Application of ultrasonic testing to describe the hydration of calcium aluminate cement at the early age

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.

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Early-age deformation, drying shrinkage and thermal dilation in a new type of dental restorative material based on calcium aluminate cement

Cement and Concrete Research ◽

10.1016/j.cemconres.2003.08.028 ◽

2004 ◽

Vol 34 (3) ◽

pp. 439-446 ◽

Cited By ~ 22

Author(s):

Lars Kraft ◽

Håkan Engqvist ◽

Leif Hermansson

Keyword(s):

Calcium Aluminate ◽

Drying Shrinkage ◽

Calcium Aluminate Cement ◽

Early Age ◽

Restorative Material ◽

New Type ◽

Thermal Dilation ◽

Dental Restorative ◽

Aluminate Cement

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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.

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