Variations in surface quality of self-consolidation and highly workable concretes with formwork material

Abstract

The effect of the forming materials on surface quality of the self-consolidating and highly workable concretes was experimentally evaluated. Several mixtures having wide ranges of workability and rheology were investigated. The mixtures were placed in a Z-shaped mold. No mechanical consolidation was applied at all. The sides of the mold were built up using plywood, PVC, steel, and permeable formwork liner using a polyester filter. The concrete surface quality was evaluated in terms of the voids, bleeding, segregation, and insufficient self-consolidation, using an image processing technique. The surface diameter and area of the voids found on the formed concrete surfaces were statistically correlated to the concrete rheology. The permeable lined formwork was shown to produce concrete surfaces with better quality compared to impermeable formwork materials. The same outcome was also noticed for the concrete mixtures having insufficient self-consolidation and even the unstable mixtures that manifested signs of bleeding. The permeable lined formwork was shown to provide an effective way for the entrapped air/water bubbles and the bleed water to escape. The maximum surface dimension of the voids found on the concrete surfaces was limited to 3, 6, 7, and 10 mm for the mixtures cast using the permeable liner, steel, PVC, and plywood formwork materials, respectively.