Carbon materials for structural self-sensing, electromagnetic shielding and thermal interfacing

Intrinsic self-sensing concrete and structures: A review

Cracks in cement concrete composites, whether autogenous or loading-initiated, are almost inevitable and often difficult to detect and repair, posing a threat to safety and durability of concrete infrastructures, especially for those with strict sealing requirements. The sustainable development of infrastructures calls for the birth of self-healing concrete composites, which has the built-in ability to autonomously repair narrow cracks. This paper reviews the fabrication, characterization, mechanisms and performances of autogenous and autonomous healing concretes. Autogenous healing materials such as mineral admixtures, fibers, nanofillers and curing agents, as well as autonomous healing methods such as electrodeposition, shape memory alloys, capsules, vascular and microbial technologies, have been proven to be effective to partially or even fully repair small cracks. As a result, the mechanical properties and durability of concrete infrastructure can be restored to some extent. However, autonomous healing techniques have shown a better performance in healing cracks than most of autogenous healing methods that are limited to healing of cracks having a width narrower than 150 μm. Self-healing concrete with biomimetic features, such as self-healing concrete based on shape memory alloys, capsules, vascular networks or bacteria, is a frontier subject in the field of material science. Self-healing technology provides concrete infrastructures with the ability to adapt and respond to the environment, exhibiting a great potential to facilitate the creation of a wide variety of resilient materials and infrastructures.

Self-healing cement concrete composites for resilient infrastructures: A review

Self-healing is a natural phenomenon whereby living organisms respond to damage. Recently, considerable research efforts have been invested in self-healing cementitious materials that are capable of restoring structural integrity and mechanical properties after being damaged. Inspired by nature, a variety of creative approaches are explored here based on the intrinsic or extrinsic healing mechanism. Research on new intrinsic self-healing cementitious materials with biomimetic features is on the forefront of material science, which provides a promising way to construct resilient and sustainable concrete infrastructures. Here, the current advances in the development of the intrinsic healing cementitious materials are described, and a new definition of intrinsic self-healing discussed. The methods to assess the efficiency of different healing mechanisms are briefly summarized. The critical insights are emphasized to guide the future research on the development of new self-healing cementitious materials.

Recent Advances in Intrinsic Self-Healing Cementitious Materials.

Immobilizing bacteria in expanded perlite for the crack self-healing in concrete

Multiscale mechanical quantification of self-healing concrete incorporating non-ureolytic bacteria-based healing agent

Self-healing of concrete cracks by use of bacteria-containing low alkali cementitious material

Bacterially induced CaCO3 precipitation is a general phenomenon in nature. It has been proposed as an environmentally friendly strategy for the protection of cementitious materials. This paper investigates the biochemistry of CaCO3 precipitation induced by non-ureolytic bacteria of the genus Bacillus. Different calcium sources are compared for their effectiveness in bacterial mediation of precipitation. Surface treatment using this biodeposition technique is evaluated by parameters affecting the durability of cementitious materials. Outcomes from this study reveal that the type of calcium source has a profound impact on the biochemical process and the crystal form, size, and morphology of bacterially mediated mineralization of CaCO3. An organic calcium source, particularly calcium glutamate, is beneficial for efficient CaCO3 precipitation. Bacterial surface treatment on specimens results in a decrease of more than 50% in capillary water absorption and an increase of nearly 50% in resistance to car...

Non-Ureolytic Bacterial Carbonate Precipitation as a Surface Treatment Strategy on Cementitious Materials

The effects of colloidal nanosilica on the interfacial transition zone (ITZ) in concrete at three days are studied. Mechanical properties are investigated at macro-scale, followed by nanoindentation characterization at micro-scale. A top-down and a bottom-up modelling are carried out, respectively, at macro- and micro-scales. Macro-mechanical results show that nanosilica addition is especially beneficial for the improvement of ITZ performance. Estimates from statistical nanoindentation provide evidence, suggesting that the hydration acceleration effect of nanosilica dominates in the modification of ITZ in an early age. It is revealed by modelling at both scale levels that the ratio of the Young's modulus of ITZ to that of bulk paste increases from around 50%–80% if nanosilica is incorporated. This work further confirms that a substantial improvement on ITZ can be obtained by ultra-fine nanosilica modification.

Jing Xu

Papers

Recent Advances in Intrinsic Self-Healing Cementitious Materials.

Multiscale mechanical quantification of self-healing concrete incorporating non-ureolytic bacteria-based healing agent

Self-healing of concrete cracks by use of bacteria-containing low alkali cementitious material

Non-Ureolytic Bacterial Carbonate Precipitation as a Surface Treatment Strategy on Cementitious Materials

Modification effects of nanosilica on the interfacial transition zone in concrete: A multiscale approach