Abstract
This paper describes the steel fiber effect on the crack permeability and crack surface topography of concrete subjected to freeze-thaw damage. The sequential crack permeability of steel fiber reinforced concrete are investigated by a vacuum permeability set-up. The topographical analysis is applied on the crack surface by an invented 3-D laser scanning equipment. The results show that the crack permeability of concrete is less than the value predicted by the Poiseuille flow model and their difference decreases gradually with the crack widening. With increment of steel fiber dosage and freeze-thaw damage level, the effect of steel fiber on reducing the crack permeability becomes strong. Topographical analysis illustrates that both steel fiber and freeze-thaw damage enhance the roughness of concrete crack surface. The relationship between roughness number of crack surface and material permeability parameter α follows an exponential function, which can be employed to quickly estimate the crack permeability of concrete.
Highlights
With the deterioration of concrete structures, durability is of great concern
In order to analyze the influence of steel fiber on crack permeability of concrete subjected to freeze-thaw damage, a series of tests were conducted: (a) the rapid freeze-thaw test was employed to induce the freeze-thaw damage of different samples, (b) the splitting tensile test was adopted to investigate the relationship between the crack opening displacement at the mid height of the samples (CODm) and the effective cracked cross-section area of crack, (c) the permeability test subjected to splitting loading was carried out (Fig. 6) to evaluate the crack permeability of concrete under external loading, (d) an invented 3-D laser scanning equipment (Fig. 8) was introduced to obtain the topographical information of crack surface of different samples
In order to accurately quantify the effect of the presence of steel fiber on the crack surface topography of concrete with different freeze-thaw damage levels, the topographical information of crack surface was estimated by the invented 3-D laser scanning equipment and the crack surface of concrete was reconstructed in accordance with topographical information of the surface
Summary
With the deterioration of concrete structures, durability is of great concern. For structures in cold regions, freeze-thaw damage is especially one of the main reasons of concrete deterioration[1]. Indicated that the addition of steel fiber decreased the crack permeability and increased the crack tortuosity and surface roughness by the feedback controlled splitting test and permeability test. In order to analyze the influence of steel fiber on crack permeability of concrete subjected to freeze-thaw damage, a series of tests were conducted: (a) the rapid freeze-thaw test was employed to induce the freeze-thaw damage of different samples, (b) the splitting tensile test was adopted to investigate the relationship between the crack opening displacement at the mid height of the samples (CODm) and the effective cracked cross-section area of crack, (c) the permeability test subjected to splitting loading was carried out (Fig. 6) to evaluate the crack permeability of concrete under external loading, (d) an invented 3-D laser scanning equipment (Fig. 8) was introduced to obtain the topographical information of crack surface of different samples. The relationship between RN of crack surface and material permeability parameter α was set up
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