Abstract
In this study, the interface between different types of bacteria-embedded self-healing polylactic acid capsules (PLA) and cement paste is investigated. Particularly, the changes in microstructure and mechanical properties of the interface with respect to bulk cement paste were studied. First, nanoindentation was performed to obtain maps of hardness and elastic modulus in the interfaces. Lattice modeling of uniaxial tensile test on the mapped locations was performed then to obtain the overall tensile strength and stiffness of the interface. Moreover, hydrates assemblage and chemical composition around the PLA particles were studied through Backscattering Electron images and Energy Dispersive X-ray Spectroscopy. The ratios between resulting tensile strength and elastic modulus of the interface with respect to bulk paste were obtained for each PLA type. The results suggest that PLA can be tailored to optimize the physico-mechanical properties of the interface and hence, the mechanical behavior and triggering efficiency of the self-healing system.
Highlights
Autonomous self-healing (SH) of cracks in concrete is a smart solution to boost the durability of cement-based materials
The results suggest that polylactic acid capsules (PLA) can be tailored to optimize the physico-mechanical properties of the interface and the mechanical behavior and triggering efficiency of the self-healing system
In a previous work [18], it was observed that similar PLA capsules, as in this study, interfered in the hydration of cement paste
Summary
Autonomous self-healing (SH) of cracks in concrete is a smart solution to boost the durability of cement-based materials. A key feature of an autonomous system is the way that SH is triggered, which is closely linked to how the healing agents are incorporated into the composite To this purpose, the healing agents are either placed in prone to crack zones of the structural element (i.e. vascular systems) [1] or randomly distributed in the cement matrix, i.e. capsules [2,3,4], (coated) fibres [5], where the inclusions themselves steer the crack patterns. The healing agents are either placed in prone to crack zones of the structural element (i.e. vascular systems) [1] or randomly distributed in the cement matrix, i.e. capsules [2,3,4], (coated) fibres [5], where the inclusions themselves steer the crack patterns In the latter case, mechanical triggering should be such that the overall mechanical performance of the SH composite approaches the one of the non-SH material. Encapsulation of bacterial spores is needed as a mechanical triggering mechanism and to protect the alkaliphilic bacterial spores during mixing of concrete, to prevent their germination prior to cracking and to contain calcium sources and activation nutrients so necessary for their metabolic activity [15,16]
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