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

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.

Download Full-text

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

Journal of Physics Conference Series ◽

10.1088/1742-6596/2076/1/012035 ◽

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.

Download Full-text

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

Canadian Journal of Civil Engineering ◽

10.1139/l07-115 ◽

2008 ◽

Vol 35 (4) ◽

pp. 400-407 ◽

Cited By ~ 4

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.

Download Full-text

Development of Strength for Calcium Aluminate Cement Mortars Blended with GGBS

Advances in Materials Science and Engineering ◽

10.1155/2019/9896012 ◽

2019 ◽

Vol 2019 ◽

pp. 1-12 ◽

Cited By ~ 2

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.

Download Full-text

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

Journal of Materials Research ◽

10.1557/jmr.2004.0139 ◽

2004 ◽

Vol 19 (4) ◽

pp. 1062-1067 ◽

Cited By ~ 12

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.

Download Full-text

Physicochemical, Mineralogical, and Mechanical Properties of Calcium Aluminate Cement Concrete Exposed to Elevated Temperatures

Materials ◽

10.3390/ma14143855 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3855

Author(s):

Amirmohamad Abolhasani ◽

Bijan Samali ◽

Fatemeh Aslani

Keyword(s):

Temperature Rise ◽

Calcium Aluminate ◽

Elevated Temperatures ◽

Ultrasonic Pulse Velocity ◽

Pulse Velocity ◽

Calcium Aluminate Cement ◽

Cement Concrete ◽

Sem Images ◽

Strength Deterioration ◽

Aluminate Cement

One commonly used cement type for thermal applications is CAC containing 38–40% alumina, although the postheated behavior of this cement subjected to elevated temperature has not been studied yet. Here, through extensive experimentation, the postheated mineralogical and physicochemical features of calcium aluminate cement concrete (CACC) were examined via DTA/TGA, X-ray diffraction (XRD), and scanning electron microscopy (SEM) imaging and the variation in the concrete physical features and the compressive strength deterioration with temperature rise were examined through ultrasonic pulse velocity (UPV) values. In addition, other mechanical features that were addressed were the residual tensile strength and elastic modulus. According to the XRD test results, with the temperature rise, the dehydration of the C3AH6 structure occurred, which, in turn, led to the crystallization of the monocalcium dialuminate (CA2) and alumina (Al2O3) structures. The SEM images indicated specific variations in morphology that corresponded to concrete deterioration due to heat.

Download Full-text