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-ofthe-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.

Production of Portland cement (PC) binders contributes substantially to global CO 2 production and various bodies including the Intergovernmental Panel on Climate Change (IPCC) have identified geopolymers as alternative binders with the potential to reduce these emissions. The hypothesis of this research is to investigate whether this is a realistic proposition in the light of limited waste materials such as fly ash and ground granulated blast furnace slag commonly used as geopolymer precursors. The effect of use of natural clay minerals as alternative precursors on global warming potential (GWP) is investigated. Methods of designing mixes with the lowest possible GWP are presented and these are compared to the GWP of PC and currently available metakaolin based geopolymer binders. It is concluded that it is possible to reduce the GWP by approximately 40 %, but other impacts may increase. Highlights A life cycle inventory (LCI) for Metakaolin is presented  A new methodology for geopolymer mix design is described  A reduction in Global Warming Potential of approximately 40% is achievable  The lowest Global Warming Potential can relate to the strongest mixes

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The compatibility of three nano-montmorillonite (NMt) dispersions in hydrating cement binders was investigated and a new theory linking the nanostructure of nanoclay dispersions to their effect on the macroscale performance of cement pastes is presented. Two aqueous organomodified NMt dispersions (one dispersed with non-ionic fatty alcohol and the other with anionic alkyl aryl sulfonate) and one aqueous inorganic NMt dispersion (dispersed with sodium tripolyphosphate) were characterized via transmission electron microscopy imaging and crystallography, X-ray diffraction, Scanning electron microscopy/X-ray energy dispersive spectroscopy, and thermogravimetric analysis/differential thermogravimetry. With this characterization protocol, the way carbon loading and surfactants interact with the nanostructure of the nanoclay dispersions in light of their addition in composite cements was clarified. The suggested methodology is suited for the characterization of nanoclay dispersions and the new theory developed will open up a new horizon for the understanding and exploitation of nano-montmorillonite as a supplementary cementitious material.

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