Ultrasound monitoring of the influence of different accelerating admixtures and cement types for shotcrete on setting and hardening behaviour

Journal Article · Tue Nov 15 00:00:00 EST 2005 · Cement and Concrete Research

DOI:https://doi.org/10.1016/J.CEMCONRES.2005.0· OSTI ID:20793253

Belie, N de ^[1]; Grosse, C U ^[2]; Kurz, J ^[2]; Reinhardt, H -W ^[2]

---

1. Magnel Laboratory for Concrete Research, Department. of Structural Engineering, Ghent University, Technologiepark Zwijnaarde 904, B-9052 Ghent (Belgium)
2. Department of Construction Materials, Stuttgart University, Pfaffenwaldring 4, D-70550 Stuttgart (Germany)

The possible use of ultrasound measurements for monitoring setting and hardening of mortar containing different accelerating admixtures for shotcrete was investigated. The sensitivity to accelerator type (alkaline aluminate or alkali-free) and dosage, and accelerator-cement compatibility were evaluated. Furthermore, a new automatic onset picking algorithm for ultrasound signals was tested. A stepwise increase of the accelerator dosage resulted in increasing values for the ultrasound pulse velocity at early ages. In the accelerated mortar no dormant period could be noticed before the pulse velocity started to increase sharply, indicating a quick change in solid phase connectivity. The alkaline accelerator had a larger effect than the alkali-free accelerator, especially at ages below 90 min. The effect of the alkali-free accelerator was at very early age more pronounced on mortar containing CEM I in comparison with CEM II, while the alkaline accelerator had a larger influence on mortar containing CEM II. The increase of ultrasound energy could be related to the setting phenomenon and the maximum energy was reached when the end of workability was approached. Only the alkaline accelerator caused a significant reduction in compressive strength and this for all the dosages tested.

• OSTI ID: 20793253
• Journal Information: Cement and Concrete Research, Vol. 35, Issue 11; Other Information: DOI: 10.1016/j.cemconres.2005.03.011; PII: S0008-8846(05)00083-9; Copyright (c) 2005 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved; Country of input: International Atomic Energy Agency (IAEA); ISSN 0008-8846
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINATES
CEMENTS
COMPARATIVE EVALUATIONS
COMPRESSION STRENGTH
HARDENING
MONITORING
MORTARS
VELOCITY