scholarly journals Mechanism of Degradation of the Properties of Recycled Plaster Mixed Aluminate Cement

2020 ◽  
Vol 2020 ◽  
pp. 1-8
Author(s):  
Zhixin Li ◽  
Kaidong Xu ◽  
Jina Wang ◽  
Jianwu Zhang ◽  
Xianwei Ma ◽  
...  
Keyword(s):  
Degradation Mechanism ◽  
Setting Time ◽  
Hydration Rate ◽  
Mechanism Of Degradation ◽  
Degradation Of Properties ◽  
Aluminate Cement

This manuscript investigates the degradation of the properties of recycled plaster-mixed aluminate cement (RAP) and analyzes its degradation mechanism by DSC/TG and SEM. The results showed that the setting time of RAP was shortened due to the fast formation of recycled ettringite (AFt) and its strength was decreased relative to the pure recycled plaster (RP) in the absence of aluminate cement. Different from the properties of RP and RAP, the hydration of commercial plaster was slowed down by the addition of aluminate cement for its low hydration rate, and its strength was increased with respect to the pure commercial plaster (CP) without aluminate cement. Therefore, the properties of RP and RAP could be seen to decrease in relation to CP and commercial plaster mixed aluminate cement (CAP). The SEM and DSC/TG analyses confirm the presence of cluster and fine crystals and noncementing AH3 in RAP, which demonstrates its degradation of properties.

scholarly journals The Influence of Water Reducing Agents on Early Hydration Property of Ferrite Aluminate Cement Paste

Crystals ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 731
Author(s):  
Chunlong Huang ◽  
Zirui Cheng ◽  
Jihui Zhao ◽  
Yiren Wang ◽  
Jie Pang
Keyword(s):  
Setting Time ◽  
Critical Role ◽  
Hydration Product ◽  
Reducing Agents ◽  
Reducing Agent ◽  
Hydration Process ◽  
Early Hydration ◽  
Cement Pastes ◽  
Hydration Rate ◽  
Aluminate Cement

The ferrite aluminate cement (FAC) could rapidly lose fluidity or workability due to its excessive hydration rate, and greatly reduce the construction performance. Chemical admixtures are commonly used to provide the workability of cement-based materials. In this study, to ensure required fluidity of FAC, chemically different water reducing agents are incorporated into the FAC pastes. The experiments are performed with aliphatic water reducing agent (AP), polycarboxylic acid water reducing agent (PC) and melamine water reducing agent (MA), respectively. Influence of the water reducing agents on fluidity, setting time, hydration process, hydration product and zeta potential of the fresh cement pastes is investigated. The results show that PC has a better dispersion capacity compared to AP and MA. Besides decreasing water dosage, PC also acts as a retarder, significantly increasing the setting times, delaying the hydration rate and leading to less ettringite in the hydration process of FAC particles. The water reducing agents molecules are adsorbed on the surface of positively charged minerals and hydration products, however, for PC, steric hindrance from the long side chain of PC plays a critical role in dispersing cement particles, whereas AP and MA acting through an electrostatic repulsion force.

scholarly journals Preparation of Self-leveling Mortar Based on Anhydrite-II Phosphogypsum

2021 ◽  
Vol 2076 (1) ◽  
pp. 012035
Author(s):  
Yu Zhang ◽  
Jiahao Yang ◽  
Yu Liu ◽  
Bin Liu ◽  
Fengqing Zhao
Keyword(s):  
Sulfuric Acid ◽  
Calcium Aluminate ◽  
Water Resistance ◽  
Construction Material ◽  
Setting Time ◽  
Steel Slag ◽  
Calcium Aluminate Cement ◽  
Hydration Rate ◽  
Softening Coefficient ◽  
Aluminate Cement

Abstract The construction material from anhydrite-II phosphogypsum is dense in structure and has good water resistance. But its disadvantages are low hydration activity and long setting time. In this work, anhydrite-II phosphogypsum is modified by adding a composite activator, which is made of sulfuric acid modified steel slag, β-hemihydrate gypsum and calcium aluminate cement. With this, the hydration rate of anhydrite-II phosphogypsum is clearly increased and setting time shortened. The performance of self leveling mortar prepared is as per JC/T 1023-2021, with softening coefficient of 0.8.

Using of Different Type Cement in Solidification/Stabilization of MSWI Fly Ash

2011 ◽  
Vol 291-294 ◽  
pp. 1870-1874 ◽  
Author(s):  
Guo Xia Wei ◽  
Han Qiao Liu ◽  
Shu Guang Zhang
Keyword(s):  
Heavy Metals ◽  
Compressive Strength ◽  
Fly Ash ◽  
Setting Time ◽  
Solid Matrix ◽  
Cement Type ◽  
Calcium Sulfoaluminate Cement ◽  
Mswi Fly Ash ◽  
Calcium Sulfoaluminate ◽  
Aluminate Cement

Solidification tests of MSWI fly ash (FA) with three types of cement including ordinary Portland cements (OPC), calcium sulfoaluminate cement(CSA) and calcium aluminate cement (CAC) were carried out to discuss the effect of cement type on of the FA-cement solid matrix by means of setting time, compressive strength and heavy metals leachability. Results show that the setting time of the FA-cement mixtures using CSA and CAC is shorter than that of OPC. According to compressive strengths demand and the standard of landfill site of municipal solid waste, the dosage of OPC should be limited about 35% by weigh, the dosage of CAC should be limited about 25% by weigh, and the dosage of CSA should be limited more than 40% by weigh.

Modifying Stucco Mortars with Additions of Sulphoaluminate Cement and Aluminate Cement

2018 ◽  
Vol 276 ◽  
pp. 198-203 ◽  
Author(s):  
Wacław Brachaczek
Keyword(s):  
Portland Cement ◽  
Physical Properties ◽  
Significant Influence ◽  
Setting Time ◽  
Good Adhesion ◽  
Specific Nature ◽  
Research Results ◽  
Sulphoaluminate Cement ◽  
Short Time ◽  
Aluminate Cement

Stucco products due to the specific nature should be characterized by a short time of the beginning and end of setting, low shrinkage, good adhesion to the substrates and workability at running. The type of cement used has a significant influence on this parameter. The change in the physical properties of stucco mortars in which Portland cement was gradually replaced with AliCem sulphoaluminate cement and Górkal 70 aluminate cement. For this purpose, two sets of samples were prepared, in the first set the percentage of Górkal 70 cement in relation to the entire cement was 15, 20, 25, 30 and 33%, in the second set the percentage of Alicem cement was 25, 50, 75 and 100%. The research results indicate that both cements significantly shortened the setting time of the mortars, reduced the shrinkage and improved adhesion to the substrates.

Hydration Kinetics of Aluminate Cement Containing Magnesium Aluminate Spinel

2011 ◽  
Vol 295-297 ◽  
pp. 945-948
Author(s):  
Bi Ya Cai ◽  
Jin Hong Li ◽  
Hong Wen Ma ◽  
Xiao Qian Jiang
Keyword(s):  
Diffusion Process ◽  
Hydration Heat ◽  
Magnesium Aluminate ◽  
Magnesium Aluminate Spinel ◽  
Hydration Kinetics ◽  
Hydration Rate ◽  
Kinetics Of ◽  
And Diffusion ◽  
Aluminate Cement ◽  
Reaction And Diffusion

The hydration heat of aluminate cement containing magnesium aluminate spinel (MA-spinel) and Commercial Lafarge cement are studied. The results show that five stages exist in the hydration processes of both cements, e.g. pre-induction, induction, acceleration, deceleration and stabilization stage. TheNvalues of the two cements are both lower than 1 in acceleration stage, on the contary higher than 1 in stabilization stage. As a result, the hydration is mainly controlled by nucleation reaction and diffusion process in acceleration stage and stabilization stage respectively. The hydration heat of aluminate cement containing MA-spinel is lower than Lafarge cement. Accordingly, the hydration rate of aluminate cement containing MA-spinel is slower than that of Lafarge cement.

Investigation of the Degradation Mechanism of Platinum-Rhodium Catalytic Wires during Oxidation of Ammonia Process

2015 ◽  
Vol 227 ◽  
pp. 229-232 ◽  
Author(s):  
Jarosław Pura ◽  
Piotr Kwaśniak ◽  
Piotr Wiecinski ◽  
Halina Garbacz ◽  
Joanna Zdunek ◽  
...  
Keyword(s):  
Cross Sections ◽  
Gas Flow ◽  
Flow Direction ◽  
Degradation Mechanism ◽  
Extreme Conditions ◽  
Chemical Application ◽  
Catalytic Systems ◽  
Aggressive Environment ◽  
Mechanism Of Degradation ◽  
Deposition Processes

In our investigation we focused on effects of the degradation of Pt-Rh gauzes from three different industrial catalytic systems. The aim of the study was to compare the degree and the mechanism of degradation under different conditions (pressure, temperature, gas flow direction). The investigation was performed on about 80μm diameter wires after long (6 months) exposition to chemically aggressive environment. Microscope observations and microtomography analysis showed that all wires surfaces were strongly developed by etching and deposition processes occurring under extreme conditions. Each wire differed in rate of degradation and morphology of the characteristic cauliflower-shape growths. Also differences in elements distribution on both, surface and cross sections, were observed. Obtained results can be basis of further investigation on improvement of endurance of PtRh alloys in high temperature chemical application.

Evaluation of strength and set behavior of mortar containing shotcrete set accelerators

2008 ◽  
Vol 35 (4) ◽  
pp. 400-407 ◽  
Author(s):  
Jincheol Kim ◽  
Jonghyun Ryu ◽  
R. D. Hooton
Keyword(s):  
Compressive Strength ◽  
Calcium Aluminate ◽  
Setting Time ◽  
Strength Loss ◽  
Test Methods ◽  
Calcium Aluminate Cement ◽  
Cement Matrix ◽  
Early Age ◽  
Rapid Setting ◽  
Aluminate Cement

The influence of rapid-set accelerating admixtures on the setting behavior and early-age strength of a cement matrix was investigated to evaluate the appropriateness of the specification and test methods for shotcrete set accelerators. The results verified two different rapid setting behaviors according to the types of accelerator. The aluminate-base and the calcium aluminate cement-base accelerators facilitate hydration by formation of a calcium aluminate solid solution, whereas the alkali-free set accelerating agents present rapid setting time by the formation of ettringite. It was also found that the Vicat test was more desirable than the Gillmore test as the standard for setting time evaluation. Additionally, the cement mortar mixed with the aluminate-base and the calcium aluminate cement-base accelerators exhibited very fast development of early-age compressive strength. However, most of the set accelerators, except for alkali-free accelerators, failed to satisfy the specification because of greater than 40% compressive strength loss at 28 d.

Development of a Calcium Aluminate Cement from steelmaking slag by altering its mineralogical compositions

2021 ◽  
pp. 1-29
Author(s):  
Sanghamitra Bharati ◽  
Manjini Sambandam ◽  
Pankaj Lochan
Keyword(s):  
Calcium Aluminate ◽  
Setting Time ◽  
Calcium Aluminate Cement ◽  
Steel Ladle ◽  
Steelmaking Slag ◽  
Preferential Growth ◽  
Crushing Strength ◽  
Mineral Compositions ◽  
Mineralogical Compositions ◽  
Aluminate Cement

Strict environmental norms and raising concern to recycle solid wastes generated during ironmaking and steelmaking processes has been the key driving force in developing various technologies. The present study describes a calcium-aluminate clinker prepared from steel ladle slag by modifying its mineral compositions. The slag paste prepared by mixing with water exhibited flash setting behaviour due to the presence of C12A7 and C3A phases. In contrast, the slag clinker, developed by sintering a mixture of pre-determined quantity of slag and Al2O3 at 1400°C for 2h and 4h, contained CA, CA2, Gehlenite and ‘Q’ phases. Hydration of slag clinker contained stable C3AH6, AH3 and stratlingite with preferential growth of calcium-aluminate hydrate prisms along c-axis that provided a well-defined raceme like morphology with interlinked structure. It improved the setting time and crushing strength of the clinkers after 6h and 24h curing at room temperature. Additionally, presence of ‘Q’ phase with lamellar prismatic crystals also helped in enhancing the strength. The developed clinker also exhibited superior crushing strength as compared to commercially available calcium aluminate cement of medium purity. The slag, used as a source of CaO could replace CaCO3 completely and thus contributed to reduction in CO2 emission during clinker making process.

scholarly journals Development of Strength for Calcium Aluminate Cement Mortars Blended with GGBS

2019 ◽  
Vol 2019 ◽  
pp. 1-12 ◽  
Author(s):  
Hee Jun Yang ◽  
Ki Yong Ann ◽  
Min Sun Jung
Keyword(s):  
Calcium Aluminate ◽  
Setting Time ◽  
Isothermal Condition ◽  
Microscopic Analysis ◽  
Calcium Aluminate Cement ◽  
Cement Matrix ◽  
Strength Development ◽  
Hydration Kinetics ◽  
Calorimetric Analysis ◽  
Aluminate Cement

In the present study, the development of strength in different calcium aluminate cement (CAC) mixture mortars with granulated ground blast-furnace slag (GGBS) was investigated. The substitution of GGBS levels was 0, 20, 40, and 60% weight of binder, of which the CAC used in this study naturally contained C2AS clinker as a secondary phase. To activate a hydraulic nature of the phase, in addition to the mineral additive, all specimens were cured at 35 ± 2°C for the first 24 hours and then stored in a 95% humidity chamber at 25 ± 2°C. The penetration resistance of fresh mortar was measured immediately after pouring, and the mortar compressive strength was monitored for 365 days. Simultaneously, to evaluate the hydration kinetics at early ages, in terms of heat evolution, the calorimetric analysis was performed at the isothermal condition (35°C) for 24 hours. The hydration behavior in the long term was characterized by X-ray diffraction, which was supported by microscopic observation using scanning electron microscopy with energy dispersive spectroscopy. Furthermore, an examination of the pore structure was accompanied to quantify the porosity. As a result, it was found that an increase in the GGBS content in the mixture resulted in an increased setting time, as well as total heat evolved for 24 hours in normalized calorimetry curves. In addition, the strength development of mortar showed a continuous increased value up to 365 days, accounting 43.8–57.5 MPa for the mixtures, due to a formation of stratlingite, which was identified at the pastes cured for 365 days using chemical and microscopic analysis. However, GGBS replacement did not affect on the pore size distribution in the cement matrix, except for total intrusion volume.

Influence of Tricalcium Aluminate Phase on In Vitro Biocompatibility and Bioactivity of Calcium Aluminate Bone Cement

2004 ◽  
Vol 19 (4) ◽  
pp. 1062-1067 ◽  
Author(s):  
S.H. Oh ◽  
R. Finones ◽  
S. Jin ◽  
S.Y. Choi ◽  
K.N. Kim
Keyword(s):  
Bone Cement ◽  
Calcium Aluminate ◽  
Setting Time ◽  
Simulated Body Fluid Solution ◽  
Compound Layer ◽  
Calcium Aluminate Cement ◽  
In Vitro Biocompatibility ◽  
Tricalcium Aluminate ◽  
Aluminate Cement

The influence of tricalcium aluminate (3CaO·Al2O3) phase doping on in vitro biocompatibility and bioactivity of calcium aluminate (CaO·Al2O3) based bone cement has been investigated. It is demonstrated that the presence of approximately 25% tricalcium aluminate in the bone cement remarkably improves the bioactivity, yet still retains desirable mechanical strength and biocompatibility. An intermediary compound layer such as Ca3Al2(OH)12 was formed on the surface of the doped sample onto which hydroxyapatite (HAp) began to form soon, after only 2 days of immersion in a simulated body fluid solution. This is about seven-fold acceleration in the HAp formation over undoped calcium aluminate cement on which it took approximately15 days to nucleate the HAp phase. The depth of the HAp-containing layer after60 days of soaking was as much as 85 μm, about an order of magnitude more than the undoped calcium aluminate cement. The dramatically accelerated nucleation and growth of hydroxyapatite caused by the presence of tricalcium aluminate is attributed to the occurrence of intermediate layer materials such as Ca3Al2(OH)12, which most likely acts as the nuclei for HAp formation. This doped bone cement can be useful for injectable orthopedic applications, as the setting time for hardening has also been significantly reduced (by a factor of at least 4) to a practical regime of tens of minutes.

Sign in / Sign up

Export Citation Format

Share Document