Title:
Effect of Water Velocity on Performance of Underwater, Self-Consolidating Concrete
Author(s):
M. Sonebi and K. H. Khayat
Publication:
Materials Journal
Volume:
96
Issue:
5
Appears on pages(s):
519-528
Keywords:
concretes; repair; stability; tremie construction; workability
DOI:
10.14359/653
Date:
9/1/1999
Abstract:
Although considerable advances have been made in enhancing in situ properties of concrete cast in standing water, little is known about the performance of concrete cast in flowing water. A hydraulic channel measuring 6 m in length was constructed in the laboratory to cast concrete in water flowing at velocities up to 1.0 m/s. A detailed investigation was carried out to determine the effect of the dosage of welan gum and cellulose-based anti-washout admixtures on the washout resistance of concrete placed in flowing water. The investigated mixes were prepared with water-cementitious materials ratio (w/cm) of 0.41 and 0.47 and contained up to 10 percent silica fume replacement. The high-range water reducer dosage was adjusted to maintain an approximate slump flow consistency of 500 mm to insure self consolidation and obtain relatively flat underwater surfaces. A concrete having a slump flow and a standard washout mass loss of 500 mm and 5 percent, respectively, was cast in water circulating at 0, 0.10, 0.40, and 0.65 m/s to evaluate in situ strength and unit weight. The selected mix incorporated a medium dosage of welan gum and 8 percent silica fume and had a w/cm of 0.41. Test results show that despite the highly fluid nature of the concrete, considerably greater washout resistance can be secured when the dosage of anti-washout admixture is increased, the w/cm is reduced, and 10 percent silica fume is incorporated. The increase in water velocity can lead to a net reduction in in situ strength. The optimized high-performance concrete developed in situ compressive and splitting tensile strengths greater than 70 percent of control samples along the 5-m blocks cast in water current inferior to 0.4 m/s. Such strengths ranged between 50 and 65 percent and 70 to 80 percent, respectively, when the velocity increased to 0.65 m/s.