Abstract
From the perspective of improving the self-healing method in construction, a tubular healing fiber was adopted as a container to improve the encapsulation capacity, which was available using a micro-capsule as a container. Knowing the direction of the stresses to which structure members are subjected, this research investigated the influence of aligning tubular healing fibers parallel to intended stress into a cementitious composite to increase the self-healing capability. For that, a healing agent was encapsulated into a tubular healing fiber made with polyvinylidene of fluoride resin (PVDF). Then, the healing fiber was combined with steel fibers to align both fibers together parallel to the direction of an intended splitting tensile stress when subjected to a magnetic field in a cylindrical cementitious composite. The alignment method and the key point through which the alignment of the healing fibers could efficiently improve autonomic self-healing were investigated. Since the magnetic field is known to be able to drag steel to an expected direction, steel fibers were combined with the healing fibers to form a hybrid fiber that aligned both fibers together. The required mixture workability was investigated to avoid the sinking of the healing fibers into the mixture. The healing efficiency, according to the orientation of the healing fibers in the composite matrix, was evaluated through a permeability test and a repetitive splitting tensile test. The aligned healing fibers performed better than the randomly distributed healing fibers. However, according to the healing efficiency with aligned healing fibers, it was deduced that the observed decreasing effect of the container’s alignment on the specimen’s mechanical properties was low enough to be neglected.
Highlights
Concrete is one of the most widely used materials for construction, mainly because of its excellent ability to withstand stresses and the possibility of manufacturing it according to the intended properties
The self-healing process proceeded by first manufacturing new specimen groups which were specimens containing aligned healing fibers in cementitious composites (AHFCC) and specimens containing randomly distributed healing fibers in cementitious composites (RHFCC)
The self-healing method presented in this study suggests using mainly hybrid fibers in the cementitious mixture for the container for encapsulation, with a device that allows applying a sufficient magnetic field to automatically align the fibers according to the intended direction in the structure
Summary
Concrete is one of the most widely used materials for construction, mainly because of its excellent ability to withstand stresses and the possibility of manufacturing it according to the intended properties. To efficiently improve the healing capability without necessarily using a high container content, which could affect the material’s mechanical properties, aligning tubular containers parallel to the direction of the intended stress into the structure can eventually ensure the crack crosses several containers, increasing the number of containers across the crack-section and, at the same time increasing the available volume of healing agent It is in this manner our research inscribes itself, planning to align a healing fiber parallel to the direction of an intended splitting tensile stress, using a magnetic field in a cementitious composite for autonomic self-healing. A container with a tubular shape was used to ensure a good enough encapsulation capacity, made with polyvinylidene of fluoride resin as the basis material, especially because of the proven properties this material provides These properties include good adhesion, good resistance to high temperatures and chemical attacks, as well as good mechanical properties, meeting the container’s requirements for effective autonomic self-healing. A high hardening time contributes to ensuring good conservation of the healing agent into the composite material and a good flow after having been released
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