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Microencapsulated rejuvenator powder has been used to repair microcracks and improve self‐healing ability of aged bitumen. These microcapsules must retain their integrity in bitumen matrix with necessary special characters such as excellent mechanical properties, thermal stability, and compactability. Herein, novel self‐healing microcapsules containing bituminous rejuvenator with nano‐CaCO3/organic composite shells were developed by in situ polymerization using methanol‐modified melamine‐formaldehyde as organic shell material. The effect of nano‐CaCO3 particle contents on the mechanical properties, thermal stability, and compactability of microcapsules were examined utilizing nanoindentation, thermogravimetric analysis, and visible spectrophotometer. Nano‐CaCO3 particles had greatly enhanced the thermal stability and mechanical properties of the microcapsule because of the higher thermal resistance of nano‐inorganic/organic composite shells. These microcapsules could survive in melting bitumen without destruction. The release curves of microcapsules in ethyl alcohol, relationship between time and logarithmic residual weight of rejuvenator, showed that the nano‐CaCO3/organic composite shell structure led to a higher compactability of microcapsules. POLYM. COMPOS., 39:E1441–E1451, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

A review of the research activities and achievements at Shenzhen University is conducted in this paper concerning the creation and further development of novel microcapsule based self-resilience systems for their application in concrete structures. After a brief description of pioneering works in the field starting about 10 years ago, the principles raised in the relevant research are examined, where fundamental terms related to the concept of resilience are discussed. Several breakthrough points are highlighted concerning the three adopted comprehensive self-resilience systems, namely physical, chemical and microbial systems. The major challenges regarding evaluation are emphasized and further development concerning self-resilience in concrete structures will be addressed.

The aim of this work was to evaluate the self-healing behaviors of bitumen using microcapsules containing rejuvenator by a modified fracture healing-refracture method through a repetitive tension test. Microcapsules had mean size values of 10, 20 and 30 μm with a same core/shell ratio of 1/1. Various microcapsules/bitumen samples were fabricated with microcapsule contents of 1.0, 3.0 and 5.0 wt. %, respectively. Tension strength values of microcapsules/bitumen samples were measured by a reparative fracture-healing process under different temperatures. It was found that these samples had tensile strength values larger than the data of pure bitumen samples under the same conditions after the four tensile fracture-healing cycles. Fracture morphology investigation and mechanism analysis indicated that the self-healing process was a process consisting of microcapsules being broken, penetrated and diffused. Moreover, the crack healing of bitumen can be considered as a viscosity driven process. The self-healing ability partly repaired the damage of bitumen during service life by comparing the properties of virgin and rejuvenated bitumen.

Adequate selection of material constituents and test methods are necessary for workability specifications and performance of hardened concrete. An experimental program was performed to evaluate the suitability of various test methods for workability assessment and to propose performance specifications of prestressed concrete. In total, 33 self-consolidating concrete (SCC) mixtures made with various mixture proportioning parameters, including maximum size and type of aggregate, type and content of binder, and w/cm were evaluated. Correlations among various test results used in evaluating the workability responses are established. It is recommended that SCC should have slump flow values of 635-760 mm. To ensure proper filling capacity greater than 80%, such concrete should have a passing ability that corresponds to L-box blocking ratio (h₂/h₁) ≥ 0.5, J-Ring flow of 570-685 mm, slump flow minus J-Ring flow diameter ≤75 mm. Moreover, Stable SCC should develop a column segregation index lower than 5%, and rate of settlement at 30 min of 0.27%/h for SCC proportioned with 12.5 or 9.5 mm MSA. It is recommended that SCC should have a plastic viscosity of 100-225 Pa·s and 100-400 Pa·s for concrete made with crushed aggregate and gravel, respectively, to ensure proper workability.