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Abstract The concrete industry is the largest consumer of natural resources and the Portland cement, the binder of modern concrete mixtures, is not environmentally friendly. The world's cement production, in fact, contributes to the earth's atmosphere about 5–7% of the total CO 2 emissions, CO 2 being mainly responsible for global warming and climate change. As a consequence, concrete industry in the future has to feed the growing population needs – expected to rise up to ten billion in 2050 - being sustainable by means of the "3R-Green Strategy": Reduction in consumption of gross energy, Reduction in polluting emissions and Reduction in consuming not renewable natural resources. At the same time, the concept of sustainable development in the concrete industry is not well defined and, currently, there are no holistic models capable of assessing the environmental footprint of cement-based materials. For this reason, a new Empathetic Added Sustainability Index (EASI) was developed taking into account both the environmental impact of mortars and concretes through the global warming potential (GWP), the gross energy requirement (GER) and the natural raw materials consumption (NRMC) but also the durability performance and the engineering performance (such as compressive and tensile strength, bond to reinforcing steel, shrinkage and creep, shear properties, etc) required as a function of the specific application. EASI demonstrated that Alkali Activated Slag (AAS) and High Volume Fly Ash (HVFA) reinforced concretes are characterized by the lower environmental impact in chloride-rich environments. On the other hand, in CO 2 -rich environments, the best solution in terms of sustainability is represented by the HVFA concretes. Finally, for a thermal plaster exposed to freeze and taw cycles, EASI clearly showed that AAS lightweight plaster is the most appropriate solution. [ABSTRACT FROM AUTHOR]

This paper is aimed to study a ground granulated blast furnace slag activated with alkali powder to manufacture Portland-free mortars for conservation, restoration and retrofitting of existing masonry buildings and concrete structures. Activator/precursor represents the key parameter – not only for elasto-mechanical performances – influencing the rheological properties and the shrinkage: the higher the activator dosage, the higher the consistency class and shrinkage. Moreover, elastic modulus of slag-based mortars is lower than that of OPC-mortars at the same strength class. AAMs seem to be more promising for a sustainable future in construction since the GER and GWP are reduced by about 80% compared with traditional Portland cement mortars with the same compressive strength. [ABSTRACT FROM AUTHOR]

• TiO 2 -doped alkali-activated slag-based mortars were investigated. • Limited effects of TiO 2 on properties of AAS at fresh and hardened state can be found. • TiO 2 nanoparticles are effective in promoting self-cleaning ability of AAS systems. • The higher the alkali content, the higher the photocatalytic efficiency. Titanium dioxide (TiO 2) is considered one of the most efficient photocatalysis to produce self-cleaning cementitious materials. At the same time, alkali activated binders have become one of the most interesting low-carbon alternatives to Portland cement. For this, the addition of titanium dioxide nanoparticles in one-part alkali-activated slag-based (AAS) mortars was analyzed to evaluate the effect on the rheological and mechanical properties, dirt pick-up resistance as well as self-cleaning capability. This paper reports a two-year campaign of outdoor exposure in an industrial environment in Northern Italy to investigate the natural photoactivity of the mortars doped with different TiO 2 dosages. The experimental results indicated limited effect of nanoparticles on the rheology and mechanical properties of AAS mortars. It was also highlighted the beneficial effect of TiO 2 addition in self-cleaning capability under natural and accelerated conditions and the fundamental role in photocatalytic efficiency of the alkali content. [ABSTRACT FROM AUTHOR]

This paper covers a wide range of alternative strategies to improve the sustainability of concrete. It firstly considers the relatively easy application of the latest technologies to manufacture traditional Portland cement, including carbon capture, utilization and storage technologies, and the use supplementary cementitious materials as Portland cement replacement. It then focuses on more complex processes such as the substitution of traditional constituents with alternative binders (both non-Portland clinker or alkali-activated materials), recycled aggregates and non-drinking water, up to the description of high-durability/high performance mixtures. This review also underlines the significant need to upgrade the existing standards, and the relevance of thriving the education of designers, researchers and contractors for the development and the diffusion, also thanks to good practice, of new concrete technologies. This research also proposes a new sustainability index for mortars and concretes, also manufactured with negative carbon footprint materials, modifying the Empathetic Added Sustainability Index (EASI). [ABSTRACT FROM AUTHOR]

• Effects of combined use of admixtures on one-part AAS were evaluated. • The use of expansive agent with SRA can mitigate the high shrinkage of AAS. • A linear correlation between shrinkage and moisture loss of admixed AAS was found. Binders obtained by alkaline activation of ground granulated blast furnace slag (GGBFS) represent an interesting alternative to Portland cement to manufacture sustainable mortars and concretes. However, several issues prevent them to have a ready and wide marketplace, such as high-magnitude shrinkage and lack of knowledge about advanced admixtures to control and regulate their properties and desired performance. The purpose of this research is, thus, to evaluate the effect of the combined addition of ethylene glycol-based shrinkage reducing admixture (SRA), calcium oxide-based expansive agents (EA), methylcellulose (MC) and modified starch (MS) on fresh properties, elasto-mechanical parameters and shrinkage behaviour of one-part alkali activated slag-based (AAS) pastes and mortars at equal alkali content and silica modulus. Experimental data evidenced that the addition of methylcellulose, modified starch as well as ethylene glycol determines slower initial and final setting times respect to reference mixtures, while the CaO addition strongly reduces the setting times. Moreover, both SRA and EA reduce the elastic modulus (up to 5%) and mechanical strength of AAS mixtures (up to 20%) compared to pastes without admixtures. Results indicated that both the CaO-based expansive agents (EA) and ethylene glycol-based shrinkage reducing admixture (SRA) are effective to reduce the shrinkage of AAS mortars up to 50%. In particular, the combined use of expansive agents and SRA further limits the shrinkage, allowing to reach values close to 1000 μm/m after 150 days, typical of mortars based on Portland cement. Finally, a linear correlation between shrinkage and moisture loss was found, independently of the admixture used. [ABSTRACT FROM AUTHOR]

• The Ca(OH) 2 pre-treatment improves thermal stability of hemp fibers. • Hemp fiber-reinforced mortars show higher pre-cracking flexural stiffness values. • Treated hemp fiber-reinforced mortars show higher load-carrying capacity. • Treated hemp fiber-reinforced mortars show higher energy absorption capacity. • Latex and defoamer increase resistance to penetration of fibers-reinforced mortars. In this study, authors propose and investigate a strategy aimed to improve the interaction at the fiber–matrix interface, while tailoring matrix resistance to penetration, in hemp fiber-reinforced cement based mortars. It consists of a chemical modification of the hemp fibers carried out through a Ca(OH) 2 pre-treatment and of a matrix modification using an acrylic elastomeric polymer dispersion as additive. The effect of the pre-treatment, on the thermal and chemical properties of the hemp fibers, has been investigated using X-ray diffractometry, Fourier-transform infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. Results showed that chemical pre-treatment is effective in removing hemicelluloses, lignin and waxes thus providing a clean fibers' surface and a higher thermal stability. Fiber-reinforced cement based mortars have been manufactured using pristine and treated 12 mm long hemp fibers at 0.5 wt%, 1 wt% and 1.5 wt% on cement. Their mechanical performance, capillary water absorption and drying shrinkage behavior have been investigated. Hemp fiber-reinforced mortars show a post peak response in flexural tests, being their energy absorption capacity and load-carrying capacity after crack onset positively affected by hemp fibers content and remarkably improved by chemical pre-treatment. Shrinkage behavior of fiber reinforced mortars is characterized by an initial limited expansion that can be associated to fibers swelling due to water absorption. The acrylic latex fills the matrix pores and reduces by 50% the sorpitivity of the composites. [ABSTRACT FROM AUTHOR]