A review on five key sensors for monitoring of concrete structures

This article presents the results of an interlaboratory experimental study performed by 13 international research groups within the framework of the activities of the RILEM Technical Committee 225-SAP “Applications of Superabsorbent Polymers in Concrete Construction”. Two commercially available superabsorbent polymers (SAP) were tested in terms of their influence on the freeze–thaw resistance of ordinary concrete. To test the robustness of the method, all participating laboratories used locally produced materials. Furthermore, following this aim, various accelerated methods were used to estimate the resistance of the concrete to freeze–thaw cycles. The effect of adding SAP was from insignificant to considerably positive in terms of improvement in material performance as determined by reduced mass loss after freeze–thaw cycles; only one participant observed worsening of the material behaviour. At the same time, due to the addition of SAP, a much less pronounced decrease in the dynamic Young’s modulus was observed as a result of freeze–thaw testing without deicing salt.

Effect of Superabsorbent Polymers (SAP) on the Freeze-Thaw Resistance of Concrete: Results of a RILEM Interlaboratory Study

First UK field application and performance of microcapsule-based self-healing concrete

Presently, the construction industries worldwide are looking for materials with low carbon footprint and environment friendliness. Yet, ordinary Portland cements (OPC) based materials are widely used in building sectors and remain majorly responsible for carbon pollution. The deterioration that happens in such concretes from the very beginning of the service not only life reduces their lifespan but also demands more OPC. Furthermore, the continuation and repairing are mostly laboured intensive and too expensive. Thus, self-recovery of the damaged concretes is significant concerning environmental mitigation and energy saving. Lately, nanomaterials based concretes have been exploited diversely in the construction engineering owing to their enhanced mechanical and durable attributes. The design as well as production of self-healing and sustainable concrete is an intensely research topic in nanotechnology. In this view, this article provides a comprehensive assessment on nanomaterials based self-healing concretes. The past development, recent trends, environmental impact, sustainability, merits and demerits of several methods of self-healing concrete production are discussed.

Sustainability of nanomaterials based self-healing concrete: An all-inclusive insight

Preparation and application of microcapsules containing toluene-di-isocyanate for self-healing of concrete

The increasing concern for safety and sustainability of structures is calling for the development of smart self-healing materials and preventive repair methods. The appearance of small cracks (<300 µm in width) in concrete is almost unavoidable, not necessarily causing a risk of collapse for the structure, but surely impairing its functionality, accelerating its degradation, and diminishing its service life and sustainability. This review provides the state-of-the-art of recent developments of self-healing concrete, covering autogenous or intrinsic healing of traditional concrete followed by stimulated autogenous healing via use of mineral additives, crystalline admixtures or (superabsorbent) polymers, and subsequently autonomous self-healing mechanisms, i.e. via, application of micro-, macro-, or vascular encapsulated polymers, minerals,or bacteria. The (stimulated) autogenous mechanisms are generally limited to healing crack widths of about 100–150 µm. In contrast, most autonomous self-healing mechanisms can heal cracks of 300 µm, even sometimes up to more than 1 mm, and usually act faster. After explaining the basic concept for each self-healing technique, the most recent advances are collected, explaining the progress and current limitations, to provide insights toward the future developments. This review addresses the research needs required to removehindrances that limit market penetration of self-healing concrete technologies.

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Pawel Lukowski

Papers

A review of self-healing concrete for damage management of structures