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This study evaluates the chloride binding capacity and the migration of chloride in sodium carbonate-activated slag cements and mortars. The effect on chloride mobility and binding of adding a calcined layered double hydroxide (CLDH) to the binder mix was also assessed. Significantly improved durability characteristics can be achieved for sodium carbonate-activated slag mortars by the addition of small fractions of CLDH, as a consequence of a higher degree of reaction, higher chloride binding capacity, and the refined pore structures present in these modified materials, in comparison with alkali-activated cements produced without CLDH. The addition of CLDH enables the production of sodium carbonateactivated slag cements with notably reduced chloride ingress compared to silicate activated slag cements.

This study presents for the first time a systematic investigation of the thermodynamic properties of sodium aluminosilicate hydrate (N-A-S-H), through dissolution of pure synthetic N-A-S-H gels. Changes to the chemical...

Lightweight foamed mortars are produced through the addition of foaming agents into the cement blend, so that voids of different sizes are formed within the matrix, reducing the density of the material and therefore also its weight. However, the increased porosity of these materials usually compromises their mechanical strength, limiting their application as a structural material. Modern infrastructure demands high-strength lightweight concrete formulations that can be adjusted to develop more ambitious projects, both in design and application. In this study, lightweight pastes and mortars were produced using Portland cement blended with fly ash and silica fume, with varying water contents, and foamed using aluminium metal powder. To stabilise the bubbles produced through oxidation of the aluminium metal, polyethylene glycol was added to the mixes, and proved effective in yielding more uniform bubbles than were observed in the samples with no added stabiliser. This led to improvements in both the bulk density and compressive strength of the materials produced according to this new methodology.

The effect of ultrafine fly ash (UFA) and fly ash (FA) on the physical properties, phase assemblage, and microstructure of magnesium potassium phosphate cement (MKPC) was investigated. This study revealed that the UFA addition does not affect the calorimetry hydration peak associated with MKPC formation when normalized to the reactive components (MgO and KH 2 PO 4 ). However, there is an indication that greater UFA additions lead to an increased reaction duration, suggesting the potential formation of secondary reaction products. The addition of a UFA:FA blend can delay the hydration and the setting time of MKPC, enhancing workability. MgKPO 4 •6H 2 O was the main crystalline phase observed in all systems; however, at low replacement levels in the UFA-only system (<30 wt %), Mg 2 KH(PO 4 ) 2 •15H 2 O was also observed by XRD, SEM/EDS, TGA, and NMR ( 31 P MAS, 1 H-31 P CP MAS). Detailed SEM/EDS and MAS NMR investigations ( 27 Al, 29 Si, 31 P) demonstrated that the role of UFA and UFA:FA was mainly as a filler and diluent. Overall, the optimized formulation was determined to contain 40 wt % fly ash (10 wt % UFA and 30 wt % FA (U10F30)), which achieved the highest compressive strength and fluidity and produced a dense microstructure.