The authors’ research groups have undertaken for about 5 years, a collaborative comprehensive research project, focusing on both experimental characterization and numerical predictive modelling of the self-healing capacity of a broad category of cementitious composites, ranging from normal strength concrete to high performance cementitious composites reinforced with both steel and natural fibers. Both “autogenous” healing capacity as well as self-healing triggered by engineering techniques, including the use of pre-saturated natural fibers or tailored admixtures, have been investigated. Tailored methodologies, which are based on comparative permeability analysis of cracked concrete specimens and evaluation of the mechanical performance measured through 3- or 4- point bending tests, have been employed to characterize the healing capacity. Healing performance was investigated on concrete specimens, previously pre-cracked to target values of crack opening, after scheduled conditioning times through selected exposure conditions (ranging from water immersion, wet and dry cycles and exposure to humid and dry climates). Particularly, the healing capacity has been quantified by means of suitably defined “healing indices”, based on the recovery of the permeability and of the mechanical properties. These indices were correlated to the amount of crack closure, measured by means of optical microscopy and/or also “estimated” through suitable indirect methodology. Chemical characterization of the healing products has also been performed. As a further step, predictive modeling approaches based on either a coupled poro-plasticity fracture-based approach and on modified micro-plane model, have been formulated. The first proposal was based on a zero-thickness interface formulation extended to take into account the self-healing effects in the maximum strength criterion and softening rules under mode I, II and mixed types of fracture. The relevant novel aspect in this interface formulation was the inclusion of a self-healing porosity-based rule in the softening rules and the continuous damage mechanisms accounted for the description of the model. The microplane-based model incorporates the self-healing effects by considering a delayed cement hydration rule, as well as accounting for the effects of cracking on the (moisture) diffusivity and the opposite repairing effect of the self-healing on the microplane constitutive laws. The investigation represents a comprehensive and solid step towards the reliable and consistent incorporation of self-healing concepts and effects into a durability-based design framework for engineering applications or retrofitted solutions with self-healing cementitious composites.

Five Years of International Collaborative Research on Self-Healing Capacity of Cementitious Composites

FERRARA, LIBERATO;DI LUZIO, GIOVANNI;KRELANI, VISAR;
2016

Abstract

The authors’ research groups have undertaken for about 5 years, a collaborative comprehensive research project, focusing on both experimental characterization and numerical predictive modelling of the self-healing capacity of a broad category of cementitious composites, ranging from normal strength concrete to high performance cementitious composites reinforced with both steel and natural fibers. Both “autogenous” healing capacity as well as self-healing triggered by engineering techniques, including the use of pre-saturated natural fibers or tailored admixtures, have been investigated. Tailored methodologies, which are based on comparative permeability analysis of cracked concrete specimens and evaluation of the mechanical performance measured through 3- or 4- point bending tests, have been employed to characterize the healing capacity. Healing performance was investigated on concrete specimens, previously pre-cracked to target values of crack opening, after scheduled conditioning times through selected exposure conditions (ranging from water immersion, wet and dry cycles and exposure to humid and dry climates). Particularly, the healing capacity has been quantified by means of suitably defined “healing indices”, based on the recovery of the permeability and of the mechanical properties. These indices were correlated to the amount of crack closure, measured by means of optical microscopy and/or also “estimated” through suitable indirect methodology. Chemical characterization of the healing products has also been performed. As a further step, predictive modeling approaches based on either a coupled poro-plasticity fracture-based approach and on modified micro-plane model, have been formulated. The first proposal was based on a zero-thickness interface formulation extended to take into account the self-healing effects in the maximum strength criterion and softening rules under mode I, II and mixed types of fracture. The relevant novel aspect in this interface formulation was the inclusion of a self-healing porosity-based rule in the softening rules and the continuous damage mechanisms accounted for the description of the model. The microplane-based model incorporates the self-healing effects by considering a delayed cement hydration rule, as well as accounting for the effects of cracking on the (moisture) diffusivity and the opposite repairing effect of the self-healing on the microplane constitutive laws. The investigation represents a comprehensive and solid step towards the reliable and consistent incorporation of self-healing concepts and effects into a durability-based design framework for engineering applications or retrofitted solutions with self-healing cementitious composites.
Performance based approaches for concrete structures
9782883941205
Self-healing, HPFRCC, natural fibers, crystalline admixtures, numerical modeling.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/1004555
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