Abstract
Self-healing cementitious materials are a promising means for ensuring sustainable concrete infrastructure and promoting long-term service lives. To obtain microcapsules that are versatile in varying environments, in this study, absorbing microcapsules with calcium alginate as the shell and epoxy resin as the core were prepared. The absorbing microcapsules exhibit self-healing and can reduce the shrinkage of cementitious materials. Volume changes of the microcapsules in the hardened paste with increasing hydration age were observed using three-dimensional X-ray computed tomography. In the hardened cement paste with a water-cement ratio of 0.29, the absorption of the microcapsules lasted for several days, and the release of water lasted for 28 days. The absorption of microcapsules affected the fluidity of cement paste, and it was significantly weakened and delayed due to the lower absorption rate. The addition of absorbing microcapsules significantly reduced the autogenous and drying shrinkage of mortars. For microcapsules with a core content of 55% added at 3.5% of cement weight, autogenous shrinkage was almost eliminated. Most importantly, the addition of absorbing microcapsules could achieve a certain degree of recovery of compressive strength as well as satisfactory recovery of impermeability in dry and wet environments.
Highlights
Concrete is prone to cracks in the process of construction and service, which has a great impact on the durability of concrete, considerably shortening its service life [1] and leading to high costs for the repair of structures [2]
We propose novel superabsorbent polymers (SAPs) microcapsules for self-healing of concrete; in this method, calcium alginate is used as the shell of the microcapsule and epoxy resin is used as the liquid core
Research should focus on whether the absorption of the shell causes the workability of concrete to deteriorate, whether it still has the internal curing effect to reduce the shrinkage of the concrete, and its influence on the self-healing of the concrete
Summary
Concrete is prone to cracks in the process of construction and service, which has a great impact on the durability of concrete, considerably shortening its service life [1] and leading to high costs for the repair of structures [2]. The core plays two roles: one, it reduces the water absorption and swelling rate of the microcapsules [35], thereby mitigating the disadvantages of SAPs in the workability of concrete, and two, it acts as a self-healing unit that heals cracks under dry conditions. The core flows out and bonds the crack under anhydrous conditions, while the shell absorbs water under wet conditions for self-sealing and promoting the autogenous healing of cracks. Research should focus on whether the absorption of the shell causes the workability of concrete to deteriorate, whether it still has the internal curing effect to reduce the shrinkage of the concrete, and its influence on the self-healing of the concrete. The recovery of impermeability and compressive strength of the mortars was tested to evaluate the self-healing effect
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