarly journals Compressive Strength of Concrete with Nano Cement

2021 ◽  
Author(s):  
Jemimah Carmichael Milton ◽  
Prince Arulraj Gnanaraj
Keyword(s):  
Compressive Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Cement Paste ◽  
Cement Mortar ◽  
Setting Time ◽  
Replacement Level ◽  
Initial Setting Time ◽  
Initial Setting

Nano technology plays a very vital role in all the areas of research. The incorporation of nano materials in concrete offers many advantages and improves the workability, the strength and durability properties of concrete. In this study an attempt has been made to carry out an experimental investigation on concrete in which cement was replaced with nano sized cement. Ordinary Portland cement of 53 grade was ground in a ball grinding mill to produce nano cement. The characterization of nano cement was studied using Scanning Electron Microscope (SEM), Brunauer Emmett–Teller (BET), Energy Dispersive X ray microanalysis (EDAX) and Fourier Transform Infrared Spectroscopy (FTIR). From the characterization studies, it was confirmed that particles were converted to nano size, the specific surface area increased and the chemical composition remained almost the same. The properties of cement paste with and without nano cement were found. For the experimental study, cement was replaced with 10%, 20%, 30%, 40% and 50% of nano cement. Cement mortar of ratio 1:3 and concrete of grades M20, M30, M40 and M50 were used. Compressive strength of cement mortar and concrete with different percentages of nano cement was found. The cement mortar was also subjected to micro structural study. It was found that the strength increased even up to the replacement level of 50%. Further increase in the replacement is not possible since the addition of nano cement reduces the initial and final setting time of cement paste. At 50% replacement level, the initial setting time got reduced to 30 minutes which the least permitted value as per IS 12269: 2013. The increase in strength was due to the fact that nano cement acts not only as a filler material but also the reactivity increased due to the higher specific surface area. The SEM image shows the formation of additional C-S-H gel. The percentage increase in compressive strength was found to increase up to 32%. The workability of concrete with nano cement was found to be significantly more than that of the normal cement concrete.

scholarly journals COMPOSITE BINDERS BASED ON CONCRETE SCRAP

2020 ◽  
pp. 8-18
Author(s):  
A. Ahmed ◽  
R. Lesovik ◽  
S. Al Mamouri ◽  
T. Gunchenko
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Setting Time ◽  
Normal Density ◽  
Composite Binder ◽  
Construction Products ◽  
Normative Documentation ◽  
Optimal Strength ◽  
Vibration Mill

The object of research is composite binders obtained from concrete scrap of destroyed buildings and structures for the production of various construction products and structures. Fractions of concrete scrap of 0,0–0,16 mm and 0,16–0,315 mm are used, since x-rayphase analysis of various fractions of concrete scrap shows that these fractions have the highest content of non-hydrated particles of alite and belite. The influence of the specific surface area on the normal density of cement dough and the setting time of binders is established. Comparative physical and mechanical indicators of hardening of binders with different specific surfaces indicate that the most stable results with a uniform increase in strength is the composition of a binder with a specific surface of 964 m2 / kg, with an increase in strength from 2 to 7 days – 27 % and from 7 to 28 days – 21 %. This binder is characterized by optimal strength at the age of 28 days – 25,5 MPa. With a specific surface of 964 m2/kg, the best conditions are created for the formation of the primary frame and its further fouling with various calcium crystalline hydrates, which ensure optimal density and strength. This composite binder has a specific surface area of 964 m2/kg and is more energyefficient. Composite binders obtained in a vibration mill from concrete scrap fractions (0,0–0,16 and 0,16–0,315 mm) meet the requirements of normative documentation on setting time and physico-mechanical parameters, which allows to recommend them for use as binders in the production of construction products and structures for various purposes.

Comparative Assessment of Effectiveness of Calcium Silicate Dispersions Produced Using Sucrose and Lactose as Components of Composite Cement Binder

2021 ◽  
Vol 1017 ◽  
pp. 11-20
Author(s):  
Evgeny A. Shoshin ◽  
Valeria V. Strokova ◽  
Zheng Mao Ye
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Calcium Silicate ◽  
Setting Time ◽  
Inhibitory Effect ◽  
Main Element ◽  
Residual Content ◽  
Nucleation Effect ◽  
Wide Range

Silicate micro- and nano-additives are multifunctional in relation to cement systems. Their application can solve a wide range of technological problems while maintaining the economic efficiency of technical solutions. The effect of silicate additives and fillers is determined by their level of dispersion, due to which the technologies for producing nano- and submicro-sized dispersed materials are being developed. The combination of mechanochemical synthesis of modified calcium hydrosilicates with subsequent thermolysis makes it possible to produce calcium silicate dispersions (SCD), which differ in polymodality of the fractional composition including submicro (10–7–10–6 m) and microdimensional (≥10–6 m) modes. The main element of the technology is the use of modifying carbohydrate, which acts as a stabilizer of hydrated phases of silicates. A comparative study of SCD produced using sucrose (sSCD) and lactose (lSCD) revealed the effect of these carbohydrates on the properties of sSCD and lSCD, as well as their effectiveness as a component of cementitious composite binder. It was found that the level of adsorption of modifying carbohydrate determines the physical properties of SCD (granulometry, specific surface area). The relatively high residual content of free sucrose (0.24%) in the composition of sSCD prevents the consolidation of silicates nanoparticles formed during the thermolysis, causes a high content of submicro sized fractions and a high specific surface area with sSCD (26.3 ± 0.7 m2/g). Lactose is absorbed by the silicate phase; the residual content of free lactose does not exceed 0.028% of lSCD. The low content of stabilizing carbohydrate contributes to the development of nanoparticle consolidation, a decrease in the specific surface area of lSCD to 13.0 ± 0.2 m2/g and content of submicrosized fractions. The residual content of free carbohydrates and particle size characteristics of sSCD and lSCD determine the nature of their influence on Cement-SCD-based concrete setting and hardening. The presence of residual sucrose in the composition of sSCD and fine fractions determines the competitive nature of the processes of retardation of hardening and acceleration of hardening of the cement system due to the nucleation effect, as a result of which the curve of the setting time is extreme. In addition, the inhibitory effect of sucrose reduces the strength of concrete on the 7th day. By the 28th day, the inhibitory effect of sucrose has been overcome, and concrete samples demonstrate an 18% increase in compressive strength with a sSCD content of 30%. The low content of residual free lactose in the composition of lSCD causes the nucleation effect. As a result, there is a monotonous reduction in the setting time of concrete mix with an increase in the content of lSCD in the composition of HF, as well as a significant increase in concrete strength (up to 127%) on the 7th day. At the same time, on the 28th day the strength of concrete increases slightly

scholarly journals Properties of calcium sulfoaluminate cement-based grouting materials with LiAl-layered double hydroxides slurries

2020 ◽  
Vol 29 ◽  
pp. 2633366X2092652 ◽  
Author(s):  
Haiyan Li ◽  
Xianping Wang ◽  
Xuemao Guan ◽  
Dinghua Zou
Keyword(s):  
Compressive Strength ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Layered Double Hydroxides ◽  
Setting Time ◽  
Hydration Products ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Double Hydroxides

In this study, LiAl-layered double hydroxides Lithium aluminum hydrotalcite (LiAl-LDH) with different specific surface area were prepared by the separate nucleation and aging steps (SNAS) method and then were employed to prepare calcium sulfoaluminate cement-based grouting material (CBGM) paste. The influence of LiAl-LDH slurries on fresh and hardened properties of the CBGM paste was investigated in terms of fluidity, stability, setting time, and compressive strength. Additionally, the hydration process and hydration products of the CBGM paste were characterized by hydration heat, X-ray diffraction, differential thermal analysis–thermogravimetry, and Fourier transform infrared analyses. The acquired results illustrated that LiAl-LDH with larger specific surface area led to a faster hydration rate at early age, a lower fluidity, a shorter setting time, and a higher stability. Furthermore, due to the crystal nucleation effect, the addition of LiAl-LDH slurries did not cause a new phase to form but changed the morphology and increased the amount of hydration products, yielding higher compressive strength.

scholarly journals A influência do tamanho de partícula na reação de presa de cimentos de silicate de cálcio produzidos por sol-gel

2021 ◽  
Vol 62 (1) ◽  
pp. 63-70
Author(s):  
Fabio De Cesare ◽  
Gabriela De Souza Balbinot ◽  
Vicente Castelo Branco Leitune ◽  
Fabrício Mezzomo Collares
Keyword(s):  
Particle Size ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Calcium Silicate ◽  
Setting Time ◽  
Sol Gel ◽  
Nitrogen Adsorption ◽  
Setting Reaction ◽  
Fourier Transformed Infrared Spectroscopy

Introduction: This study aims to analyze the influence of particles size of sol-gel derived calcium silicate particles in the setting reaction of bioactive endodontic cements. Materials and Methods: Sol-gel derived calcium silicate particles were synthesized and sieved to separate the particles in different sizes: CS400, CS200, and CS100. A commercial MTA (Control) was used as control. The particle size and the specific surface area were assessed by laser diffraction and nitrogen adsorption. The cements were prepared with water as the liquid for the reaction. The setting time was conducted according to ISO 6876, and the setting kinetics was analyzed by Fourier transformed infrared spectroscopy (FTIR) at different time points between 120s to 72h. Results: The particle size varied from 9.45µm (CS400 ) to 31.01 (Control). The higher specific surface area valuer reached 15.14g/cm2 in the CS400. The smallest particle sizes, the higher specific surface area, and the lowest setting time were found for CS400 (p < 0.05). Control presented the highest setting time (p < 0.05). The FTIR analyses showed the differences in materials structure over time, with faster hydration and crystallization for CS400. The setting kinetics was slower for Control even when compared to a sol-gel derived group with similar particle size. Conclusion: The route of synthesis and the particle size influences the setting reaction of calcium silicate-based cements. The reduction of particle size for sol-gel derived calcium silicates lead to the acceleration of the setting reaction of the produced bioactive endodontic cement.

scholarly journals Chemical and Physical Analyses of Selected Cement Samples in Nigerian Market

1970 ◽  
Vol 44 (1) ◽  
pp. 41-50 ◽  
Author(s):  
FJ Faleye ◽  
S Ogunnubi ◽  
O Olaofe
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Setting Time ◽  
Mean Value ◽  
Insoluble Residue ◽  
Physical Analysis ◽  
Loss On Ignition ◽  
Free Lime ◽  
Mean Values

The chemical and physical analysis of Diamond, Pure Chem, Dangote and Elephant cements in Nigerian market have been carried out by analysis of metal oxides (A12O3, SiO2, CaO, etc.), physical characteristics of the samples (setting time, loss on ignition, insoluble residue, specific surface area, etc.) and important factors for predicting effectiveness of the cement samples.The mean value of CaO, SiO2, K2O, and A12O3 were 61.45 ± 0.22 and 5.57 ± 0.38 with percentage coefficient of variance as 2.15, 0.92, 53.66 and 6.82, respectively. Dangote had the least CaO (59.60%), insoluble residue (4.70) and setting time (195 sec) while pure chem had the highest specific surface area of 412 m2/kg with Diamond having the least percentage loss on ignition of 5.50. The mean values for time saturation factor, silica ratio, free lime and alumina ratio were 90.10 ± 3.02, 2.23 ± 0.10, 169.00 ± 0.13 and ± 0.79 respectively. The coefficient of variation suggests that there were no significant differences between all these factors except free lime. Pure chem has a free lime value of 2.28 which is highly significance compared with others. An empirical equation has been suggested to predict the variation of the compressive strength against time, which agrees very well with the experimental results. Key words: Cement, Diamond, Dangote, Metal oxide, Pure Chem and Quality paramaters.   doi: 10.3329/bjsir.v44i1.2712 Bangladesh J. Sci. Ind. Res. 44(1), 41-50, 2009

scholarly journals Effects of different preparing conditions and annealing on the photocatalytic activity of hydrothermal grown BiVO4

2018 ◽  
Author(s):  
Shanglong Peng ◽  
Jiachi Zhang ◽  
Yuxiang Wen ◽  
Wei Ji ◽  
Jiang Yu ◽  
...  
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Annealing Temperature ◽  
Ph Value ◽  
Heating Temperature ◽  
Heating Time ◽  
Hydrothermal Time ◽  
Bet Specific Surface Area ◽  
Photocatalytic Activities

BiVO4 was hydrothermally synthesized under different preparing conditions and characterized by XRD, SEM, Raman spectrum and BET specific surface area. The influence of different PH value and annealing temperature and hydrothermal time on the morphologies and structures of the BiVO4 samples was investigated systematically. It can be found that annealing would eliminate the effects caused by the pH of precursor, heating temperature and heating time, but preparing conditions still influenced the size and specific surface area of samples. Furthermore, the photocatalytic activities of the fabricated BiVO4 was also evaluated by the degradation of methyl blue in aqueous solution under UV and visible light irradiation.

Development of SPD Technologies and Establishment of a Production Line for Rod-Shaped Semiproducts out of Nanostructured Titanium for Medical Application

2010 ◽  
Vol 667-669 ◽  
pp. 1159-1164
Author(s):  
Georgy I. Raab ◽  
Farid Z. Utyashev
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Production Line ◽  
Deformation Zone ◽  
High Strength ◽  
Medical Application ◽  
Scale Factor ◽  
Nanostructured Titanium ◽  
Cp Ti

The paper reports on the investigation results for the criteria required for estimation of the SPD technologies. It has been demonstrated that one of the important criteria is specific surface area of the deformation zone, which enables considering the scale factor during processing and predicting the properties of the processed semi-products and items. Practical use of the results of conducted studies is demonstrated on the example of establishment of a production line for high-strength nanostructured semi-products from CP Ti for medical application.

scholarly journals CHARACTERISTICS OF NEW PROMISING BENTONITE COAL SORBENTS MODIFIED BY DIFFERENT COMPOUNDS

2021 ◽  
Vol 17 (3) ◽  
pp. 87-95
Author(s):  
Ilkhom Tagaev ◽  
Manzura Muratova ◽  
Lyudmila Andriyko ◽  
Mohigul Yusuf Kizi Boykhonova
Keyword(s):  
Activated Carbon ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Mechanical Stability ◽  
Low Cost ◽  
Industrial Process ◽  
High Strength ◽  
Activation Process ◽  
Carbon Sorbents

Introduction. Bentonite clays are traditional inexpensive and effective adsorbents that have a high potential for removing heavy metals from wastewater due to their abundance, chemical and mechanical stability, high exchange ability, and unique structural properties.Problem Statement. To obtain activated carbon, high-temperature muffle furnaces are used with the consumption of a large amount of electricity, which is economically unprofitable. In addition, the resulting sorbents must be in the form of granules or tablets, have high strength and the ability to be repeatedly used in technological processes.Purpose. Development of a method for the production of low-cost granular sorbents based on bentonite as amineral component, activated carbon, as well as natural production waste (sunflower husk, straw, sawdust, etc. as modifiers), which can be removed from the activation process to increase porosity of these materials.Materials and Methods. Angren brown coal; bentonite of the Navbakhor deposit was used as a sorbent and a basic substance for the granules formation; modifiers were sodium chloride, potassium, chopped straw, sawdust. Methods of thermal decarbonization and activation of the obtained granules under the optimal conditions (950 °С, 45 min) were applied; the bulk density, the specific surface area, pore types and their total volume was determined by optical microscopy and nitrogen adsorption methods.Results. Inexpensive hybrid bentonite-carbon sorbents in the form of high-strength granules were synthesized.The optimal ratio of the main components is Bentonite:Coal = 1 : 2, size (2.5 mm) and strength of granules (83—99%), total pore volume 0.863—1.01 cm3/g, confirmed the presence of macro-, meso- and micropores. The most promising sample has a specific surface area (Langmuir) 184 m2/g.Conclusions. The method for obtaining new effective granular carbon sorbents of low cost, having high sorption capacity relative to organic and inorganic pollutants for purification of industrial process waters has been proposed.

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