|M.Sc Student||Ronit Tirosh|
|Subject||Bonding Mechanism Between Cement Matrices and Glass Fabric|
Treated by Nano-Particles
|Department||Department of Civil and Environmental Engineering||Supervisor||Full Professor Bentur Arnon|
|Full Thesis text - in Hebrew|
Textile reinforced concrete (TRC) is a relatively new material in the field of civil engineering. Composites made out of a combination of cement matrix and alkaline resistant glass fabrics have many advantages from the ability to control filaments orientation to the creation of thin elements with high tensile strength.
Between the glass fabric and cement matrix system there is an interesting and unique bond. The basic unit of the textile reinforcement is a multifilament bundle, which is composed of an assembly of several hundred to several thousands of filaments. When one considers the particulate nature of the cement, which is composed of grains ranging in size from several microns to tens of microns, it becomes obvious that the matrix around the filaments cannot be uniform, as the cement grain size is relatively large compared to the spaces between the filaments. As a result, the grains cannot penetrate in between the filaments and hydration products gradually deposit in between the filaments. The deposit starts from the external filaments inward, creating gradients of microstructure, whereby the external filaments will be at closer proximity to the cement matrix compared to the internal ones. Thus, the interfacial microstructure developed can be quite complex and exhibit changes over time as the matrix hydrates and various hydration products deposit in between the filaments, changing the nature of bonding. These effects are dependent on the nature of the matrix and geometric characteristics.
The object of this study was to drastically change the nature of the bonding mechanisms in fiber-cement composites in order to keep the telescopic pull-out mechanism stable over time and prevent its degradation. The strategy is based on introducing sub-micron nano-size particles (200nm or smaller) in between the filaments in the bundle. These particles generate interactions between the core and sleeve filaments and fill the voids between them and thus modify drastically the mode of bundle-matrix interactions upon aging. Within the framework of the study the influence of fillers with diverse properties was studied, to resolve the influence of fillers reactivity (pozzolnic\ inert), composition (organic\ unorganic) and size. The differences in behavior and influence on the pull-out nature provided fundamental insight into the bonding mechanisms.