Improving Self-Healing and Shrinkage Reduction of Cementitious Materials Using Water-Absorbing Polymer Microcapsules

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.

Comparative Analysis of the Use of Expansion Agents in Repair Solutions of Dry Building Mixtures for Improving Hardening Conditions

“…As can be seen from Table 1, it should be noted that with the same working consistency of all solutions, the water consumption in all compositions containing SAP expanding polymer agents is higher than the basic composition by an average of 22%, which is explained by the high absorption capacity of free SAP granules due to the ionic nature, internal linked structure and the formation of secondary chemical bonds [9][10][11]. The largest amount of water while maintaining the working consistency indicator was required for composition 7 with a content of 3 g/kg of AquaGel superabsorbent, which can be explained by the fact that, unlike most polymer products that absorb water, the superabsorbent based on the cross-linked copolymer of acrylamide and potassium acrylate has a lower amount of crosslinking agent than the other two SAPs in the study.…”

“…In recent years, the regulatory framework for such materials has expanded in the direction of increasing the set of requirements for solutions and accounting for the parameters of joint work when creating compatible systems (in technological and physicochemical terms) [4][5][6][7][8], while in practice it becomes necessary to ensure additional properties. In addition to the appropriate UDC 691.535 DOI: 10.31650/2786-6696-2022-1-55-62 indicators of strength, rheological properties and reduction of setting and hardening time to reduce the period of repair work and to put the facility into operation as soon as possible, one of the most important characteristics of such materials is the increase of adhesion to the base (substrate) being repaired to create conditions for compatible work with a damaged structure and reduction of shrinkage deformations to prevent cracking of the material and the occurrence of defects in the contact zone between solution and substrate, which can be achieved by improving the hardening conditions when using polymer additives for internal care of the hardening material [9][10][11].…”

“…Analysis of research and publications. Along with the classic methods of reducing shrinkage deformations [12][13][14][15], expanding polymeric agents (superabsorbents) of various chemical nature are increasingly used recently [9,16].…”

“…Thus, stored water quickly migrates inside the polymer mesh. In the process of hardening of the repair material, water encapsulated in SAP moves back into the solution, ensuring a normal hydration process and improving the conditions of hardening of the repair material [9,16,21].…”

Preparation and characterization of soy polyols‐based PU shell microencapsulated phase change materials for reliable thermal energy storage

“…6,7 In general, the shells of MEPCMs can be divided into organic shells and inorganic shells. 8 Inorganic materials such as calcium carbonate (CaCO 3 ), 1,9 titanium dioxide (TiO 2 ), 10,11 calcium alginate 12 and silica (SiO 2 ) 13,14 are often used as shell materials for microcapsules because of their excellent thermal stability and chemical inertness. SiO 2 is a typical inorganic material with wide source, low price and good mechanical properties.…”