Distinct-layer casting of SCC: The mechanical consequences of thixotropy

• Published in: Cement and concrete research Vol. 38; no. 5; pp. 624 - 632
• Main Authors: Roussel, N., Cussigh, F.
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Ltd 01-05-2008; Elsevier Science
• Subjects: Applied sciences; Buildings. Public works; Concretes. Mortars. Grouts; Exact sciences and technology; Fresh concrete; Materials; Other special applications (sand concrete, roller compacted concrete, heavy concrete, architectural concrete, etc.); Properties and performance of fresh concrete; Rheology; Thixotropy; Workability; Workability; Thixotropy; Rheology; Fresh concrete; Experimental result; Construction materials; Concrete workability; Numerical simulation; Forecast model; Modeling; Self compacting concrete; Strength
• ISSN: 0008-8846; 1873-3948
• DOI: 10.1016/j.cemconres.2007.09.023

It is demonstrated in this paper that thixotropic behavior of Self Compacting Concrete (SCC) may induce, in specific conditions, distinct-layer casting of the material that can generate lowered mechanical resistances in the final structure. First, the distinct-layer casting phenomenon is defined and described along with its potential consequences. Then, experimental results obtained for various SCC show that there exists a critical delay between layers casting above which separated layers are created in the element and generate losses of mechanical strength. This critical delay depends strongly on the thixotropic behavior of the SCC, the thickness of the layers and on the roughness of the interface between the two layers. Finally, an analytical method allowing for a rough prediction of this critical delay is proposed.