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h i g h l i g h t s " Geopolymers can be used as sealers for concrete structures. " Geopolymers could replace epoxy adhesives in FRP retrofitting. " Geopolymers are potential low toxicity, cost-efficient lining materials.

h i g h l i g h t s " This paper reviews current knowledge on concrete carbonation when SCMs and/or RAC are used. " The use of the phenolphthalein indicator underestimate real concrete carbonation by as much as 100%. " The use of SCMs and and/or RAC increase the carbonation depth unless low w/b is used. " The most relevant factors that influence concrete carbonation are analysed.

Ordinary Portland cement (OPC) is the dominant binder in the construction industry with a global production that currently reaches a total of 3 Gt per year. As a consequence, the cement industry's contribution to the total worldwide CO 2 emissions is of about 7% of the total emissions. Publications on the field of alkali-activated binders (also termed geopolymers), state that this new material is, potentially, likely to become an alternative to Portland cement. However, recent LCA studies show that the environmental performance of alkali-activated binders depends, to great extent, of their composition. Also, researchers report that these binders can be produced in a more eco-efficient manner if the use of sodium silicate is avoided. This is due to the fact that the referred component is associated to a high carbon footprint. Besides, most alkali-activated cements suffer from severe efflorescence, a reaction originated by the fact that the alkaline and/or soluble silicates that are added during processing cannot be totally consumed. This paper presents experimental results on hybrid alkaline cements. The compressive strength results and the efflorescence observations show that some of the new mixes already exhibit a promising performance.

h i g h l i g h t s " Portland cement is unsuitable to produce HPC with a high volume of recycled aggregates. " Recycled aggregates have impurities that can be deleterious for Portland cement concrete. " Geopolymers may have the potential to reuse high volume of recycled aggregates in HPC.

Increasing building energy efficiency is one the most cost-effective ways to reduce emissions. The use of thermal insulation materials mitigates heat loss in buildings, therefore minimising heat energy needs. In recent years, several papers were published on the subject of foam alkali-activated cements with enhanced thermal conductivity. However, on those papers cost analysis was strangely avoided. This paper presents experimental results on one-part alkali-activated cements. It also includes global warming potential assessment and cost analysis. Foam one-part alkali-activated cements cost simulations considering two carbon dioxide social costs scenarios are also included. The results show that one-part alkali-activated cements mixtures based on 26%OPC + 58.3%FA + 8%CS + 7.7%CH and 3.5% hydrogen peroxide constitute a promising cost-efficient (67 euro/m 3), thermal insulation solution for floor heating systems. This mixture presents a low global warming potential of 443 KgCO 2eq /m 3. The results confirm that in both carbon dioxide social cost scenarios the mixture 26 OPC + 58.3 FA + 8 CS + 7.7 CH with 3.5% hydrogen peroxide foaming agent is still the most cost efficient.

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h i g h l i g h t sComprehensive, systematic review on current state of the art concerning the utilization of a wide array of wastes as aggregates, in ordinary Portland cement concrete compositions, for structural applications. Analysis of the advantages and shortcomings for each recycling material in the context of the adoption of circular patterns in the construction sector life cycle. Evaluation of alkali-activated binders as an alternative for overcoming important shortcomings of Portland cement-based structural concretes.