An investigation of the hydration of calcium aluminate through ultrasonic wave propagation
TL;DR: In this paper, the hydration process of a high alumina cement was investigated through ultrasonic wave propagation techniques, and a correlation between wave amplitude and velocity and breaking strength of the cement was demonstrated.
Abstract: The hydration process of a high alumina cement was investigated through ultrasonic wave propagation techniques A correlation between wave amplitude and velocity and breaking strength of the cement is demonstrated The wave behaviour through hydrating cements was found to be a function of the cement-to-water ratio between values of 2 and 4 Changes in the temperature of the hydrating samples were found to exhibit a similar dependence
Citations
More filters
TL;DR: In this article, the ultrasonic properties of three oil field cement slurries were studied during the early stages of the hydration process and the ratios of the shear wave onset times were in good agreement with the corresponding ratios of API thickening times.
Abstract: The ultrasonic properties of three oil field cement slurries are studied during the early stages of the hydration process. As a percolating solid framework is established, the slurries develop mechanical integrity and shear waves begin to propagate. This transition is also apparent in the behavior of the compressional wave, but is considerably more clear-cut in the shear signals. For the three samples examined here, the ratios of the shear wave onset times are in good agreement with the corresponding ratios of the American Petroleum Institute (API) thickening times.
52 citations
TL;DR: Differential scanning calorimeter has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively.
Abstract: Differential scanning calorimeter (DSC) has been used to study the dehydration characteristics of hydrated calcium aluminates such as CA, CA2 and C12A7 where C and A stand for CaO and Al2O3 respectively. Dehydration of CAH10 and C2AH8 (whereH=H2O) occur ∼ at 160–180°C and 200–280°C respectively. These two phases are unstable and ultimately get transformed to AH3 and C3AH6. Dehydration of AH3 and C3AH6 occur between 290 and 350°C and overlap at lower scanning rate. The activation energy for dehydration of the stable AH3 and C2AH6 phases has been found to be 107.16 and 35.58 kJ mol−1 respectively. The compressive strength of the hydrated calcium aluminates has been determined. The result shows that in the case of CA, almost 90% of ultimate strength has been attained in 1 day whereas in CA2, ultimate strength has been attained in 14 days and in C12A7 in 1 day. DSC results have been correlated with the rate of strength developments.
33 citations
TL;DR: In this article, the performance of alternative additive to induce faster and safer drying of self-flowing high-alumina refractory castables bonded with calcium aluminate cement (CAC) or hydratable alumina (HA) was investigated.
Abstract: The drying step of dense refractory castables containing hydraulic binders is a critical process, which usually requires using slow heating rates due to the high explosion trend of such materials during their first thermal treatment. Thus, this work investigated the performance of alternative additives to induce faster and safer drying of self-flowing high-alumina refractory castables bonded with calcium aluminate cement (CAC) or hydratable alumina (HA). The following materials were analyzed for this purpose: polymeric fibers, a permeability enhancing compound (RefPac MIPORE 20) and an organic additive (aluminum salt of 2-hydroxypropanoic acid). The drying behavior and explosion resistance of the cured samples were evaluated when subjecting the prepared castables to heating rates of 2, 5 or 20 °C/min and the obtained data were then correlated to the potential of the drying agents to improve the permeability and mechanical strength level of the refractories at different temperatures. The collected results attested that the selected additives were more efficient in optimizing the drying behavior of the CAC-bonded compositions, whereas the HA-containing castables performed better when the aluminum-based salt was blended with a small amount of CAC (0.5 wt%), which changed the binders hydration reaction sequence and optimized the permeability level of the resulting microstructure. Consequently, some of the designed compositions evaluated in this work showed improved drying behavior and no explosion was observed even during the tests carried out under a high heating rate (20 °C/min).
16 citations
Cites background from "An investigation of the hydration o..."
...5) in the resulting mixture, leading to the castable’s stiffening in a proper period of time [1]....
[...]
...Although the continuous progress of refractory castables has focused on finding alternatives to reduce the use of hydraulic binders in formulations, calcium aluminate cement (CAC) is still the most used one in a large number of commercial products due to its ability to provide higher green mechanical strength, presenting a suitable setting time (around 6-24h) and chemical resistance to a variety of corrosive environments [1-3]....
[...]
TL;DR: In this article, the variations of ultrasonic pulse velocity, peak amplitude of transmitted pulse and heat evolution rate were measured during the hydration process of ordinary Portland cement with water/cement ratio (W/C ratio) ranging from 0.4 to 0.6 at environmental temperatures between 20 and 40° C.
Abstract: The variations of ultrasonic pulse velocity, peak amplitude of transmitted pulse and heat evolution rate were measured during the hydration process of ordinary Portland cement with water/cement ratio (W/C ratio) ranging from 0.4 to 0.6 at environmental temperatures between 20 and 40° C. The change of heat evolution rate reflected the kinetics of hydration and was sensitively affected by the W/C ratio and environmental temperature. The velocity and peak amplitude were compared with the heat evolution rate to investigate the correlation of elastic properties and structural development with the kinetics of hydration. The dependence of the velocity and the peak amplitude on W/C ratio and environmental temperature are discussed in terms of the concentration of solid phase in the cement paste varying with W/C ratio and the extent of hydration.
15 citations
TL;DR: In this article, the amplitude and velocity of ultrasonic wave transmitted through a hydrating high alumina cement were found to have no corresponding changes in X-ray phase analyses.
Abstract: Observations of changes in the amplitude and velocity of the ultrasonic wave transmitted through a hydrating high alumina cement were found to have no corresponding changes in X-ray phase analyses A continuous X-ray scan of an hydrating sample showed no evidence for the completion of hydration X-ray patterns from a sample aged for two months and from one aged for 24 hours were basically identical
2 citations
References
More filters
Book•
01 Dec 1968
TL;DR: In this article, the authors present the following properties of concrete: Elasticity, Shrinkage and Creep, Durabilty of Concrete, Freezing and Thawing, and Chlorides.
Abstract: 1. Portland Cement. 2. Cementitious Materials Of Different Types. 3. Properties Of Aggregate. 4. Fresh Concrete. 5. Admixtures. 6. Strength Of Concrete. 7. Further Aspects Of Hardened Concrete. 8. Temperature Effects In Concrete. 9. Elasticity, Shrinkage And Creep. 10. Durabilty Of Concrete. 11. Effects Of Freezing And Thawing And Of Chlorides. 12. Testing Of Hardened Concrete. 13. Concretes With Particular Properties. 14. Selection Of Concrete Mix Proportions (Mix Design). Appendices. Index.
5,713 citations
TL;DR: In this article, Lanthanum-doped lead zirconate-titanate ferroelectric ceramics (PLZT) were tested using the pulse-echo technique at 20 MHz and phase transitions occurring within the range 269° to 300°C were detected in poled and unpoled Pb1.02-xLax(Zr0.65Ti0.35)O3 with x=0.00 to 0.15.
Abstract: Lanthanum-doped lead zirconate-titanate ferroelectric ceramics (PLZT) were tested acoustically using the pulse-echo technique at 20 MHz. Phase transitions occurring within the range –269° to 300°C were detected in poled and unpoled Pb1.02-xLax(Zr0.65Ti0.35)O3 with x=0.00 to 0.15. For x=0.00 to 0.08 a phase transition observed between 0° and 100°C was defined by changes in the longitudinal sound velocity as great as 5% accompanied by pronounced absorption peaks. Measurements of resonance and electromechanical coupling in poled samples indicate that this transition involves 2 ferroelectric phases. The acoustic techniques reported made possible the detection of the subtler phase transitions in PLZT ceramics with a degree of sensitivity much higher than that available from the more conventional techniques. Both poled and unpoled samples may be tested by this technique, so that the influence of domain orientation on the transitions observed can be demonstrated.
25 citations
TL;DR: In this article, the amplitude and velocity of ultrasonic wave transmitted through a hydrating high alumina cement were found to have no corresponding changes in X-ray phase analyses.
Abstract: Observations of changes in the amplitude and velocity of the ultrasonic wave transmitted through a hydrating high alumina cement were found to have no corresponding changes in X-ray phase analyses A continuous X-ray scan of an hydrating sample showed no evidence for the completion of hydration X-ray patterns from a sample aged for two months and from one aged for 24 hours were basically identical
2 citations