Porous network concrete: A new approach to make concrete structures self-healing using prefabricated porous layer (abstract)

In order to optimize concrete durability which undergoes changes during its lifetime effectively, healing intervention at the right time and location is needed. Inspired by nature researchers develop several concepts and techniques such as capsule based, vascular, and intrinsic self healing system which have been used for different materials ranging from polymer to ceramic [1], including concrete. The author proposed idea to mimic nature that makes novel vascular system in concrete similar as spongy part of the bones. Imitating bone structures, we created hierarchical composite cementious material using prefabricated thin porous network concrete layers which are placed internally (or at the surface) in the concrete structure. Although this research is still on going in the beginning phase, demonstration that the concept and idea proposed is feasible was performed with simple experiment. Figure 1. (a) Outer compact bone and inner cancellous (spongy) bone, (b) A new vascular concrete with porous network concrete inside apparently solid outer concrete cylinder, and (c) 3D reconstruction after x-Ray μCT scans. Producing porous concrete cylinder of Ø35 mm has been tried successfully based on mix design proposed by other researchers [2-3]. Then the speciments which has been covered with PVA film was put in the middle of mould of Ø56 mm whereas outer solid concrete cylinder made with self compacting concrete was casted around this porous core. Figure 1b shows a new vascular or porous network concrete have been developed in which pore connection can be used as media for healing agents to be injected to fill and repair cracks and to make it dense. In general the proposed self healing mechanism which makes use of this porous network concrete will be carried out using intelligent structures technology concepts which have capabilities of sensing, processing/controlling, and actuating with minimum human intervention. Figure 2 show the flow of information in this proposed self healing concrete. Deformation controlled tensile stress was applied to create crack close to notch in the middle of sample height up to displacement about 200 μm (fig 3a). After crack developed and can be detected visually tensile load is removed. Then, sample is put in vacuum chamber and depressurized for ten minutes. Healing agents was flown through pore upper area until its impregnate all pores and crack spaces. Epoxy based was chosen for healing agents explicitly to seal the crack [4]. Senot Sangadji and Erik Schlangen Figure 2. General concept proposed for self healing process which makes use of porous network concrete Figure 3b shows longitudinal section of the samples which is portrayed under UV light to show different material phase. Bright green epoxy polymer can be seen fill up all space including seal crack in the middle of the sample. Boundary line between solid phase and porous concrete is visible and filled with epoxy which can be concluded that PVA film was dissolved during casting self compacting concrete. This phenomenon ensures that porous concrete can be keep porous in the interior concrete structure. Figure 3. (a) Visible crack, (b) longitudinal cross section showing the crack which have been sealed by epoxy and (c) 3D reconstruction of the vascular concrete after crack propagation. The authors acknowledge the support of HARKE chemical GmbH Germany for supplying SOLUBLON PVAL-film grade KA 40 micron for this experiment. We express gratitude to the authors of ImageJ for image processing, DeVIDE for 3D reconstruction, and MeshLab for 3D visualization. We thank Mr. Gerrit Nagtegaal and Mr. Arjan Thijssen for great help during the experiment. REFERENCES [1] Blaiszik, B. J., S. L. B. Kramer, et al. (2010). Self-Healing Polymers and Composites. Annual Review of Materials Research, Vol 40 40: 179-211. [2] Yang, J. and G. Jiang (2002). Experimental study on properties of pervious concrete pavement materials. Cement and Concrete Research 33: 381–386. [3] Mahboub, K. C. , J. Canler, et al. (2009). Pervious Concrete: Compaction and Aggregate Gradation. ACI Materials Journal 106(6): 523-528. [4] Schlangen, E. and C. Joseph (2009). Self-healing Processes in Concrete. Self-healing Materials: Fundamentals, Design Strategies, and Applications. S. K. Ghosh. Weinheim, WILEY-VCH Verlag GmbH & Co. Activated repaired e.g. engineered autonomous healing Monitoring e.g. structural health monitoring / technology concrete Self powered sensor/actuators Pressure device Healing agents Porous network concrete layer Input: concrete damage output: self healed concrete Pump Actuator Micro controler