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The use of phase-change materials (PCM) in concrete has revealed promising results in terms of clean energy storage. However, the negative impact of the interaction between PCM and concrete on the mechanical and durability properties limits field applications, leading to a shift of the research to incorporate PCM into concrete using different techniques to overcome these issues. The storage of clean energy via PCM significantly supports the UN SDG 7 target of affordable and clean energy. Therefore, the present study focuses on three aspects: PCM type, the effect of PCM on concrete properties, and connecting the outcome of PCM concrete composite to the United Nations sustainable development goals (UN SDGs). The compensation of reduction in strength of PCM-contained concrete is possible up to some extent with the use of nanomaterials and supplementary cementitious materials. As PCM-incorporated concrete is categorized a type of building material, the large-scale use of this material will affect the different stages associated with building lifetimes. Therefore, in the present study, the possible amendments of the different associated stages of building lifetimes after the use of PCM-incorporated concrete are discussed and mapped in consideration of the UN SDGs 7, 11, and 12. The current challenges in the widespread use of PCM are lower thermal conductivity, the trade-off between concrete strength and PCM, and absence of the link between the outcome of PCM-concrete composite and UN SDGs. The global prospects of PCM-incorporated concrete as part of the effort to attain the UN SDGs as studied here will motivate architects, designers, practicing engineers, and researchers to accelerate their efforts to promote the consideration of PCM-containing concrete ultimately to attain net zero carbon emissions from building infrastructure for a sustainable future. [ABSTRACT FROM AUTHOR]

• Marble slurry (MS) was calcined to develop it as SCM. • Calcination of MS resulted in decomposition of CaCO 3 to CaO. • Addition of calcined MS had a positive effect on strength development cement. • Incorporation of calcined MS refined the pore structure of cement binder. • Increased degree of hydration was observed for binder mixes containing calcined MS. The production of cement concrete composites usually results in high emissions of CO 2 which results in severe damage to environment. Therefore, investigations are required to study and report materials that can be used as environmentally friendly binders. The present study is aimed at investigating and improving the supplementary cementitious behavior of marble slurry by calcination. The compressive strength, microstructure and physio-mechanical properties were investigated. The compressive strength results indicated that as compared to raw marble slurry paste the specimens fabricated with calcined marble slurry presented improved compressive strength. It was observed that up to 10% incorporation of calcined marble slurry resulted in almost 7% increase in 28 days compressive strength. The microstructure observations revealed that use of calcined marble slurry results in lower porosity and average pore diameter. The use of 10% calcined marble slurry resulted in 7.5% reduction of porosity. Moreover, the data obtained from 29Si NMR spectra revealed that use of calcined marble slurry as cement replacement resulted in increased degree of hydration and chain length. Based on the results obtained up to 10% of calcined marble slurry can be used as supplementary cementitious material to develop environmentally friendly binary blended cement. In conclusion it can be stated that supplementary cementitious behavior of raw marble slurry can be enhanced by calcination. [ABSTRACT FROM AUTHOR]

This study presents an investigation of the effects of the precursor, alkalinity and temperature on the rheology and structural buildup of alkali activated materials. Here, 100% fly ash, 100% slag and blended mixes of fly ash and slag were activated by 4 M, 6 M, 8 M or 10 M (only for sodium hydroxide) solutions at 25 °C, 35 °C, 45 °C and 55 °C. The rheological properties were investigated to obtain the flow curves, viscosity, storage modulus, and loss factor of these materials. The results showed that for the presence of slag, a higher molarity of the alkali activating solution and a high temperature all caused greater interparticle force, leading to an increase in the shear stress and viscosity of the alkali activated materials. It was also observed that slag had the greatest effect on the increase in the storage modulus of the blended mixes. Furthermore, the higher alkalinity and temperature levels were instrumental in initiating the dissolution of fly ash and improving its rate of structural buildup. Moreover, the interdependence of various factors showed that the type of precursor, as well as the concentration of alkali activating solution, were the primary influencing factors on the polymerization process, as well as the rheological measurements of alkali-activated materials. [ABSTRACT FROM AUTHOR]

This article presents test results of aggressive environment impact, i.e., seawater, acid solutions and carbonation, on the durability of cement–ash mortars. Tests were conducted on CEM I 42.5R-based mortars containing 35 to 70% by mass of FBC fly ash from brown and black coal combustion in a homogeneous form and mixtures of 35% by mass of siliceous fly ashes (CFA) and 35% by mass of FBC fly ash. It was demonstrated that in normal conditions (20 °C), FBC ashes showed higher pozzolanic activity than CFA, except when their curing temperature was increased to 50 °C. FBC ashes increased mortars' water demands, which led to an accelerated carbonation process. In an environment of Cl- ions, cement–ash mortars showed more Ca2+ ions leached and no expansive linear and mass changes, which, with their increased strength, might be an argument in favour for their future use in construction of coastal structures resistant to seawater. FBC ash content may be increased to 35% by mass, maintaining mortars' resistance to seawater, acid rain and carbonation. A favourable solution turned out to be a FBC and CFA mixed addition to cement of 35% by mass each, in contrast to mortars containing 70% of FBC fly ash in homogeneous form. [ABSTRACT FROM AUTHOR]

In the present study, the efficiency of five different carbonation and/or water curing conditions on the properties of belite-rich cement mortar and ordinary Portland cement mortar was investigated. The hybrid curing of samples was carried out by submerging samples at different levels in water or in a lime-saturated solution kept under carbonation curing conditions. The compressive strength was measured to compare the physical properties of the cement mortars, and X-ray diffraction and thermogravimetric analysis results were analyzed to compare the physicochemical properties. The results revealed that the supply of additional moisture during carbonation curing tends to decrease carbonation curing efficiency and that the hydration products of cement paste are predominantly affected by the depth at which the specimen was immersed in the liquid rather than the type of liquid used. [ABSTRACT FROM AUTHOR]

• Seawater was used to produce alkali activating solution. • Seawater based alkali activated fly ash paste was subjected to chemical attack. • Acid attack was severe on seawater based samples. • Seawater specimen registered improved durability against sulfate attack. The present study investigates the microstructure and durability of alkali-activated fly ash made with seawater against acid and sulfate attacks. Seawater along with pure water and tap water was used as solvent to produce alkali-activated fly ash. Investigations were carried out to examine the effects of 3% acidic and 3% sulfate environments on the properties of alkali-activated fly ash. MIP, XRD, FT-IR and 29Si NMR were employed to observe the microstructure and chemical properties of samples. The durability of alkali-activated fly ash made with seawater was primarily governed by the refined microstructure and presence of calcium chloride. From a microstructural perspective, alkali-activated fly ash made with seawater presented enhanced resistance to adverse conditions, as indicated by the corresponding higher Si/Al ratio. [ABSTRACT FROM AUTHOR]

Cement-based materials play an irreplaceable role in building and sustaining our society by meeting the performance demand imposed on structures and sustainability. Cement-based materials are no longer limited to derivatives of Portland cement, and appreciate a wider range of binders that come from various origins. It is therefore of utmost importance for understanding and expanding the relevant knowledge on their microstructure and likely durability performance. This Special Issue "Microstructures and Durability of Cement-Based Materials" presents recent studies reporting microstructural and durability investigation revealing the characteristics of cement-based materials. [ABSTRACT FROM AUTHOR]